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Sheahan Diamond Literature Technical Reference Compilation 2022


The Sheahan Diamond Literature Reference Compilation
The Sheahan Diamond Literature Reference Compilation is compiled by Patricia Sheahan who publishes on a monthly basis a list of new scientific articles related to diamonds as well as media coverage and corporate announcementscalled the Sheahan Diamond Literature Service that is distributed as a free pdf to a list of followers. Pat has kindly agreed to allow her work to be made available as an online digital resource at Kaiser Research Online so that a broader community interested in diamonds and related geology can benefit. The references are for personal use information purposes only; when available a link is provided to an online location where the full article can be accessed or purchased directly. Reproduction of this compilation in part or in whole without permission from the Sheahan Diamond Literature Service is strictly prohibited. Return to Diamond Resource Center
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
A-An Ao+ B-Bd Be-Bk Bl-Bq Br+ C-Cg Ch-Ck Cl+ D-Dd De-Dn Do+ E F-Fn Fo+ G-Gh Gi-Gq Gr+ H-Hd He-Hn Ho+ I J K-Kg Kh-Kn Ko-Kq Kr+ L-Lh
Li+ M-Maq Mar-Mc Md-Mn Mo+ N O P-Pd Pe-Pn Po+ Q R-Rh Ri-Rn Ro+ S-Sd Se-Sh Si-Sm Sn-Ss St+ T-Th Ti+ U V W-Wg Wh+ X Y Z
Sheahan Diamond Literature Reference Compilation - Media/Corporate References by Name for all years
A B C D-Diam Diamonds Diamr+ E F G H I J K L M N O P Q R S T U V W X Y Z
Tips for Users
Posted/Published Reference CodesThe SDLRC provides 3 types of references identified in the reference code. DS for scientific article, DM for a media article, and DC for a corporate announcement. Consider DS0512-0001. The DS stands for "diamond scientific". 05 stands for 2005, the year the reference was posted. 12 represents the month the reference was posted. For all years prior to 2015 the default month is 12. -0001 is the reference's identifier and it does not mean anything. The number below the refence code, ie 2015, is the year the article was published. Note that the posted year may sometimes be later than the published year.
Sort OrderReferences are sorted by the "author" name and when the reference was posted to the compilation.
Most RecentIf the reference code is highlighted yellow, the reference was made available through the most recent monthly compilation of new literature. Use this to check out new references. When new references are posted, we make it our priority to track down an online link and obtain an abstract. With regard to older references, tracking down an abstract and an online link is a work in progress.
Link to external location of article: If the title has a link, it means we have found a location online where you can either retrieve the full article free, or purchase access to it. The Sheahan Diamond Literature Service is not a technical article procurement service; if you want a restricted article, you must deal directly with the vendor who controls the copyright to the article.
Searching this page for a specific term or authorIn your Firefox browser click Edit in the menu bar and then Find. In the Find box that shows up at the bottom of the web page enter your search term. Firefox will highlight all occurrences. This is particularly helpful when the author you are seeking was not the lead author by whom the compilation is sorted.
Sending or sharing a referenceThe left column (Posted/Published) has an embedded hyperlink for each reference. In Firefox, if you right click on it, you can obtain the link url for that reference's location within the page, which you can copy and paste into an email or any other document. You can also use the "share this link" option to tweet, facebook etc the link.
Monthly Sheahan Diamond Newsletters for 2022
January 2022 May 2022 September 2022
February 2022 June 2022 October 2022
March 2022 July 2022 November 2022
April 2022 August 2022 December 2022
2022 Technical Reference Compilation
Posted/
Published
AuthorTitleSourceRegionKeywords
DS202202-0186
2021
Adushkin, V.V., Goev, A.G., Sanina, I.A., Fedorov, A.V.The deep velocity structure of the Central Kola Peninsula obtained using the receiver function technique.Doklady Earth Sciences, Vol. 501, pp. 1049-1051.Russia, Kola Peninsulageophysics - seismics

Abstract: New results are presented on the features of the deep velocity structure of two of the three main tectonic blocks that make up the Kola region-Murmansk and Belomorskii-by the P receiver function technique. The research is based on data from the broadband seismic stations Teriberka and Kovda. The results are compared with the models obtained by mutual inversion of PRF and SRF using the data from the stations Apatity and Lovozero. It is shown that the crust has a two-layer structure with the border at a depth of 11 km under the Murmansk block and at a depth of 15 km under the Kola and Belomorskii blocks. The crust thickness of the Murmansk, Belomorskii, and Kola blocks are 35, 33, and 40 km, respectively. The presence of the MLD was revealed in all tectonic structures analyzed for the first time, with a top at a depth of about 70 km for the Murmansk and Belomorskii blocks and 90 km for the Kola block and a bottom at 130-140 km for all structures.
DS202205-0672
2022
Afonso, J., Ben-Mansour, W., O'Reilly, S.Y., Griffin, W.L., Salajeghegh, F., Foley, S., Begg, G., Selway, K., Macdonald, A., Januszczak, N., Fomin, I., Nyblade, A.A., Yang, Y.Thermochemical structure and evolution of cratonic lithosphere in central and southern Africa.Nature Geoscience, Apr. 26, 329p. FreeAfrica, South AfricaCraton

Abstract: The thermochemical structure of the subcontinental mantle holds information on its origin and evolution that can inform energy and mineral exploration strategies, natural hazard mitigation and evolutionary models of Earth. However, imaging the fine-scale thermochemical structure of continental lithosphere remains a major challenge. Here we combine multiple land and satellite datasets via thermodynamically constrained inversions to obtain a high-resolution thermochemical model of central and southern Africa. Results reveal diverse structures and compositions for cratons, indicating distinct evolutions and responses to geodynamic processes. While much of the Kaapvaal lithosphere retained its cratonic features, the western Angolan-Kasai Shield and the Rehoboth Block have lost their cratonic keels. The lithosphere of the Congo Craton has been affected by metasomatism, increasing its density and inducing its conspicuous low-topography, geoid and magnetic anomalies. Our results reconcile mantle structure with the causes and location of volcanism within and around the Tanzanian Craton, whereas the absence of volcanism towards the north is due to local asthenospheric downwellings, not to a previously proposed lithospheric root connecting with the Congo Craton. Our study offers improved integration of mantle structure, magmatism and the evolution and destruction of cratonic lithosphere, and lays the groundwork for future lithospheric evolutionary models and exploration frameworks for Earth and other terrestrial planets.
DS202203-0334
2021
Anenburg, M., Broom-Fendley, S., Chen, W.Formation of rare earth deposits in carbonatites. Burbankite, alkaline complexes.Elements, Vol. 17, 327-232.GlobalRare earths, REE

Abstract: Carbonatites and related rocks are the premier source for light rare earth element (LREE) deposits. Here, we outline an ore formation model for LREE-mineralised carbonatites, reconciling field and petrological observations with recent experimental and isotopic advances. The LREEs can strongly partition to carbonatite melts, which are either directly mantle-derived or immiscible from silicate melts. As carbonatite melts evolve, alkalis and LREEs concentrate in the residual melt due to their incompatibility in early crystal-lising minerals. In most carbonatites, additional fractionation of calcite or ferroan dolomite leads to evolution of the residual liquid into a mobile alkaline “brine-melt” from which primary alkali REE carbonates can form. These primary carbonates are rarely preserved owing to dissolution by later fluids, and are replaced in-situ by monazite and alkali-free REE-(fluor)carbonates.-
DS202201-0001
2021
Ashchepkov, I.V., Logvinova, A.M., Spetsius, Z.V.Thermobarometry of inclusions: implications to the structure of lithospheric mantle and evolution in time and diamond formation.Acta Geologica Sinica, Vol. 95, 1, pp. 18-21.Mantlegeobarometry
DS202201-0002
2021
Ashchepkov, I.V., Zinchenko, V.N., Ivanov, A.S.Mantle transects in Africa according to data of mantle xenocrysts and diamond inclusions.Acta Geologica Sinica, Vol. 95, 1, pp. 15-17.Africatectonics
DS202201-0003
2021
Bachynski, R.Carbonatite-associated REE exploration in the Squalus Lake alkaline complex.NWTgeoscience.ca, 1p. AbstractCanada, Northwest Territoriescarbonatite

Abstract: A preliminary field evaluation of rare earth elements (REE) mineralization in the Squalus Lake Alkaline Complex (SLAC) was undertaken for 9 days in the summer of 2021. The focus of the fieldwork was on identifying and characterizing sources of historical anomalous REE assays contained in assessment and government survey reports. The Squalus Lake Alkaline Complex is a syenite-dominated concentric Proterozoic intrusion within the Archean Morose Granite. The intrusion is situated along the Phoenix Fault - a major NNE-trending crustal structure. The core of the complex coincides with a regional-scale magnetic high. These features suggest a classic concentric lithological zonation of the complex with a syenite rim and a carbonatite core. The magnetic anomaly is probably associated with a magnetite-rich ferro-carbonatite phase that typically occurs in the cores of most zoned alkaline/carbonatite complexes. During the fieldwork, evidence for several carbonatite dykes were observed, both in outcrop and in angular float. The dykes are probably emanating from a carbonatite intrusion at the core of the complex, which is interpreted to be underneath Squalus Lake. Sites with reported anomalies were visited and re-sampled. An effort was also made at sampling the different lithological units that were observed. Historically anomalous samples (obtained from the previous prospector) have been re-analyzed to confirm the results and attempts are being made at characterizing the potentials of the various host units. In classic alkaline/carbonatite complex models, high grade REE mineralization is generally associated with the younger ferro-carbonatite phase at the core of the complex. High grade REE mineralization tends to occur in late ferro-carbonatite phases. Previously collected ground-magnetic surveys provide strong discrete targets for the locations of the theorized ferro-carbonatite core, which is a primary target for REE endowment. Curiously, the ~2180 Ma age of the SLAC is similar to the age of several other alkaline complexes in the Slave structural province, including the Big Spruce Lake Complex (~2188Ma) and the Grace Lake Granite (~2176Ma). The Grace Lake Granite is part of the Blatchford Lake Intrusive Suite, which is host to Canada's first REE mine at the Nechalacho Deposit at Thor Lake.
DS202202-0187
2022
Bao, X., Lithgow-Bertelloni, C.R., Jackson, M.G., Romanowicz, B.On the relative temperatures of Earth's volcanic hotspots and mid-ocean ridges. ** not specific to diamondsScience, Vol. 375, 6576, pp. 57-61.Mantleplumes

Abstract: Volcanic hotspots are thought to be fed by hot, active upwellings from the deep mantle, with excess temperatures (Tex) ~100° to 300°C higher than those of mid-ocean ridges. However, Tex estimates are limited in geographical coverage and often inconsistent for individual hotspots. We infer the temperature of oceanic hotspots and ridges simultaneously by converting seismic velocity to temperature. We show that while ~45% of plume-fed hotspots are hot (Tex ? 155°C), ~15% are cold (Tex ? 36°C) and ~40% are not hot enough to actively upwell (50°C ? Tex ? 136°C). Hot hotspots have an extremely high helium-3/helium-4 ratio and buoyancy flux, but cold hotspots do not. The latter may originate at upper mantle depths. Alternatively, the deep plumes that feed them may be entrained and cooled by small-scale convection.
DS202203-0335
2022
Barbosa, N.A., Fuck, R.A., Souza, V.S., Dantas, E.L., Tavares Jr., S.S.Evidence of Paleoproterozoic SLIP, northern Amazonian craton, Brazil.Journal of South American Earth Sciences, Vol. 111, 19p. PdfSouth America, Brazilgeophysics - seismics

Abstract: The Orocaima SLIP consists of an association of acid-intermediate volcanic-plutonic rocks. The volcanic rocks were generated in explosive eruptions through low eruptive columns, probably associated with fissural volcanism in the north of the Amazonian Craton, Brazil, between 2.0 and 1.98 Ga. It generated ignimbrites, whose facies (volcanic breccia rich in lithic, lapilli-tuff and lithic lapilli-tuff) show the proximity of the source. The extensive area of ca. 200.000 km2 of ignimbrite, rhyolite and dacite deposits, as well as the age range (2.0-1.98 Ga) and geochemical signatures suggest that the Orocaima volcano-plutonism may correspond to one of the oldest silicic LIPs in the world. The silicic volcanism is essentially subaerial and characterized by high-grade ignimbrites (densely welded) and subordinate lava, the ages of which indicate the longevity of the volcanic event in the Orosirian. They are included in the Surumu Group and comprise rocks with high-K calc-alkaline affinities and were emplaced in a subduction-related setting, similar to the rocks that extend through Venezuela, Guyana and Suriname (Cuchivero-Surumu-Iwokrama-Dalbana metavolcanic belt - CSID). The occurrence of mafic fragments disseminated in volcanic and granitic rocks in the north of Roraima, Brazil and in other segments of the CSID belt suggests the coexistence of acid and basic magmas. Except for one sample (?Nd(t) = -2.3), the Nd isotopic data of analyzed Surumu Group volcanic rocks yielded positive ?Nd(t) values (0.5-4.48; TDM = 2.0-2.47 Ga), suggesting generation from magmas derived from the mantle or from the melting of new juvenile crust. The Orocaima volcanism bears no evidence of involvement of Archean sources in the generation of the rocks. Thus, the Orocaima volcano-plutonism may represent one of the most significant ignimbrite eruption events during the Palaeoproterozoic in the world.-
DS202204-0515
2022
Barrett, N., Jaques, A.L., Gonzalez-Alvarez, I., Walter, M.J., Pearson, G.Ultra-refractory peridotites of Phanerozoic mantle origin: the Papua New Guinea ophiolite mantle tectonites. ( harzburgites and peridotites)Journal of Petrology, 10.1093/petrology/egac014Asia, Papua New Guineaperidotites

Abstract: Harzburgites and dunites forming the base of the Late Cretaceous-Paleocene Papuan Ultramafic Belt (PUB) and Marum ophiolites of Papua New Guinea (PNG) are amongst the most refractory mantle peridotites on Earth. We present a new integrated dataset of major element, bulk plus mineral trace element and Re-Os isotopic analyses aimed at better understanding the genesis of these peridotites. The PUB harzburgites contain olivine (Fo92-93), low-Al enstatite (less than or equal to 0.5 wt. % Al2O3 and CaO), and Cr-rich spinel (Cr# = 0.90-0.95). The Marum harzburgites are less refractory with olivine (Fo91.9-92.7), enstatite (~0.5-1.0 wt. % Al2O3 and CaO), minor clinopyroxene (diopside), and spinel (Cr# = 0.71-0.77). These major element characteristics reflect equivalent or greater levels of melt depletion than that experienced by Archean cratonic peridotites. Whereas bulk-rock heavy rare earth element (HREE) abundances mirror the refractory character indicated by the mineral chemistry and major elements, large-ion lithophile elements (LILEs) indicate a more complex melting and metasomatic history. In-situ olivine and orthopyroxene REE measurements show that harzburgites and dunites have experienced distinct melt-rock interaction processes, with dunite channels/lenses, specifically, showing higher abundances of HREE in olivine. Distinctive severe inter-element fraction of platinum group elements and Re result in complex patterns that we refer to as “M-shaped”. These fractionated highly siderophile element (HSE) patterns likely reflect the dissolution of HSE-rich phases in highly depleted peridotites by interaction with subduction-related melts/fluids, possibly high-temperature boninites. Osmium isotope compositions of the PNG peridotites are variable (187Os/188Os = 0.1204 to 0.1611), but fall within the range of peridotites derived from Phanerozoic oceanic mantle, providing no support for ancient melt depletion, despite their refractory character. This provides further evidence that highly depleted peridotites can be produced in the modern Earth, in subduction zone environments. The complex geochemistry indicates a multi-stage process for the formation of the PNG mantle peridotites in a modern geodynamic environment. The first stage involves partial melting at low-pressure (<2 GPa) and high-temperature (~1250-1350 0C) to form low-K, low-Ti tholeiitic magmas that formed the overlying cumulate peridotite-gabbro and basalt (PUB only) sequences of the ophiolites. This is inferred to have occurred in a fore-arc setting at the initiation of subduction. Later stages involved fluxing of the residual harzburgites with hydrous fluids and melts to form replacive dunites and enstatite dykes, and interaction of the residual peridotites in the overlying mantle wedge with high-temperature hydrous melts from the subducting slab to generate the extremely refractory harzburgites. This latter stage can be linked to the eruption of low-Ca boninites at Cape Vogel, and other arc-related volcanics, in a nascent oceanic island arc. Both ophiolites were emplaced shortly after when the embryonic oceanic island arc collided with the Australian continent.
DS202205-0673
2022
Barrett, N., Jaques, A.L., Gonzalqez-Alvarez, I., Walter, M.J., Pearson, G.Ultra-refractory peridotites of Phanerozoic mantle origin: the Papua New Guinea ophiolite mantle tectonites.Journal of Petrology, 10.1093/petrology/egac014 99p. pdf Asia, Papua New Guineatectonites

Abstract: Harzburgites and dunites forming the base of the Late Cretaceous-Paleocene Papuan Ultramafic Belt (PUB) and Marum ophiolites of Papua New Guinea (PNG) are among the most refractory mantle peridotites on Earth. We present a new integrated dataset of major element, bulk plus mineral trace element and Re-Os isotopic analyses aimed at better understanding the genesis of these peridotites. The PUB harzburgites contain olivine (Fo92-93), low-Al enstatite (less than or equal to 0.5 wt. % Al2O3 and CaO), and Cr-rich spinel (Cr#?=?0.90-0.95). The Marum harzburgites are less refractory with olivine (Fo91.9-92.7), enstatite (~0.5-1.0 wt. % Al2O3 and CaO), minor clinopyroxene (diopside), and spinel (Cr#?=?0.71-0.77). These major element characteristics reflect equivalent or greater levels of melt depletion than that experienced by Archean cratonic peridotites. Whereas bulk-rock heavy rare earth element (HREE) abundances mirror the refractory character indicated by the mineral chemistry and major elements, large-ion lithophile elements indicate a more complex melting and metasomatic history. In situ olivine and orthopyroxene REE measurements show that harzburgites and dunites have experienced distinct melt-rock interaction processes, with dunite channels/lenses, specifically, showing higher abundances of HREE in olivine. Distinctive severe inter-element fraction of platinum group elements and Re result in complex patterns that we refer to as ‘M-shaped’. These fractionated highly siderophile element (HSE) patterns likely reflect the dissolution of HSE-rich phases in highly depleted peridotites by interaction with subduction-related melts/fluids, possibly high-temperature boninites. Osmium isotope compositions of the PNG peridotites are variable (187Os/188Os?=?0.1204 to 0.1611), but fall within the range of peridotites derived from Phanerozoic oceanic mantle, providing no support for ancient melt depletion, despite their refractory character. This provides further evidence that highly depleted peridotites can be produced in the modern Earth, in subduction zone environments. The complex geochemistry indicates a multi-stage process for the formation of the PNG mantle peridotites in a modern geodynamic environment. The first stage involves partial melting at low-pressure (<2 GPa) and high-temperature (~1250°C-1350°C) to form low-K, low-Ti tholeiitic magmas that formed the overlying cumulate peridotite-gabbro and basalt (PUB only) sequences of the ophiolites. This is inferred to have occurred in a fore-arc setting at the initiation of subduction. Later stages involved fluxing of the residual harzburgites with hydrous fluids and melts to form replacive dunites and enstatite dykes and interaction of the residual peridotites in the overlying mantle wedge with high-temperature hydrous melts from the subducting slab to generate the extremely refractory harzburgites. This latter stage can be linked to the eruption of low-Ca boninites at Cape Vogel, and other arc-related volcanics, in a nascent oceanic island arc. Both ophiolites were emplaced shortly after when the embryonic oceanic island arc collided with the Australian continent.
DS202201-0004
2021
Bassoo, R., Befus, K.Cold and fast hypabyssal kimberlite emplacement within the upper crust demonstrated using cold seal experiments. GAC/MAC Meeting UWO, 1p. Abstract p. 34.Globalmonticellite

Abstract: Syn- to post-emplacement alteration of hypabyssal kimberlite may represent an overlooked opportunity to better understand kimberlite volcanism and diamond preservation potential. To learn more about these effects, we conducted a series of short duration (0.25 - 4 h), high-temperature (300 - 900 °C) cold seal experiments designed to test mineral abundances and textures in the hypabyssal environment. A combined approach of petrography, Raman spectroscopy, SEM, and optical cathodoluminescence demonstrates that both calcite and olivine are sensitive to temperature in the hypabyssal environment. Primary calcite and olivine are pervasive hypabyssal kimberlite minerals but they will react in a decarbonation reaction to produce monticellite when exposed to elevated temperatures. Monticellite is an indicator of decarbonation and elevated temperature. Decarbonation rates vary directly with temperature and indirectly with CO2 in the fluid, with +12 wt.% CO2 increasing the stability range of calcite by 100 °C. Decarbonation rates are relatively fast, ranging from 1 to 6 area% h-1. To replicate the observed mineral assemblage and textures in natural hypabyssal kimberlites, the rocks could only be exposed to elevated temperatures by syn- to post-emplacement processes with timescales ranging from hours to days. Additionally, calcite preservation in hypabyssal kimberlite provides an observational constraint that diamond grade has not been diminished by post-emplacement conditions. Hypabyssal kimberlites may record other post-emplacement alteration features, which lead to the exsolution of unaccounted for volatiles.
DS202202-0188
2022
Behera, L., Kumar, D.Deep crustal structure and compositions for tectonic and geodynamic implications of the Dharwar Craton ( southern India) inferred from 3-C wide-angle seismic data.Journal of Asian Earth Sciences, in press available 10.1016/j.jseaes.2021.105092 99 p. PdfIndiageophysics - seismics

Abstract: The Dharwar Craton of southern India is an important stable cratonic province of the world with complex geology and tectonic settings. Extensive studies provide insights of crustal velocity structure for the tectonic and geodynamic evolution of this Archean craton. This region has experienced several tectonically disturbed zones like Chitradurga Shear Zone (CSZ), Bababudan Shear Zone (BSZ) and Closepet Granites (CG). We have developed a comprehensive geologically plausible tectonic model using both P- and S-wave velocity structures to image major structural elements like shear zones and decipher the compositional distinctions of different rock assemblages of Western Dharwar Craton (WDC) and Eastern Dharwar Craton (EDC) part using 3-C wide-angle seismic data acquired along the 200-km long Perur-Chikmagalur deep seismic profile. The tectonic model show large compositional changes of subsurface rocks with anomalous high , , , Poisson’s ratio () and density () forming a major tectonic divide or suture zone called CSZ between EDC and WDC blocks. Significant crustal thinning (37-41 km) is observed due to Moho upwarping towards the Neo-Archean EDC block mainly composed of felsic granites and granodiorites. The WDC block show relatively thick crust (48-50 km) due to mafic underplating and mantle plume activity below CSZ forming Meso-Archean greenschist-facies-gneisses with dominant mafic/ultra-mafic compositions. Hence, crustal velocity, density, heat-flow, geology and geochronology studies support a plume-arc model with evidence of thick magmatic underplating of the lower-crust, complex subduction and development of highly strained shear zones like CSZ as suture juxtaposing EDC and WDC blocks.
DS202201-0005
2021
Beyer, C., Myhill, R., Marquardt, K., McCammon, C.A.A reversed redox gradient in Earth's mantle transition zone.Earth and Planetary Science Letters, Vol. 575, 12p.Mantleredox

Abstract: The Earth's mantle hosts a variety of reduced and oxidized phases, including iron-bearing alloys, diamond, and sulfide and carbonate melts. In the upper mantle, increasing pressure favors the stabilization of reduced iron-bearing phases via disproportionation of ferrous iron into ferric and metallic iron. Pressure-driven disproportionation is thought to continue into the transition zone, based on the extrapolation of experiments conducted at lower pressures. To test this hypothesis, we performed high-temperature and high-pressure experiments on basaltic and peridotitic compositions at pressures of 10 to 20 GPa, buffered at different oxygen fugacities. Under these conditions, majoritic garnet is the dominant ferric-iron bearing phase. We analyze our experimental run products for their ferric iron concentrations with EELS and Mössbauer spectroscopy. Contrary to expectations, results show that at iron saturation, ferric iron content of majorite peaks in the upper transition zone and then decreases between 500 and 650 km depth, destabilizing and resorbing reduced phases. This peak can be explained by decreases in the effective volume of ferrous minerals in transition zone assemblages. We also show that natural diamond-hosted majorite inclusions that equilibrated in the sublithospheric mantle grew from variably reduced fluids. These results are consistent with the idea that these diamonds formed during progressive reduction of an originally carbonatitic melt.
DS202201-0006
2021
Blumentritt, F., Fritsch, E.Photochromism and photochromic gems: a review and some new data. Part 1.Journal of Gemmology, Vol. 37, 8, 780-800. pdfGlobalspectra - EM radiation
DS202205-0674
2022
Boldyrev, K.N., Sedov, V.S., Vanpoucke, D.E.P., Ralchenko, V.G., Mavrin, B.N.Photoluminescence and first principles phonon study.Diamond and Related Materials, Vol. 126, 6p. PdfGlobalLuminescence
DS202203-0336
2022
Boone, S.C., Dalton, H., Prent, A., Kohlman, F., Theile, M., Greau, Y., Florin, G., Noble, W., Hodgekiss, S-A., Ware, B., Phillips, D., Kohn, B., O'Reilly, S., Gleadow, A., McInnes, B., Rawling, T.AusGeochem: an open platform for geochemical data preservation, dissemination and synthesis. Lithodat Pty *** not specific to diamonds but excellent concept/platformGeostandards and Geoanalysis Research, doi.org/10.1111/GGR.12419 34p. PdfAustraliageochemistry

Abstract: To promote a more efficient and transparent geochemistry data ecosystem, a consortium of Australian university research laboratories called the AuScope Geochemistry Network (AGN) assembled to build a collaborative platform for the express purpose of preserving, disseminating, and collating geochronology and isotopic data. In partnership with geoscience-data-solutions company Lithodat Pty Ltd, the open, cloud-based AusGeochem platform (https://ausgeochem.auscope.org.au) was developed to simultaneously serve as a geosample registry, a geochemical data repository, and a data analysis tool. Informed by method-specific groups of geochemistry experts and established international data reporting practices, community-agreed database schemas were developed for rock and mineral geosample metadata and secondary ion mass spectrometry U-Pb analysis, with additional models for laser ablation inductively-coupled mass spectrometry U-Pb and Lu-Hf, Ar-Ar, fission-track and (U-Th-Sm)/He under development. Collectively, the AusGeochem platform provides the geochemistry community with a new, dynamic resource to help facilitate FAIR (Findable, Accessible, Interoperable, Reusable) data management, streamline data dissemination and advanced quantitative investigations of Earth system processes. By systematically archiving detailed geochemical (meta-)data in structured schemas, intractably large datasets comprising thousands of analyses produced by numerous laboratories can be readily interrogated in novel and powerful ways. These include rapid derivation of inter-data relationships, facilitating on-the-fly data compilation, analysis, and visualisation.
DS202203-0337
2022
Borisova, A.Y., Nedelec, A.A simple recipe for making the first continental crust. EOS.org, Feb. 2p.Mantleexperiments

Abstract: Earth’s continental crust, on which billions of people and countless land animals and plants spend their lives, is distinguished by its predominantly felsic composition. That is, this crust contains large proportions of silicon, oxygen, aluminum, and alkali metals like sodium and potassium, and it is largely made up of quartz and feldspar minerals. Felsic continental crust as old as 4 billion years has been recognized on Earth’s surface, and we know it was associated with basaltic oceanic crust made of minerals rich in calcium, magnesium, and iron, such as plagioclase feldspar, olivine, and pyroxenes. But the planet’s earliest rigid outer shell-its primordial crust, which crystallized from the magma ocean covering the nascent Earth about 4.5 billion years ago-probably looked very different. When and how the first felsic crust formed are questions researchers have pondered for decades. Unfortunately, a handful of microscopic zircons, accessory minerals commonly found in felsic rocks, from a few places around the world are the only remnants from the Hadean eon, the first 500 million years of Earth’s existence. In the almost complete absence of early crustal rocks, scientists have thus had to piece together their hypotheses from indirect evidence. Recently, our research group completed laboratory experiments and numerical modeling that revealed evidence of a felsic rock-forming reaction that may have occurred on Hadean Earth and may have been responsible for creating the planet’s first continental crust.-
DS202204-0516
2022
Boscaini, A., Marzoli, A., Bertrand, H., Chiagradia, M., Jourdan, F., Faccende, M., Meyzen, C.M., Callegaro, S., Duran, L. Cratonic keels controlled the emplacement of the Central Atlantic Magmatic Province ( CAMP)Earth and Planetary Science Letters, Vol. 584, doi 10.1016/j.espl.2022.117480Africa, Mali, Mauritaniacraton

Abstract: Large Igneous Provinces (LIPs) are exceptionally voluminous magmatic events frequently related to continental break-up, global climate changes and mass extinctions. One interesting aspect of many LIPs is their spatial proximity to cratons, begging the question of a potential control of thick lithosphere on their emplacement. In this study, we investigate the relationship between the emplacement of the Central Atlantic Magmatic Province (CAMP) and the thick lithospheric mantle of the Precambrian cratons that formed the central portion of Pangea and are currently located on the continents surrounding the Central Atlantic Ocean. CAMP outcrops are frequently located over the margins of the thick cratonic keels, as imaged by recent tomographic studies, suggesting a role of lithosphere architecture in controlling magma genesis and emplacement. Here we focus on CAMP dykes and sills from the Hank, Hodh, and Kaarta basins in North-Western Africa (NW-Africa, Mali and Mauritania) emplaced at the edge of the Reguibat and Leo-Man Shields. The investigated intrusive rocks show compositions similar to most CAMP magmas, in particular those of the Tiourjdal geochemical group, limited to NW-Africa, and of the Prevalent group, occurring all over the CAMP. Geochemical modelling of CAMP basalts requires a Depleted MORB Mantle (DMM) source enriched by recycled continental crust (1-4%) and melting beneath a lithosphere of ca. 80 km in thickness. On the contrary, melting under a significantly thicker lithosphere (>110 km) does not produce magmas with compositions similar to those of CAMP basalts. This suggests that CAMP magmatism was likely favoured by decompression-induced partial melting of the upwelling asthenospheric mantle along the steep lithospheric boundaries of stable cratons. The architecture of the pre-existing lithosphere (i.e., the presence of stable thick cratonic keels juxtaposed to relatively thinner lithosphere) appears to have been a critical factor for localizing mantle upwelling and partial melting during extensive magmatic events such as in the CAMP.
DS202202-0189
2022
Brahma, S., Sahoo, S., Durai, P.R.First report of carbonatite from Gundlupet area, western Dharwar Craton, Karnataka, southern India.Journal of the Geological Society of India, Vol.98, pp. 35-40. Indiacarbonatite

Abstract: A new carbonatite body has been discovered from Gundlupet area, western Dharwar craton, southern India which is located at juncture of major shear zones namely, Kollegal shear zone to the east, Sargur shear zone to the west and Moyar shear zone to the south. The carbonatite and associated syenite have intruded into the peninsular gneissic complex. The southern margin of the syenite has a tectonic contact with the peninsular gneissic complex suggesting their emplacement is related to the splay shear of Moyar shear zone. The Gundlupet carbonatite is dominantly sövite with minor beforsite and iron rich carbonatite which are associated with phenocrystic magnetite, apatite, amphibole, pyroxene and monazite. Fenitisation is observed in local scale along the contact of carbonatite and syenite where metasomatic alterations took place to give rise to alkali amphibole and pyroxene rich rock. Geochemically, the carbonatite is characterised by high CaO content (48.86%-51.80%), P2O5 (0.35%-3.23%) and low SiO2 (3.09%-5.30%). The high Sr (5750-13445 ppm) content and low Ni, Cr, Zn and Cu content indicates that the melt has undergone some degree of fractionation before crystallization. Gundlupet carbonatite is enriched in LREE with values ranging from 5666 ppm to 7530 ppm and average LREE of 6248 ppm.
DS202205-0675
2022
Brooke, K.Melilites ( minerals explained)Geology Today, Vol. 38, 1, 5p.Globalmelilites

Abstract: The melilites are a group of little-known silicate minerals. In nature, the commonest are rock-forming minerals found in the igneous rocks characterized by a low silica content (undersaturated rocks), in contact metamorphic rocks formed where igneous rocks invade impure limestones. They are also found in artificial slags and primitive meteorites, where they are an important component of the oldest material in the Solar System.
DS202201-0007
2021
Burness, S.M., Thomassot, E., Smart, K., Tappe, S.Sulphur isotopes ( 34S and 33S ) in sulphides from cratonic mantle eclogites: a glimpse of volatile cycling in ancient subduction zones.Earth and Planetary Science Letters, Vol. 572, 13p. PdfMantleeclogites

Abstract: Multiple sulphur isotopic compositions of sulphides from Kaapvaal craton mantle eclogites allow to elucidate the recycling of sulphur into the deep Earth and to differentiate between recycled crust and mantle origins of eclogite-hosted sulphides, including the precious metals that they capture. We present multiple sulphur isotope ratio measurements by secondary ion mass spectrometry for sulphides from a collection of mantle-derived eclogite xenoliths from Proterozoic and Mesozoic kimberlite occurrences in South Africa (Premier, Roberts Victor, Jagersfontein). Previous work established that the host eclogites have elemental and oxygen isotopic compositions in support of seawater-altered oceanic lithosphere protoliths, and for many of these xenolith suites Archean ages have been suggested. The eclogite-hosted sulphides have ?34S values from -5.7 to + 29 ‰, with the upper end of this wide range representing the highest-ever recorded ?34S composition of material derived from the Earth's mantle. The ?33S values range from -0.29 to + 0.18 ‰ and do not record significant mass-independent sulphur isotope fractionation, i.e., there is no compelling S-MIF signature. Most of the sulphide grains have ?34S values that fall within a range between -6 and + 4 ‰, and they probably retain an isotopic record of sulphides that formed originally within altered oceanic crust. In contrast, the highly positive ?34S values from +13 to + 29 ‰ detected in sulphide grains from a single eclogite xenolith are similar to those of marine sulphates, which were probably a minor sulphur component of the oceanic crustal protolith. The lack of a significant S-MIF signature in the eclogitic sulphides that show ?34S evidence for a recycled crust origin implies that this sulphur component stems from a < 2.4Ga post-Archean surficial reservoir. This finding suggests that the cratonic mantle eclogites may have formed from post-Archean oceanic crust (e.g., Paleoproterozoic eclogite protoliths), or - as is preferred here - the 'surficial' sulphur was introduced into the cratonic root during relatively young metasomatic events and is thus unrelated to eclogite petrogenesis and Archean continent formation.
DS202203-0338
2022
Campamor, A.C.Toppling a market friendly regime: the repression and economic growth. Academia Letters, Doi.org/10.20935/AL640 6p. PdfAfrica, Asia, Europeeconomics

Abstract: Let us consider a country ruled by a market-friendly dictatorship, which is threatened by a collectivist opposition. The members of the opposition will try to topple the dictatorship, expropriate the returns to the productive capital and distribute the existing resources among the working class. In order to achieve this goal, they need to demonstrate and take to the streets.-
DS202205-0676
2022
Cao, C., Zeng, F., Liu, Y.W., Yang, J., Shenbiao, Y.Morphology and FTIR characteristics of the alluvial diamond from the Yangtze craton, China.Crystals, April 15p. PdfChinadiamond morphology

Abstract: A total of 48 natural alluvial diamonds from the Yangtze Craton, China, also called Hunan diamonds, were studied using morphology and IR spectroscopy. These diamond samples, collected downstream of the Yuan River, Hunan Province, with unknown host-rock source(s), were observed by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR). Most Hunan diamonds are monocrystal forms of octahedra, tetrahexahedra (THH) and dodecahedra; octahedral-rhom-dodecahedral transitional behaviors and irregular forms are also visible. Trigons and tetragons, terraces and shield-shaped laminae are surface features that frequently indicate dissolution and reabsorption; green and brown spots, network patterns, and other mechanical abrasion marks are typical evidence of long-time deposition and transportation of Hunan diamonds. The main types of Hunan diamonds are type IaAB and type ?a. Diamond samples have a wide range of total nitrogen content (Ntot) from 196-1094 ppm. Two populations are distinguished by two-peak distribution models of NA (A-center concentrations) and %B (proportion of aggregated nitrogen). Hunan diamonds are low in structure hydrogen (0.03-4.67 cm?1, mostly below 1 cm?1) and platelets (0.23-17 cm?1, mostly below 2 cm?1). Moreover, there is a significant positive correlation between the hydrogen correlation peak and Ntot, which is similar to Argyle diamonds. The temperature conditions of the diamond formation have been estimated at 1075-1180 °C, mainly conforming to the kimberlite diamond range. Besides, some samples with slightly higher temperatures are close to the ultramafic-related Juina diamonds. Therefore, the FTIR characteristics analysis and comparison indicate the multiple sources of Hunan diamonds.
DS202201-0008
2021
Celestian, A.JNew mineral names: diamonds, dumps and fumaroles.: crowningshieldite.American Mineralogist, Vol. 106, p. 208 1/4p.Africa, LesothoCLIPPIR - Letseng

Abstract: In this series of New Mineral Names, a thematic approach is used to help provide context for advances and discoveries in mineralogy. Planet Earth is ever-changing, and unique crystals are found in the tiniest of micro-geologic niches. With emerging analytical techniques, the formerly inaccessible becomes accessible. New minerals inspire creative approaches to overcoming chemical and technological challenges and can reveal what the Earth was like billions of years ago. In this issue, we look at recently described minerals that are associated with diamonds, dumps, and fumaroles: crowningshieldite, goldschmidtite, breyite, cardite, grimmite, hrabákite, freitalite, dioskouriite, dobrovolskyite, ferroefremovite, and vasilseverginite.
DS202205-0677
2022
Chen, C., Yao, Z-S., Yan Wang, C.Partitioning behaviours of cobalt and manganese along diverse melting paths of peridotitic and MORB-like pyroxenite mantle.Journal of Petrology, Vol. 63, 4, 10.1093/perology/egac021Mantleperidotite

Abstract: The Co, Mn, Fe, and Ni contents of olivine phenocrysts and host basalts are sensitive to source mantle lithology, which suggests they may be used to constrain the processes of mantle melting and identify basalts formed from non-peridotitic (i.e. pyroxenitic) mantle sources. Here, we use a new comprehensive, forward model involving multiple parameters to simulate partitioning of Co and Mn during partial melting of the mantle in different tectonic settings: (1) polybaric continuous melting of peridotite mantle in mid-ocean ridges can generate melts that show decreasing Co and Mn with increasing degrees of melting so that the mid-ocean ridge basalts (MORBs) contain ~39-84 ?g/g Co and?~900-1600 ?g/g Mn; (2) flux-melting of the mantle wedge in subduction zones tends to produce a melt that has Co increasing from ~24 to 55 ?g/g and Mn from ~500 to 1110 ?g/g with increasing temperature; (3) melts produced by isobaric melting of the subcontinental lithospheric mantle are also sensitive to increasing temperature and have ~35-160 ?g/g Co and ~800-2600 ?g/g Mn; (4) decompression melting of peridotite related to the mantle plume generates melts containing ~45-140 ?g/g Co and?~1000-2000 ?g/g Mn, and the abundances of these metals decrease with increasing degrees of melting; and (5) partitioning behaviors of Co, Mn, and Ni during decompression melting of MORB-like pyroxenite contrast with those during decompression melting of peridotite due to the different mineralogy and compositions in mantle lithologies, and the MORB-like pyroxenite-derived melt is metal-poor with ~25-60 ?g/g Co, ~290-1600 ?g/g Mn, and?~160-340 ?g/g Ni. Although high-Ni, low-Mn forsteritic olivine phenocrysts and high melt Fe/Mn ratio have been proposed as diagnostic indicators of pyroxenitic components in the mantle, our models show that these features can be also generated by melting of peridotite at greater depth (i.e. a high pressure and temperature). To quantify the effect of high-pressure melting of peridotite on these diagnostic indicators, we modeled the correlations of melt Fe/Mn and olivine Co, Mn, and Ni contents with melting depth along the decompression melting path of a thermal plume. When Fe/Mn ratios of basalts and/or compositions of olivine phenocrysts deviate significantly from our modeled correlation lines, high-pressure melting of peridotite cannot explain these data, and the existence of pyroxenitic component in the mantle source is likely required. The pyroxenite-derived melt is modeled to be Ni-poor, but mixing with a peridotite-derived melt can strongly increase the partition coefficient of Ni between olivine and mixed melt, resulting in the generation of high-Ni olivine phenocrysts in plume-associated magmatic suites.
DS202204-0517
2022
Chen, M., Li, C., Palumbo, G., Zhu, Y-Q., Goldman, N., Cappellaro, P.A synthetic monopole source of Kalb- Raman field in diamond.Science, Vol. 375, 6584 pp. 1017-1020.Globalgeophysics - magnetics

Abstract: Magnetic monopoles play a central role in various areas of fundamental physics, ranging from electromagnetism to topological states of matter. While their observation is elusive in high-energy physics, monopole sources of artificial gauge fields have been recently identified in synthetic matter. String theory, a potentially unifying framework that encompasses quantum mechanics, promotes the conventional \emph{vector} gauge fields of electrodynamics to \emph{tensor} gauge fields, and predicts the existence of more exotic \emph{tensor monopoles} in 4D space. Here we report on the characterization of a tensor monopole synthesized in a 4D parameter space by the spin degrees of freedom of a single solid-state defect in diamond. Using two complementary methods, we characterize the tensor monopole by measuring its quantized topological charge and its emanating Kalb-Ramond field. By introducing a fictitious external field that breaks chiral symmetry, we further observe an intriguing transition in the spectrum, characterized by spectral rings protected by mirror symmetries. Our work represents the first detection of tensor monopoles in a solid-state system and opens up the possibility of emulating exotic topological structures inspired by string theory.
DS202201-0009
2022
Chen, X., Wang, M., Inoue, T., Liu, Q., Zhang, L., Bader, T.Melting of carbonated pelite at 5.5-15.5 Gpa: implications for the origin of alkali-rich carbonatites and the deep water and carbon cycles.Contributions to Mineralogy and Petrology, Vol. 177, 2, 21p.pdfMantlemetasomatism

Abstract: Melting experiments on a carbonated pelite were performed at 5.5-15.5 GPa, 800-1875 °C using multi-anvil apparatuses to determine the melting phase relations and the P-T stability fields of various phases, which may shed some light on the source of silica-undersaturated magmas and the deep Earth carbon and water cycles. The subsolidus assemblages contain garnet, clinopyroxene, coesite/stishovite at all investigated pressures. Phengite, aragonite or magnesite, and topaz-OH occur below 9.5 GPa. Phase egg, K-hollandite, Ti-oxide, and CAS phase appear at 12-15.5 GPa. Phengite is stable up to 6 GPa and 800 °C, with the phengite-out boundary overlapping with the carbonate-out curve. Thus, the initial melt is carbonatitic and extremely potassium-rich, with K2O/Na2O weight-ratios larger than 40 at fluid-present conditions. The melting reaction phase egg?+?magnesite?+?aragonite?+?(clinopyroxene)?+?stishovite???melt?+?garnet?+?kyanite defines the solidus at 9.5 GPa, 1000-1100 °C. With increasing pressure, the composition of the near-solidus melts gradually evolves from potassium-rich to sodium-rich due to the formation of K-hollandite and the destabilization of clinopyroxene, and as a result of the clinopyroxene-out, the near-solidus melt has the lowest K2O/Na2O value and partitioning coefficient of sodium between clinopyroxene and melt (Dcpx/meltNa) at 15.5 GPa. In addition, phase egg remains stable up to 1400 °C at 15.5 GPa. Thus, phase egg is a good candidate as a deep-water carrier during subduction of pelitic sediments. This study concludes that low degree partial melting of carbonated pelite produces alkali-rich carbonatite melts evolving from potassium-rich (6-12 GPa) to sodium-rich (above 12 GPa) with increasing pressure, and if a slab stagnates at depth, and/or subduction slows down, the produced carbonatite melts will be more silicate-rich with increasing temperature. Moreover, the produced melts generally evolve from relatively silicate-rich to carbonatite-rich with increasing pressure. These alkali-rich carbonatite melts are compositionally similar to those in diamond inclusions, which provides strong evidence for the origin of deep-seated silica-undersaturated carbonatitic magma. Such magma is an ideal metasomatic agent that can give rise to mantle heterogeneity.
DS202204-0518
2022
Chmyz, L., Azzone, R.G., Ruberti, E., Marks, M.A.W.Olivines as probes into assimilation of silicate rocks by carbonate magmas: unraveling the genesis of reaction rocks from the Jacupiranga alkaline-carbonatite complex, southern Brazil.Lithos, Vol. 416-417, 18p. 106647South America, Brazildeposit - Jacupiranga
DS202204-0519
2022
Chow, B.H.Y., Reyes-Aldasoro, C.CAutomatic gemstone classification using computer vision.MDPI, Vol. 12, 1, 21p.dor.org/10.3390/min12010060Globalgemstones

Abstract: This paper presents a computer-vision-based methodology for automatic image-based classification of 2042 training images and 284 unseen (test) images divided into 68 categories of gemstones. A series of feature extraction techniques (33 including colour histograms in the RGB, HSV and CIELAB space, local binary pattern, Haralick texture and grey-level co-occurrence matrix properties) were used in combination with different machine-learning algorithms (Logistic Regression, Linear Discriminant Analysis, K-Nearest Neighbour, Decision Tree, Random Forest, Naive Bayes and Support Vector Machine). Deep-learning classification with ResNet-18 and ResNet-50 was also investigated. The optimal combination was provided by a Random Forest algorithm with the RGB eight-bin colour histogram and local binary pattern features, with an accuracy of 69.4% on unseen images; the algorithms required 0.0165 s to process the 284 test images. These results were compared against three expert gemmologists with at least 5 years of experience in gemstone identification, who obtained accuracies between 42.6% and 66.9% and took 42-175 min to classify the test images. As expected, the human experts took much longer than the computer vision algorithms, which in addition provided, albeit marginal, higher accuracy. Although these experiments included a relatively low number of images, the superiority of computer vision over humans is in line with what has been reported in other areas of study, and it is encouraging to further explore the application in gemmology and related areas.
DS202203-0339
2021
Christy, A.G., Pekov, I.V., Krivobichev, S.V.The distinctive mineralogy of carbonatites.Elements, Vol. 17, pp. 333-338.Mantlemagmatism

Abstract: The mineralogy of carbonatites reflects both the diversity of the sources of their parent magmas and their unusual chemistry. Carbonatites contain diverse suites of both primary magmatic minerals and later hydrothermal products. We present a summary of the variety of minerals found in carbon-atites, and note the economic importance of some of them, particularly those that are major sources of "critical elements", such as Nb and rare earth elements (REEs), which are essential for modern technological applications. Selected mineral groups are then discussed in detail: the REE carbonates, the alkali-rich ephemeral minerals that are rarely preserved but that may be important in the petrogenesis of carbonatites and their metasomatic haloes in adjacent rocks, and the Nb-rich oxides of the pyrochlore supergroup.-
DS202201-0010
2021
Ciadullo, E., Flemming, R., Currie, L., Duk-Rodkin, A.Provenance of kimberlite indicator minerals from Saglek basin, Labrador Sea, Canada.GAC/MAC Meeting UWO, 1p. Abstract p. 72.Canada, Labradordeposit - Saglek

Abstract: The Mokami and Saglek formations are comprised of Middle Eocene to Plio-Pleistocene deltaic deposits in the Labrador Sea, at the mouth of the Hudson Strait. In this study we use the provenance of KIM minerals to investigate the origin of these sediments. Fifty one mineral grains were obtained from Miocene to possibly Pliocene Mokami and Saglek formation strata by sub-sampling ocean cuttings from the Petro-Canada et al. Rut H-11 well. These grains were examined by optical methods, micro X-ray diffraction (?XRD) and Electron Probe Microanalysis (EPMA) at Western University for identification purposes, and 20 grains were determined to be of peridotitic mantle origin, based on the well-established compositional and mineral-formula discrimination criteria. The compositions of these Kimberlite Indicator Minerals (KIMs) have been compared to equivalent mineral grains from known Canadian kimberlite deposits, in a preliminary attempt to determine their provenance. Out of eleven garnets in the suite, nine garnets were classified as G9, thus establishing their lherzolitic mantle origin; one garnet was wehrlitic (G12), and one garnet was crustal (G0) (Fig 1A). The presence of G9 garnets, however, does not indicate provenance, as G9 garnets are ubiquitous in the mantle. Three Cr-diopside grains were found in the suite. They all passed compositional and mineral-formula criteria established by Ziberna et al. (2016) to be recognized as peridotitic. On Al+Cr-Na-K versus Ca/(Ca+Mg+Fe) plots (e.g. Grütter 2009, Fig. 4), these grains plotted in a region occupied by both garnet peridotite and spinel-garnet peridotite, such that formation in the presence of garnet is confirmed, but the type of peridotite is not definitive. These grains were used to calculate P-T conditions of formation using the Nimis and Taylor (2000) thermobarometer, and the Cr-diopside grains revealed P-T formation conditions ranging from 1304-1417 °C and 4.5-5.2 GPa (Fig 1B). These grains plot in the P-T region representing an extension of that occupied by both Somerset and Kirkland Lake kimberlites, however, calculated temperatures significantly above 1300 °C should be treated the caution because this has not been reported for Cr-diopside from any Canadian kimberlites. It is worth noting that the Cr-diopside grains definitively do not match those from the Chidliak kimberlites, although that kimberlite field is located geographically proximal to the Saglek deposit. Seven orthopyroxene grains found in the suite had compositions matching kimberlites from the Slave craton (Fig. 1C). This provenance agrees with the paleo-drainage pattern of the Bell River basin, which extended from the Northern Interior plains to the Sea of Labrador until the late Pleistocene.
DS202203-0340
2022
de Moura Almeida, Y., Marotta, G.S., Franca, G.S., Vidotti, R.M., Fuck, R.A.Crustal thickness estimation and tectonic analysis of the Amazonian craton from gravity data.Journal of South American Earth Sciences, Vol. 111, 10p. PdfSouth America, Brazilgeophysics - seismics

Abstract: The crustal thickness in South America has been mostly determined using seismological techniques. However, because these techniques provide point constraint or profile-specific results, the crustal thickness maps become especially dependent on both the number and spatial distribution of seismological stations. In the Amazonian Craton, the extensive forest cover restricts the number of existing stations, not allowing to elaborate a solely seismological crustal thickness model with homogeneous data coverage. Therefore, to overcome this difficulty, this work proposes a crustal thickness model for the Amazonian Craton developed based on the Parker-Oldenburg method and the Global Geopotential Model called GECO, considering the relationships between wavelengths and depths of the investigation sources. Furthermore, the developed iterative process allowed to determine the average depth of the crust-mantle interface, the density contrast at the interface, and the minimum and maximum frequencies used in the signal filtering process, making the model more robust for defining the used constants. The average crustal thickness of the Amazonian Craton was estimated as 40.25 km, with a standard deviation of the differences of 4.91 km, compared to crustal thickness defined by the seismological data. The estimated model shows great consistency with the data set used while allowing important inferences about craton compartmentation. Also, the geological provinces displayed an N-S connecting trend under the Amazonas, Solimões, and Acre basins, correlating the Guyana Shield with the Central Brazil Shield. Additionally, we observed various tectonic cycles acting on the craton while significantly modifying the structure of the provinces, possibly removing cratonic roots and rejuvenating the crust in older provinces.
DS202203-0341
2022
de Paulo Garcia, P.M., Weske, R.K., Dantas, E.L.Sedimentology, geomorphology, structural controls, and detrital zircon ages of the Itiquira River diamond placer deposits, Mato Grosso, western Brazil.Journal of South American Earth Sciences, Vol. 114, 103712, 20p. PdfSouth America, Brazil, Mato Grossodeposit - Itiquira, alluvials

Abstract: The Itiquira River, Mato Grosso state (western Brazil), hosts several diamond placer deposits, mined intermittently over the last century. It runs over volcanic and sedimentary rocks of the Paraná Basin until it discharges in the northern Pantanal Basin. The bedrocks were deposited in marine, continental desertic, alluvial deltaic, and fluvial environments. The meanders of the Itiquira River are controlled by NE-SW, ENE-WSW, NNW-SSE, N-S, and NW-SE fractures and normal faults, developed in response to the evolution of the Paraná Basin and by neotectonics, linked with the development of the Pantanal Basin since the Paleogene. The Itiquira River middle valley, in which the diamondiferous placers are found, is controlled by NE-SW structures inherited from the Neoproterozoic Transbrasiliano Lineament. The landscape comprises dissected plateaus and structure-controlled valleys formed by Cretaceous, Paleogene, and Neogene planation processes. The diamonds occur in the muddy-sandy matrix of the current stream bed and older terraces gravels. In the Itiquira River, the diamond deposits are related to the following traps: point bars, cut-and-fill channels, pockets, and potholes. Sapphire, garnet (including kimberlitic), ilmenite, zircon, rutile, gold, and iron oxides are documented as heavy minerals in the gravels. Detrital zircon dating of grains extracted from the Itiquira River diamond deposits resulted in the ages of 2057, 1184, 873, 645-508, 307-207, and 144-142 Ma. The potential zircon sources are the Goiás Magmatic Arc granitoids, Paraguay Belt metavolcanics and granites, and Serra Geral Formation volcanics. The ages between 307 and 207 Ma are likely to be from an unknown (possibly kimberlitic) source. The Itiquira River tectonic, geomorphological, and sedimentological evolutions suggest potential sources for the diamond placers and paleoplacers.
DS202201-0011
2021
Deljanin, B., Collins, A., Zaitsev, A.,Lu, T., Vins, V., Chapman, J., Hainschwang, T.Diamonds - natural, treated & laboratory grown.Gemmological Research Industries Inc. Vancouver B.C., isbn 978-1777369231 184p.GlobalBook - notice

Abstract: For those who have some portable and advanced instruments, this book will serve as a handbook with many useful spectra, cross polarised filters and fluorescence reactions to compare, plus an Appendix with results of tests conducted using 11 portable instruments on 64 samples, and suggestions as to what instruments to use depending on budget and needs. Even if you are not a diamond specialist but are merely interested in the science of diamond, or you trade in diamonds, the information in this book will make you more knowledgeable and confident to talk about this beautiful gem with friends and clients.
DS202203-0342
2022
Dergachev, A.L.The mineral resource sectors of BRICS countries: mutual supples and regulation of the global market of mineral raw materials. *** not specific to diamondsMoscow University Bulletin, Vol. 76, 5, pp. 471-481.South America, Brazil, Russia, India, Chinalegal

Abstract: The mineral resource sectors of BRICS countries complement each other perfectly; one of the possible areas for their cooperation in this field is the expansion of mutual trade in mineral commodities and metals in order to provide continuous supplies and price stability. In 2006-2018, the principal beneficiaries of such cooperation were Republic of South Africa and Brazil, which managed to sharply increase their exports of mineral commodities. At the same time, close cooperation with these countries allowed China to become the largest purchaser of mineral commodities and metals in the global market, to ensure continuous supplies and price stability, and to obtain access to mineral resources of the other countries from the organization. However, the expectations of future cooperation among BRICS countries relating to regulation of the global market of mineral resources were to be too high for a number of reasons.
DS202203-0343
2022
Desbarats, A.J., Percival, J.B., Bilot, I., Polivchuk, M.J., Venance, K.E.Drainage geochemistry of mine tailings from a carbonatite-hosted Nb-REE deposit, Oka Quebec, Canada.Applied Geochemistry, Vol. 138, 14p. PdfCanada, Quebecdeposit - Oka

Abstract: Potential environmental issues associated with the mining of carbonatites are receiving increased attention due to the importance of critical metals for green technologies. This study investigates the chemistry of tailings seepage at the former Saint Lawrence Columbium mine near Oka, Québec, Canada, which produced pyrochlore concentrate and ferroniobium from a carbonatite-hosted Nb-REE deposit. Detailed field sampling and laboratory methods were used to characterize the hydraulic properties of the tailings, their bulk chemistry, mineralogy, pore water and effluent chemistries. The tailings are composed of REE-enriched calcite (64-89 wt %) and fluorapatite (2-22 wt %), as well as biotite (6-17 wt %) and chlorite (0-7 wt %). Minor minerals include ankerite, pyrite, sphalerite, molybdenite, magnetite and unrecovered pyrochlore. Secondary minerals include gypsum, barite, strontianite and rhodochrosite. Geochemical mass balance modeling, constrained by speciation modeling, was used to identify dissolution, precipitation and exchange reactions controlling the chemical evolution of pore water along its flow path through the tailings impoundment. In the unsaturated zone, these reactions include sulfide oxidation and calcite dissolution with acid neutralization. Below the water table, gypsum dissolution is followed by sulfate reduction and FeS precipitation driven by the oxidation of organic carbon in the tailings. Incongruent dissolution of biotite and chlorite releases K, Mg, Fe, Mn, Ba and F and forms kaolinite and Ca-smectite. Cation exchange reactions further remove Ca from solution, increasing concentrations of Na and K. Fluoride concentrations reach 23 mg/L and 8 mg/L in tailings pore water and effluent, respectively. These values exceed Canadian guidelines for the protection of aquatic life. In the mildly alkaline (pH 8.3) pore waters, Mo is highly mobile and reaches an average concentration of 83 ?g/L in tailings effluent, which slightly exceeds environmental guidelines. Concentrations (unfiltered) of Zn reach 1702 ?g/L in tailings pore water although values in effluent are usually less than 20 ?g/L. At the ambient pH, Zn is strongly adsorbed by Fe-Mn oxyhydroxides. Although U forms mobile complexes in tailings pore water, concentrations do not exceed 16 ?g/L due to the low solubility of its pyrochlore host. Adsorption and the low solubility of pyrochlore limit concentrations of Nb to less than 49 ?g/L. Cerium, from calcite dissolution, is strongly adsorbed although it reaches concentrations (unfiltered) in excess of 1 mg/L and 100 ?g/L in pore water and effluent, respectively. Results of this study show that mine tailings from carbonatite deposits are enriched in a wide variety of incompatible elements with multiple mineral hosts of varying solubility. Some of these elements, such as F and Mo, may represent contaminants of concern because of their mobility in alkaline tailings waters.
DS202205-0678
2022
Discover MagazineThe origin of the Earth's helium. Not specific to diamonds just for interest.Discover Magazine, https://www.discovermagazine.com/the-sciences/the-origin-of-earths-heliumMantlehelium
DS202202-0190
2022
Dora, M.L., Randive, K., Meshram, R., Meshram, T., Baswani, S.R., Korakoppa, M., Malviya, V.P.Petrogenesis of a calc-alkaline lamprophyre ( minette) from Thanewasna western Bastar craton, central India: insights from mineral, bulk rock and in-situ trace element geochemistry.Geological Society of London Special Publication 513, pp. 179-207.Indiaminette

Abstract: The lamproites and kimberlites are well known from the Eastern Bastar Craton, Central India. However, a Proterozoic lamprophyre dyke is discussed here, from the Western Bastar Craton (WBC). The field geology, petrographic, mineralogical and whole-rock and in-situ trace element geochemistry of biotite are described to understand the petrogenesis and lithospheric evolution in the WBC. The Thanewasna lamprophyre (TL) is undeformed and unmetamorphosed, intruded into c. 2.5 Ga charnockite and metagabbro but closely associated with c. 1.62 Ga undeformed Mul granite. The TL has a characteristic porphyritic texture, dominated by phenocrysts of biotite, microphenocryst of amphibole, clinopyroxene and a groundmass controlled by feldspar. Mineral chemistry of biotite and amphibole suggest a calc-alkaline (CAL) type, and pyroxene chemistry reveals an orogenic setting. The TL is characterized by high SiO2 and low TiO2, MgO, Ni and Cr, consistent with its subcontinental lithospheric origin. The presence of crustal xenolith and ocelli texture followed by observed variations in Th/Yb, Hf/Sm, La/Nb, Ta/La, Nb/Yb, Ba/Nb indicate substantial crustal contamination. Whole-rock and in-situ biotite analysis by laser ablation inductively coupled plasma mass spectrometry show low concentrations of Ni (30-50 ppm) and Cr (70-150 ppm), pointing to the parental magma evolved nature. Enrichment in H2O, reflected in magmatic mica dominance, combined with high large ion lithophile element, Th/Yb ratios, and striking negative Nb-Ta anomalies in trace element patterns, is consistent with a source that was metasomatized by hydrous fluids corresponding to those generated by subduction-related processes. Significant Zr-Hf and Ti anomalies in the primitive mantle normalized multi-element plots and the rare earth element pattern of the TL, similar to the global CAL average trend, including Eastern Dharwar Craton lamprophyres. Our findings provide substantial petrological and geochemical constraints on petrogenesis and geodynamics. However, the geodynamic trigger that generated CAL magmatism and its role in Cu-Au metallogeny in the WBC, Central India, is presently indistinct in the absence of isotopic studies. Nevertheless, the lamprophyre dyke is emplaced close to the Cu-(Au) deposit at Thanewasna.
DS202205-0679
2022
Dutta, R., Tracy, S.J., Cohen, R.E. , Miozzi, F., Luo, K., Yang, J., Burnley, P.C., Smith, D., Meng, Y., Chariton, S., Prakapenka, V.B., Duffy, T.S.Ultrahigh-presssure disordered eight-coordinated phase of Mg2GeO4: analogue for super Earth mantles. GermaniumPNAS, https://doi.org/10.1073/pnas.2114424119Mantlegeodynamics

Abstract: Mg2GeO4 is important as an analog for the ultrahigh-pressure behavior of Mg2SiO4, a major component of planetary interiors. In this study, we have investigated magnesium germanate to 275 GPa and over 2,000 K using a laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction and density functional theory (DFT) computations. The experimental results are consistent with the formation of a phase with disordered Mg and Ge, in which germanium adopts eightfold coordination with oxygen: the cubic, Th3P4-type structure. DFT computations suggest partial Mg-Ge order, resulting in a tetragonal I4¯2d structure indistinguishable from I4¯3d Th3P4 in our experiments. If applicable to silicates, the formation of this highly coordinated and intrinsically disordered phase may have important implications for the interior mineralogy of large, rocky extrasolar planets.
DS202205-0680
2022
Eppelbaum, L.V., Katz, Y.I.Paleomagnetic-radiometric mapping of the transistion zone from ocean to the continent: a review.Applied Sciences, , Preprints 2022, 2022040226 (doi: 10.20944/preprints202204.0226.v1) 24p. PdfMantlegeophysics

Abstract: The easternmost Mediterranean is a distinct transition zone from the ocean to the continent located at the junction between the largest Earth's lithospheric segments: Eurasian and African. The methodology of paleomagnetic mapping of such transition zones is based on integrating the mapping techniques for both continental and oceanic platforms: paleomagnetic reconstructions, results of radiometric dating of magnetized rocks, tectonic-structural reconstructions, biogeography, and utilization of the results of various geophysical surveys. The geodynamic-paleomagnetic mapping makes it possible to reveal the multilevel structural heterogeneity and display complex elements of the geodynamics of different ages inherent in this transition zone. Northern Israel is obviously the most complex area in the easternmost Mediterranean. For the combined paleomagnetic mapping, well-studied paleomagnetically and radiometrically areas were selected: (1) the Carmel area, (2) the Atlit area (internal part of the Carmel area), (3) the Sea of Galilee with the adjoining zones (primarily, the Kinnarot Valley), and (4) the area of the Hula Basin with adjacent areas of the Golan Plateau, Hermon Mt., and Galilea uplift. The constructed paleomagnetic profiles for the Carmel area (on the top of the accumulative surface of the Lower Cretaceous traps), and the Kinnarot Valley - Sea of Galilee - Hula Basin, evidently indicate the complex history of the paleogeodynamic evolution of the region. These studies demonstrate the effectiveness of paleomagnetic mapping interated with paleomagnetic profiling, which crosses these geologically complex areas.
DS202205-0681
2021
Eppelbaum, L.V., Katz, Y.I.Tectono-paleomagnetic mapping as unique combined interpretation tool: implication in geologically complex regions of Israel ( eastern mediterranean).VIII Int. Scientific Conference, 5p. PdfEurope, Israelgeophysics - magnetics

Abstract: The eastern Mediterranean is a tectonically complex region evolving in the long term located in the midst of the progressive Afro-Eurasian collision. Despite years of investigation, its geological-geophysical structure is not completely known. At the same time, the recent discovery of large gas deposits has attracted the attention of many researchers to this region. For instance, the latest U. S. Geological Survey estimates using conventional assessment methodology suggest that there are on the order of 1.7 billion barrels of recoverable oil and more than 4 trillion m3 of recoverable gas in the Levant Basin [1]. This highlights the need for analysis of the paleogeographical conditions that can yield deep paleotectonic criteria for oil and gas discovery in this region. For this purpose, isopach maps of the Middle-Upper Jurassic and Lower Cretaceous were generated from detailed examinations of numerous well sections and the most significant outcroppings in the eastern Mediterranean. The maps confirm an earlier model of continental accretion [2]. In particular, abrupt changes in the trend and thickness of the Early Mesozoic formations coincide with the terrane boundaries. These compiled isopach maps also pinpoint significant distinctions between the Arabian and Sinai plates on the one hand and the Syrian arc on the other. A new tectonic map of the eastern Mediterranean is presented that first of all integrates geophysical satellite-derived gravity and airborne magnetic fields, as well as tectonic-structural, paleogeographical and facial analyses. The results have clear implications for hydrocarbon prospecting in this region.
DS202201-0012
2021
Fairhurst, L., Fedortchouk, Y., Chinn, I., Normandeau, P.Reaction rims on ilmenite macrocrysts from different kimberlite facies in class 1 kimberlites, Orapa kimberlite cluster, Botswana.GAC/MAC Meeting UWO, 1p. Abstract p. 89.Africa, Botswanadeposit - Orapa

Abstract: Kimberlites are mantle-derived igneous rocks emplaced in the upper crust. Class 1 kimberlite are multi-phase bodies consisting of coherent kimberlite (CK) and different pyroclastic facies, including diatreme Kimberley-type pyroclastic kimberlite (KPK). The composition, crystallisation conditions and emplacement processes of these multiphase kimberlites are poorly understood, especially the formation of KPK. CK facies include hypabyssal kimberlite (HK) and ambiguous partially fragmented CK. Ilmenite macrocrysts from some Orapa kimberlites show reaction rims, the composition of which correlates with kimberlite facies. The goal of this study is to document the reaction products on ilmenite from different kimberlite facies and to use them to determine crystallisation temperature (T) and oxygen fugacity (fO2). Obtaining a better understanding of fO2 is important not only scientifically, but also for economic reasons, because highly oxidising conditions would have promoted resorption of diamonds in the kimberlite. This study used thin sections taken in well constrained depth intervals from drillholes in AK15 and BK1 kimberlites from the Orapa kimberlite cluster (Botswana). The AK15 intrusion consists of a single phase of CK facies. The BK1 pipe consists of two CK facies (CK-A and CK-B) and one KPK facies. CK-B is a HK and CK-A shows areas of partial fragmentation. Kimberlite textures were examined with a petrographic microscope. Ilmenite reaction rims were identified with SEM. EMP analyses were performed on perovskite, ilmenite and magnetite grains for T and fO2 calculation. We found that ilmenite macrocrysts in CK-A develop rims composed of magnetite and rutile. The reaction rims on ilmenite macrocrysts in KPK are highly variable and are distinguished by the presence of titanite. In CK-B, ilmenite macrocrysts are replaced by a symplectic intergrowth of magnetite and perovskite. In AK15, ilmenite macrocrysts consist of magnetite rims. fO2 estimated using ferric iron content in CaTiO3 perovskite varies from NNO -5.74 to -1.30 showing progressive oxidation upwards and within KPK facies. Such fO2 conditions require T during perovskite crystallisation between 560 and 700 °C. The observed textures suggest that BK1 ilmenite macrocrysts reacted with the melt to produce magnetite and perovskite rims followed by full ilmenite replacement by symplectic intergrowth of perovskite and magnetite in CK-B and replacement of perovskite with TiO2 oxide in CK-A. Development of titanite in KPK indicates assimilation of crustal xenoliths, while variability of reaction rims and fO2 estimates within the same sample confirm the high degree of material mixing in KPK. Similarities of ilmenite rims in CK-A and KPK indicate similarity in the process of their formation.
DS202203-0344
2022
Fedortchouk, Y., Chinn, I., Zhang, Z., Stern, R.A., Perritt, S.H., Li, Z.Diamond-destructive mantle metasomatism: evidence from the internal and external textures of diamonds and their nitrogen defects.Lithos, Vol. 414-415, 19p. Mantlemetasomatism

Abstract: Metasomatic processes modify the composition of the subcratonic lithospheric mantle and can either form or destroy diamonds. The composition of these metasomatic agents is uncertain and has been mostly deduced from chemical zonation and overprints recorded by associated mantle silicates. Diamonds experience partial dissolution (resorption) during their residence in the mantle due to mantle metasomatism and later during their ascent in kimberlite magma. Diamonds, enclosed inside mantle xenoliths during the whole duration of ascent in kimberlite magma, can preserve their pre-kimberlite surface features, which record the last diamond-destructive metasomatic event to have occurred in the mantle. The geometry of diamond dissolution features acquired during mantle storage can provide information about diamond-destructive metasomatic events in the mantle. Diamond samples recovered from inside mantle xenoliths are extremely rare and mostly limited to eclogitic lithology, which suggests that variable resistance of different mantle lithologies to disintegration in kimberlite magma may affect representativity of these sample. Here we use whole diamond populations from exploration parcels and apply our earlier developed set of criteria to distinguish between kimberlitic and pre-kimberlitic surface features on diamonds. The study used diamonds (<1 to 4.5 mm size) from eight kimberlites in three localities: Orapa cluster, Botswana (BK1, AK15, and AK1 kimberlites), Ekati Mine, Northwest Territories, Canada (Grizzly, Leslie, Koala, and Misery kimberlites), and Snap Lake kimberlite dyke, Northwest Territories, Canada. The host kimberlites cover seven different volcaniclastic and coherent kimberlite lithologies, and our previous studies demonstrated a correlation between the style of kimberlitic resorption on diamonds and the host kimberlite lithology for these samples. From the total of 3256 studied diamonds, we identified 534 diamonds with pre-kimberlite surface textures. These pre-kimberlite surface textures display six distinct types, which are present in all the studied diamond parcels regardless of their geographic locality and host kimberlite lithology. The relative proportions of these types depend on the geographic locality showing linkage to a specific mantle source. We examined the relationship between the surface features on diamonds, their growth patterns revealed in cathodoluminescence (CL) images, the content and aggregation of nitrogen defects using Fourier transform infrared spectroscopy (FTIR), and nitrogen content in specific growth zones of diamonds obtained using secondary ion mass spectrometry (SIMS) for 82 Ekati diamonds. Our data show that growth step-faces develop on diamonds with complex multi-crystal cores, whereas flat-faced octahedra with simple oscillatory-zoned growth patterns derive from single growth events. Initial stages of dissolution affecting only outer growth zones develop simple serrate laminae on diamonds, while more extensive dissolution exposes more complex growth zones developing various shapes of laminae and etch features (trigons and irregular asperities). The effect of internal growth patterns on dissolution features is more profound during pre-kimberlitic than kimberlite-related resorption likely due to the greater role of defects in diamond dissolution at mantle conditions. Comparison with the results of diamond dissolution experiments shows that metasomatism by C-O-H fluid is not destructive to diamond, while carbonate-silicate melt-driven metasomatism causes diamond dissolution. Continuous change in the silicate content of silicate?carbonate melts and temperature variations within 200 °C can explain all pre-kimberlite dissolution features observed in this study. Similar pre-kimberlite dissolution features on diamonds from both the Zimbabwe and Slave cratons suggests that these metasomatic processes are widespread and affected the mantle below the eight studied kimberlites.
DS202202-0191
2022
Ferreira, A.C.D., Vierira Conceicao, R., Pimentel Mizusaki, A.M. Mesozoic to Cenozoic alkaline and tholeiitic magmatism related to West Gondwana break up and dispersal of south American kimberlites.Gondwana Research, Vol. 106, pp. 15-33. pdfSouth Americacraton - Amazon

Abstract: For over 50 years, Mesozoic tholeiites, kimberlites and carbonatites from the South American platform have been enabled the understanding of melting processes in the Earth’s upper mantle. However, the genetic relationship between alkaline and tholeiitic magmatism remains unknown. In this context, an extensive review, based on a compilation of published geochemical and isotopic data, shows an integrated evolution for mantle-derived magmatism in South America. The K-rich alkaline-carbonatite intrusions occur widespread through time at 255-209 Ma, 146-106 Ma and 91-71 Ma. Moreover, the Na-rich magmatic episodes are also documented at 130-120 Ma and 66-32 Ma. Tholeiitic basaltic lavas and dikes are recorded at ?200 Ma in Northern Brazil and mainly between 134 and 131 Ma in the Paraná Magmatic Province. Simultaneous tholeiitic lavas and carbonatitic complexes are related to near isothermal decompression of enriched asthenospheric and lithospheric mantle sources at different depths (80-200 km). Likewise, the 267-226 Ma kimberlites in the Amazonian Craton, ?128 Ma Rosário kimberlite in the Rio de la Plata Craton and 88-80 Ma Alto Paranaíba kimberlites in the western edge of the São Francisco Craton provide evidence for deeper (>200 km) metasomatized mantle sources. Compiled numerical, geophysical and geological data support the proposal that the thickness of the lithosphere, extension rates and the presence of previous weak crustal structures contributed to the generation and emplacement of multiple tholeiitic and alkaline intrusions from 250 to 30 Ma. We propose that several crustal extension events induced repeated thermal convection cells in the metasomatized asthenosphere, which triggered partial melting in the previously enriched and heterogeneous lithospheric mantle. The local mantle composition, depth and crustal extension ratios controlled the magma composition. Thus, West Gondwana break-up and dispersal played a crucial role in the Mesozoic to Paleogene melting processes of the metasomatized mantle in South America.
DS202205-0682
2022
Flament, N., Meredith, A., Bodur, O.F., Williams, S. Volcanoes, diamonds and blobs.The Conversation.com, Mar. 31, 5p.Mantlediamond genesis
DS202203-0345
2021
Forattini, F.For a broader understanding of corruption as a cultural fact, and its influence in society. *** Not specific to diamondsAcademia Letters, dor.org/10.20935/AL2245 7p.Globallegal

Abstract: This brief article intends to demonstrate some of the problems with the main theories on corruption and introduce the reader to the new field of Anthropology of Corruption, a type of research that tries to understand one of the most pressing issues nowadays through a non-binary point of view, but trying to understand the root of corruption, and its multifaceted characteristic, especially through its cultural aspect; and why it is, contemporary, the most effective political-economic discourse - most at the times used in a populistic fashion, at the expense of democratic institutions. Therefore, we will briefly analyze the three main theoretical strands on corruption and point at some of its faults; then indicate to the reader what are the main goals Anthropology of Corruption, and what questions it seeks to answer; and, the political impact that corruption discourses have on society, and its perils when instrumentalized in populistic discourses.
DS202203-0346
2021
France, L., Brouillet, F., Lang, S.Early carbonatite magmatism at Oldoinyo Lengai volcano ( Tanzania): carbonatite-silicate melt immiscibility in Lengai 1 melt inclusions.Comptes Rendus Geoscience, Vol. 353, no S2, pp. 273-288. pdfAfrica, Tanzaniadeposit - Oldoinyo Lengai

Abstract: Carbonatites are unusual C-rich alkaline magmas that have been reported throughout the geological record. Nevertheless, there is only one currently active carbonatite system on Earth: Oldoinyo Lengai stratovolcano in northern Tanzania (God’s mountain in Maasai culture). Present-day Lengai carbonatites are natrocarbonatites, peculiar Na-rich carbonatites that, under atmospheric conditions, alter and leach to compositions similar to the more common Ca-carbonatites within weeks, preventing any long-term geological record of such Na-rich magmas. It follows that the oldest report of natrocarbonatites at Oldoinyo Lengai dates to the 19th century. Here, by using samples from the Lengai I cone (11 ka), we show that immiscible silicate-carbonatite melts were already present at reservoir conditions at that time. Measurements of three-phase (carbonatite silicate gas) melt inclusions from Lengai I highlight that their chemical compositions were similar to those of immiscible melts recently present in the reservoir. Alkaline carbonatites in melt inclusions from both Lengai I and historical explosive eruptions are enriched in Ca relative to those historically effused at the surface and likely record higher equilibrium temperatures (1100 °C). We also report chemical maps that qualitatively document elemental partitioning between immiscible silicate-carbonatite melts. We show that at the melt inclusions’ entrapment conditions Si, Fe, K, Na, and Cl are compatible with the silicate phase when C, Ca, P, Sr, Ba, and F are compatible with the carbonate phase.
DS202201-0013
2021
Frazer, W.D., Korenaga, J.Dynamic topography and the nature of deep thick plumes.Earth and Planetary Science Letters, in press available 8p. PdfMantletectonics

Abstract: Deep mantle plumes imaged by seismic tomography have much larger radii (?400 km) than predicted by conventional geodynamic models (?100 km). Plume buoyancy fluxes estimated from surface topography concur with narrow plumes with low viscosities expected from their high temperatures. If plumes are thick as imaged by tomography, buoyancy flux estimates may require very viscous or thermochemical plumes. Here we assess the dynamical plausibility of an alternative model, a ponding plume, which has been suggested to explain thick plumes as well as buoyancy fluxes estimated from surface topography. In the ponding plume model, a thick conduit in the lower mantle narrows significantly after passing through the mantle transition zone, below which excess material from the thick lower-mantle plume, which cannot be accommodated by the narrow upper-mantle plume, spreads laterally. Such excess material in the mid-mantle, however, should still manifest itself in surface topography, the amplitude of which can be quantified via topography kernels. We find that the ponding of a purely thermal plume would lead to unrealistic excess topography, with the scale of ponding material large enough to be detected by seismic tomography. If mantle plumes are as thick as indicated by seismic tomography, it appears to be necessary to deviate from either conventional temperature-dependent viscosity or the assumption of purely thermal origins.
DS202201-0014
2021
Galzyrin, G., Mukherjee, D.Synthesis and compression study of orthorhombic Fe7 (C,Si)3: a possoible constituent of the Earth's core.International Journal of High Pressure Research, Vol. 41, 3, pp. 290-305.Mantlemineralogy

Abstract: The orthorhombic phase of Si-doped Fe carbide is synthesized at high-pressures and temperatures using laser-heated diamond anvil cell (LHDAC), followed by its characterization using X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman spectroscopy. Room-temperature high-pressure XRD measurements are carried out up to about 104 GPa for the determination of the equation of state parameters. No evidence of structural transition is observed. Pressure evolution of isothermal bulk modulus shows elastic stiffening around 28 GPa followed by softening around 78 GPa, which are possibly related to magnetic transitions driven by pressure-induced anisotropic strain in the unit cell. Extrapolation of the density profile of our study to the inner core conditions agrees very well with PREM data with an uncertainty of about 3-4%. Our estimated bulk modulus value at core pressures seems to be 8-9% less than that of PREM data and is best matched in comparison to other reported values.
DS202201-0015
2021
Gao, S., Campbell, K., Flemming, R., Kupsch, B., Armstrong, K.Characterizing zinc-bearing chromite cores in uvarovite garnets from the Pikoo diamondiferous kimberlite field, central eastern Saskatchewan, Canada.GAC/MAC Meeting UWO, 1p. Abstract p. 100.Canada, Saskatchewandeposit - Pikoo

Abstract: Zinc-rich chromite [(Fe,Zn)Cr2O4] is an important repository for chromium (Cr) that has been observed sporadically in kimberlite-bearing deposits worldwide. As another source reservoir for Cr, the green uvarovite garnet [ideally Ca3Cr2(SiO4)3] is the rarest variety among anhydrous garnets. Despite being reported from a wide range of localities, the occurrences of uvarovite are predominately restricted to hydrothermal and metamorphic settings rarely associated with kimberlite. Here, we present a detailed petrographic, mineralogical, and geochemical characterization of 71 uvarovite garnets with zinc-bearing chromite cores recovered from the Pikoo Property (central eastern Saskatchewan), which also hosts recently discovered kimberlites proven to be diamondiferous. In this work, euhedral to anhedral unzoned chromite occurs as kernels or cores and, in some cases, as irregular inclusions enclosed by uvarovite mantles. They contain moderate to high Cr [41.63-66.70 wt.% Cr2O3; Cr/(Cr+Al) = 0.64-0.99], Fe2+ (16.71-28.67 wt.% FeO) and Zn (1.64-15.52 wt.% ZnO) contents (Fig. 1), accompanied by an appreciable amount of Mn (0.63-2.32 wt.% MnO). The core with the highest Zn content gave structural formula (Zn0.409Fe2+0.555Mg0.018Mn0.019)1.00(Cr1.174Al0.674Fe3+0.152)2.00O4, which corresponds to Zn-rich chromite with a minor proportion of other end-members (e.g., hercynite, FeAl2O4). The garnets are compositionally zoned and occasionally devoid of inclusions. Formula calculations indicate that they are mainly members of the uvarovite-grossular series (up to 93% mol.% Uv) enriched in Ca (22.99-35.57 wt.% CaO) and Cr (up to 28.10 wt.% Cr2O3), but consistently depleted in Mg (mean = 0.10 wt.% MgO) and Ti (mean = 0.26 wt.% TiO2). Most garnets exhibit a core-rim zoning pattern, whereas the remainder are irregularly zoned and show evidence of resorption. The core to rim trend is characterized by an increase in grossular proportion at the expense of the uvarovite component. Morphological characteristics, textural interrelations, and compositional trends suggest that uvarovite garnet formed through interaction of Zn-rich chromite with late metasomatic (Ca,Al)-enriched hydrothermal fluids capable of precipitating secondary grossular.
DS202205-0683
2022
Gems & JewelleryThe rebirth of Yogo sapphire production at historic mine.Gems&Jewellery, Vol. 31, 1, pp. 19-21.United States, Montanadeposit - Yogo
DS202205-0684
2022
Gems & JewelleryLarge diamonds: why now?Gems&Jewellery, Vol. 31, pp. 30-31.Africa, Botswanadeposit - Karowe
DS202205-0685
2022
Gems & JewelleryThe cut or the stone? ( Large carbonado auction)Gems&Jewellery, Vol. 31, pp. 40-41.Globalcarbonado
DS202203-0347
2022
Ghobadi, M., Brey, G.P., Gerdes, A., Hofer, H.E., Keller, J.Accessories in Kaiserstuhl carbonatites and related rocks as accurate and faithful recorders of whole rock age and isotopic composition.International Journal of Earth Science, Vol. 111, 2, 16p.Europe, Germanycarbonatite

Abstract: The accessories perovskite, pyrochlore, zirconolite, calzirtite and melanite from carbonatites and carbonate-rich foidites from the Kaiserstuhl are variously suited for the in situ determination of their U-Pb ages and Sr, Nd- and Hf-isotope ratios by LA-ICP-MS. The 143Nd/144Nd ratios may be determined precisely in all five phases, the 176Hf/177Hf ratios only in calzirtite and the 87Sr/86Sr ratios in perovskites and pyrochlores. The carbonatites and carbonate-rich foidites belong to one of the three magmatic groups that Schleicher et al. (1990) distinguished in the Kaiserstuhl on the basis of their Sr, Nd and Pb isotope ratios. Tephrites, phonolites and essexites (nepheline monzogabbros) form the second and limburgites (nepheline basanites) and olivine nephelinites the third. Our 87Sr/86Sr isotope data from the accessories overlap with the carbonatite and olivine nephelinite fields defined by Schleicher et al. (1990) but exhibit a much narrower range. These and the ?Nd and ?Hf values plot along the mantle array in the field of oceanic island basalts relatively close to mid-ocean ridge basalts. Previously reported K-Ar, Ar-Ar and fission track ages for the Kaiserstuhl lie between 16.2 and 17.8 Ma. They stem entirely from the geologically older tephrites, phonolites and essexites. No ages existed so far for the geologically younger carbonatites and carbonate-rich foidites except for one apatite fission track age (15.8 Ma). We obtained precise U-Pb ages for zirconolites and calzirtites of 15.66, respectively 15.5 Ma (±?0.1 2?) and for pyrochlores of 15.35?±?0.24 Ma. Only the perovskites from the Badberg soevite yielded a U-P concordia age of 14.56?±?0.86 Ma while the perovskites from bergalites (haüyne melilitites) only gave 206Pb/238U and 208Pb/232Th ages of 15.26?±?0.21, respectively, 15.28?±?0.48 Ma. The main Kaiserstuhl rock types were emplaced over a time span of 1.6 Ma almost 1 million years before the carbonatites and carbonate-rich foidites. These were emplaced within only 0.32 Ma.
DS202202-0192
2022
Gong, Z., Evans, D.A.D.Paleomagnetic survey of the Goulburn Supergroup, Kilohigok Basin, Nunavut Canada: toward an understanding of the Ososirian apparent polar wander path of the Slave craton.Precambrian Research, Vol. 369, 106516, 16p.Canada, Nunavutgeophysics - magnetics

Abstract: The Orosirian paleopoles from the three circum-Slave basins (i.e., the Great Slave, Coronation, and Kilohigok Basins) of the Slave craton show large (?110°) and back-and-forth swings at 1.96-1.87 Ga, known as the Coronation loops. The Coronation loops, taken at face value, would imply rapid and substantial spin motions of the Slave craton, which is at odds with modern plate tectonics. Alternatively, the Coronation loops have been interpreted as a product of basin-scale rotations, local-scale vertical-axis rotations, or inertial interchange true polar wander (IITPW). One way to differentiate these models is to take advantage of the well-correlated stratigraphy in three circum-Slave basins and directly compare the time-equivalent paleomagnetic results. In this study, we collected ?300 samples from nine formations from the Goulburn Supergroup of the Kilohigok Basin, in shallowly dipping autochthonous sections east of the Bathurst Fault. We provide seven new reconnaissance-level paleopoles of the Slave craton, namely from the Kenyon, Hackett, Rifle, Beechey, Link, Kuuvik, and Brown Sound Formations of the Goulburn Supergroup. Our results and the compiled Orosirian paleomagnetic data of the Slave craton suggest that although basin-scale rotation or local vertical-axis rotation in fault zones are able to explain some of the disagreements among time-correlative paleopoles, they could not account for the large declination variation within the homoclinal sections in individual basins. Notably, our results from the ?1963 Ma Rifle Formation show progressive changes in declination through the stratigraphy, which cannot be explained by either basin-scale or local vertical-axis rotations. Selective remagnetization is also considered unlikely to be the cause. Instead, we suggest that IITPW could potentially be responsible for the Coronation loops, which could also provide an explanation for some discrepant paleomagnetic data observed globally during the Orosirian time.
DS202203-0348
2021
Goodenough, K., Mills, K.Reflecting on the colonial legacy of Geoscience in Africa. Dawson and Oldoinyo LengaiElements, Vol. 17, (5) p. 302.Africa, Tanzaniahistory
DS202202-0193
2021
Goodrich, C.A., Nestola, F., Jakubek, R.S.Diamonds in ureilites: the never ending story.Cosmo Elements, 10.2138/gselements.17.4.292 2p. PdfCosmosUreilites
DS202203-0349
2022
Grabarczyk, A., Gil, G., Liu, Y., Kotowski, J., Jokubauskas, P., Barnes, J.D., Nejbert, K., Wisniewska, J., Baginski, B.Ultramafic-alkaline-carbonatite Tajno intrusion in NE Poland: a new hypothesis.Ore Geology Reviews, doi.org/10.1016/j.oregeorev.2022.104772 Europe, Polandcarbonatite

Abstract: This manuscript presents results of the newest petrographic, mineralogical and bulk chemical, as well as H, C and O stable isotope study of carbonatites and associated silicate rocks from the Tajno Massif (NE Poland). The Tajno Intrusion is a Tournaisian-Visean ultramafic-alkaline-carbonatite body emplaced within the Paleoproterozoic rocks of the East European Craton (EEC). Carbonatites of the Tajno Massif can be subdivided into the calciocarbonatite (calcite), ferrocarbonatite (ankerite), and breccias with an ankerite-fluorite matrix. Due to location at the cratonic margin and abundance in the REE, Tajno classifies (Hou et al., 2015) as the carbonatite-associated REE deposit (CARD), and more precisely as the Dalucao-Style orebody (the breccia-hosted orebody). High Fe2O3 (13.8 wt%), MnO (2.1 wt%), total REE (6582 ppm), Sr (43895 ppm), Ba (6426 ppm), F (greater than10000 ppm) and CO2 contents points for the involvement of the slab - including pelagic metalliferous sediments - in the carbonatites formation. Spatial relations and Sr isotope composition ((87Sr/86Sr)i = 0.7043-0.7048; Wiszniewska et al., 2020) of alkali clinopyroxenite and syenite suggest that these are products of differentiation of the magma, generated by the initial melting of the SCLM due to influx of F-rich fluids from subducted marine sediments. Carbonatites Sr isotope composition ((87Sr/86Sr)i = 0.7037-0.7038), and Ba/Th (16-20620) and Nb/Y (0.01-6.25) ratios, link their origin with a more advanced melting of the SCLM, triggered by CO2-rich fluids from the subducted AOC and melts from sediments. The Tajno Massif - and coeval mafic-alkaline intrusions - age, high potassic composition, and location along the craton margin nearly parallel the Variscan deformation front, are suggesting Variscan subduction beneath the EEC. The oxygen isotope compositions of clinopyroxene (?18O value = 5.2‰) and alkali feldspar (?18O value = 5.7‰), from alkali clinopyroxenite and foid syenite, respectively, are consistent with mantle-derived magmas. Isotopic compositions of carbonatites and breccias (carbonate ?18O = 8.7‰ to 10.7‰; ?13C = -4.8‰ to ?0.4‰) span from values of primary carbonatites to carbonatites affected by a fractionation or sedimentary contamination. The highest values (?18O = 10.7‰; ?13C = -0.4‰) were reported for breccia cut by numerous veins confirming post-magmatic hydrothermal alteration. The lowest carbonate ?18O (9.3‰ to 10.7‰) and ?13C (?5.0‰ to ?3.8‰) values are reported for veins in alkali clinopyroxenites, whereas the highest ?18O (11.2‰) and ?13C (?1.2‰ to ?1.1‰) values are for veins in syenites and trachytes. Isotopic composition of veins suggests hydrothermal origin, and interaction with host mantle-derived rocks, as well as country rocks. In silicate rocks of the Tajno Massif, fluid influx leads to the development of Pb, Zn, Cu, Ag, Au sulfide mineralization-bearing stockwork vein system, with carbonate, silicate and fluorite infilling the veins. Bulk-rock contents of molybdenum (925 ppm), rhenium (905 ppb) and palladium (29 ppb) are notable. The Re-rich molybdenite association with galena, pyrite and Th-rich bastnäsite in carbonate veins is similar as in Mo deposits associated with carbonatites, implying the mantle source of Mo and Re.
DS202204-0520
2022
Griffin, W.L., Gain, S.E.M., Saunders, M.J., Huang, J-X., Alard, O., Toledo, V., O'Reilly, S.Y.Immiscible metallic melts in the upper mantle beneath Mount Carmel, Israel: silicides, phosphides, and carbides.American Mineralogist, Vol. 107, pp. 532-549.Europe, Israeldeposit - Mount Carmel

Abstract: Xenolithic corundum aggregates in Cretaceous mafic pyroclastics from Mount Carmel contain pockets of silicate melts with mineral assemblages [SiC (moissanite), TiC, Ti2O3 (tistarite), Fe-Ti-Zr silicides/phosphides] indicative of magmatic temperatures and oxygen fugacity (fO2) at least 6 log units below the iron-wüstite buffer (?IW ? -6). Microstructural evidence indicates that immiscible, carbon-rich metallic (Fe-Ti-Zr-Si-P) melts separated during the crystallization of the silicate melts. The further evolution of these metallic melts was driven by the crystallization of two main ternary phases (FeTiSi and FeTiSi2) and several near-binary phases, as well as the separation of more evolved immiscible melts. Reconstructed melt compositions fall close to cotectic curves in the Fe-Ti-Si system, consistent with trapping as metallic liquids. Temperatures estimated from comparisons with experimental work range from ?1500 °C to ca. 1150 °C; these probably are maximum values due to the solution of C, H, P, and Zr. With decreasing temperature (T), the Si, Fe, and P contents of the Fe-Ti-Si melts increased, while contents of Ti and C decreased. The increase in Si with declining T implies a corresponding decrease in fO2, probably to ca. ?IW-9. The solubility of P in the metallic melts declined with T and fO2, leading to immiscibility between Fe-Ti-Si melts and (Ti,Zr)-(P,Si) melts. Decreasing T and fO2 also reduced the solubility of C in the liquid metal, driving the continuous crystallization of TiC and SiC during cooling. The lower-T metallic melts are richer in Cr, and to some extent V, as predicted by experimental studies showing that Cr and V become more siderophile with decreasing fO2. These observations emphasize the importance of melt-melt immiscibility for the evolution of magmas under reducing conditions. The low fO2 and the abundance of carbon in the Mt. Carmel system are consistent with a model in which differentiating melts were fluxed by fluids that were dominated by CH4+H2, probably derived from a metal-saturated sublithospheric mantle. A compilation of other occur-rences suggests that these phenomena may commonly accompany several types of explosive volcanism.
DS202201-0016
2021
Grutter, H., Stachel, T., Sarkar, C., Pearson, G.Profound ~ 1075 Ma (re)fertilization of the central Superior craton lithosphere, based on composition and Pb-isotope data for clinopyroxenes from the Victor mine, Ontario, Canada.GAC/MAC Meeting UWO, 1p. Abstract p.117.Canada, Ontariodeposit - Victor

Abstract: The Victor diamond mine in Ontario, Canada opened in 2008 and ceased operations in June 2019. Previous researchers documented that Victor diamonds are unusually young (~ 720 Ma, Aulbach et al., 2018) and grew predominantly in unusually fertile peridotite substrates, specifically garnet lherzolite and garnet wehrlite (Stachel et al., 2018). Our recent work on n=157 lherzolitic clinopyroxene (Cpx) xenocrysts from the Victor mine reveals profound major- and trace-element (re)fertilization of the deepest 1/3rd of the central Superior craton lithosphere. For example, Cpx Mg/(Mg+Fe) of 0.93 in shallow peridotite decreases across a steep gradient to Mg/(Mg+Fe) of 0.89 at depths of 4.2 to 5.6 GPa. We document marked compositional gradients over a similar depth range for certain minor (Ti, Mn, Ni) and trace elements (LREE and HREE) and attribute the gradients to chromatographic and/or crystal-chemical fractionation effects. We carefully categorized the Victor cpx xenocrysts in nine depth-composition classes and determined Pb-isotope ratios for representative grains from each class in a bold experiment aimed at capturing geochronological data from mantle Cpx. A resultant 207Pb/206Pb secondary isochron array at ~ 1075 Ma identifies craton-scale events related to the Mid-Continent Rift as the source of fluids and/or melts that (re)fertilized the central Superior craton at depth, some 355 Ma prior to diamond growth. Coordinated, systematic major- and trace-element relationships in clinopyroxene permit compositional discrimination of mantle (re)fertilization at ~1075 Ma from fluid-metasomatism attending diamond growth at ~ 720 Ma. Roughly 10% of the clinopyroxene xenocrysts analyzed in this work exhibit diamond-associated compositions.
DS202204-0521
2022
Guiliani, A., Drysdale, R.N., Woodhead, J.D., Planavsky, N.J., Phillips, D., Hergt, J., Griffin, W.L., Oesch, S., Dalton, H., Davies, G.R.Pertubation of the deep-Earth carbon cycle in response to the Cambrian explosion.Science Advances, doi.10.1126/sciadv.abj1325 1p. PdfMantlesubduction

Abstract: Earth’s carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth’s history, but the impact of these changes on the mantle carbon cycle is unclear. Here, we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The 13C/12C of kimberlites before ~250 Ma preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios-a switch coincident with a recognized surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low 13C/12C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth’s surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.
DS202201-0017
2021
Harris, J.W.Diamond. IN: Encyclopedia of Geology 2nd edition Alderton, D., Elias, S.A. eds. Elsevier Publisher , isbn978-0-12-409548-9. 12083-4 pp. 455-472.GlobalBook - notice

Abstract: Encyclopedia of Geology, Second Edition presents in six volumes state-of-the-art reviews on the various aspects of geologic research, all of which have moved on considerably since the writing of the first edition. New areas of discussion include extinctions, origins of life, plate tectonics and its influence on faunal provinces, new types of mineral and hydrocarbon deposits, new methods of dating rocks, and geological processes. Users will find this to be a fundamental resource for teachers and students of geology, as well as researchers and non-geology professionals seeking up-to-date reviews of geologic research.
DS202202-0194
2022
Hartnady, M.I.H., Kirkland, C., Smithies, R.H., Johnson, T.E.Pb isotope insight into the formation of the Earth's first stable continents.Earth and planetary Science Letters, Vol. 578, 117319, 9p. PdfMantlegeochronolgy

Abstract: The formation of stable buoyant continental crust during the Archaean Eon was fundamental in establishing the planet's geochemical reservoirs. However, the processes that created Earth's first continents and the timescales over which they formed are debated. Here, we report the Pb isotope compositions of K-feldspar grains from 52 Paleoarchaean to Neoarchaean granites from the Pilbara Craton in Western Australia, one of the world's oldest and best-preserved granite-greenstone terranes. The Pb isotope composition of the Pilbara K-feldspars is variable, implying the granites were derived from crustal precursors of different age and/or variable time-integrated 238U/204Pb and 232Th/204Pb compositions. Trends to sub-mantle 207Pb/206Pb ratios preclude the influence of 4.3 Ga crustal precursors. In order to estimate crustal residence times we derive equations to calculate source model ages in a linearized Pb isotope evolution system. The best agreement between the feldspar Pb two-stage source model ages and those derived from zircon initial Hf isotope compositions requires crustal precursors that separated from a chondritic mantle source between 3.2 and 3.8 Ga, and rapidly differentiated to continental crust with 238U/204Pb and 232Th/238U ratios of ?14 and 4.2-4.5, respectively. The preservation of Pb isotope variability in the Pilbara Paleoarchaean granites indicates their early continental source rocks were preserved for up to 500 Ma after their formation. The apparent longevity of these early continental nuclei is consistent with the incipient development of buoyant melt-depleted cratonic lithosphere during the Eoarchaean to Paleoarchaean.
DS202203-0350
2022
He, Y., Sun, S., Kim, D.Y., Jang, B.G., Li, H., Mao, H-K.Superionic iron alloys and their seismic velocities in Earth's inner core.Nature, Vol. 602, pp. 258-276. 18p.Mantlecore

Abstract: Earth’s inner core (IC) is less dense than pure iron, indicating the existence of light elements within it1. Silicon, sulfur, carbon, oxygen and hydrogen have been suggested to be the candidates2,3, and the properties of iron-light-element alloys have been studied to constrain the IC composition4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19. Light elements have a substantial influence on the seismic velocities4,5,6,7,8,9,10,11,12,13, the melting temperatures14,15,16,17 and the thermal conductivities18,19 of iron alloys. However, the state of the light elements in the IC is rarely considered. Here, using ab initio molecular dynamics simulations, we find that hydrogen, oxygen and carbon in hexagonal close-packed iron transform to a superionic state under the IC conditions, showing high diffusion coefficients like a liquid. This suggests that the IC can be in a superionic state rather than a normal solid state. The liquid-like light elements lead to a substantial reduction in the seismic velocities, which approach the seismological observations of the IC20,21. The substantial decrease in shear-wave velocity provides an explanation for the soft IC21. In addition, the light-element convection has a potential influence on the IC seismological structure and magnetic field.
DS202203-0351
2022
Heffernan, A.Development, conservation, empowerment: the trilemma of community-based natural resource management in Namibia.Environmental Management, Vol. 69, pp.480-491.pdfAfrica, NamibiaESG

Abstract: Community-Based Natural Resource Management (CBNRM) is a form of resource governance that has been widely popularized across southern Africa. CBNRM consists of three main goals or pillars which include economic development, environmental conservation, and community empowerment. It is intended to devolve control of certain natural resources from national government to local communities. The idea being that local residents will manage resources more sustainably and break neopatrimonial webs that have led to mismanagement and protracted underdevelopment. However, with communities there are important politics that often go understudied and there are instances where the same type of issues that going local was intended to circumvent, are re-engendered at the local level. Beyond this, CBNRM cannot only be understood as a form of domestic resource governance that happens in a vacuum and instead there are important politics and power imbalances between local, national, and global actors, that sees the will of some win out over others. As a result of these power asymmetries, I argue that the three goals of CBNRM form a trilemma in which the realization of one goal undermines success in achieving one or both of the others. As a result, CBNRM programs have failed to achieve the success proponents envision. Thus, it becomes integral to understand and account for the politics involved, rather than to analyze CBNRM as an apolitical policy fix for domestic conservation as much of the literature presents it as.
DS202201-0018
2022
Heinonen, J.S., Spera, F.J., Bohrson, W.A.Thermodynamic limits for assimilation of silicate crust in primitive magmas.Geology, Vol. 50, 1, pp. 81-85.Mantlemagmatism

Abstract: Some geochemical models for basaltic and more primitive rocks suggest that their parental magmas have assimilated tens of weight percent of crustal silicate wall rock. But what are the thermodynamic limits for assimilation in primitive magmas? We pursue this question quantitatively using a freely available thermodynamic tool for phase equilibria modeling of open magmatic systems—the Magma Chamber Simulator (https://mcs.geol.ucsb.edu)—and focus on modeling assimilation of wall-rock partial melts, which is thermodynamically more efficient compared to bulk assimilation of stoped wall-rock blocks in primitive igneous systems. In the simulations, diverse komatiitic, picritic, and basaltic parental magmas assimilate progressive partial melts of preheated average lower, middle, and upper crust in amounts allowed by thermodynamics. Our results indicate that it is difficult for any subalkaline primitive magma to assimilate more than 20?30 wt% of upper or middle crust before evolving to compositions with higher SiO2 than a basaltic magma (52 wt%). On the other hand, typical komatiitic magmas have thermodynamic potential to assimilate as much as their own mass (59?102 wt%) of lower crust and retain a basaltic composition. The compositions of the parental melt and the assimilant heavily influence both how much assimilation is energetically possible in primitive magmas and the final magma composition given typical temperatures. These findings have important implications for the role of assimilation in the generation and evolution of, e.g., ultramafic to mafic trans-Moho magmatic systems, siliceous high-Mg basalts, and massif-type anorthosites.
DS202205-0686
2021
Hu, Q., Mao, H-K.Role of hydrogen and proton transportation in Earth's deep mantle.Matter Radiation Extremes, Vol. 6, 068101 2p. PdfMantlehydrogen

Abstract: Hydrogen (H) is the most abundant element in the known universe, and on the Earth’s surface it bonds with oxygen to form water, which is a distinguishing feature of this planet. In the Earth’s deep mantle, H is stored hydroxyl (OH?) in hydrous or nominally anhydrous minerals. Despite its ubiquity on the surface, the abundance of H in the Earth’s deep interior is uncertain. Estimates of the total H budget in the Earth’s interior have ranged from less than one hydrosphere, which assumes an H-depleted interior, to hundreds of hydrospheres, which assumes that H is siderophile (iron-loving) in the core. This discrepancy raises the questions of how H is stored and transported in the Earth’s deep interior, the answers to which will constrain its behavior in the deep lower mantle, which is defined as the layer between 1700 km depth and the core-mantle boundary. Hydrogen is the lightest element and exhibits superior mobility under high pressure-temperature (P-T) conditions. Hydrogen, once it has lost its only electron, is electronically equivalent to the proton and can substitute at cation sites in minerals, which in turn enhances their ionic conductivity through the Grotthuss mechanism, or “hydrogen hopping,” in which a proton or proton defect diffuses through the crystal lattice by the formation and concomitant breaking of hydroxyl bonding. Grotthuss-type diffusion is dominant for H-incorporated silicate in the asthenosphere, particularly in regions under relatively high-temperature and low-pressure conditions.1 With increasing depth, H may be liberated from hydroxyl bonding and diffuse freely in the host crystalline lattice, entering an exotic superionic phase.2,3 The concept of a superionic phase is borrowed from the electric battery industry, and the existence of such a phase in ice is widely recognized. The recent discovery of superionic ice-silica in the interiors of giant planets suggests that superionic phases may be common in planetary deep interiors.4 The electrical and seismic features of superionic phases are of great importance, and they have been the subjects of recent studies.2,4 However, what is more challenging is the nature of H in these exotic “semi-fluid” like phases. Will superionicity induce distinct behavior in the distribution of H in major mineral phases? What is the role of proton transportation in the convection of materials? Will it have a large-scale impact? We take superionic FeOOH as an illustrative example, since this is one of the few superionic phases that have been experimentally confirmed. From a survey of data in the literature, we have found that the pressure and amount of escaped H (nH) are correlated (Fig. 1). Here, we define nH as the fraction of H that has escaped from FeOOH, with nH = 0 for fully hydrous FeOOH, and nH = 1 for complete H depletion. Escape of H is inhibited by increasing pressure, and nH converges to a minimum value of ?0.2 at the pressure of the core-mantle boundary (Fig. 1), which is consistent with a recent kinetic experiment involving the heating of FeOOH and the prediction of FeOOH0.75 as a stable stoichiometry.5 The regression of P-nH indicates that cross-boundary diffusion is more intense at relatively low pressures.
DS202204-0522
2022
Huang, J., Huang, J-X., Griffin, W.L., Huang, F.Zn- Mg- and O-isotope evidence for the origin of mantle eclogites from Roberts Victor kimberlite ( Kaapvaal Craton, South Africa).Geology, doi.1130/G49780.1Africa, South Africadeposit - Roberts Victor

Abstract: We report Zn-isotope compositions of garnet, clinopyroxene, and whole rocks for 14 Type I and 10 Type II eclogites from the Roberts Victor kimberlite (Kaapvaal Craton, South Africa) that were previously analyzed for Mg-O isotopes. Type II eclogites are the protoliths of the highly metasomatized Type I. Garnet and clinopyroxene in Type II eclogites have ?66Zn from 0.14‰ to 0.50‰ and from 0.29‰ to 0.58‰, respectively; reconstructed whole-rock ?66Zn is from 0.24‰ to 0.54‰, which is higher than typical mantle values (0.16-0.20‰). Their heavy Zn- and light Mg- and O-isotope compositions (?26Mg = -1.1‰ to -0.14‰, ?18O = 2.3‰ to 4.9‰) cannot originate from subducted, carbonate-rich, altered oceanic crust, which is enriched in heavy Zn-O and light Mg isotopes. The low ?18O may be inherited from parental melts derived from low-?18O mantle sources like those that produced the Weltevreden komatiites of the Kaapvaal Craton. The high ?66Zn and low ?26Mg reflect diffusion-driven Zn-Mg-isotope exchange between peridotites and the parental melts during their emplacement in the deep lithosphere. Type I eclogites have reconstructed whole-rock ?66Zn from 0.03‰ to 0.43‰ and garnet ?18O from 6‰ to 9.1‰ but show more scatter in inter-mineral Zn-isotope fractionation than Type II, reflecting incomplete equilibration during later metasomatism by carbonatitic-to-kimberlitic melts. Our evidence from multiple isotopes thus suggests that the Roberts Victor eclogites might have crystallized from deep-seated melts at mantle depths.
DS202205-0687
2022
Huang, J., Huang, J-X., Griffin, W.L., Huang, F.Zn-, Mg- and O isotope evidence for the origin of mantle eclogites from Roberts Victor kimberlite ( Kaapvaal Craton, South Africa.Geology, Vol. 50, 5, pp. 593-597.Africa, South Africadeposit - Roberts Victor

Abstract: We report Zn-isotope compositions of garnet, clinopyroxene, and whole rocks for 14 Type I and 10 Type II eclogites from the Roberts Victor kimberlite (Kaapvaal Craton, South Africa) that were previously analyzed for Mg-O isotopes. Type II eclogites are the protoliths of the highly metasomatized Type I. Garnet and clinopyroxene in Type II eclogites have ?66Zn from 0.14‰ to 0.50‰ and from 0.29‰ to 0.58‰, respectively; reconstructed whole-rock ?66Zn is from 0.24‰ to 0.54‰, which is higher than typical mantle values (0.16-0.20‰). Their heavy Zn- and light Mg- and O-isotope compositions (?26Mg = ?1.1‰ to ?0.14‰, ?18O = 2.3‰ to 4.9‰) cannot originate from subducted, carbonate-rich, altered oceanic crust, which is enriched in heavy Zn-O and light Mg isotopes. The low ?18O may be inherited from parental melts derived from low-?18O mantle sources like those that produced the Weltevreden komatiites of the Kaapvaal Craton. The high ?66Zn and low ?26Mg reflect diffusion-driven Zn-Mg-isotope exchange between peridotites and the parental melts during their emplacement in the deep lithosphere. Type I eclogites have reconstructed whole-rock ?66Zn from 0.03‰ to 0.43‰ and garnet ?18O from 6‰ to 9.1‰ but show more scatter in inter-mineral Zn-isotope fractionation than Type II, reflecting incomplete equilibration during later metasomatism by carbonatitic-to-kimberlitic melts. Our evidence from multiple isotopes thus suggests that the Roberts Victor eclogites might have crystallized from deep-seated melts at mantle depths.
DS202203-0352
2021
Humphreys-Williams, E.R., Zahirovic, S.Carbonatites and global tectonics. 609 Occurrences and 387 known ageElements, Vol. 17, pp. 339-344.Globalplate tectonics

Abstract: Carbonatites have formed for at least the past three billion years. But over the past 700 My the incidence of carbonatites have significantly increased. We compile an updated list of 609 carbonatite occurrences and plot 387 of known age on plate tectonic reconstructions. Plate reconstructions from Devonian to present show that 75% of carbonatites are emplaced within 600 km of craton edges. Carbonatites are also associated with large igneous provinces, orogenies, and rift zones, suggesting that carbonatite magmatism is restricted to discrete geotectonic environments that can overlap in space and time. Temporal constraints indicate carbonatites and related magmas may form an ephemeral but significant flux of carbon between the mantle and atmosphere.
DS202205-0688
2022
Hutchinson, M., Slezak, P., Wendtlandt, R., Hitzman, M.Rare earth element enrichment in the weathering profile of the Bull Hill carbonatite at Bear Lodge, Wyoming, USA.Economic Geology, Vol. 117, pp. 813-831.United States, Wyomingdeposit - Bull Hill

Abstract: Bull Hill is a carbonatite diatreme within the Paleogene Bear Lodge Carbonatite Complex in Wyoming, USA. Rare earth element (REE)-bearing carbonate, fluorocarbonate, phosphate, and oxide minerals occur within near-vertical carbonatite dikes on the western margin of Bull Hill. Changes in mineralogy and REE concentrations with depth are ascribed mainly to late-stage magmatic-hydrothermal and supergene alteration. Approximately 35 m of drill core from Bull Hill was analyzed and encompasses least altered, weakly weathered, and moderately weathered carbonatite. The least altered carbonatite contains magmatic burbankite, typically as inclusions within Mn-rich calcite (stage I). Secondary REE-bearing minerals, which pseudomorphically replaced unidentified hexagonal phenocrysts, include ancylite, bastnäsite with synchysite/parisite, and an unidentified Sr-Ca-REE-phosphate (stage II). These replacive minerals generated small amounts of incipient porosity (~7-8%) and are largely stable in the lower portion of the weathering profile. Progressive weathering (stages III and IV) of the carbonatite involved the oxidation of pyrite to iron oxides and iron hydroxides, dissolution of calcite and strontianite, and the replacement of Mn-rich calcite by manganese oxides. These mineralogical changes resulted in an ~40% porosity gain in the core studied here. The volumetric concentration of weathering resistant REE-bearing minerals resulted in REE enrichment from an average of 5.4 wt % in the least weathered carbonatite to an average of 12.6 wt % in moderately weathered carbonatite, and to an overall increase in REE ore tenor of two to three times compared to the least altered carbonatite. Isocon plots confirm the increased concentration of REEs in the weathered carbonatite and demonstrate that REEs, along with TiO2, Ta, Nb, Zr, and Hf, were conserved in the lower weathered zone.
DS202205-0689
2022
Immoor, J., Miyagi, L., Liemann, H-P., Speciale, S., Schulze, K., Buchen, J., Kumosov, A., Marquardt, H.Weak cubic CaSiO3 perovskite in the Earth's mantle.Nature, Vol. 603, pp. 276-279.Mantlesubduction

Abstract: Cubic CaSiO3 perovskite is a major phase in subducted oceanic crust, where it forms at a depth of about 550?kilometres from majoritic garnet1,2,28. However, its rheological properties at temperatures and pressures typical of the lower mantle are poorly known. Here we measured the plastic strength of cubic CaSiO3 perovskite at pressure and temperature conditions typical for a subducting slab up to a depth of about 1,200?kilometres. In contrast to tetragonal CaSiO3, previously investigated at room temperature3,4, we find that cubic CaSiO3 perovskite is a comparably weak phase at the temperatures of the lower mantle. We find that its strength and viscosity are substantially lower than that of bridgmanite and ferropericlase, possibly making cubic CaSiO3 perovskite the weakest lower-mantle phase. Our findings suggest that cubic CaSiO3 perovskite governs the dynamics of subducting slabs. Weak CaSiO3 perovskite further provides a mechanism to separate subducted oceanic crust from the underlying mantle. Depending on the depth of the separation, basaltic crust could accumulate at the boundary between the upper and lower mantle, where cubic CaSiO3 perovskite may contribute to the seismically observed regions of low shear-wave velocities in the uppermost lower mantle5,6, or sink to the core-mantle boundary and explain the seismic anomalies associated with large low-shear-velocity provinces beneath Africa and the Pacific.
DS202204-0523
2022
Immoor, J., Miyagi, L., Liermann, H-P., Speziale, S., Schulkze, K., Buchen, J., Kurnosov, A., Marquardt, H.Weak cubic CaSi0s perovskite in the Earth's mantle.Nature , Vol. 603, pp. 276-279. 10.1038/s41586-021-04378-2Mantleperovskite

Abstract: Cubic CaSiO3 perovskite is a major phase in subducted oceanic crust, where it forms at a depth of about 550 kilometres from majoritic garnet1,2,28. However, its rheological properties at temperatures and pressures typical of the lower mantle are poorly known. Here we measured the plastic strength of cubic CaSiO3 perovskite at pressure and temperature conditions typical for a subducting slab up to a depth of about 1,200 kilometres. In contrast to tetragonal CaSiO3, previously investigated at room temperature3,4, we find that cubic CaSiO3 perovskite is a comparably weak phase at the temperatures of the lower mantle. We find that its strength and viscosity are substantially lower than that of bridgmanite and ferropericlase, possibly making cubic CaSiO3 perovskite the weakest lower-mantle phase. Our findings suggest that cubic CaSiO3 perovskite governs the dynamics of subducting slabs. Weak CaSiO3 perovskite further provides a mechanism to separate subducted oceanic crust from the underlying mantle. Depending on the depth of the separation, basaltic crust could accumulate at the boundary between the upper and lower mantle, where cubic CaSiO3 perovskite may contribute to the seismically observed regions of low shear-wave velocities in the uppermost lower mantle5,6, or sink to the core-mantle boundary and explain the seismic anomalies associated with large low-shear-velocity provinces beneath Africa and the Pacific7-9.
DS202202-0195
2022
Jackson, J., McKenzie, D.The exfoliation of cratonic Australia in earthquakes.Earth and planetary Science Letters, Vol. 578, 117305, 11p. PdfAustraliacratons

Abstract: The cratonic shield system of central and western Australia, with its lithosphere up to 200 km thick, is geologically similar to other ancient, stable continental interiors. But since 1968 it has experienced a number of moderate-sized (5.0-6.6) earthquakes characterised by the extreme shallowness of their sources (the deepest is 8 km and most are shallower than 4 km). At least 11 of these have produced co-seismic faulting, often very long compared to their depth, with typically no evidence of previous movement on those faults in either the local geomorphology or paleoseismological trenching. Other earthquakes show that cratonic Australia, like other shield regions, has a seismogenic layer about 30-40 km thick, but the intense very shallow seismicity in the region of thickest lithosphere stands out and is unusual. A clue to the origin of these shallow earthquakes lies in their association with some of the largest continental gravity anomalies outside the forelands of young orogenic belts, yet in essentially flat topography. The wavelength of the gravity anomalies (?240 km) is large compared with the seismogenic thickness (?30 km) of the lithosphere, and their amplitude is ?50 mGals. These anomalies need stresses to support them, which can be estimated by a simple model of a flexed elastic plate that reproduces the essential features of the earthquakes, including their focal mechanisms and shallow depth limit. The model shows that the maxima of the compressive stress occur beneath the maxima and minima of the gravity, on the upper and lower boundaries of the layer respectively. Perhaps surprisingly, the magnitude of such stresses is considerably greater than most estimates of the regional stress within plates. The maxima of the shear stress occur on planes with dips of 45°. The locations and mechanisms of the earthquakes show the same features. We conclude that the earthquakes release stored elastic stresses in an exfoliation process, perhaps activated by a reduction in strength through weathering, erosion or some other process.
DS202205-0690
2022
Jones, T.J., Russell, J.K., Brown, R.J., Hollendonner, L.Melt stripping and agglutination of pyroclasts during the explosive eruption of low viscosity magmas.Nature Communications, 10.1038/s41467-022-28633-w 12p. PdfMantlemagmatism

Abstract: Volcanism on Earth and on other planets and satellites is dominated by the eruption of low viscosity magmas. During explosive eruption, high melt temperatures and the inherent low viscosity of the fluidal pyroclasts allow for substantial post-fragmentation modification during transport obscuring the record of primary, magmatic fragmentation processes. Here, we show these syn-eruption modifications, in the form of melt stripping and agglutination, to be advantageous for providing fundamental insights into lava fountain and jet dynamics, including eruption velocities, grain size distributions and melt physical properties. We show how enigmatic, complex pyroclasts termed pelletal lapilli form by a two-stage process operating above the magmatic fragmentation surface. Melt stripping from pyroclast surfaces creates a spray of fine melt droplets whilst sustained transport in the fountain allows for agglutination and droplet scavenging, thereby coarsening the grain size distribution. We conclude with a set of universal regime diagrams, applicable for all fluidal fountain products, that link fundamental physical processes to eruption conditions and melt physical properties.
DS202203-0353
2021
Kamenetsky, V.S., Doroshkevich, A.G., Elliott, A.L., Zaitsev, A.N.Carbonatites: contrasting, complex, and controversial.Elements, Vol. 17, pp. 307-314.Mantlemelting

Abstract: Carbonatites are unique, enigmatic, and controversial rocks directly sourced from, or evolved from, mantle melts. Mineral proportions and chemical compositions of carbonatites are highly variable and depend on a wide range of processes: melt generation, liquid immiscibility, fractional crystallization, and post-magmatic alteration. Observations of plutonic carbon-atites and their surrounding metasomatic rocks (fenites) suggest that carbon-atite intrusions and volcanic rocks do not fully represent the true compositions of the parental carbonatite melts and fluids. Carbonatites are enriched in rare elements, such as niobium and rare earths, and may host deposits of these elements. Carbonatites are also important for understanding the carbon cycle and mantle evolution.
DS202205-0691
2021
Kaminsky, F.V., Voropaev, S.A.Modern Concepts on diamond genesis.Geochemistry International, Vol. 59, 11, pp.993-1007. pdfGlobaldiamond genesis

Abstract: The best-known, most well-studied diamondiferous rocks are kimberlites and lamproites. Diamonds are also found in impactites, metamorphic rocks, ophiolites, and modern volcanic rocks. Diamonds from these rocks differ from kimberlitic diamonds in size, morphology, trace-element and isotope composition, and physical properties. Differences in these characteristics are related to their different mechanisms of origin. In some cases, diamonds can be formed in “metastable” conditions under disequilibrium thermodynamic parameters, supporting the conclusion that diamond is a polygenetic mineral, formed in nature under different physicochemical and geodynamic conditions. According to thermodynamic considerations and calculations, “metastable” crystallization of diamond is mainly controlled by the size of the forming crystallites. The main effectors in decreasing the energetic barrier for nanosized diamonds are surface tension and related surface energy.
DS202202-0196
2022
Kaminsky, F.V., Zedgenizov, D.A.First find of merrillite Ca3(PO4)2 in a terrestrial environment as an inclusions in lower mantle diamond.American Mineralogist, 10.2138/am-2022-8175Mantlemineralogy
DS202205-0692
2022
Kaminsky, F.V., Zedgenizov, D.A.First find of merrillite Ca3(P04)2 in a terrestrial environment as an inclusion in lower-mantle diamond. Rio SorisoAmerican Mineralogist, in press 19p. PdfSouth America, Brazildiamond inclusions
DS202205-0693
2022
Kaminsky, F.V., Zedgenizov, D.A., Sevastyanov, V.S., Kuznetsova, O.V.Low- and high-fe ferropericlase inclusions in super-deep diamonds and their depth of origin: an example from the Juina area, Brazil.Lithos, South America, Brazildeposit - Juina

Abstract: Alluvial diamonds from the Juina area in Mato Grosso, Brazil, have been characterized in terms of their morphology, syngenetic mineral inclusions, carbon isotopes and nitrogen contents. Morphologically, they are similar to other Brazilian diamonds, showing a strong predominance of rounded dodecahedral crystals. However, other characteristics of the Juina diamonds make them unique. The inclusion parageneses of Juina diamonds are dominated by ultra-high-pressure ("superdeep") phases that differ both from "traditional" syngenetic minerals associated with diamonds and, in detail, from most other superdeep assemblages. Ferropericlase is the dominant inclusion in the Juina diamonds. It coexists with ilmenite, Cr-Ti spinel, a phase with the major-element composition of olivine, and SiO2. CaSi-perovskite inclusions coexist with titanite (sphene), "olivine" and native Ni. MgSi-perovskite coexists with TAPP (tetragonal almandine-pyrope phase). Majoritic garnet occurs in one diamond, associated with CaTi-perovskite, Mn-ilmenite and an unidentified Si-Mg phase. Neither Cr-pyrope nor Mg-chromite was found as inclusions. The spinel inclusions are low in Cr and Mg, and high in Ti (Cr2O3<36.5 wt%, and TiO2>10 wt%). Most ilmenite inclusions have low MgO contents, and some have very high (up to 11.5 wt%) MnO contents. The rare "olivine" inclusions coexisting with ferropericlase have low Mg# (87-89), and higher Ca, Cr and Zn contents than typical diamond-inclusion olivines. They are interpreted as inverted from spinel-structured (Mg, Fe)2Si2O4. This suite of inclusions is consistent with derivation of most of the diamonds from depths near 670 km, and adds ilmenite and relatively low-Cr, high-Ti spinel to the known phases of the superdeep paragenesis. Diamonds from the Juina area are characterized by a narrow range of carbon isotopic composition (ཉC=-7.8 to -2.5?), except for the one majorite-bearing diamond (ཉC=-11.4?). There are high proportions of nitrogen-free and low-nitrogen diamonds, and the aggregated B center is predominant in nitrogen-containing diamonds. These observations have practical consequences for diamond exploration: Low-Mg olivine, low-Mg and high-Mn ilmenite, and low-Cr spinel should be included in the list of diamond indicator minerals, and the role of high-Cr, low-Ti spinel as the only spinel associated with diamond, and hence as a criterion of diamond grade in kimberlites, should be reconsidered.
DS202201-0019
2021
Kanda, H.A review of forms and concentrations of nitrogen impurities in diamond.Journal of the Gemmological Society of Japan, Vol. 35, eng. Abstract only.Mantlenitrogen
DS202202-0197
2022
Karaevangelou, M., Kopylova, M.G., Luo, Y., Pearson, G., Reutsky, V.N.Mineral inclusions in Lace diamonds and the mantle below the Kroonstad kimberlite cluster in South Africa.Contribution to Mineralogy and Petrology, Vol. 1777, 2, 10.1007/s00410-021-01880-8Africa, South Africadeposit - Lace

Abstract: We studied diamond inclusions in the 133 Ma Lace kimberlite of the Kroonstad Group II kimberlite cluster (Kaapvaal craton) to compare them to diamonds beneath the adjacent coeval Voorspoed kimberlite. The studied 288 Lace diamonds are mostly colorless dodecahedral Type IaAB. Based on diamond inclusions (DI), 38 Lace diamonds were classified as eclogitic (44%, 19 samples), peridotitic (35%, 15 samples), and websteritic (9%, 4 samples). The diamonds formed from mantle carbon (?13C?=?? 9.1 to ? 2.5 ‰ for 18 samples), with the exception of one eclogitic diamond (?13C?=?? 19.2 ‰). A rare zircon inclusion provides age constraints for the Lace eclogite protolith at 3.2?±?0.4 Ga (Lu-Hf model age) and Lace eclogite diamond formation at 188?±?37 Ma (U-Pb age). The eclogite protolith age suggests its formation contemporaneous with the lower crustal magmatism and metamorphism in the Central Kaapvaal craton, complementary to the tonalite-trondhjemite-granodiorite magmatism in the region and synchronous with the consolidation of the Eastern Kaapvaal Block. Two distinct kinds of eclogites are found to host Lace diamonds, (1) Fe-rich eclogites located at 160-190 km, and (2) more calcic-magnesian eclogites with mineral compositions identical to websteritic DIs, that derive from shallower lithospheric depths. Various thermobarometric methods applied to Lace diamonds and DIs constrain the Lace geotherm as reflecting a surface heat flow below or equal to 38 mW/m2 and a lithosphere thickness of at least 220 km, at the time of kimberlite eruption. These thermal parameters demonstrate an excellent match between the thermal state of the Voorspoed and Lace mantle segments that persisted from the Archean to Cretaceous times. The Lace peridotitic-to-eclogitic diamond ratio (5/4) does not differ much from the Voorspoed DI ratio (6/4), but a hot and spatially restricted carbonatitic metasomatism event affected the Voorspoed peridotitic mantle to create the majority of Voorspoed diamonds. The contrast in the mineralogy of DIs in Lace and Voorspoed diamonds highlights the very local (ca. 10 km) extent of the metasomatism and heating, as well as the variability of the diamond-forming processes at the same spatial scale.
DS202201-0020
2021
Kargin, A., Bussweiler, Y., Nosova, A., Sazonova, L., Berndt, J., Klemme, S.Titanium-rich metasomatism in the lithospheric mantle beneath the Arkangelsk diamond province, Russia: insights from ilemenite-bearing xenoliths with HP-HT reaction experiments.Contributions to Mineralogy and Petrology, Vol. 176, 12, Russia, Arlangelskdeposit - Grib

Abstract: To provide new insights into the interaction of ultramafic alkaline melts with the subcontinental lithospheric mantle, we present results of a petrographical-mineralogical study of ilmenite-bearing mantle xenoliths from the Grib kimberlite, Archangelsk, Russia along with results from reaction experiments between harzburgite and Fe-Ti bearing carbonate-silicate melts similar to aillikite. The compositions of orthopyroxene, ilmenite and garnet from our mantle xenoliths are similar to compositions of minerals of the low-Cr megacryst suite from different kimberlite occurrences worldwide including the Grib kimberlite as well as minerals from sheared lherzolite xenoliths captured by the Grib kimberlite. This suggests that ilmenite-bearing xenoliths, megacrysts, and sheared lherzolite xenoliths could have a common origin and/or formed under similar conditions. The reaction experiments were performed at 4 GPa and 1200 °C with varying proportions of aillikite (0, 10, and 50 wt%) that reacted with harzburgite. The experimental runs with 10% and 50% aillikite resulted in two layers within the capsule, with an ilmenite-bearing reaction zone at the contact between aillikite and harzburgite, and an ilmenite-free zone characterized by higher garnet and clinopyroxene abundances. An increase of aillikite melt is directly correlated with increasing TiO2 and decreasing Cr2O3 contents and Mg# values in the mineral phases, most significantly for pyroxenes. Overall, the experiments produce a chemical gradation of minerals from Cr-rich (Fe-Ti-poor) to Cr-poor (Fe-Ti-rich) which is strikingly similar to the chemical gradation observed in minerals from natural mantle-derived xenoliths from kimberlites. In summary, comparison of our experimental data with natural samples indicates possible links between the generation of megacrysts and Ti-rich metasomatism of the lithospheric mantle by ultramafic alkaline (aillikite-related) melts and their possible evolution towards kimberlites. Our results illustrate the importance of melt-rock ratios in generating the mineralogical and chemical diversity in mantle xenolith suites.
DS202205-0694
2022
Katsura, T.A revised adiabatic temperature profile for the mantle. 410 discontinuityJournal of Geophysical Research, Solid Earth, Vol. 127, 2, 10.1029/2021JB023562 11p. PdfMantlecore-boundary

Abstract: This study estimates the temperature profile of the Earth's mantle by generally following the approach described in Katsura et al. (2010), https://doi.org/10.1016/j.pepi.2010.07.001. The estimation consists of two steps. First, the temperature at the 410-km seismic discontinuity (D410), at which the seismic wave velocities abruptly increase almost everywhere in the mantle, is evaluated. The D410 is usually attributed to the olivine-wadsleyite transition in peridotite. Comparing the globally averaged D410 depth with the phase diagram of the olivine-wadsleyite transition yields a D410 temperature of 1839 (38) K. Second, this temperature is extrapolated to shallower and deeper regions by assuming that the heat is mainly transferred by convection in the mantle. The temperature gradient in such cases is the product of the thermal expansion coefficient and the temperature divided by the density and the heat capacity. The thermal expansion coefficients of the major mantle mineral are obtained by recalculating our previous experimental data. We found that the temperatures at 50-km depth, the bottom of the mantle transition zone, the top of the lower mantle, and 2,800-km depth are found to be 1646 (35), 1994 (40), 1960 (40), and 2587 (60) K, respectively. The 50-km depth temperature is slightly higher but generally agrees to that estimated from the melting of depleted peridotite.
DS202204-0524
2022
Kedrova, T.V., Bogush, I.N., Zinchuk, N.N., Bardukhinov, L.D., Lipashova, A.N., Saltykova, V.P.Diamond placers of the Nakyn kimberlite field.Russian Geology and Geophysics, Vol. 63, 3, pp. 245-254.Russiadeposit - Nakyn

Abstract: The paper presents the results of studies of diamonds from Early Jurassic sediments making up the Nyurbinskoe buried placer of the Nakyn kimberlite field, unique in diamond reserves. The main task is to identify diamond distribution patterns in the deposits of the Dyakhtar Stratum (lower deposit) and the Ukugut Suite (upper deposit) within the placer. A comparative analysis of the typomorphic features of diamonds from the upper and lower deposits of the placer was carried out. Variations in the contents of crystals with certain properties that form the image of a diamond-bearing geologic object have been revealed. The zonal distribution of diamonds by characteristics in sedimentary deposits, regardless of their age, has been established. The properties of diamonds and their associations change within the placer, which is due to their redeposition during the Early Jurassic sedimentation.
DS202205-0695
2022
Khokhryakov, A.F., Kruk, A.N., Sokol, A.G., Nechaev, D.V.Experimental modeling of diamond reportion during mantle metasomatism.Minerals ( MDPI), Vol. 12, 4, pp. 414-MantleMetasomatism

Abstract: The morphology of resorbed diamond crystals is a valuable source of information on the composition and ascent rate of kimberlite magmas, as well as on possible redox conditions in protolith. Previously, diamond resorption was thoroughly investigated at P-T-fO2 parameters of the kimberlite magma ascent. In this study, we investigated diamond resorption using unaltered group I kimberlite and model carbonatite at P-T-fO2 parameters that are typical of the peridotite source of kimberlite magmas in the subcontinental lithospheric mantle. An analysis of previous studies made it possible to determine the rate of diamond octahedron transformation into a spherical tetrahexahedron depending on the composition of the carbonate-silicate melt. It was shown that the rate of diamond resorption at 6.3 GPa increases in all the investigated systems as fO2 and temperature rise. There is a steady decrease in the diamond resorption rate as pressure increases from 1 GPa to 6.3 GPa. The morphology comparison of the experimentally produced samples with natural diamonds is indicative of the significant contribution of metasomatic alteration of protolith by the oxidized agent and at the initial stages of kimberlite magma ascent to the resorption of natural diamonds.
DS202201-0021
2021
Kitiyama, Y., d'Eyrames, E.Geochemical evidence for carbon and chlorine enrichments in the mantle source of kimberlites ( Udachnaya pipe, Siberian craton).Geochimica et Cosmochimica Acta, Vol. 315, pp. 295-316.Russia, Siberiadeposit - Udachnaya

Abstract: Deep, carbonate-rich melts are key constituents of kimberlites and are crucial for understanding the cycle of volatile elements in the mantle. On the Siberian craton, the Udachnaya-East kimberlite hosts extremely well-preserved nodules composed of chlorides + carbonates + sulfates, that do not present any relict sedimentary textures. These salty nodules display textures that are commonly observed in quenched liquids and may thus represent the very last stage liquid of the kimberlite. Alternatively, they could represent assimilated sedimentary material, or even post-magmatic hydrothermal alteration, because kimberlites are known to ascend through the lithosphere while assimilating material from their wall rocks. Here we focus specifically on those chloride-carbonate nodules, which are composed of 70% chloride + 30% alkali-carbonate and sulfate, and used two radiogenic systems (Rb-Sr, Sm-Nd) and the isotopic composition of sulfur, in addition to their major and trace element compositions (n = 3). We then compared the results with the same geochemical data on host kimberlites (n = 4), sedimentary cover (n = 3) and hydrothermal veins (n = 3). Taken together, our results show that the nodules are not the product of a contamination by the Cambrian sedimentary cover. Trace element patterns of the nodules display extreme enrichments in the same elements that are relatively depleted in the host kimberlite but also in kimberlites worldwide (K, Rb, Sr, Pb), suggesting that chloride-carbonate nodules are snapshots of the latest stage liquid present in the kimberlite system. Their isotopic compositions (Rb-Sr, Sm-Nd and ?34S) are consistent with a common magmatic source with their host kimberlite. We propose that chloride-carbonate nodules record a missing compositional endmember, which could explain the trend towards more radiogenic Sr isotope ratios at nearly constant Nd signatures observed in their host kimberlite, as well as in other kimberlites worldwide. This observed trend suggests the presence of a recycled component with high Rb/Sr (such as salts or terrigenous sediments) in the mantle sampled by some kimberlites, either in the lithosphere or the asthenosphere. This study highlights that the role of alkalies and halogens may have been underestimated in the genesis of kimberlites at depths where diamonds are stable, as well as in more evolved magmatic stages. Segregations of chlorides and carbonates occur specifically in sulfate-bearing kimberlites, which may thus sample a mantle domain in which sulfates with ?34S > 0‰ are dominant. The existence of such a reservoir could explain the apparent imbalance observed between the chondritic value (?34S of 0‰) and the negative S isotopic compositions of mantle sulfides (MORB and peridotites).
DS202204-0525
2022
Klepikov, I., Vasilev, E.Regeneration growth as one of the principal stages of diamond crystalogenesis.MDPI, doi: 10.3390/min12030327Russiadiamond morphology

Abstract: Revealing the internal structure of diamonds is key to understanding the general regularities of crystal growth and dissolution. This paper presents and summarizes data on the internal structure of diamonds of different morphological types, colors and defect-impurity composition. In order to provide a comprehensive explanation of the stages of diamond growth, crystals and plates were observed, and panchromatic cathodoluminescence and photoluminescence techniques were applied. This article considers the mechanism of tangential growth from existing surfaces (regeneration growth) as an intermediate stage between normal and tangential crystal growth. The regeneration growth is very fast due to the absence of the limiting stage-nucleation of a new atomic layer. Cuboid diamonds were refaceted to stepped octahedrons by the regeneration growth mechanism. A schematic model of crystal habit transformation due to regeneration growth explains the internal structure of crystals in connection with their morphology and thermal history. The main variants of regeneration stage and its morphological manifestations were demonstrated. Most diamonds pass through the regeneration stage, and in many cases, it was a stage of growth termination.
DS202205-0696
2022
Klepikov, I.V., Vaselev, E.A., Antonov, A.V. Regeneration growth as one of the principal stages of diamond crystallogenesis.Minerals ( MDPI), Vol. 12, 3, p. 327 16p.Mantlediamond morphology

Abstract: Revealing the internal structure of diamonds is key to understanding the general regularities of crystal growth and dissolution. This paper presents and summarizes data on the internal structure of diamonds of different morphological types, colors and defect-impurity composition. In order to provide a comprehensive explanation of the stages of diamond growth, crystals and plates were observed, and panchromatic cathodoluminescence and photoluminescence techniques were applied. This article considers the mechanism of tangential growth from existing surfaces (regeneration growth) as an intermediate stage between normal and tangential crystal growth. The regeneration growth is very fast due to the absence of the limiting stage-nucleation of a new atomic layer. Cuboid diamonds were refaceted to stepped octahedrons by the regeneration growth mechanism. A schematic model of crystal habit transformation due to regeneration growth explains the internal structure of crystals in connection with their morphology and thermal history. The main variants of regeneration stage and its morphological manifestations were demonstrated. Most diamonds pass through the regeneration stage, and in many cases, it was a stage of growth termination.
DS202202-0198
2021
Kogarko, L.N.Geochemistry of rare earth metals in the ultrabasic-alkaline-carbonatite complex of the Kugda ( Polar Siberia).Doklady Earth Sciences, Vol. 501, pp. 1020-1022.Russia, Siberiadeposit - Kugda

Abstract: The distribution patterns of rare earth metals (REM) in the rocks of the Kugda massif (Polar Siberia) are assessed. The REM content decreases from early olivinite rocks, containing, on average, 1938 ppm, to the end products of syenite differentiation and increases again in carbonatites. The difference in the distribution coefficients of light and heavy rare earth metals is the reason for the noticeable fractionation of these elements during the evolution of the magmatic system of the Kugda massif. The ratio of light REM to heavy Ce/Yb drops by almost an order of magnitude in later differentiation products. The main process of the Kugda massif formation was continuous crystallization differentiation, characterized by a wide crystallization field of perovskite. An interesting feature of the process is the very early crystallization of perovskite, associated with the high potential of carbon dioxide.
DS202202-0199
2021
Konishhchev, V.S., Kovkhuto, A.M.Criteria and prospects of diamonds of the Vitebsk granulite massif.Journal of the Belarusian State University. Geography and Geology, Title onlyRussiadeposit - Vitebsk

Abstract: The article describes the history of studying the diamond content of tectonic structures of the territory of Belarus. Based on the results of magnetometric, mineralogical, tectonic studies carried out by industrial geologists and scientists over the past 50 years, new scientifically substantiated criteria for the search for explosion pipes have been developed using Clifford’s rule, according to which kimberlite explosion pipes are developed within the Archean cratons, where the thickness of the lithosphere is 175–270 km, and are absent in the zones of Early Proterozoic stabilisation and tectonomagmatic activation. Explosion tubes on the African-Arabian, East Siberian, Sino-Korean and East European platforms demonstrate their confinement to the Archean cratons and may be associated with zones of paleosubduction of the Proterozoic oceanic crust beneath the Archean cratons. Based on this, the authors scientifically substantiated the hypothesis that during the closure of the Early Proterozoic paleoocean separating the Fenno-Scandinavian craton from the Volga-Ural and Sarmatian cratons, subduction of the younger crust took place under these cratons, the southwestern corner of which on the territory of Belarus is the Vitebsk granulite massif. The article concludes that the Vitebsk granulite massif is the most promising in terms of diamond-bearing on the territory of Belarus, and within its limits – the Smolensk regional deep fault at the intersection of this fault of northeastern striking with the Odessa-Gomel regional deep fault of submeridional striking south of the city of Orsha. Recommendations are given for further study of promising areas in order to determine their diamond content.
DS202201-0022
2021
Kopylova, M.Carbonated cratonic mantle without carbonate.GAC/MAC Meeting UWO, 1p. Abstract p. 163.Canada, Baffin Islanddeposit - Chidliak

Abstract: Petrologists all agree that the “carbonated mantle”, i. e. peridotite with accessory carbonate, is necessary to generate CO2-bearing melts. Carbonated peridotite is also a useful theoretical concept for geochemists seeking to explain trace element enrichment of the lithospheric mantle. Melting of peridotite with addition of carbonate has been the subject of hundreds of experimental studies. Yet mantle samples from below cratons do not contain carbonate. Our work tries to reconcile the theoretical view of the carbonated mantle with the empirical observations on cratonic mantle xenoliths. Peridotite xenoliths from the Chidliak kimberlite province (SE Baffin Island, Canada) suggest that the natural carbonated mantle are peridotites with elevated modes of clinopyroxene, garnet and olivine, and with thin rims of calcic silicate minerals. Observations on Chidliak peridotites provide an excellent “reality check” for theoretical mobility models of the carbonate-rich melts in the mantle. The “carbonation freezing front” is often theoretically imagined as the solidus of mantle peridotites infiltrated by CO2-rich melts. Our observations suggest that melting is not necessary for immobilization of carbonatitic metasomatic agent. The latter is highly reactive, readily giving away Ca to silicate minerals and exsolving CO2. At Chidliak, clinopyroxene and monticellite rims produced by carbonation do not show signs of partial melting during their formation; moreover, thicker mantles of clinopyroxene in Chidliak peridotites are equilibrated at P-Ts below the CO2- saturated peridotite solidus. Petrography of Chidliak peridotites also constrains the melt flux in the carbonation freezing model. At melt fluxes >10%, the model predicts elevated fractions of the reacted melt in comparison with the reacting melt. This should lead to loss of Ca. Natural samples, on the contrary, demonstrate addition of Ca; this is observed from quantification of compositional fluxes at Chidliak and in temporal trends of mineral and bulk compositions of the cratonic mantle. This suggests that the carbonatitic fluxes are always below 10%, and the carbonate-rich melt always "freezes in" in peridotites. We further submit that CO2-rich magmas on cratons are byproducts of carbonate metasomatism, since deep decarbonation is a necessary prerequisite to generation of CO2-rich melts. Theoretically, carbonate-rich fluids should be able to traverse the peridotitic mantle in the reacted channels where the fluids overcome the limits of the mineralogical, thermal and redox instability in deep peridotites. This study suggests the channels can be made of garnet or clinopyroxene, as only these initial products of reactive decarbonation of the deep peridotitic mantle are observed to contain fluid microinclusions and modal macro- grains of carbonates. Future research will better recognize stealth signs of carbonatitic metasomatism under cratons and enable us to better document its extent and localization.
DS202202-0200
2022
Kopylova, M.G.What lamprophyres teach us about kimberlites: lessons from the Kola Peninsula alkaline carbonatitic province.VKC zoom meeting, Feb. 8 6pm PST https://us02web.zoom.us/j/8862150863?pwd=c09uSEhEckRpWU8rQlEvQ1Rrb01WQT09 Meeting ID: 886 215 0863 Passcode: n2LWa3Russia, Kola Peninsulacarbonatite
DS202202-0201
2022
Kostrivitsky, S.I., Yakolev, D.A., Sharygin, I.S., Gladkochub, D.P., Donskaya, T.V., Tretiakova, I.G., Dymshits, A.M.Diamondiferous lamproites of Ingashi field, Siberian craton.Geological Society of London Special Publication 513, pp. 45-70.Russialamproites

Abstract: Ingashi lamproite dykes are the only known primary sources of diamond in the Irkutsk district (Russia) and the only non-kimberlitic one in the Siberian craton. The Ingashi lamproite field is situated in the Urik-Iya graben within the Prisayan uplift of the Siberian craton. The phlogopite-olivine lamproites contain olivine, talc, phlogopite, serpentine, chlorite, olivine, garnet, chromite, orthopyroxene, clinopyroxene as well as Sr-F-apatite, monazite, zircon, armolcolite, priderite, potassium Mg-arfvedsonite, Mn-ilmenite, Nb-rutile and diamond. The only ultramafic lamprophyre dyke is composed mainly of serpentinized olivine and phlogopite in the talc-carbonate groundmass and is similar to Ingashi lamproites accessory assemblage with the same major element compositions. Trace element and Sr-Nd isotopic relationships of the Ingashi lamproites are similar to classic lamproites. Different dating methods have provided the ages of lamproites: 1481 Ma (Ar-Ar phlogopite), 1268 Ma (Rb-Sr whole rock) and 300 Ma (U-Pb zircon). Ingashi lamproite ages are controversial and require additional study. The calculated pressure of 3.5 GPamax for clinopyroxenes indicates that lamproite magma originated deeper than 100 km. A Cr-in-garnet barometer shows a 3.7-4.3 GPamin and derivation of Ingashi lamproites deeper than 120 km in depth. Based on the range of typical cratonic geotherms and the presence of diamonds, the Ingashi lamproite magma originated at a depth greater than 155 km.
DS202202-0202
2022
Krmicek, L., Chalapathi Rao, N.V.Lamprophyres, lamproites and related rocks: tracers to supercontinent cycles and metallogenesis.Geological Society of London Special Publication 513, pp. 1-16.Globallamproites

Abstract: Proterozoic to Cenozoic lamprophyres, lamproites and related rock types hold a unique potential for the investigation of processes affecting mantle reservoirs. They originated from primary mantle-derived melts that intruded both cratons and off-craton regions, which were parts of former supercontinents - Columbia, Rodinia and Gondwana-Pangaea. Well known for hosting economic minerals and elements such as diamonds, base metals, platinum-group elements and Au, they are also significant for our understanding of deep-mantle processes, such as mantle metasomatism and mantle plume-lithosphere interactions, as well as large-scale geodynamic processes, including subduction-related tectonics and supercontinent amalgamation and break-up. This Special Publication presents an overview of the state of the art and recent advances as achieved by individual research groups from different parts of the world, and outlines future research directions. Mineralogical, geochemical, geochronological and isotope analyses are used to decipher the complex petrogenetic and metallogenetic evolution of these extraordinary rocks and unravel a complete history of tectonic events related to individual supercontinent cycles. The Special Publication including this introductory chapter also deals with some issues related to the classification of these rocks.
DS202203-0354
2022
Krstulovic, M., Rosa, A.D., Sanchez, D.F., Libon, L., Albers. C., Merkulova, M., Grolimund, D., Irifune, T., Wilke, M.Effect of temperature on the densification of silicate melts to lower Earth's mantle.Physics of the Earth and Planetary Interiora, 13p. PdfMantlemelting

Abstract: Physical properties of silicate melts play a key role for global planetary dynamics, controlling for example volcanic eruption styles, mantle convection and elemental cycling in the deep Earth. They are significantly modified by structural changes at the atomic scale due to external parameters such as pressure and temperature or due to chemistry. Structural rearrangements such as 4- to 6-fold coordination change of Si with increasing depth may profoundly influence melt properties, but have so far mostly been studied at ambient temperature due to experimental difficulties. In order to investigate the structural properties of silicate melts and their densification mechanisms at conditions relevant to the deep Earth's interior, we studied haplo basaltic glasses and melts (albite-diopside composition) at high pressure and temperature conditions in resistively and laser-heated diamond anvil cells using X-ray absorption near edge structure spectroscopy. Samples were doped with 10 wt of Ge, which is accessible with this experimental technique and which commonly serves as a structural analogue for the network forming cation Si. We acquired spectra on the Ge K edge up to 48 GPa and 5000 K and derived the average Ge-O coordination number , and bond distance as functions of pressure. Our results demonstrate a continuous transformation from tetrahedral to octahedral coordination between ca. 5 and 30 GPa at ambient temperature. Above 1600 K the data reveal a reduction of the pressure needed to complete conversion to octahedral coordination by ca. 30 . The results allow us to determine the influence of temperature on the Si coordination number changes in natural melts in the Earth's interior. We propose that the complete transition to octahedral coordination in basaltic melts is reached at about 40 GPa, corresponding to a depth of ca. 1200 km in the uppermost lower mantle. At the core-mantle boundary (2900 km, 130 GPa, 3000 K) the existence of non-buoyant melts has been proposed to explain observed low seismic wave velocity features. Our results highlight that the melt composition can affect the melt density at such extreme conditions and may strongly influence the structural response.
DS202205-0697
2022
Kruk, A., Sokol, A.Role of volatiles in the evolution of a carbonatitic melt in peridotitic mantle: experimental constraints at 6.3 Gpa and 1200-1450C. Minerals ( MDPI), Vol. 12, 466 20p. PdfMantlecarbonatite

Abstract: Reconstruction of the mechanisms of carbonatitic melt evolution is extremely important for understanding metasomatic processes at the base of the continental lithospheric mantle (CLM). We have studied the interaction between garnet lherzolite and a carbonatitic melt rich in molecular CO2 and H2O in experiments at 6.3 GPa and 1200-1450 °C. The interaction with garnet lherzolite and H2O-bearing carbonatite melt leads to wehrlitization of lherzolite, without its carbonation. Introduction of molecular CO2 and H2O initiates carbonation of olivine and clinopyroxene with the formation of orthopyroxene and magnesite. Partial carbonation leads to the formation of carbonate-silicate melts that are multiphase saturated with garnet harzburgite. Upon complete carbonation of olivine already at 1200 °C, melts with 27-31 wt% SiO2 and MgO/CaO ? 1 are formed. At 1350-1450 °C, the interaction leads to an increase in the melt fraction and the MgO/CaO ratio to 2-4 and a decrease in the SiO2 concentration. Thus, at conditions of a thermally undisturbed CLM base, molecular CO2 and H2O dissolved in metasomatic agents, due to local carbonation of peridotite, can provide the evolution of agent composition from carbonatitic to hydrous silicic, i.e., similar to the trends reconstructed for diamond-forming high density fluids (HDFs) and genetically related proto-kimberlite melts.
DS202202-0203
2022
Kumar, A., Talukdar, D., Chalapathi Rao, N.V., Burgess, R., Lehmann, B.Mesoproterozoic 40Ar-39Ar ages of some lamproites from the Cuddapah basin and eastern Dharwar craton, southern India: implications for diamond provenance of the Banganapalle conglomerates, age of the Kurnool Group and Columbia tectonics.Geological Society of London Special Publication 513, pp. 157-178.Indialamproites

Abstract: We report Mesoproterozoic 40Ar-39Ar (whole-rock) ages of lamproites from (i) the Ramadugu field (R4 dyke : 1434 ± 19 Ma and R5 dyke: 1334 ± 12 Ma) and the Krishna field (Pochampalle dyke: 1439 ± 3 Ma and Tirumalgiri dyke: 1256 ± 12 Ma) from the Eastern Dharwar Craton (EDC) and (ii) the Garledinne (1433 ± 8 Ma) and the Chelima (1373 ± 6 Ma) dykes from within the Paleo-Mesoproterozoic Cuddapah Basin, southern India. The ages reported for the Ramadugu and Tirumalgiri lamproites constitute their first radiometric dates. Ages of the Pochampalle and the Chelima lamproites from this study are broadly comparable to their previously reported 40Ar-39Ar (phlogopite) ages of c. 1500 Ma and 1418 ± 8 Ma, respectively. The ages of all these lamproites are much older than those of the (i) c. 1.1 Ga kimberlites from the Wajrakarur and Narayanpet fields of the EDC and (ii) c. 1.09 Ga lamproitic dykes at Zangamarajupalle which intrude the Cumbum Formation of the Cuddapah Basin. However, the age of the Tirumalgiri lamproite (c. 1256 Ma) is similar to that of the Ramannapeta lamproite (c. 1224 Ma) within the Krishna field. Our study provides evidence for protracted ultrapotassic (lamproitic) magmatism from c. 1.43 to 1.1 Ga over a widespread area (c. 2500 km2) in and around the Cuddapah Basin and the EDC. Implications of the obtained new ages for the diamond provenance of the Banganapalle Conglomerates, the age of the Kurnool Group and for the timing of break-up of the Paleo-Mesoproterozoic supercontinent of Columbia/Nuna are explored.
DS202205-0698
2022
Kutcherov, V., Ivanov, K., Mukhina, E., Serovaiskii, A.Deep hydrocarbon cycle: an experimental simulation.Carbon in Earth's Interior, Geophysical Monograph , Vol. 249, Chapter 26, pp. 329- 12p. PdfMantlecarbon

Abstract: The concept of a deep hydrocarbon cycle is proposed based on results of experimental modeling of the transformation of hydrocarbons under extreme thermobaric conditions. Hydrocarbons immersed in the subducting slab generally maintain stability to a depth of 50 km. With deeper immersion, the integrity of the traps is disrupted and the hydrocarbon fluid contacts the surrounding ferrous minerals, forming a mixture of iron hydride and iron carbide. This iron carbide transported into the asthenosphere by convective flows can react with hydrogen or water and form an aqueous hydrocarbon fluid that can migrate through deep faults into the Earth's crust and form multilayer oil and gas deposits. Other carbon donors in addition to iron carbide from the subducting slab exist in the asthenosphere. These donors can serve as a source of deep hydrocarbons that participate in the deep hydrocarbon cycle, as well as an additional feed for the general upward flow of the water-hydrocarbon fluid. Geological data on the presence of hydrocarbons in ultrabasites squeezed from a slab indicate that complex hydrocarbon systems may exist in a slab at considerable depths. This confirms our experimental results, indicating the stability of hydrocarbons to a depth of 50 km.
DS202204-0526
2022
Kvasnytsya, V.Morphology of diamond crystals and mechanism of their growth ( natural and synthetic).Journal of Superhard Materials, Vol. 43, 2, pp. 75-84.Russiadiamond morphology

Abstract: Using the morphology of natural and synthetic diamond crystals as an example, the mechanisms of their growth of dislocation (spiral), non-dislocation (two-dimensional nucleation), normal (fibrous), and block (adhesive) character have been demonstrated. These mechanisms can be clearly seen in the morphological and microtopographic features of diamond polyhedra and xenocrystals. Growth occurs by the dislocation and normal mechanisms for most natural diamond crystals and the dislocation and two-dimensional nucleation mechanisms for synthetic diamond crystals.
DS202205-0699
2022
Kvasnytsya, V.The size and shape of diamond crystals of different origin. *** Abst in ENG onlyMineralogical Journal , March, pp. 32-40. pdfGlobaldiamond morphology

Abstract: The size and shape of diamond crystals of different origin are analyzed. Diamonds with a size of less than about 0.5 mm are classified as microcrystals. Diamonds found in meteorites typically show non-faceted anhedral crystals of various sizes. Only the Canyon Diablo iron meteorite has cubic microcrystals of unclear crystallogenesis. Nano, micro- and macro-sized crystals of diamond in meteorites are usually aggregate in nature. The release of diamond polyhedra in meteorites is limited by the too small size of its crystals in chondrites and by its solid-phase transformation from very fine-grained diamond and graphite in ureilites and octahedrites. The size and shape of diamond crystals found in meteorite impact craters are determined by the nature of the source carbon material. The process of solid-phase transformation of graphite or other carbon-bearing materials (e.g., coal, plant remains) to diamond in meteorite craters does not allow euhedral crystal to be formed. At the same time, in the case of diamonds formed from impacts, on the (0001) faces of impact apographitic diamonds, polyhedra of nano-microdiamonds crystallize from the gas phase. These crystals are often form autoepitaxially, because they crystallize in an oriented manner on the lonsdaleite-diamond matrix. Diamonds found in metamorphic rocks, ophiolites and modern volcanites show faceted microcrystals. A wide range of sizes, from 0.1 mm to 10 cm, is characteristic of faceted diamond crystals from kimberlites, lamproites and lamprophyres. Diamond crystals from different mantle rocks acquire a multifaceted shape after reaching certain embryo sizes — the most likely appearance of diamond polyhedra larger than 40-50 nm. Octahedra forms are dominant for natural diamond crystals of different sizes and origin. Keywords: diamond, geological-genetic types of diamond, nano-micro- and macrocrystals, crystal size, crystal shape.
DS202205-0700
2022
Kvasnytsya, V.M., Wirth, R.Impact diamonds from meteorite craters and Neogene places in Ukraine.Mineralogy and Petrology, 10.1007/s00710-022-00778-y 19p. PdfEurope, Ukrainediamond genesis
DS202205-0701
2022
Labdidi, J.The origin of nitrogen in Earth's mantle: constraints from basalts 15N/14N and N2/3He ratios.Chemical Geology, 10.1016/j.chemgeo.2022.120780Europe, Iceland, Galapogos, Hawaiibasalts

Abstract: Plate tectonics is thought to be a major driver of volatile redistribution on Earth. The budget of nitrogen in Earth's mantle has been suggested to be almost entirely surface-derived. Recycling would contribute nitrogen with relatively heavy 15N/14N isotope ratios to Earth's mantle. This could explain why the Earth's mantle 15N/14N isotope ratio is substantially higher than both solar gases and chondritic parent bodies akin to enstatite chondrites. Here, published nitrogen isotope data of mid-ocean ridge and ocean island basalts are compiled and used to evaluate the nitrogen subduction hypothesis. Nitrogen isotope ratios are used in conjunction with published N2/3He and K2O/TiO2 ratios on the same basalts. Assuming that 3He is not recycled, N2/3He ratios are argued to trace nitrogen addition to mantle sources via subduction. Various mantle source enrichments for basalts are tracked with K2O/TiO2 ratios: elevated K2O/TiO2 ratios are assumed to primarily reflect the contributions of recycled components in the basalts mantle sources. The main result of our data compilation is that for most basalts, ?15N and N2/3He remain constant across a vast range of K2O/TiO2 ratios. Mid-ocean ridge basalts have ?15N signatures that are lower than air by ~4‰ and an average N2/3He ratio of 3.7 (±1.2) x106 (95% confidence, n = 30). Published ?15N and N2/3He are invariant across K2O/TiO2 ratios that vary over a factor of ~20. Using estimates of slab K2O/TiO2 and [TiO2], the observed invariant ?15N and N2/3He may be fit with slabs containing ~0.1 ppm N. A mass balance shows that adding ~10% recycled slabs to the convective mantle only raises the N2/3He by <5%. Lavas from Iceland, Galapagos and Hawaii have high 3He/4He and 15N/14N ratios relative to the convective mantle. Only seven samples show nitrogen isotopic signatures that are unaffected by air contamination, although those samples are poorly characterized for N2/3He. The seven basalts show ?15N between ?2 and 0‰ that do not vary systematically with K2O/TiO2 ratios that vary over a factor of ~5. The N2/3He ratios of these seven basalts is unknown, but the high 3He/4He mantle may be estimated by combining published N2/36Ar to 3He/36Ar ratios. This yields a N2/3He of 2.3 (±1.2) x 106 (1? uncertainty). This is indistinguishable from the MORB estimate of 3.7 (±1.2) x 106. Invariant ?15N across variable degrees of mantle enrichments and MORB-like N2/3He for the high 3He/4He mantle are not consistent with nitrogen addition to plume sources with elevated 3He/4He ratios. A ?15N between ?2 and 0‰ for plume sources, only marginally higher than MORB, could be a primordial feature of undegassed mantle reservoirs. Nonetheless, nitrogen subduction may have contributed to a specific array of mantle sources, as revealed by the few published data on basalts with low 3He/4He ratios. Lavas from the Society plume with low 3He/4He ratios show an enriched mantle source, and they have elevated ?15N ? +0.5‰ and N2/3He > 107. For those, the addition of slabs with concentrations of ~0.1 ppm N to a mantle source can account for the integrated dataset. To summarize, the published data suggest that nitrogen subduction may explain a sub-set of published N isotope data on basalts, but that N recycling has an overall more limited impact on mantle nitrogen than previously thought.
DS202204-0527
2022
Lai, M.Y., Stachel, T., Stern, R.A., Hardman, M.F., Pearson, D.G., Harris, J.W.Formation of mixed paragenesis diamonds during multistage growth - constraints from- in situ Delta 13C-delta 15N-[N] analyses of Koidu diamonds.Geochimica et Cosmochimica Acta, Vol. 323, pp. 20-39.Africa, Sierra Leonedeposit - Koidu

Abstract: Inclusion-bearing diamonds from the Koidu kimberlite complex, Sierra Leone (West African Craton) were analyzed in situ for carbon and nitrogen isotope compositions, nitrogen concentrations and nitrogen aggregation states. In a suite of 105 diamonds, 78% contain eclogitic mineral inclusions, 17% contain peridotitic mineral inclusions, and 5% - an unusually high proportion - contain co-occurring eclogitic and peridotitic mineral inclusions indicating a mixed paragenesis. Major and trace element compositions of mineral inclusions from two mixed paragenesis diamonds (one with omphacite + Mg-chromite, the other with eclogitic garnet + forsteritic olivine) were determined. The presence of positive Eu anomalies in centrally located omphacite and eclogitic garnet inclusions indicates derivation from subducted protoliths, formed as igneous cumulates in lower oceanic crust. Mg-chromite (Cr# 85.5; Mg# 65.2) and olivine (Mg# 94.5) inclusions, located in outer portions of the mixed paragenesis diamonds, have compositions indicative of derivation from strongly depleted cratonic peridotites. Given that the olivine Mg# of 94.5 is the highest reported to date for the West African Craton, the eclogitic and peridotitic inclusions in these mixed paragenesis diamonds cannot have precipitated during infiltration of peridotitic substrates by eclogite-derived fluids, as the consequent fluid-rock interaction should lead to Mg# lower than that for the original peridotitic diamond substrate. The different origins of eclogitic and peridotitic inclusions could be explained by physical transport of their host diamonds from eclogitic into peridotitic substrates, possibly along high-strain shear zones, before renewed diamond growth. Based on the ?¹³C-?¹?N systematics of the entire inclusion-bearing diamond suite from Koidu, three major compositional clusters are identified. Cluster 1 (eclogitic diamond cores; ?¹³C = -33.2 to -14.4 ‰ and ?¹?N = -5.3 to +10.1 ‰) bears the isotopic signature of recycled crustal material (± a mantle component). Cluster 2 (peridotitic diamonds and including the core of a diamond containing omphacite + Mg-chromite; ?¹³C = -6.0 to -1.1 ‰ and ?¹?N = -4.2 to +9.7 ‰) likely involves mixing of carbon and nitrogen from subducted and mantle sources. Cluster 3 (rims of eclogitic diamonds and including the eclogitic garnet + olivine included diamond and the rim of the omphacite + Mg-chromite included diamond; ?¹³C = -7.8 to -3.6 ‰ and ?¹?N = -7.9 to -2.1 ‰) matches convecting mantle-derived fluids/melts. The distinct isotopic signatures of the three diamond clusters, together with differences in nitrogen aggregation and cathodoluminescence response between diamond cores and rims, suggest episodic diamond growth during multiple fluid/melt pulses.
DS202204-0528
2022
Layton-Matthews, D.Current techniques and applications of mineral chemistry to mineral exploration; examples from glaciated terrain.MDPI, Vol. 12, 1, 21p.Globalgeochemistry

Abstract: This paper provides a summary of traditional, current, and developing exploration techniques using indicator minerals derived from glacial sediments, with a focus on Canadian case studies. The 0.25 to 2.0 mm fraction of heavy mineral concentrates (HMC) from surficial sediments is typically used for indicator mineral surveys, with the finer (0.25-0.50 mm) fraction used as the default grain size for heavy mineral concentrate studies due to the ease of concentration and separation and subsequent mineralogical identification. Similarly, commonly used indicator minerals (e.g., Kimberlite Indicator Minerals—KIMs) are well known because of ease of optical identification and their ability to survive glacial transport. Herein, we review the last 15 years of the rapidly growing application of Automated Mineralogy (e.g., MLA, QEMSCAN, TIMA, etc) to indicator mineral studies of several ore deposit types, including Ni-Cu-PGE, Volcanogenic Massive Sulfides, and a variety of porphyry systems and glacial sediments down ice of these deposits. These studies have expanded the indicator mineral species that can be applied to mineral exploration and decreased the size of the grains examined down to ~10 microns. Chemical and isotopic fertility indexes developed for bedrock can now be applied to indicator mineral grains in glacial sediments and these methods will influence the next generation of indicator mineral studies.
DS202205-0702
2022
Lenardic, A., J. SealesInternal planetary feedbacks, mantle dynamics, and plate tectonics.Researchgate preprint Chapter from book Elsevier, March 61p. PdfMantlegeodynamics

Abstract: Isolating planetary feedbacks, and feedback analysis, are prevalent aspects of climate and Earth surface process science. An under appreciation of internal planet feedbacks, and feedback analysis for plate tectonics research, motivate this chapter. We review feedbacks that influence the Earth's thermal evolution and expand them to include magmatic history and planetary water budgets. The predictions from feedback models are shown to be consistent with petrological constraints on the Earth's cooling. From there, we isolate feedbacks that connect structural elements within the mantle dynamics and plate tectonics system. The feedbacks allow for a reciprocal causality between plates, plumes, the asthenosphere, and mantle flow patterns, with each element being co-dependent on the others. The linked elements and feedbacks define plate tectonics are part of a self-sustaining flow system that can bootstrap itself into existence. Within that framework, plate tectonics involves the co-arising of critical system factors. No single factor is the cause of another. Rather, they emerge with the links between them and the generation of functional elements coincides, within relatively narrow time windows, with the co-emergence of factors that are critical for the maintenance of the elements themselves. What emerges is not a tectonic state but a process. That is, a set of feedbacks that can transform the tectonics of a planet and/or maintain plate tectonics. The feedback functions are not permanent but can operate over extended time frames such that plate tectonics can remain stable. The nature of the feedbacks, and their stability, can be studied at various levels of detail but questions of origin can become ill-defined. Observational tests of a feedback framework for plate tectonics and mantle dynamics are presented, along with research paths that apply feedback methodology to solid planet dynamics and comparative planetology.
DS202201-0023
2021
Lenardic, A.,Jellinek, M.,Seales, J., Lee, C-T.Global tectonic and climatic fluctuations: from Pangea grounding to planetary speculation. * just for interestResearchgate , Dec. 51p. PdfGlobalGeotectonics

Abstract: The Earth's paleo-climate record indicates climate fluctuations, from cool to warm to cool conditions, over the last ~300 My. Over that time, the Earth's most recent super-continent, Pangea, formed and broke apart. Data constraints together with numerical models indicate that Pangea formation and breakup affected spatial and temporal patterns of heat loss from the Earths' interior. This, in turn, affected global tectonic and volcanic behavior. The tectonic/volcanic fluctuations can be linked to climate models to explore the degree to which they could drive long time scale (~100 My) climate variations. The coupled models indicate that Pangea-driven tectonic fluctuations can lead to climate fluctuations consistent with data constraints. Global variations in the tectonic behavior of the Earth, linked to climate variations, has implication for understanding how the internal evolution of a planet can affect surface environments. We will end with some speculations on how that could feed into planetary habitability.
DS202202-0204
2022
Li, D., Fu, Y., Hollings, P., Mitchell, R.H., Zurevinski, S., Kamo, S., Zhang, R., Zhang, Y., Liu, Q., Liao, J., Liang, Y., Sun, X.PL57 garnet as a new natural reference material for in situ U-Pb isotope analysis and its perspective for geological applications.Contribution to Mineralogy and Petrology, Vol. 177, 19 , 18p. PdfGlobalgarnet

Abstract: Garnet is a common U-bearing mineral in various magmatic and metamorphic rocks with a high U-Pb closure temperature (>?850 °C), rendering it a potentially valuable U-Pb geochronometer. However, a high U (>?10 ppm) garnet reference material that suits both quadrupole and/or multi-collector inductively coupled plasma mass spectrometry (ICP-MS) is yet to be established. This study evaluates a potential reference material for in situ garnet U-Pb analysis with anomalously high U content from the Prairie Lake alkaline complex, Canada. The PL57 garnet, occurring in a calcite ijolite, has high TiO2 (6.5-15.0 wt%, average 12.7 wt%) and Fe2O3 (17.1-21.3 wt%) contents and is a member of the andradite (26-66 mol.%)-morimotoite (18-41 mol.%)-schorlomite (16-35 mol.%) solid solution series. Four samples were dated by U-Pb ID-TIMS to assess reproducibility. Twelve TIMS analyses produced concordant, equivalent results. Garnet PL57 yielded a concordant age of 1156.2?±?1.2 Ma (2?, n?=?10, MSWD?=?1.0), based on ten analyses with two results discarded due to possible mineral inclusions (if included, the concordia age is 1156.6?±?1.8 Ma; n?=?12, MSWD?=?2.0). PL57 had 27-76 ppm (average 41 ppm) U with Th/U of 0.51-0.68 (average 0.63). The total common Pb content ranged from 0.4 to 3.9 pg (average 1.1 pg). Laser ablation coupled with ICP-MS and high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging provide direct evidence that U is incorporated and homogeneously distributed within the garnet lattice rather than as defects or pore spaces. Published garnet samples and standards were then tested by calibrating the Willsboro, Mali, Qicun, and Tonglvshan garnet against PL57, which gave accurate ages within the recommended values. Case studies of garnet from the Archean Musselwhite orogenic gold deposit in Canada and the Cenozoic Changanchong and Habo skarn deposits in China yield reliable ages. This suggests that PL57 is a robust U-Pb isotope reference material. The limited variations of U and Pb isotopic ratios, together with the high U concentration and extremely low initial common Pb, make PL57 an ideal calibration and monitor reference material for in situ measurements.
DS202202-0205
2022
Lin, Y., van Westrenen, W., Mao, H-K.Oxygen controls on magmatism rocky exoplanets. Proceedings of the National Academy of Sciences, Vol. 78, 10.1073/pnas2110427118 6p. PdfCosmosmelting

Abstract: Refractory oxygen bound to cations is a key component of the interior of rocky exoplanets. Its abundance controls planetary properties including metallic core fraction, core composition, and mantle and crust mineralogy. Interior oxygen abundance, quantified with the oxygen fugacity (fO2), also determines the speciation of volatile species during planetary outgassing, affecting the composition of the atmosphere. Although melting drives planetary differentiation into core, mantle, crust, and atmosphere, the effect of fO2 on rock melting has not been studied directly to date, with prior efforts focusing on fO2-induced changes in the valence ratio of transition metals (particularly iron) in minerals and magma. Here, melting experiments were performed using a synthetic iron-free basalt at oxygen levels representing reducing (log fO2 = ?11.5 and ?7) and oxidizing (log fO2 = ?0.7) interior conditions observed in our solar system. Results show that the liquidus of iron-free basalt at a pressure of 1 atm is lowered by 105 ± 10?°C over an 11 log fO2 units increase in oxygen abundance. This effect is comparable in size to the well-known enhanced melting of rocks by the addition of H2O or CO2. This implies that refractory oxygen abundance can directly control exoplanetary differentiation dynamics by affecting the conditions under which magmatism occurs, even in the absence of iron or volatiles. Exoplanets with a high refractory oxygen abundance exhibit more extensive and longer duration magmatic activity, leading to more efficient and more massive volcanic outgassing of more oxidized gas species than comparable exoplanets with a lower rock fO2.
DS202203-0355
2022
Loginova, A.M., Serebryannikov, A.O., Sobolev, N.V.Compositional variations and rare paregeneses of multiple magnesiochromite inclusions in Yakutian diamonds.Doklady Earth Sciences, Vol. 501, pt. 1, pp. 919-924. pdfRussia, Yakutiacathodluminescence

Abstract: The zoning of diamonds was studied using cathodoluminescence (CL) and the chemical composition of mineral inclusions in six typical diamonds from kimberlites of Yakutia. The diamonds were ground on special equipment until inclusions with dimensions of 10-200 ?m were brought to the surface. The inclusions are characterized by a morphology reflecting the influence of the host diamonds. Multiple inclusions and intergrowths of magnesiochromite, olivine, pyrope, and phlogopite are located in both the central and peripheral zones of diamonds. In three diamonds, significant differences in the composition of magnesiochromites in different growth zones were observed, while in the other three such differences were not found. The overwhelming majority (five out of the six diamonds studied), according to the compositional features of magnesiochromite, olivine, and phlogopite, belong to the dunite-harzburgite paragenesis prevailing in diamonds from various diamond-bearing provinces of the Earth. In one of the diamonds, a lherzolite paragenesis, identified by the composition of the pyrope inclusion in magnesiochromite, was observed for the first time. The complex history of diamond growth and the variations in the chemical composition of the included minerals indicate the possibility of coexistence of syngenetic and protogenetic inclusions in the same diamond crystal.
DS202201-0024
2021
Lorenzon, S., Nestola, F., Pamato, M.G., Harris, J.Genesis and depth of formation of ferropericlase inclusions within superdeep diamonds.Goldshmidt2021, 1p. abstractSouth America, Brazil, Africa, Guineadeposit - Juina, Kankan

Abstract: Diamonds containing fluid and mineral inclusions that were trapped during formation are the only natural samples capable of probing the deepest portions of the Earth’s mantle (down to ~800 km depth). In order to precisely interpret the mineralogical and geochemical information they provide, the growth relationships between diamonds and inclusions (i.e., whether they formed before or during diamond formation) and the depth at which the inclusions were trapped need to be determined. Ferropericlase [(Mg,Fe)O] is the most abundant inclusion within super-deep diamonds (i.e., those forming between ~300 and more than 800 km depth). Experiments and numerical models using a pyrolitic bulk composition indicate that ferropericlase, comprising 16-20% of the mantle phase assemblage, is stable at depths between 660 and 2900 km and is Mg-rich with XFe ranging from 0.10 to 0.27 (1,2). However, ferropericlase represents 48-53% of the inclusions reported within super-deep diamonds and has a more variable Fe content, with XFe between 0.10 and 0.64 (3). In spite of different efforts explanations of these discrepancies, the precise origin of ferropericlase-bearing diamonds remains unclear. In this study we performed in-situ single-crystal X-ray diffraction analyses on a set of ferropericlase inclusions in super-deep diamonds from Juina (Brazil) and Kankan (Guinea), to determine inclusion-host crystallographic orientation relationships. These analyses were coupled with synchrotron X-ray tomographic microscopy in order to apply elastic and elasto-plastic geobarometry and determine the diamond depth of formation. Electron microprobe analyses on a set of inclusions that were released from the diamond hosts were also conducted to investigate possible relationships between crystallographic data and chemical composition. We assess the most likely scenario for the genesis of ferropericlase inclusions in super-deep diamonds, their depth distribution in the Earth’s mantle and their implications for mantle geochemistry.
DS202201-0025
2021
Madsen, A.C.Diamonds: diamond stories. ( only natural diamonds)Assouline Publishing, isbn 978-1649800114GlobalBook - notice

Abstract: Formed billions of years ago deep below the surface of the earth, natural diamonds have always had an ethereal mysticism about them. Once reserved only for royals, red carpets, and life’s most celebratory moments, diamonds were seen as symbols of wealth and prosperity that only few could access. But with a new century comes a new expression of luxury, as a new crop of young designers and heritage jewelry houses alike including Sabyasachi, Messika, Anita Ko, Boucheron, and Fernando Jorge are celebrating natural diamonds as an everyday indulgence. Today’s tastemakers are incorporating diamonds into their designs in unexpected ways, unafraid to play around with interesting cuts and colorful hues. In telling the story of today’s expression of natural diamonds and their continous impact on the world, this new volume dives into tales of the world’s most captivating stones, from the Hope Diamond to the legend of the Beau Sancy Diamond. Featuring stunning images; tall tales; and interviews with top designers, tastemakers, and enthusiasts alike; Diamonds is the definitive book on the world’s most sought-after jewel.
DS202205-0703
2021
Mansoor, M., Mansoor, M., Mansoor, M., Aksoy, A., Seyhan, S.N., Yildirim, B., Tahiri, A., Solak, N., Kazmanli, K., Er, Z., Czelej, K., Urgen, M.Ab-nitro calculation of point defect equilibria during heat treatment: nitrogen, hydrogen, and silicon doped diamond.Researchgate preprint Istanbul Technical University , 18p. PdfGlobaldiamond morphology

Abstract: Point defects are responsible for a wide range of optoelectronic properties in materials, making it crucial to engineer their concentrations for novel materials design. However, considering the plethora of defects in co-doped semiconducting and dielectric materials and the dependence of defect formation energies on heat treatment parameters, process design based on an experimental trial and error approach is not an efficient strategy. This makes it necessary to explore computational pathways for predicting defect equilibria during heat treatments. The accumulated experimental knowledge on defect transformations in diamond is unparalleled. Therefore, diamond is an excellent material for benchmarking computational approaches. By considering nitrogen, hydrogen, and silicon doped diamond as a model system, we have investigated the pressure dependence of defect formation energies and calculated the defect equilibria during heat treatment of diamond through ab-initio calculations. We have plotted monolithic-Kröger-Vink diagrams for various defects, representing defect concentrations based on process parameters, such as temperature and partial pressure of gases used during heat treatments of diamond. The method demonstrated predicts the majority of experimental data, such as nitrogen aggregation path leading towards the formation of the B center, annealing of the B, H3, N3, and NVHx centers at ultra high temperatures, the thermal stability of the SiV center, and temperature dependence of NV concentration. We demonstrate the possibility of designing heat treatments for a wide range of semiconducting and dielectric materials by using a relatively inexpensive yet robust first principles approach, significantly accelerating defect engineering and high-throughput novel materials design.
DS202203-0356
2022
Manuilova, E.A.The relationships of the dislocations of the basement and sedimentary cover with the newest structural plan of the west Siberian plate.Moscow University Bulletin, Vol. 76, 5, pp. 425-500.Russiacraton

Abstract: Comparison of the newest structural plan of the West Siberian Plate with the dislocations of the basement and sedimentary cover allowed us to rank the latest plicative and disjunctive structures by the degree of inheritance. As a result, the inherited, reversed, and newly formed plicative structural forms were distinguished. It is shown that the orientation of ancient structures differs from the modern ones and the inheritance occurs only fragmentarily. The inherited and newly formed faults were distinguished by comparison of the newest faults with the ancient ones. The discovered inherited newest structures may be considered as promising areas for prospecting for hydrocarbon deposits.
DS202205-0704
2022
Maritz, L., Pillay, D., Branch, G.M.The ecology of coastal wetland ponds created by diamond mining in southern Namibia. 1. Physical Conditions.African Journal of Marine Science, Vol. 44, 1, pp. 49-60.Africa, Namibiamining

Abstract: Coastal diamond mining in southern Namibia involves constructing seawalls to hold the sea at bay, and seaward accretion of the shoreline by up to 800 m opens what was previously the surf zone for excavation and extraction of bedrock alluvial diamonds. This has created large coastal wetland ponds of up to 380 000 m2 as the sea overtops the seawalls or seeps into the excavated areas. The ages of these ponds span 1-38 years. We investigated physical conditions in the ponds to determine whether they can function as saline wetlands equivalent to blind estuaries. Water temperatures were 6-10 °C higher than in the sea, as expected of shallow enclosed waterbodies. Dissolved oxygen was 82-137%, peaking at midday owing to photosynthesis, and the ponds were never hypoxic. Correlated with oxygen levels, pH values spanned 7.7-8.3, and always exceeded the pH of seawater. Chlorophyll a concentrations matched or exceeded the levels in seawater, reaching 76 µg l?1. The southern and central ponds had salinities close to those of seawater, but the salinity of northern ponds exceeded 80 after ?15 years, thus limiting their capacity to support wetland communities. Apart from this, these ponds are viable habitat that can support flora and fauna typical of saline wetlands, a habitat that is scarce along this arid coastline.
DS202205-0705
2022
Maritz, L., Pillay, D., Branch, G.M.The ecology of coastal wetland ponds created by diamond mining in southern Namibia. 2. Saltmarsh vegetation.African Journal of Marine Science, Vol. 44, 1, pp. 61-68.Africa, Namibiamining

Abstract: Coastal diamond mining in southern Namibia involves constructing seawalls to hold the sea at bay, and seaward accretion of the shoreline by up to 800 m opens what was previously the surf zone for excavation and extraction of bedrock alluvial diamonds. This has created large coastal wetland ponds of up to 380 000 m2 as the sea overtops the seawalls or seeps into the excavated areas. The ages of these ponds span 1-38 years. We investigated physical conditions in the ponds to determine whether they can function as saline wetlands equivalent to blind estuaries. Water temperatures were 6-10 °C higher than in the sea, as expected of shallow enclosed waterbodies. Dissolved oxygen was 82-137%, peaking at midday owing to photosynthesis, and the ponds were never hypoxic. Correlated with oxygen levels, pH values spanned 7.7-8.3, and always exceeded the pH of seawater. Chlorophyll a concentrations matched or exceeded the levels in seawater, reaching 76 µg l?1. The southern and central ponds had salinities close to those of seawater, but the salinity of northern ponds exceeded 80 after ?15 years, thus limiting their capacity to support wetland communities. Apart from this, these ponds are viable habitat that can support flora and fauna typical of saline wetlands, a habitat that is scarce along this arid coastline.
DS202204-0529
2022
Massonne, H-J., Fockenberg, T.Melting of phengite-bearing eclogite at pressures of 4 and 9 GPA relevant to deep regions of a subduction zone.Earth and Planetary Science Letters, Vol. 584, 14p. 117475Mantlesubduction

Abstract: Melting experiments undertaken with finely ground powder of phengite-bearing eclogite yielded solidus temperatures of about 970 °C at 4 GPa and 1250 °C at 9 GPa. Additional experiments with a rock powder of psammopelitic composition established a solidus at 9 GPa at a temperature of 1350 °C. Initial melts produced from both rocks are rich in potassium. The melts generated from eclogite tend to become richer in Na and Ca with rising temperature due to increasing decomposition of clinopyroxene. At the maximum temperatures of the experiments with eclogite, up to 450 °C above the solidus at 4 GPa, this phase is still present in the restite together with abundant garnet. In the temperature interval of 1100-1300 °C, when 22-30% of the studied eclogite was melted, the melts are quartz monzonitic in composition. According to the reported experimental results, we suggest that partial melting of oceanic crust is unlikely in a subduction zone. However, ascending melange diapirs, composed of material from the upper portion of a deep-seated subducted oceanic slab, can partially melt in the hot mantle wedge. The thus generated melts further ascend to contribute to lavas of magmatic arc systems.
DS202205-0706
2022
Meisel, T.C., Webb, P.C. , Rachetti, A.Highlights from 25 years of the GeoPT programme: what can be learnt for the advancement of geoanalysis. Geostandards and Geoanalytical Research, 21p. Open accessGlobalGeoPT

Abstract: Data submitted over the past 25?years to GeoPT, the highly successful proficiency-testing programme for the geochemical analysis of geological materials, organised by the International Association of Geoanalysts, provide a valuable resource that permits detailed investigation of contrasting results associated with different sample preparation and measurement principles. Highlighted issues include the following: recurring problems with the dissolution of the refractory minerals zircon and chromite, which produce a large dispersion in data obtained when acid digestion is involved; issues related to different XRF sample preparation methods, whereby a significant divergence of pressed powder pellet results compared with those from fused glass discs is observed; high relative dispersion of data both at low mass fractions, and those higher than normally found in silicate rocks, due to incomplete method validation, in particular due to an overconfidence in estimating reporting limits and to the employment of limited working ranges. In addition, an example for Sr in an ancient pegmatite with extremely high Rb abundance is presented, where ICP-MS results amount to only to a third of the XRF results, severely underestimated due to the disregard of the radiogenic ingrowth from 87Rb decay. Recommendations are made both for improving data quality and the selection of test materials for future GeoPT rounds.
DS202205-0707
2022
Mikhailenko, D., Aulbach, S., Korsakov, A.V., Xu, Y-g., Kaminsky, F.V.Titanite in coesite-kyanite-bearing eclogite from kimberlite pipe Udachnaya.Doklady Earth Science, Vol. 503, pp. 206-212.Russiadeposit - Udachnaya

Abstract: The mineralogical and geochemical features of titanite and associated minerals in a rare sample of kyanite-coesite-rutile-bearing eclogite from the Udachnaya-East (Vostochnaya) kimberlite pipe have been studied in detail. Subidiomorphic titanite grains (100-300 ?m) were identified in the intergranular space. The composition of individual grains of titanite is characterized by a constant presence of Al2O3, F, P2O5, Zr, and Sr impurities but varies within the xenolith. Based on the absence of titanite inclusions in the rock-forming minerals and their presence in the intergranular space, titanite was formed in the studied sample at a late stage of its formation, most likely in the process of metasomatic action of the fluid/melt. Crystallization of rock-forming minerals (garnet + omphacite + kyanite) and accessory rutile occurred jointly at 3.5 ± 0.32 GPa and 920 ± 65°?. The value of Eu/Eu* = 1.06 in the reconstructed bulk composition of the rock, the high modal content of kyanite (~17 vol %), and the value of Ca# = Ca/(Ca + Mg + Fe + Mn) > 0.5 in garnet indicate a subduction nature of the studied eclogite. Most likely, the formation of titanite in the studied sample occurred as a result of the metasomatic action of a fluid/melt enriched in calcium, strontium, large lithophilic elements, and lead, by a mechanism similar to the formation of eclogites in the units of the Western Tien Shan.
DS202203-0357
2021
Molle, V., Gaillard, F., Nabyl, Z., Tuduri, J., Di Carlo, I., Erdmann, S.Crystallisation sequence of a REE-rich carbonate melt: an experimental approach. Bastanaesite, natrocarbonatiteComptes Rendus Geoscience, Vol. 353, no S2, pp. 217-231.Globalcarbonatite

Abstract: Carbonatites host Earth’s main REE deposits, with bastnaesite (LREE)CO F being the main economic REE-bearing mineral. However, bastnaesite mineralisation processes are debated between hydrothermal or magmatic origin. This study aims to assess if bastnaesite can be magmatic, and to characterise the REE behaviour during carbonatite crystallisation. Crystallisation experiments have been performed from 900 to 600 °C at 1 kbar, on a REE-rich calciocarbonatitic composition. REE-bearing calcite is the dominant crystallising mineral, driving the residual melt towards natrocarbonatitic compositions. Both halogens (i.e., Cl and F) and water decrease the temperature of calcite saturation. REE are slightly incompatible with calcite: for all REE, partition coefficients between carbonate melt and calcite are comprised between 1 and 11, and increase with temperature decrease. Britholite (REE, Ca) (Si,P)O) (F,OH) crystallises at high temperatures (700-900 °C), while pyrochlore (Ca,Na,REE) NbO (OH,F) crystallises at low temperatures (600-700 °C), as well as REE-rich apatite (600-650 °C). No bastnaesite is found in crystallisation experiments. We thus performed a bastnaesite saturation experiment at 600 °C. The bastnaesite-saturated melt contains 20 wt% of REE: such magmatic saturation is unlikely to happen in nature. Textural evidences imply a Na, Cl, REE-rich fluid at high temperatures and hydrous conditions. We propose that fluids are the main mineralising agent for bastnaesite at hydrothermal stage (600 °C).
DS202202-0206
2022
Montagner, J-P., Burgos, G., Capdeville, Y., Beucler, E., Mocquet, A.The mantle transition zone dynamics as revealed through seismic anisotropy.Tectonophysics, Vol. 821, 229133, 11p. PdfMantlegeophysics - seismics

Abstract: The mantle transition zone (MTZ) of the Earth lies between 410 and ?1000 km in depth and has a key role in mantle convection processes. In particular, the discontinuity at 660 km and its associated endothermic mineralogical transformation can slow or inhibit the passage of matter between the upper and lower mantle. The MTZ thus acts as a boundary layer within the mantle. The depth variations of radial and azimuthal seismic anisotropies enable the detection of boundary layers within the mantle. However, the 3D imaging is difficult due to the lack of sensitivity of surface waves of fundamental modes, and the poor global coverage of this depth range by body-wave data. We present a new 3D general anisotropy model (both radial and azimuthal anisotropies) of the mantle down to 1200 km in depth using surface-wave overtone datasets. We find that there is little seismic anisotropy in most of the MTZ, except below subduction zones around the Pacific Ocean and, more surprisingly, in a large area beneath eastern Eurasia where the Pacific subducting plate is stagnant. Seismic anisotropy is usually associated with intense deformation processes but also possibly to water transportation or to fine layering. This significant anisotropy in this part of MTZ might reveal a large water ‘reservoir’ associated with hydrous minerals or a strong stratification. It reflects a complex history beneath central Asia, where the Tethys, Izanagi and Pacific plates appear to have strongly interacted during the last 100 My, having subducted in orthogonal directions under the Asian continent, with the Tethys plate descending into the lower mantle, and the Izanagi plate remaining stagnant in the MTZ. The Asian continent is the only region in the world where subducting slabs originating from different plates can interact. This unique slab distribution might explain why some plates descend while others remain in the lower transition zone.
DS202205-0708
2022
Moore, A.E., Cotterill, F.P.D., Main, M., Williams, H.B.The Zambesi: origins and legacies of Earth's oldest river system.Chapter , on requestAfrica, Angola, Zambia, Botswana, Zimbabwe, MozambiqueHistory

Abstract: The Zambezi rises with considerable modesty in north-west Zambia from a small spring on the gentle upland of the Southern Equatorial Divide - the watershed that separates the river from north-west-flowing tributaries of the Congo. The evolution of the Zambezi River has repeatedly modified the distribution of riverine plant and animal species. The hydrology of the Zambezi is further influenced by water exploitation by different users, along its main channel and tributaries. The dams have had severe ecological impacts on the major floodplains, as a result of the reduction of the supply of water and sediment. The major Early Cretaceous Zambezi-Limpopo River system entered the Mozambique coastal plain via a line of crustal weakness that was exploited by a major west-north-west trending dyke swarm. Drainage evolution of the Palaeo-Chambeshi system has been invoked as the primary cause of the recent evolution of the molerats.
DS202201-0027
2021
Mukakami, M., Goncharov, A,F., Miyajimac, N., Yamazakid, D., Holtgrewe, N.Radiative thermal conductivity of single-crystal bridgmanite at the core-mantle boundary with implications for thermal evolution of the Earth.Earth and Planetary Science Letters, Vol. 578, 9p. PdfMantlebridgmanite

Abstract: The Earth has been releasing vast amounts of heat from deep Earth's interior to the surface since its formation, which primarily drives mantle convection and a number of tectonic activities. In this heat transport process the core-mantle boundary where hot molten core is in direct contact with solid-state mantle minerals has played an essential role to transfer thermal energies of the core to the overlying mantle. Although the dominant heat transfer mechanisms at the lowermost mantle is believed to be both conduction and radiation of the primary lowermost mantle mineral, bridgmanite, the radiative thermal conductivity of bridgmanite has so far been poorly constrained. Here we revealed the radiative thermal conductivity of bridgmanite at core-mantle boundary is substantially high approaching to ?5.3±1.2 W/mK based on newly established optical absorption measurement of single-crystal bridgmanite performed in-situ under corresponding deep lower mantle conditions. We found the bulk thermal conductivity at core-mantle boundary becomes ?1.5 times higher than the conventionally assumed value, which supports higher heat flow from core, hence more vigorous mantle convection than expected. Results suggest the mantle is much more efficiently cooled, which would ultimately weaken many tectonic activities driven by the mantle convection more rapidly than expected from conventionally believed thermal conduction behavior.
DS202202-0207
2021
Mukherjee, S., Ray, L., Maurya, S., Shalivahan, K.P.Nature of the lithosphere boundary beneath the eastern Dharwar craton of the Indian Shield.Journal of Asian Earth Sciences, in press available 10.1016/j.jseaes.2021.105701 46 p. PdfIndiaCraton

Abstract: The lithosphere-asthenosphere boundary (LAB) is a fundamental element of the plate tectonic hypothesis that accommodates the differential motion of rigid lithosphere over the weaker asthenosphere. In recent times, various usages have been used to define the LAB, depending on the nature of their measurements. Here, we investigate the lithospheric structure beneath the Eastern Dharwar Craton (EDC) of the Indian Shield using geochemical, thermal and seismological data sets. We analysed S-receiver functions from the stations deployed in the EDC along with the surface wave dispersion tomography. We also added thermal measurements from 5 different locations and geochemical data from 34 Kimberlite/Lamproite xenolith samples to constrain the nature of the LAB. The seismological measurements using Rayleigh wave dispersion and receiver function analysis indicate the lithospheric thickness of 98-118 and 94-118 km respectively, with sharp transition across the LAB. The P-T results from xenoliths are interpreted in concurrence with the heat-flow measurements suggesting a thick thermal lithosphere of ?200 km for the normal mantle solidus with cold geotherm. To reconcile our observations, we invoke partial melts or enriched in volatiles, which significantly lowers the viscosity of mantle rocks inducing a zone of weakness between the rigid lithosphere (?125km) and the convective asthenosphere. Further, we favour the view that the thick lithosphere beneath the Indian plate has been thinned by a plume during the Gondwanaland breakup at ?130Ma. The presence of younger kimberlites from the Indian shield support that it is further degenerated by the delamination leading to an uneven topography in the LAB.
DS202202-0208
2022
Murakami, M., Goncharov, A.F., Miyajima, N., Yamazaki, D., Holtgrewe, N.Radiative thermal conductivity of single-crystal bridgmanite at the core-mantle boundary with implications for thermal evolution of the Earth.Earth and planetary Science Letters, Vol. 578, 117328, 9p. PdfMantlebridgmanite

Abstract: The Earth has been releasing vast amounts of heat from deep Earth's interior to the surface since its formation, which primarily drives mantle convection and a number of tectonic activities. In this heat transport process the core-mantle boundary where hot molten core is in direct contact with solid-state mantle minerals has played an essential role to transfer thermal energies of the core to the overlying mantle. Although the dominant heat transfer mechanisms at the lowermost mantle is believed to be both conduction and radiation of the primary lowermost mantle mineral, bridgmanite, the radiative thermal conductivity of bridgmanite has so far been poorly constrained. Here we revealed the radiative thermal conductivity of bridgmanite at core-mantle boundary is substantially high approaching to ?5.3±1.2 W/mK based on newly established optical absorption measurement of single-crystal bridgmanite performed in-situ under corresponding deep lower mantle conditions. We found the bulk thermal conductivity at core-mantle boundary becomes ?1.5 times higher than the conventionally assumed value, which supports higher heat flow from core, hence more vigorous mantle convection than expected. Results suggest the mantle is much more efficiently cooled, which would ultimately weaken many tectonic activities driven by the mantle convection more rapidly than expected from conventionally believed thermal conduction behavior.
DS202203-0358
2021
Nabyl, Z., Gaillard, F., Turduri, J., Di Carlo, I.No direct effect of F, Cl, and P on REE partitioning between carbonate and alkaline silicate melts.Comptes Rendus Geoscience, Vol. 353, no S2, pp. 233-272. pdfGlobalcarbonatites

Abstract: This study presents new insights into the effects of halogens (F and Cl) and phosphorous (P) on rare earth element (REE) partitioning between carbonatite and alkaline silicate melts. F, Cl and P are elements that are abundant in carbonatites and alkaline magmatic systems and they are considered to play an important role on the REE behaviour. Nonetheless, their effect on REE partitioning between carbonate and alkaline silicate melts has not yet been constrained. Here we present new experimental data on REE partitioning between carbonate and alkaline silicate melts doped in F, Cl and P, in order to (1) test the Nabyl et al. [2020] REE partitioning model in F-, Cl- and P-rich systems, and (2) identify the possible role of F, Cl and P in carbonate melt REE enrichments during alkaline–carbonatite magma differentiation. The experiments were performed at 850–1050 °C and 0.8 GPa using piston-cylinder devices. Starting materials consisted of carbonatite and phonolite compositions doped in F, Cl and P. The experimental results show that REE partitioning is similar in F-Cl-P-rich and -poor systems. The silicate melt composition and its molecular structure (i.e. SiO contents, the alumina saturation index and the alkali/alkaline-earth element ratio), which have already been identified as controlling REE partitioning in F-, Cl- and P-poor systems, still operate in doped systems. No direct effect of the F, Cl or P melt concentrations on REE partitioning has been identified. We also propose an application to natural systems.
DS202203-0359
2022
Nance, R.D., Murphy, J.B.The supercontinent cyle and the proxy case for Pannotia.Academia.edu, 18 ppts. PdfAfricageotectonics

Abstract: Disagreement about the existence of the late Neoproterozoic supercontinent Pannotia highlights the limitation of defining supercontinents simply on the basis of size, which, for pre-Pangaean supercontinents, is difficult to determine. In the context of the supercontinent cycle, however, supercontinent assembly and break-up, respectively, mark the end of one cycle and the beginning of the next and can be recognized by the tectonic, climatic and biogeochemical trends that accompany them. Hence supercontinents need only be large enough to influence mantle circulation in such a way as to enable the cycle to repeat.
DS202201-0028
2021
Newman, R.Diamonds: their history, sources, qualities and benefits.Firefly Books, Richmond Hill, Ontario, isbn 978-0228103318 272p. GlobalBook - notice

Abstract: The beauty and sparkle and mystique of diamonds is unmatched by that of any other gem in the world. Since early times, diamonds have been treasured as good luck charms, remarkable tools and status symbols and have been worn, collected and presented as lavish gifts. Today, diamonds remain among the most sought-after gemstones and continue to hold their value through good times and bad. In Diamonds, author Renée Newman, a graduate gemologist and author of many trade-level handbooks on gemstones, invites the reader on a journey into the fascinating world of diamonds. This lavishly illustrated guide -- which features hundreds of photos, maps and diagrams -- covers everything from mining, cutting and evaluating diamonds to the romantic histories of some of the world's most valuable stones.
DS202205-0709
2022
Niayzova, S., Kopylova, M., Gaudet, M., de Stefano, A.Petrographic and geochemical characteristics associated with felsic xenolith assimilation in kimberlite.Canadian Mineralogist, Vol. 60, 2, pp. 283-307.Canada, Quebecdeposit - Renard

Abstract: Assimilation of country rock xenoliths by the host kimberlite can result in the development of concentric reaction zones within the xenoliths and a reaction halo in the surrounding contaminated kimberlite. Petrographic and geochemical changes across the reaction zones in the xenoliths and the host kimberlite were studied using samples with different kimberlite textures and contrasting xenolith abundances from the Renard 65 kimberlite pipe. The pipe, infilled by Kimberley-type pyroclastic (KPK) and hypabyssal kimberlite (HK) and kimberlite with transitional textures, was emplaced into granitoid and gneisses of the Superior Craton. Using samples of zoned, medium-sized xenoliths of both types, mineralogical and geochemical data were collected across xenolith-to-kimberlite profiles and contrasted with those of fresh unreacted country rock and hypabyssal kimberlite. The original mineralogy of the unreacted xenoliths (potassium feldspar-plagioclase-quartz-biotite in granitoid and plagioclase-quartz-biotite-orthopyroxene in gneiss) is replaced by prehnite, pectolite, and diopside. In the kimberlite halo, olivine is completely serpentinized and diopside and late phlogopite crystallized in the groundmass. The xenoliths show the progressive degrees of reaction, textural modification, and mineral replacement in the sequence of kimberlite units KPK — transitional KPK — transitional HK. The higher degree of reaction observed in the HK-hosted xenoliths as compared to the KPK-hosted xenoliths in this study and elsewhere may partly relate to higher temperatures in xenoliths included in an HK melt. The correlation between the degree of reaction and the kimberlite textures suggests that the reactions are specific to and occur within each emplaced batch of magma and cannot result from external post-emplacement processes that should obliterate the textural differences across the kimberlite units. Xenolith assimilation may have started in the melt, as suggested by the textures in the xenoliths and the surrounding halos and proceeded in the subsolidus. Elevated CaO at the kimberlite-xenolith contact appears to be an important factor in producing the concentric mineralogical zoning in assimilated xenoliths.
DS202204-0530
2022
Niyazova, S., Kopylova, M., Gaudet, M.Petrographic and geochemical characteristics associated with felsic xenolith assimilation in kimberlite.The Canadian Mineralogist, Vol. 60, pp. 1-25. pdfCanada, Quebecdeposit - Renard

Abstract: Assimilation of country rock xenoliths by the host kimberlite can result in the development of concentric reaction zones within the xenoliths and a reaction halo in the surrounding contaminated kimberlite. Petrographic and geochemical changes across the reaction zones in the xenoliths and the host kimberlite were studied using samples with different kimberlite textures and contrasting xenolith abundances from the Renard 65 kimberlite pipe. The pipe, infilled by Kimberley-type pyroclastic (KPK) and hypabyssal kimberlite (HK) and kimberlite with transitional textures, was emplaced into granitoid and gneisses of the Superior Craton. Using samples of zoned, medium-sized xenoliths of both types, mineralogical and geochemical data were collected across xenolith-to-kimberlite profiles and contrasted with those of fresh unreacted country rock and hypabyssal kimberlite. The original mineralogy of the unreacted xenoliths (potassium feldspar-plagioclase-quartz-biotite in granitoid and plagioclase-quartz-biotite-orthopyroxene in gneiss) is replaced by prehnite, pectolite, and diopside. In the kimberlite halo, olivine is completely serpentinized and diopside and late phlogopite crystallized in the groundmass. The xenoliths show the progressive degrees of reaction, textural modification, and mineral replacement in the sequence of kimberlite units KPK — transitional KPK — transitional HK. The higher degree of reaction observed in the HK-hosted xenoliths as compared to the KPK-hosted xenoliths in this study and elsewhere may partly relate to higher temperatures in xenoliths included in an HK melt. The correlation between the degree of reaction and the kimberlite textures suggests that the reactions are specific to and occur within each emplaced batch of magma and cannot result from external post-emplacement processes that should obliterate the textural differences across the kimberlite units. Xenolith assimilation may have started in the melt, as suggested by the textures in the xenoliths and the surrounding halos and proceeded in the subsolidus. Elevated CaO at the kimberlite-xenolith contact appears to be an important factor in producing the concentric mineralogical zoning in assimilated xenoliths.
DS202204-0531
2022
Novikov, D.A., Ilin, A.V., Kashnirtsev, V.A., Chernykh, A.V., Pyryaev, A.N.Geochemistry of brines and oil occurrences in the Udachnaya kimberlite pipe ( Siberian platform).Russian Geology and Geophysics, Vol. 63, pp. 166-183.Russia, Siberiadeposit - Udachnaya

Abstract: Results of a geochemical study of brines and oil occurrences in the Udachnaya kimberlite pipe are presented. Like other intrusions in the Daldyn-Alakit diamondiferous region, this diamond deposit is a unique cryohydrogeologic microstructure differing from the host sedimentary rocks and other diamond pipes of the Yakutian diamond-bearing province. Two waterlogged zones distinguished in the section of orebodies at the explored depths of the deposit correspond to the upper and middle Cambrian aquifers. Predominantly acidic (average pH = 5.5) Cl-Ca and Cl-Ca-Na brines with TDS from 94.3 to 391.3 g/dm3 are widespread within the orebodies and host rocks. The brine mineralization and contents of major salt-forming components increase with depth, to the horizon at the -365 m elevation, where TDS reaches 391 g/dm3, while below, at the -650 m level with noted hydrogeochemical-field inversion, TDS is 253 g/dm3. The mineralization of Cl-Ca, Cl-Ca-Na, Cl-Ca-Mg, and Cl-Ca-Mg-Na brines in the upper Cambrian rocks varies from 102.9 to 192.9 g/dm3, and the pH values, from 4.9 to 6.2, averaging 5.6. Among the microcomponents, the highest average concentrations (mg/dm3) are found for Br1292.8 > S875.7 > Sr453.7 > Fe79.7 > Li53.4 > B32.7 > I13.3 > Si10.8 > Mn6.4 > Se3.6 > Rb2.3. The values of genetic coefficients vary widely: The rNa/rCl coefficient ranges from 0.18 to 0.31; rCa/rMg, from 1.03 to 3.60; Ca/Cl, from 0.2 to 0.3; and the integrated metamorphism index S (according to S.L. Shvartsev) varies from 193 to 277. The middle Cambrian rock complex, containing more saline brines, has been examined in much more detail. It hosts Cl-Ca, Cl-Ca-Na, Cl-Ca-Mg, and Cl-Na-Mg brines with TDS from 94.3 to 391.3 g/dm3 and high average concentrations (mg/dm3) of microcomponents: Br2224.9 > Sr1024.9 >S500.1 > B202.9 > Li147.1 > Fe97.0 > I33.2 > Rb11.4 > Si9.6 > Se9.5 > Mn3.6 > Ni1.7. As compared with brines in the overlying rocks, the middle Cambrian brines show a wider variation in element ratios: rNa/rCl from 0.14 to 0.34, rCa/rMg from 0.66 to 9.71, and Ca/Cl from 0.03 to 0.45. These brines are also characterized by a significantly higher metamorphism grade, which is indicated not only by the rNa/rCl and rCa/rMg ratios but also by the S index varying from 278 to 316. The composition of stable isotopes ?D and ?18O) and dissolved inorganic carbon ?13C) of the brines was investigated. The studied waters are assumed to be of sedimentary-metamorphic origin. Their isotopic composition reflects the climatic conditions existing at the time of their burial, which were probably aggravated by the contribution of the oxygen isotope exchange with water-bearing rocks. The ?13C values of carbon dioxide dissolved in water allow an inference about its biogenic origin. The biogenic carbon isotope exchange is governed by the relationship between methanogenic and SMT processes. Analysis of the 87Rb/86Sr and 87Sr/86Sr isotope ratios of the studied brines has revealed affinity between the isotopic compositions of waters in the Cambrian deposits and in ancient seawaters. The mass chromatograms of saturated-hydrocarbon (HC) fractions show at least two individual types of oils and malthas (naphthides). The third variety resulted from their mixing at different stages of migration. The fourth is from the contact zone; it changed during the explosion of kimberlites. The first, most common, type of naphthides (“postexplosive”) is similar in all geochemical parameters to oils from the Nepa-Botuobiya anteclise, in particular, to those from the Mirnyi arch. Oils of the second (pre-explosive) type are found only in the Udachnaya Formation, within the depth range 1130-1430 m.
DS202203-0360
2022
Nutman, A.P.Seeking Earth's oldest geological record: an unexpected discovery of well preserved 3834 Ma metatonalite.Australian Journal of Earth Science, Vol. 69, pp. 188-199. Europe, Greenlandgeochronology

Abstract: One of Greenland’s largest bodies of Archean (meta)sedimentary rocks occurs on the ?5.5 by 2.0?km nunatak Isortup Nunataa (?65°31?N 49°54?W) and is ?35?km north of the Eoarchean Isua supracrustal belt with its world’s best record of early sedimentary and volcanic systems. The nunatak was visited to ascertain if its metasedimentary rocks are also Eoarchean and thereby provide extra insight into the early Earth. The metasedimentary rocks are derived from a ca 3060?Ma arc-like volcanogenic source and can be assigned to the Akia terrane that crops out immediately to the west. However, glacial erratics scattered over the nunatak indicate there are well-preserved Eoarchean rocks including 3834?Ma metatonalite hidden to the east under the Inland Ice. This demonstrates there are still occurrences of Eoarchean rocks out there to be found-by a mix of logic and luck. These findings will all enhance our knowledge of the early Earth, to help answer the big questions about the important early events that shaped our planet.
DS202201-0026
2021
NWT & Nunavut Chamber of MinesEkati future.Northern Mining News - November 2021, Vol 15, No. 11, pages 7-8Canada, Northwest Territoriesdeposit - Ekati
DS202205-0710
2022
Ontario Geological SurveyRecommendation for exploration special edition: Critical mineral compilation 2000-2022., Apr. 26, 329p. FreeCanada, OntarioREE

Abstract: Pdf, 150MB, 329 pages.
DS202201-0029
2021
Oskin, B.Deep mantle krypton reveals Earth's outer solar system ancestry. * not specifc to diamondslettersandscience.ucdavis.edu, Dec. 14, 2p.Mantlekrypton

Abstract: Krypton from the Earth's mantle, collected from geologic hot spots in Iceland and the Galapagos Islands, reveals a clearer picture of how our planet formed, according to new research from the University of California, Davis. The different isotopes of krypton are chemical fingerprints for scientists sleuthing out the ingredients that made the Earth, such as solar wind particles and meteorites from the inner and outer solar system. The findings indicate Earth's volatile elements -- essentials such as carbon, water and nitrogen -- arrived as Earth was growing and becoming a planet. This contradicts the popular theory that Earth's volatile elements were mostly delivered near the end of Earth's formation, which is marked by the moon-forming giant impact. Instead, the krypton isotopes suggest planetesimals from the cold outer solar system bombarded the Earth early on, millions of years before the big crunch. The young Earth also hoovered up dust and gas from the solar nebula (the cloud surrounding the sun) and was bombarded by meteorites. "Our results require concurrent delivery of volatiles from multiple sources very early in Earth's formation," said Sandrine Péron, the lead author of the study. Péron, currently a Marie Sk?odowska-Curie Actions Fellow at ETH Zürich in Switzerland, conducted the research at UC Davis as a postdoctoral fellow working with Professor Sujoy Mukhopadhyay in the Department of Earth and Planetary Sciences." This study provides clues for the sources and timing of volatile accretion on Earth, and will help researchers better understand how not only Earth formed, but also other planets in the solar system and around other stars," Péron said. The study is published Dec. 15 in the journal Nature.
DS202204-0532
2022
Ozaydin, S., Selway, K., Griffin, W.L., Moorkamp, M.Probing the southern African lithosphere with magnetotellurics, Part II, linking electrical conductivity, composition and techonomagamatic evolution.Journal of Geophysical Research: Solid Earth, doi: 10.1029/2021JB023105Africageophysics

Abstract: The present-day composition of Earth's tectonic plates results from past geological processes. We can learn about Earth's composition from deep rock samples that are carried to the surface during volcanic eruptions and by probing its physical properties, like electrical conductivity, with geophysics. In southern Africa, there are extensive deep rock samples, which have been brought to the surface by kimberlite volcanoes that also host diamonds, and also extensive geophysical data. In this article, we compare the rock compositions with electrical conductivity to learn more about Earth's composition. Our results show that the oldest parts of the plates, which retain compositions similar to their initial composition, appear resistive. On the other hand, regions that have been intruded by deep fluids or molten rock can be resistive or conductive, depending on the types of minerals that were formed during the intrusion. The kimberlite volcanoes mostly erupted through the edges of the most resistive parts of the plates and did not erupt through the conductors. These results will help us to make more accurate interpretations about the composition of parts of the Earth where we do not have deep rock samples.
DS202205-0711
2021
Ozaydin, S., Selway, K., Griffin, W.L., Moorkamp, M.Probing the southern African lithosphere with magnetotellurics: 2 linking electrical conductivity, composition, and tectonomagmatic evolution.Journal of Geophysical Research, 10.1029/2021JB023105, 28p.Africa, South Africageophysics - magnetotellurics

Abstract: The present-day composition of Earth's tectonic plates results from past geological processes. We can learn about Earth's composition from deep rock samples that are carried to the surface during volcanic eruptions and by probing its physical properties, like electrical conductivity, with geophysics. In southern Africa, there are extensive deep rock samples, which have been brought to the surface by kimberlite volcanoes that also host diamonds, and also extensive geophysical data. In this article, we compare the rock compositions with electrical conductivity to learn more about Earth's composition. Our results show that the oldest parts of the plates, which retain compositions similar to their initial composition, appear resistive. On the other hand, regions that have been intruded by deep fluids or molten rock can be resistive or conductive, depending on the types of minerals that were formed during the intrusion. The kimberlite volcanoes mostly erupted through the edges of the most resistive parts of the plates and did not erupt through the conductors. These results will help us to make more accurate interpretations about the composition of parts of the Earth where we do not have deep rock samples.
DS202201-0030
2021
Palyanovx, Y.N.,, Borzdovi, Y.M., Kupriyanov, I.N., Khohkhryakov, A.F.,, Nechaev, D.V.Rare - earth metal catalysis for high pressure synthesis of rare diamonds.Nature Communications, https://doi.org/10.1038/s41598-021-88038-5 12p.GlobalREE

Abstract: The combination of the unique properties of diamond and the prospects for its high-technology applications urges the search for new solvents-catalysts for the synthesis of diamonds with rare and unusual properties. Here we report the synthesis of diamond from melts of 15 rare-earth metals (REM) at 7.8 GPa and 1800-2100 °C. The boundary conditions for diamond crystallization and the optimal parameters for single crystal diamond synthesis are determined. Depending on the REM catalyst, diamond crystallizes in the form of cube-octahedrons, octahedrons and specific crystals bound by tetragon-trioctahedron and trigon-trioctahedron faces. The synthesized diamonds are nitrogen-free and belong to the rare type II, indicating that the rare-earth metals act as both solvent-catalysts and nitrogen getters. It is found that the REM catalysts enable synthesis of diamond doped with group IV elements with formation of impurity-vacancy color centers, promising for the emerging quantum technologies. Our study demonstrates a new field of application of rare-earth metals.
DS202203-0361
2022
Patel, A., Mishra, B., Upadhyay, D., Pruseth, K.L.Mineralogical and geochemical evidence of dissolution-reprecipitation controlled hydrothermal rare earth mineralization in the Amba Dongar carbonatite complex, Gujarat, western India.Economic Geology, Vol. 117, pp. 683-702.Indiadeposit - Amba Dongar

Abstract: The Amba Dongar carbonatite complex in western India comprises an inner ring of carbonatite breccia surrounded by a sövite ring dike. The various carbonatite units in the body include calcite carbonatite, alvikite, dolomite carbonatite, and ankerite carbonatite. The carbonate phases (calcite and ankerite) occur as phenocrysts, groundmass phases, fresh primary grains, and partially altered grains and/or pseudomorphs when hydrothermally overprinted. Rare earth element (REE) enrichment in the groundmass/altered calcite grains compared to the magmatic ones is ascribed to the presence of micron-sized REE phases. Fluorapatite and pyrochlore constitute important accessory phases that are altered to variable extents. Higher concentrations of Sr, Si, and REEs in fluorapatite are suggestive of a magmatic origin. Fresh pyrochlore preserves its magmatic composition, characterized by low A-site vacancy and high F in the Y-site, which on alteration becomes poorer in Na, Ca, and F and displays an increase in vacancy. The C-O isotope compositions of the carbonates also corroborate the extensive low-temperature hydrothermal alteration of the carbonatites. The REE mineralization is the result of interaction of the carbonatite with a sulfur-bearing, F-rich hydrothermal fluid that exsolved from late-stage carbonatitic magmas. The hydrothermal fluids caused dissolution of the primary carbonates and simultaneous precipitation of REEs and other high field strength element (HFSE)-bearing minerals. Complex spatial associations of the magmatic minerals with the REE fluorocarbonates, [synchysite-(Ce), parisite-(Ce), bastnäsite-(Ce)] and florencite-(Ce) point to the formation of these REE phases as a consequence of postmagmatic hydrothermal dissolution of the REEs from fluorapatite, pyrochlore, and carbonates. Ubiquitous association of fluorite and barite with REE minerals indicates transport of REEs as sulfate complexes in F-rich fluids. Precipitation of REE fluorocarbonates/florencite resulted from fluid-carbonate interaction, concomitant increase in pH, and decrease in temperature. Additionally, REE precipitation was aided and abetted by the removal of sulfur from the fluid by the precipitation of barite, which destabilized the REE sulfate complexes.
DS202201-0031
2021
Pearson, G., Schaeffer, A., Stachel, T., Kjarsgaard, B., Grutter, H., Scott, J., Liu, J., Chacko, T., Smit, K.Revisiting the craton concept and its relevance for diamond exploration. *** See also Nature article previously listedGAC/MAC Meeting UWO, 1p. Abstract p. 238. Globalcratons

Abstract: The term craton has a complex and confused etymology. Despite originally specifying only strength and stability - of the crust - the term craton, within the context of diamond exploration, has widely come to refer to a region characterised by crustal basement older than 2.5 Ga, despite the fact that some such “cratons” no longer possess their deep lithospheric root. This definition often precluded regions with deep lithospheric roots but basement younger than 2-2.5 Ga. Viscous, buoyant lithospheric mantle roots are key to the survival and stability of continental crust. Here we use a revised craton definition (Pearson et al., 2021, in press), that includes the requirement of a deep (~150 km or greater) and intact lithospheric root, to re-examine the link between cratons and diamonds. The revised definition has a nominal requirement for tectonic stability since ~ 1 Ga and recognises that some regions are “modified cratons” - having lost their deep roots, i.e., they may have behaved like cratons for an extended period but subsequently lost much of their stabilising mantle roots during major tectono-thermal events. In other words, despite being long-lived features, cratons are not all permanent. The 150 km lithospheric thickness cut-off provides an optimal match to crustal terranes with 1 Ga timescale stability. In terms of regional diamond exploration, for a given area, the crucial criterion is when a deep mantle root was extant, i.e., over what period was the lithospheric geotherm suitable for diamond formation, stability and sampling? A thick lithospheric root is key to the formation of deep-seated magmas such as olivine lamproites and to the evolution of sub-lithospheric sourced proto-kimberlites, all capable of carrying and preserving diamonds to Earth's surface. This criterion appears essential even for sub-lithospheric diamonds, that still require a diamond transport mechanism capable of preserving the high-pressure carbon polymorph via facilitating rapid transport of volatile-charged magma to the surface, without dilution from additional melting that takes place beneath thinner (<120 km) lithospheric "lids". Seismology can help to define the lateral extent of today's cratons, but a detailed understanding of the regional geological history, kimberlite eruption ages and geothermal conditions is required to evaluate periods of past diamond potential, no-longer evident today. This revised craton concept broadens the target terranes for diamond exploration away from only the Archean cores of cratons and an associated mentality that "the exception proves the rule". The revised definition is compatible with numerous occurrences of diamond in Proterozoic terranes or Archean terranes underpinned by Proterozoic mantle.
DS202201-0032
2021
Pedersen, C.Geology and mining of the Nechalacho rare earth deposits, Thor Lake, Northwest Territories.NWTgeoscience.ca, 1p. AbstractCanada, Northwest TerritoriesREE

Abstract: Cheetah’s Nechalacho rare earth deposits are located at Thor Lake, 110 kms southeast of Yellowknife, 8 kms north shore of the Hearne Channel on Great Slave Lake. The two principal deposits are the North T deposit, the focus of the current Stage 1 rare earth mining program, and the Nechalacho Tardiff deposit currently in the planning stages for Stage 2 mining. The North T deposit, at 101,000 tonnes grading 9.01% TREO, consists of a 4-metre thick layer of the light rare earth (LREE) mineral bastnaesite, which occurs in coarse grained to massive aggregates in a gangue of pure quartz. The ellipsoidal sub-zone is one of several concentric mineralogically-distinct zones in the ovoid North-T deposit, which is approximately 150 metres in diameter and 150 metres in depth. The bastnaesite sub-zone crops out on surface and dips inward before flattening out in the centre at an average depth of 30 metres. Open-cast extraction commenced in June of 2021, providing feed-stock ore which was processed by XRT sensor-based ore sorting technology which produced a high-grade bastnaesite concentrate for shipment to Hay River and ultimately to Cheetah’s Saskatoon will facility. Stage 2 will see the development of the much larger Tardiff deposit, one of several high-grade LREE sub-zones in the 94.7 million tonnes Nechalacho deposit. The mineralogy is similar to the North T deposit, consisting primarily of bastnaesite, with sub-ordinate REE minerals monazite and allanite. Cheetah has off-take agreements with the Norwegian firm REEtec for Stage 1 production of 1000 tonnes REE (ex-Ce)/year for an initial 5-year period, and an MOU with UCore Rare Metals Inc to supply rare-earth concentrate to their planned separation facility in Alaska.
DS202203-0362
2022
Peireira, R.S., de Carvallo, L.D.V., Fuck, R.A.Primary source of alluvial diamonds from the Santo Antonio do Bonito, Santo Inacio and Douradinho rivers, Coromandel region, Minas Gerais, Brazil.Journal of South American Earth Sciences, Vol. 111, 15p. PdfSouth America, Brazil, Minas Geraisdeposit - Coromandel

Abstract: In the midwestern Minas Gerais, Brazil, kimberlite intrusions, particularly kamafugite and alkaline complexes, occur along the NW-SE-oriented Alto Paranaíba structural high. Diamonds in this region were discovered in the Bagagem River and later in the alluvial deposits of the Santo Antônio do Bonito, Santo Inácio and Douradinho rivers. Diamond-bearing kimberlites observed in the region are the primary sources of diamond deposits, as in the case of the Vargem Bonita diggings-in the upper São Francisco River. However, the primary sources of the alluvial diamonds that occur in the Santo Antônio do Bonito, Santo Inácio, and Douradinho rivers have not been clarified. These diamond populations have characteristics common to all three drainage area, where large stones are frequently recovered. Diamond accumulation in the alluvium is due to the erosion and re-concentration of material from basal conglomerate of the Capacete Formation. There is evidence that the sources that fed the conglomerate are local diamond-bearing kimberlites of approximately 90-120 Ma underlying the Capacete Formation, which in an upper unit of the Mata da Corda Group. Recent fieldwork led to the location of a kimberlite intrusion in the Santo Inácio River Basin, southeast of Coromandel. The intrusion fulfills the requirements constituting a primary source of diamonds in the area.
DS202204-0533
2022
Peng, Y., Manthilake, G., Mookherjee, M.Electrical conductivity of metasomatized lithology in subcontinental lithosphere.American Mineralogist, Vol. 107, pp. 343-349.Mantlemetasomatism

Abstract: A plausible origin of the seismically observed mid-lithospheric discontinuity (MLD) in the subcontinental lithosphere is mantle metasomatism. The metasomatized mantle is likely to stabilize hydrous phases such as amphiboles. The existing electrical conductivity data on amphiboles vary significantly. The electrical conductivity of hornblendite is much higher than that of tremolite. Thus, if hornblendite truly represents the amphibole varieties in MLD regions, then it is likely that amphibole will cause high electrical conductivity anomalies at MLD depths. However, this is inconsistent with the magnetotelluric observations across MLD depths. Hence, to better understand this discrepancy in electrical conductivity data of amphiboles and to evaluate whether MLD could be caused by metasomatism, we determined the electrical conductivity of a natural metasomatized rock sample. The metasomatized rock sample consists of ~87% diopside pyroxene, ~9% sodium-bearing tremolite amphibole, and ~3% albite feldspar. We collected the electrical conductivity data at ~3.0 GPa, i.e., the depth relevant to MLD. We also spanned a temperature range between 400 to 1000 K. We found that the electrical conductivity of this metasomatized rock sample increases with temperature. The temperature dependence of the electrical conductivity exhibits two distinct regimes. At low temperatures <700 K, the electrical conductivity is dominated by the conduction in the solid state. At temperatures >775 K, the conductivity increases, and it is likely to be dominated by the conduction of aqueous fluids due to partial dehydration. The main distinction between the current study and the prior studies on the electrical conductivity of amphiboles or amphibole-bearing rocks is the sodium (Na) content in amphiboles of the assemblage. Moreover, it is likely that the higher Na content in amphiboles leads to higher electrical conductivity. Pargasite and edenite amphiboles are the most common amphibole varieties in the metasomatized mantle, and our study on Na-bearing tremolite is the closest analog of these amphiboles. Comparison of the electrical conductivity results with the magnetotelluric observations constrains the amphibole abundance at MLD depths to <1.5%. Such a low-modal proportion of amphiboles could only reduce the seismic shear wave velocity by 0.4-0.5%, which is significantly lower than the observed velocity reduction of 2-6%. Thus, it might be challenging to explain both seismic and magnetotelluric observations at MLD simultaneously.
DS202202-0209
2022
Petite, B.Vertical Rewind: Dr. Hans Lundberg: The prospecting pioneer. History of H. Lundberg and EM survey … ** not specific to diamonds https://verticalmag.com/features/vertical-rewind-dr-hans-lundberg-the-prospecting-pioneer/, 10p. Photographs and textCanadageophysics - history
DS202201-0033
2021
Pjyu, K.M., Zaw, K., Mernagh, T.P., Aung, T.Z.Characteristics and genesis of sapphires from the Yenya-U area, Thabeikkyin Township, Mandalay region, Myanmar.Journal of Gemmology, Vol. 37, 8, pp. 802-815.Asia, Myanmarsapphires
DS202201-0034
2021
Podolsky, M.What is a primary rock hosted diamond deposit, resource and reserve? Desktop to feasibility study governance example under CIM and NI 43-101 guidelines and definition standards and De Beers scorecard classification, Gahcho Kue mine, Northwest Territories.GAC/MAC Meeting UWO, 1p. Abstract p. 245.Canada, Northwest Territoriesdeposit - Gahcho Kue

Abstract: A primary Rock Hosted Diamond Deposit, Resource and Reserve Asset Development Standard (ADS) model governed under the 2014 Canadian Institute of Mining, Metallurgy and Petroleum (CIM) Definition Standards on Mineral Resources and Reserves and 2016 Toronto Stock Exchange National Instrument 43-101 - Standards of Disclosure for Mineral Projects (NI 43-101), is presented. The De Beers Canada - Mountain Province Diamonds joint venture Gahcho Kué Project roadmap from exploration commencing in 1992, reporting of initial Desktop Study in 2000 to definitive Feasibility Study in 2010 and 2014 Study update is reviewed under the incorporated 2003 Guidelines for the Reporting of Diamond Exploration Results and 2008 Estimation of Mineral Resources and Mineral Reserves Best Practices Guidelines for Rock Hosted Diamonds. A published De Beers system of diamond Deposit to Resource geo-scientific scorecard classification is summarized and compared against the CIM and NI 43-101 Definition Standards and reporting guidelines. The ADS governance model utilizes the De Beers classification system, that is aligned with reporting of Desktop, Conceptual and Pre-Feasibility to Feasibility Studies.
DS202201-0035
2021
Pratesi, G., Franz, a., Hirata, A.It is hard to be a gem in a rhinestone world: a diamond Museum collection between history and science. ( Firenza)Geoheritage, Vol. 13, 103 Europe, ItalyFTIR spectroscopy

Abstract: The goal of this work is to investigate the diamond collection preserved at the Natural History Museum of the University of Firenze (MSN-FI) using a multidisciplinary approach. The mixed methods combine historical research with spectroscopic techniques to gain a deeper understanding of this collection of great historical, scientific and gemmological interest. This study concerns the analysis of 61 diamonds that are relatively small in both size and weight, mostly unworked and sometimes rich in inclusions. These specimens were acquired by MSN-FI from diverse collectors and institutions from 1824 until the most recent acquisitions in the 1990s. The FTIR spectroscopy was performed on 45 specimens. The results show the physical classification of diamonds in three groups (IaAB, IaA, and IaB) and reveal the presence of hydrogen as ethylene -CH?=?CH- or vinylidene?>?C?=?CH2 group.
DS202202-0210
2021
Pucharovsky, D., Balitsky, D.V., Bindi, L.The importance of crystals and crystallography in Space research programs.Crystallography Reports, Vol. 66, 6, pp. 934-939. 10.1134/S1063774521060298CosmosCrystallography

Abstract: The Mars exploration rovers have used various remote-sensing instruments over the last two and a half decades. The Chemistry and Camera tool uses laser-induced breakdown spectroscopy to obtain semi-quantitative elemental abundances. The SuperCam instrument is a response to the requirement for remote mineralogy and is also adapted for Raman spectroscopy studies. Both analyzers contain pulsed laser units with Nd:YAG rods and Pockels cells with crystals of rubidium titanyl phosphate, potassium titanyl phosphate and lithium triborate. The specific features of their structure, chemistry, and crystal growth are discussed.
DS202202-0211
2022
Raghuvanshi, S., Chalapathi Rao, N.V., Talukdar, D., Sharma, A., Pandey, R.Chrome-diopside xenocrysts entrained in a Neoproterozoic lamprophyre dyke from the Mysuru area: their origin and implications for lithospheric thickness beneath the western Dharwar craton, southern India.Journal of the Geological Society of India, Vol.. 98, 12p. PdfIndiacraton - Dharwar

Abstract: In comparison to the eastern Dharwar Craton, the mantle-derived xenocrysts/xenoliths are extremely rare or even unreported from the western Dharwar Craton, southern India. A Neoproterozoic (ca. 800-900 Ma) lamprophyre cropping out in the Mysuru area of southern India contains chrome-diopside xenocrysts (Cr2O3 content varying from 0.2-1.23 wt%) which provide important evidence about the pressure-temperature conditions and lithospheric thickness beneath the western Dharwar Craton. Studied chrome-diopsides show compositional zoning which is lacking in the liquidus phases (amphiboles and feldspars) of the lamprophyre which additionally favors a non-cognate origin of the former. Based on the compositional zoning, all the chrome-diopside xenocrysts can be divided into three groups: (i) Group I- which are euhedral and show reverse zoning with increasing Cr-content from core to rim; (ii) Group II- which are characterized by fractures and resorption textures, show complex reverse zoning and display up to three distinct compositional layers, and (iii) Group III- which evidence the reaction of chrome-diopsides with lamprophyric melt and are marked by alteration phases, such as actinolite and chlorite, together with relicts of some unaltered xenocrysts. High Cr2O3, moderate MgO and low Al2O3 content of all the three varieties of chrome-diopside suggest them to represent disaggregated xenocrysts of mantle-derived garnet peridotite. Temperature-pressure estimates for chrome-diopside xenocrysts ranges from 895-1026 °C (± 30 °C) and 32-38 kbar respectively and correspond to depth range of 106-127 km. The study reveals that lithospheric thickness during the Neoproterozoic beneath the western Dharwar craton was at least ?115 km and is similar in composition to that of the cratonic lithosphere found in the other cratonic domains.
DS202205-0712
2022
Raghuvanshi, S., Chalapthi Rao, N.V., Talukdar, D., Sharma, A., Pandey, R.Chrome-diopside xenocrysts entrained in a Neoproterozoic lamprophyre dyke from the Mysuru area: their origin and implcations for lithospheric thickness beneath the western Dharwar craton, southern India.Journal of the Geological Society of India, Vol. 98, 12p. PdfIndiachrome-diopside

Abstract: In comparison to the eastern Dharwar Craton, the mantle-derived xenocrysts/xenoliths are extremely rare or even unreported from the western Dharwar Craton, southern India. A Neoproterozoic (ca. 800-900 Ma) lamprophyre cropping out in the Mysuru area of southern India contains chrome-diopside xenocrysts (Cr2O3 content varying from 0.2-1.23 wt%) which provide important evidence about the pressure-temperature conditions and lithospheric thickness beneath the western Dharwar Craton. Studied chrome-diopsides show compositional zoning which is lacking in the liquidus phases (amphiboles and feldspars) of the lamprophyre which additionally favors a non-cognate origin of the former. Based on the compositional zoning, all the chrome-diopside xenocrysts can be divided into three groups: (i) Group I- which are euhedral and show reverse zoning with increasing Cr-content from core to rim; (ii) Group II- which are characterized by fractures and resorption textures, show complex reverse zoning and display up to three distinct compositional layers, and (iii) Group III- which evidence the reaction of chrome-diopsides with lamprophyric melt and are marked by alteration phases, such as actinolite and chlorite, together with relicts of some unaltered xenocrysts. High Cr2O3, moderate MgO and low Al2O3 content of all the three varieties of chrome-diopside suggest them to represent disaggregated xenocrysts of mantle-derived garnet peridotite. Temperature-pressure estimates for chrome-diopside xenocrysts ranges from 895-1026 °C (± 30 °C) and 32-38 kbar respectively and correspond to depth range of 106-127 km. The study reveals that lithospheric thickness during the Neoproterozoic beneath the western Dharwar craton was at least ?115 km and is similar in composition to that of the cratonic lithosphere found in the other cratonic domains.
DS202201-0036
2022
Raghuvanshi, S., Sharma, A., Talukdar, D., Chalapathi Rao, N.V.Chrome-diopside xenocrysts entrained in a Neoproterozoic lamprophrye dyke from the Mysuru area: their origin and implications or lithospheric thickness beneath the Western Dharwar craton, southern India.Journal of Geological Society of India, in press available 12p. PdfIndiacraton
DS202205-0713
2022
Rakhmanova, M.I., Komarovskikh, A.Y., Ragozin, A.L., Yuryeva, O.P., Nadolinny, V.A.Sprectroscopic features of electron-irradiated diamond crystals from the Mir kimberlite pipe, Yakutia.Diamond and Related Materials, Vol. 126, 109057Russiadeposit - Mir

Abstract: The behavior of characteristic centers in diamond crystals from the Mir pipe (Yakutia) was investigated upon electron irradiation. A series of diamond crystals of different types was chosen for experiments based on the nitrogen content and aggregation parameters. In electron-irradiated diamonds of the IaAB type, a new characteristic photoluminescence system was found with a zero-phonon line (ZPL) at 615 nm together with phonon replicas of 41 and 90 meV. The phonons' energies pointed to multiphonon interactions with a quasilocal vibration of a vacancy. According to our data, the nitrogen-related defect responsible for this phenomenon contains a vacancy and may be accompanied by some other impurity. Conversely, in an almost nitrogen-free crystal, a specific system with the ZPL at 558 nm was noted. The center in question is known to be vacancy-related and was formed in type IIa crystals from the Mir pipe not only by electron irradiation but also by high-pressure high-temperature annealing when vacancies were released as a result of motion or annihilation of dislocations. Regardless of the nitrogen impurity, specific systems with the ZPL at 454, 491, and 492 nm were registered in the irradiated diamond crystals from the Mir pipe. To examine the generated defects, the irradiated diamond crystals were subjected to low-temperature annealing at ?600 °C. Although the 454 and 491 nm systems persisted, the annealing of the 492 nm system along with well-known 523.6, 489.0, and 503.4 nm (3H) centers indicated the interstitial-vacancy nature of the defect.
DS202204-0534
2022
Rezvukhin, D.I., Nikolenko, E.I., Sharygin, I.S., Rezvukhina, O.V., Chervyaovskaya, M.V., Korsakov, A.V.Cr-pyrope xenocrysts with oxide mineral inclusions from the Chompolo lamprophyres ( Aldan shield): insights into mantle processes beneath the southeastern Siberian craton.Mineralogical Magazine, Vol. 86, pp. 60-77.Russia, Siberialamproite

Abstract: Pyrope xenocrysts (N = 52) with associated inclusions of Ti- and/or Cr-rich oxide minerals from the Aldanskaya dyke and Ogonek diatreme (Chompolo field, southeastern Siberian craton) have been investigated. The majority of xenocrysts are of lherzolitic paragenesis and have concave-upwards (normal) rare earth element (REEN) patterns that increase in concentration from light REE to medium-heavy REE (Group 1). Four Ca-rich (5.7-7.4 wt.% CaO) pyropes are extremely low in Ti, Na and Y and have sinusoidal REEN spectra, thus exhibiting distinct geochemical signatures (Group 2). A peculiar xenocryst, s165, is the only sample to show harzburgitic derivation, whilst demonstrating a normal-to-weakly sinusoidal REEN pattern and the highest Zr (93 ppm) and Sc (471 ppm). Chromite-magnesiochromite, rutile, Mg-ilmenite and crichtonite-group minerals comprise a suite of oxide mineral inclusions in the pyrope xenocrysts. These minerals are characteristically enriched in Cr with 0.6-7.2 wt.% Cr2O3 in rutile, 0.7-3.6 wt.% in Mg-ilmenite and 7.1-18.0 wt.% in the crichtonite-group minerals. Complex titanates of the crichtonite group enriched in large ion lithophile elements (LILE) are high in Al2O3 (0.9-2.2 wt.%), ZrO2 (1.5-5.4 wt.%) and display a trend of compositions from the Ca-Sr-specific varieties to the Ba-dominant species (e.g. lindsleyite). In the pyrope xenocrysts the oxides coexist with silicates (clino- and orthopyroxene and olivine), hydrous silicates (talc, phlogopite and amphibole), carbonate (magnesite), sulfides (pentlandite, chalcopyrite, breakdown products of monosulfide and bornite solid solutions), apatite and graphite. P-T estimates imply the inclusion-bearing pyrope xenocrysts have been derived from low-temperature peridotite assemblages that resided at temperatures of ~600-800°C and a pressure range of ~25-35 kbar in the graphite stability field. Pyrope genesis is linked to the metasomatic enrichment of peridotite protoliths by Ca-Zr-LILE-bearing percolating fluid-melt phases containing significant volatile components. These metasomatic agents are probably volatile-rich melts or supercritical C-O-H-S fluids that were released from a Palaeo-subduction slab.
DS202202-0212
2021
Roche, V., Leroy, S., Guillocheau, F., Revillon, S., Ruffet, G., Watremez, L., d'Acremont, E., Nonn, C., Vetel, W., Despinois, F.The Limpopo magma-rich transform margin, south Mozambique - pt. 2. Implications for the Gondwana breakup.Tectonics, e2021TC006914 Africa, Mozambiquegeophysics - seismics

Abstract: The rifted continental margins of Mozambique provide excellent examples of continental passive margins with a significant structural variability associated with magmatism and inheritance. Despite accumulated knowledge, the tectonic structure and nature of the crust beneath the South Mozambique Coastal Plain (SMCP) are still poorly known. This study interprets high-resolution seismic reflection data paired with data from industry-drilled wells and proposes a structural model of the Limpopo transform margin in a magma-rich context. Results indicate that the Limpopo transform margin is characterized by an ocean-continent transition that links the Beira-High and Natal valley margin segments and represents the western limit of the continental crust, separating continental volcano-sedimentary infilled grabens from the oceanic crust domain. These basins result from the emplacement of the Karoo Supergroup during a Permo-Triassic tectonic event, followed by an Early Jurassic tectonic and magmatic event. This latter led to the establishment of steady-state seafloor spreading at ca.156 Ma along the SMCP. A Late Jurassic to Early Cretaceous event corresponds to formation of the Limpopo transform fault zone. Which accommodated the SSE-ward displacement of Antarctica with respect to Africa. We define a new type of margin: the magma-rich transform margin, characterized by the presence of voluminous magmatic extrusion and intrusion coincident with the formation and evolution of the transform margin. The Limpopo transform fault zone consists of several syn-transfer and -transform faults rather than a single transform fault. The intense magmatic activity was associated primarily with mantle dynamics, which controlled the large-scale differential subsidence along the transform margin.
DS202202-0213
2022
Rollinson, H.The rare earth element geochemistry of mafic granulites from the Neoarchean northern marginal zone of the Limpopo belt, Zimbabwe: insights into mantle processes during an episode of crustal growth,Journal of African Earth Science, Vol. 186, 104434, 12p. PdfAfrica, ZimbabweREE

Abstract: The granulites of the Northern Marginal Zone of the Limpopo belt, Zimbabwe represent the lower crust of the Zimbabwe Craton. They are predominantly felsic in composition and represent magmas of the tonalite-trondhjemite-granodiorite suite which formed during a period of major crustal growth in the Neoarchaean. However, enclosed within the felsic gneisses of the NMZ are mafic granulites (metabasalts) which make up between 5 and 10% of the rock volume and which both predate and post-date the main TTG magmatism. These rocks show a diverse range of trace element compositions and are used here to characterize those mantle processes which were taking place during this period of crustal growth. The mafic granulites can be subdivided into two main groups. 1. Large metabasite lenses, associated with banded iron formation, represent a supracrustal suite of basalts which predate the emplacement of the TTGs and may be time equivalents of the lower greenstones of the Zimbabwe Craton. Samples can be grouped into three different types of REE pattern - depleted, chondritic and enriched - which is interpreted to show that they were partial melts of a depleted mantle source, which in places interacted with and was contaminated with older felsic crust. 2. Narrow dykes post-date the emplacement of the NMZ TTG suite. There are two geochemical types. Dykes with light-enriched REE patterns are derived from a depleted mantle source but were contaminated with felsic crust during their emplacement. Dykes highly enriched in light REE were derived from an enriched mantle source formed through the refertilisation of a previously depleted mantle source. The deep melting of this refertilised source gave rise to highly enriched mafic melts. The large metabasite lenses could be indicative of the metabasaltic source which subsequently partially melted to form the NMZ TTG magmatic suite. Later deep mantle melting to form the post TTG dykes may be related to the creation of thick Neoarchaean continental crust and associated mantle lithosphere.
DS202203-0363
2021
Schmetzer, K.History of emerald mining in the Habachtal deposit of Austria. Part 1.Gems & Gemology, Vol. 57, 4, pp. 338-371. pdfEurope, Austriaemerald

Abstract: The sources of emeralds used in Roman jewelry as well as jeweled pieces (including crowns and book covers) dating from antiquity to the Middle Ages and before the discovery of the Colombian emerald deposits in the sixteenth century remain an ongoing matter of controversy. Two potential localities dominate the discussion: the mines in the Eastern Desert of Egypt and the Habachtal deposit in Austria. The first published reference to the Habachtal emerald occurrence dates to 1797. The majority of publications from the nineteenth and twentieth centuries agree that Samuel Goldschmidt, a jeweler from Vienna, purchased the mountain area in which the Habachtal emerald occurrence is located and commenced mining soon thereafter, in the early 1860s. A later period from the mid-1890s to about 1914 is frequently mentioned, in which the mine was owned and worked by an English company. However, further details regarding both periods and the various transitions of ownership and further circumstances of emerald mining before World War I are rarely given and often are not consistent, and activities in the times before the 1860s and between 1870 and 1890 are obscure. Using a wide selection of materials from Austrian and German archives, largely unpublished, the author seeks to trace the history of the Habachtal mine through several centuries and to fill gaps left by existing publications.
DS202201-0037
2021
Seales, J., Lenardic, A.Deep-water recycling, planetary self-regulation, and the maintenance of melting on Earth. * just for interestResearchgate , Dec. 22p. PdfMantlewater
DS202205-0714
2022
Seales, J., Lenardic, A.Plate tectonics, mixed heating convection and the divergence of mantle and plume temperatures.Researchgate preprint, 12p. PdfMantlegeothermometry

Abstract: Petrological data indicate that upper mantle and mantle plume temperatures diverged 2.5 billion years ago. This has been interpreted as plate tectonics initiating at 2.5 Ga with Earth operating as a single plate planet before then. We take an Occam’s razor view that the continuous operation of plate tectonics can explain the divergence. We validate this hypothesis by comparing petrological data to results from mixed heating mantle convection models in a plate tectonic mode of mantle cooling. The comparison shows that the data are consistent with plate tectonics operating over geologic history.
DS202205-0715
2022
Seals, J., Lenardic, A., Garrido, J.Plate tectonics, mixed heating convection and the divergence.Researchgate preprint, 12p. PdfMantleplate tectonics

Abstract: Petrological data indicate that upper mantle and mantle plume temperatures diverged 2.5 billion years ago. This has been interpreted as plate tectonics initiating at 2.5 Ga with Earth operating as a single plate planet before then. We take an Occam’s razor view that the continuous operation of plate tectonics can explain the divergence. We validate this hypothesis by comparing petrological data to results from mixed heating mantle convection models in a plate tectonic mode of mantle cooling. The comparison shows that the data are consistent with plate tectonics operating over geologic history.
DS202201-0038
2021
Shanker, S., Barve, A.Analysing sustainable concerns in diamond supply chain: a fuzzy ISM-MICMAC and DEMATEL approach.International Journal of Sustainable Engineering, Vol. 14, 5, pp. 1269-1285. pdfGlobal, Indiamarkets

Abstract: Sustainable supply chain management has become one of the significant areas of concern for modern industries. Enterprises are now adopting management that implements viable practices involving environmental protection and financial savings in a combined form. In this aspect, this study focuses on detecting various concerns associated with sustainable supply chain management in the diamond mining industry globally. These parameters are classified based on their dependency and driving power (DP) with the help of fuzzy MICMAC analysis. In addition to this, a structural model of the recognised concerns has been established using the interpretive structural modelling technique. Furthermore, the interdependence among the respective concerns have been identified by utilising the decision-making trial and evaluation laboratory (DEMATEL) approach. Also, an integrated ISM-DEMATEL model has been employed to form an evident understanding of these concerns. The findings of this study illustrate that ‘Awareness Programmes’ and ‘Proper Infrastructure Investment’ should be given due consideration to ensure a sustainable competitive advantage.
DS202201-0039
2021
Sharygin, V.V., Britvin, S., Kaminsky, F.V., Wirth, R.Ellinaite, CaCr204, a new natural post-spinel oxide from Hatrurim Basin, Israel, and Juina kimberlite field, Brazil.European Journal of Mineralogy, Dec.Europe, Israel, South America, Brazildeposit - Juina

Abstract: Ellinaite, a natural analog of the post-spinel phase ?-CaCr2O4, was discovered at the Hatrurim Basin, Hatrurim pyrometamorphic formation (the Mottled Zone), Israel, and in an inclusion within the super-deep diamond collected at the placer of the Sorriso River, Juína kimberlite field, Brazil. Ellinaite at the Hatrurim Basin is confined to a reduced rankinite-gehlenite paralava, where it occurs as subhedral grains up to 30?µm in association with gehlenite, rankinite and pyrrhotite or forms the rims overgrowing zoned chromite-magnesiochromite. The empirical formula of the Hatrurim sample is (Ca0.960FeNa0.012Mg0.003)0.992(Cr1.731VTiAl0.023TiO4. The mineral crystallizes in the orthorhombic system, space group Pnma, unit-cell parameters refined from X-ray single-crystal data: a 8.868(9), b 2.885(3), c 10.355(11)?Å, V 264.9(5)?Å3 and Z=4. The crystal structure of ellinaite from the Hatrurim Basin has been solved and refined to R1=0.0588 based on 388 independent observed reflections. Ellinaite in the Juína diamond occurs within the micron-sized polyphase inclusion in association with ferropericlase, magnesioferrite, orthorhombic MgCr2O4, unidentified iron carbide and graphite. Its empirical formula is Ca1.07(Cr1.71FeV0.06Ti0.03Al0.03Mg0.02Mn0.02)?1.93O4. The unit-cell parameters obtained from HRTEM data are as follows: space group Pnma, a 9.017, b 2.874?Å, c 10.170?Å, V 263.55?Å3, Z=4. Ellinaite belongs to a group of natural tunnel-structured oxides of the general formula AB2O4, the so-called post-spinel minerals: marokite CaMn2O4, xieite FeCr2O4, harmunite CaFe2O4, wernerkrauseite CaFeMn4+O6, chenmingite FeCr2O4, maohokite MgFe2O4 and tschaunerite Fe(FeTi)O4. The mineral from both occurrences seems to be crystallized under highly reduced conditions at high temperatures (>1000??C), but under different pressure: near-surface (Hatrurim Basin) and lower mantle (Juína diamond).
DS202203-0364
2022
Shatskiy, A., Bekhtenova, A., Podborodnikov, I.V., Arefiev, A.V., Litasov, K. S.Towards composition of carbonatite melts in peridotitic mantle.Earth and Planetary Science Letters, Vol. 581, 11p.Mantlemetasomatism

Abstract: It is generally accepted that carbonatite metasomatism in the subcontinental lithospheric mantle (SCLM) inevitably causes wehrlitization of the primary lherzolite substrate. However, the K-rich carbonatite inclusions in kimberlitic diamonds containing orthopyroxene indicate that this is not always the case. In the present study, we equilibrated natural garnet lherzolite with carbonate melts containing 33-38 wt% K2O with various Ca# = 10, 20, 30, and 40 at 6 GPa and 1200-1500 °C, where Ca# = 100?Ca/(Ca+Mg+Fe). The original ratio of peridotite to carbonate was 58 to 42 by weight. In the studied temperature range, the melt retains essentially carbonate composition with silica content increasing from 1 to 11-12 wt%. The melt with Ca# 10 alters lherzolite to harzburgite, replacing clinopyroxene by orthopyroxene and decreasing CaO content in garnet below 4 wt%. The melts with Ca# 20-30 also consume clinopyroxene; although CaO content in garnet remains in the range of lherzolitic compositions. The melt with Ca# 40 yields wehrlitization, consuming orthopyroxene, increasing clinopyroxene fraction, and increasing CaO content in garnet above 6 wt%. After the interaction, the Ca# of the melt changes as follows 10 ? 16-28, 20 ? 20-33, 30 ? 27-34, and 40 ? 30-34. The olivine + orthopyroxene + clinopyroxene + garnet assemblage was found in equilibrium with carbonatite melt with Ca# 34 at 1200 °C and Ca# 30 at 1400 °C. Thus, K-rich (26-35 wt% K2O) carbonatite melts with Ca# = 30-34 can appear in equilibrium with garnet lherzolite, while the melts with Ca# < 30 and > 34 can be in equilibrium with harzburgite and wehrlite, respectively, at 6 GPa and 1200-1400 °C. Considering that Ca-Mg-Fe carbonates do not melt at the geothermal conditions of the SCLM, while sodic, dolomitic melt causes wehrlitization, high-Mg (Ca# < 35) K-rich dolomitic melt is the only possible carbonatite fluids that are thermodynamically stable in equilibrium with garnet harzburgites and lherzolites in the SCLM at a depth of about 200 km. At higher temperatures corresponding to the underlying asthenosphere, the high alkalinity ceases to be a requirement for the stability of the carbonate melt. Nevertheless, the regularities established here for the K-rich melts remain valid for less alkaline (4-15 wt% Na2O+K2O) primary kimberlite (i.e., mantle carbonatite) melts in the sublithospheric mantle.
DS202202-0214
2022
Shatskiy, A., Bekhtenova, A., Podborodnikov, I.V., Arefiev, A.V., Vinogradova, Y.G., Litasov, K.D.Solidus of carbonated phlogopite eclogite at 3- 6 Gpa: implications for mantle metasomatism and ultra high pressure metamorphism.Gondwana Research, Vol. 103, pp. 108-204. pdfMantlemetasomatism

Abstract: The interaction of natural eclogite (Ecl) with synthetic hydrous carbonate melts with Na:K = 0:1 (KH2) and 1:1 (NKH2) was studied in multianvil experiments at 3-6 GPa and 850-1250 °C. The interaction with KH2 consumes garnet and clinopyroxene producing phlogopite and calcite-dolomite solid solution. Besides, the interaction yields a decrease in the jadeite component of clinopyroxene, evolving eclogite toward pyroxenite. This is consistent with a metasomatic alteration of eclogite xenoliths, manifested as Na-poor “spongy” clinopyroxene, replacing primary omphacite, and kelyphitic rims around garnet, containing phlogopite and carbonates. The interaction with NKH2 also produces phlogopite and carbonate, but the latter is more magnesian and represented by magnesite, above the solidus, and magnesite + dolomite below the solidus. The interaction with NKH2 increases the jadeite component in clinopyroxene and grossular component in garnet, evolving eclogite Group A to eclogite Group B. The studied systems have H2O/K2O = 2, like that in phlogopite, and therefore correspond to carbonated phlogopite eclogite under fluid-absent conditions. Based on the obtained results its solidus is situated near 1050 °C at 3 GPa and decreases to 950 °C at 6 GPa. Thus, hydrous K- and Na-K-carbonatite melts can coexist with eclogite in SCLM at depths exceeding 120-170 km, and solidify as temperature decreases below 950-1050 °C according to the following solidus reactions: pyrope + diopside + melt ? phlogopite + dolomite, below 6 GPa, and pyrope + diopside + melt ? phlogopite + magnesite + grossular, at 6 GPa. The melting reaction, involving phlogopite and dolomite, suggests the partial melting at the peak of ultrahigh-pressure metamorphism (UHPM) during continent-continent plate collision. The prograde P-T path of UHPM crosses the solidus of clinopyroxene + garnet + phlogopite + dolomite assemblage at 4.7-5.2 GPa and 970-990 °C and yields the formation of hydrous K-carbonatite melt-fluid in situ. This melt could be responsible for the formation of K-bearing clinopyroxenes and microdiamonds in the UHPM marbles in the Kokchetav massif, Kazakhstan. The retrograde P-T path intersects the solidus that has a negative Clapeyron slope in the diamond stability field. Thus, the hydrous K-carbonatite melt should disappear soon after the peak of metamorphism reacting with garnet to produce Ca-Mg carbonates and phlogopite.
DS202202-0215
2021
Shatsky, V.S., Ragozin, A.L., Sitnikova, E.S.The nature of heterogeneity of high-chromium garnets in xenolite of deformed lherzolite from Udachnaya kimberlite pipe ( Yakutia).Doklady Earth Sciences, Vol. 501, pp. 1029-1037.Russia, Yakutiadeposit - Udachnaya

Abstract: Significant variations in the composition of garnets, both within individual grains and in the rock, are found in the xenolith of deformed garnet lherzolite from the Udachnaya kimberlite pipe. The central parts of the grains, corresponding in composition to the garnets of the lherzolite paragenesis, demonstrate a sinusoidal distribution of rare earth elements (REEs). At the same time, the edge portions have a distribution characteristic of garnet mega-crystals from kimberlites. Despite being depleted in Y and HREE, the cores are enriched in light rare earth elements, Nb, Ta, Th, and U relative to garnet from primitive garnet peridotite. In terms of the REE distribution, the model melts, which are in equilibrium with the edge parts of garnet, are close to kimberlite but are significantly enriched in comparison with kimberlite in Nb, Ta, and Hf and depleted in Sr. Melts in equilibrium with the central parts of garnet are characterized by a steeper negative slope in the region of heavy and medium REEs and approach kimberlite in the region of light REEs. Based on the data obtained, several stages in the evolution of deformed garnet lherzolite are distinguished. The first stage involves the interaction of depleted peridotite with a melt similar in composition to carbonatite melts. This stage is associated with the formation of garnet with a sinusoidal REE distribution. At the next stage, which was preceded by the dissolution of garnet grains, garnet rims with increased Ti, Zr, and Y contents were formed and clinopyroxene appeared. At the final stage, garnet melted, caused by the inflow of a water-carbon dioxide fluid with a high potassium content, leading to polymineral inclusions and kelyphite rims.
DS202202-0216
2021
Shephard, G.E., Houser, C., Hernlund, J.W., Valencia-Cardona, J.J., Tronnes, R.G., Wentzcovitch, R.M.Seismological expression of the iron spin crossover in ferropericlase in the Earth's lower mantle.Nature Communications, Vol. 12 5905 10.1038/s41467-021-26115-zMantletomography

Abstract: The two most abundant minerals in the Earth’s lower mantle are bridgmanite and ferropericlase. The bulk modulus of ferropericlase (Fp) softens as iron d-electrons transition from a high-spin to low-spin state, affecting the seismic compressional velocity but not the shear velocity. Here, we identify a seismological expression of the iron spin crossover in fast regions associated with cold Fp-rich subducted oceanic lithosphere: the relative abundance of fast velocities in P- and S-wave tomography models diverges in the?~1,400-2,000 km depth range. This is consistent with a reduced temperature sensitivity of P-waves throughout the iron spin crossover. A similar signal is also found in seismically slow regions below?~1,800 km, consistent with broadening and deepening of the crossover at higher temperatures. The corresponding inflection in P-wave velocity is not yet observed in 1-D seismic profiles, suggesting that the lower mantle is composed of non-uniformly distributed thermochemical heterogeneities which dampen the global signature of the Fp spin crossover.
DS202205-0716
2022
Shim, S-H., Chizmeshya, A., Leinenweber, K.Water in the crystal structure of CaSiO3 perovskite.American Mineralogist, Vol. 107, pp. 631-641.Mantleperovskite

Abstract: While the water storage capacities of the upper 700 km depths of the mantle have been constrained by high-pressure experiments and diamond inclusion studies, the storage capacity of the lower mantle remains controversial. A recent high-pressure experimental study on CaSiO3 perovskite, which is the third most abundant mineral in the lower mantle, reported possible storage of H2O up to a few weight percent. However, the substitution mechanism for H in this phase remains unknown. We have conducted a series of density functional theory calculations under static-lattice conditions and high pressures to elucidate hydration mechanisms at the atomic scale. All of the possible dodecahedral (Ca2+ ? 2H+) and octahedral (Si4+ ? 4H+) substitution configurations for a tetragonal perovskite lattice have very small energy differences, suggesting the coexistence of multiples of H configurations in CaSiO3 perovskite at mantle pressures and temperatures. The dodecahedral substitutions decrease the bulk modulus, resulting in a smaller unit-cell volume of hydrous CaSiO3 perovskite under pressure, consistent with the experimental observations. Although the octahedral substitutions also decrease the bulk modulus, they increase the unit-cell volume at 1 bar. The H atoms substituted in the dodecahedral sites develop much less hydrogen bonding with O atoms, leading to a large distortion in the neighboring SiO6 octahedra. Such distortion may be responsible for the non-cubic peak splittings observed in experiments on hydrous CaSiO3 perovskite. Our calculated infrared spectra suggest that the observed broad OH modes in CaSiO3 perovskite can result from the existence of multiples of H configurations in the phase. Combined with the recent experimental results, our study suggests that CaSiO3 can be an important mineral phase to consider for the H2O storage in the lower mantle.
DS202203-0365
2022
Shiryaev, A., Pavlushin, A., Pakhnevich, A.V., Kovalenko, E.S., Averin, A., Ivanova, A.G.Vol. Structural pecularities, mineral inclusions, and point defects in yakutites - a variety of impact-related diamond.Meteoritics & Planetary Science, 15p. PdfRussiadeposit - Popogai

Abstract: An unusual variety of impact-related diamond from the Popigai impact structure - yakutites - is characterized by complementary methods including optical microscopy, X-ray diffraction, radiography and tomography, infra-red, Raman and luminescence spectroscopy providing structural information at widely different scales. It is shown that relatively large graphite aggregates may be transformed to diamond with preservation of many morphological features. Spectroscopic and X-ray diffraction data indicate that the yakutite matrix represents bulk nanocrystalline diamond. For the first time, features of two-phonon infra-red absorption spectra of bulk nanocrystalline diamond are interpreted in the framework of phonon dispersion curves. Luminescence spectra of yakutite are dominated by dislocation-related defects. Optical microscopy supported by X-ray diffraction reveals the presence of single crystal diamonds with sizes of up to several tens of microns embedded into nanodiamond matrix. The presence of single crystal grains in impact diamond may be explained by CVD-like growth in a transient cavity and/or a seconds-long compression stage of the impact process due to slow pressure release in a volatile-rich target. For the first time, protogenetic mineral inclusions in yakutites represented by mixed monoclinic and tetragonal ZrO2 are observed. This implies the presence of baddeleyite in target rocks responsible for yakutite formation.
DS202201-0040
2021
Shumlyanskyy, L., Kamenetsky, V.S., Borodyna, B.V.Age and composition of zircons from the Devonian Petrivske kimberlite pipe of the Azov domain, the Ukrainian shield.Mineralogical Journal, Dec.Asia, Ukrainedeposit - Petrivske

Abstract: Zircon megacrysts are commonly found in kimberlites and, together with olivine, low-Cr garnet, pyroxene, phlogopite, and ilmenite megacrysts, they constitute a mineral assemblage known as the “low-Cr suite”. The generally close similarity of ages and similar isotope geochemical characteristics of megacrysts and matrix minerals in the host kimberlites support a cognate origin. However, alteration rims commonly develop on zircon and ilmenite megacrysts, providing evidence for a lack of chemical equilibrium between the megacrysts and kimberlitic melts. Here, we report results of a detailed geochronological and geochemical study of zircon megacrysts found in the Middle Devonian Novolaspa kimberlite pipe and dyke located in the Azov Domain of the Ukrainian Shield. The concordia age of zircons is 397.0 ± 2.0 Ma, and it is 14 m.y. older than the age of kimberlite emplacement as defined by a Rb-Sr isochron on phlogopite. The average ?Hf(397) value for unaltered zircon megacrysts is 6.8 ± 0.14, with the alteration rims having similar Hf isotope systematics. These hafnium isotope data indicate a moderately depleted mantle source for zircon. Unaltered megacrystic zircons have low abundances of trace elements and fractionated REE, with pronounced positive Ce/Ce* anomalies and almost no Eu/Eu* anomalies. In contrast, alteration rims have very high and variable concentrations of trace elements, indicating a reaction between zircon and kimberlite melt. The melt or fluid responsible for zircon and ilmenite megacryst formation, in contrast to kimberlitic melt, was poor in incompatible trace elements, except for the HFSE (Zr, Hf, Nb, Ta, and Ti). The oxygen fugacity during crystallization of the megacryst suite was close to the FMQ buffer. Azov zircon megacrysts do not demonstrate close geochronological and isotope-geochemical similarities with their host kimberlites. They are cognate in the broad sense of being related to the same plume event, but their direct affinity is not clearly defined. The megacryst suite may have crystallized from the earliest melts/fluids that separated from the ascending mantle plume, whereas kimberlite magmas were emplaced 14 m.y. after this event.
DS202205-0717
2022
Sieber, M.J., Yaxley, G.M., Hermann, J.COH-fluid induced metasomatism of peridotites in the forearc mantle.Contributions to Mineralogy and Petrology, Vol. 177, 44, 10.1007/s00410-022-01905-w.Mantleperidotites

Abstract: Devolatilization of subducting lithologies liberates COH-fluids. These may become partially sequestered in peridotites in the slab and the overlying forearc mantle, affecting the cycling of volatiles and fluid mobile elements in subduction zones. Here we assess the magnitudes, timescales and mechanism of channelized injection of COH-fluids doped with Ca2+aq, Sr2+aq and Ba2+aq into the dry forearc mantle by performing piston cylinder experiments between 1-2.5 GPa and 600-700 °C. Cylindrical cores of natural spinel-bearing harzburgites were used as starting materials. Based on mineral assemblage and composition three reaction zones are distinguishable from the rim towards the core of primary olivine and orthopyroxene grains. Zone 1 contains carbonates?+?quartz?±?kyanite and zone 2 contains carbonates?+?talc?±?chlorite. Olivine is further replaced in zone 3 by either antigorite?+?magnesite or magnesite?+?talc within or above antigorite stability, respectively. Orthopyroxene is replaced in zone 3 by talc?+?chlorite. Mineral assemblages and the compositions of secondary minerals depend on fluid composition and the replaced primary silicate. The extent of alteration depends on fluid CO2 content and fluid/rock-ratio, and is further promoted by fluid permeable reaction zones and reaction driven cracking. Our results show that COH-fluid induced metasomatism of the forearc mantle is self-perpetuating and efficient at sequestering Ca2+aq, Sr2+aq, Ba2+aq and CO2aq into newly formed carbonates. This process is fast with 90% of the available C sequestered and nearly 50% of the initial minerals altered at 650 °C, 2 GPa within 55 h. The dissolution of primary silicates under high COH-fluid/rock-ratios, as in channelized fluid flow, enriches SiO2aq in the fluid, while CO2aq is sequestered into carbonates. In an open system, the remaining CO2-depleted, Si-enriched aqueous fluid may cause Si-metasomatism in the forearc further away from the injection of the COH-fluid into peridotite.
DS202204-0535
2022
Sinaice, B.B., Owada, N., Ikeda, H., Toriya, H., Bagai, Z., Shemang, E., Adachi, T., Kawamura, Y.Spectral angle mapping and AI methods applied in automatic identification of placer deposit magnetite using multispectral camera mounted on UAV. *** not specific to diamondsMDPI, Vol. 12, 1., 19p.Globalalluvials

Abstract: The use of drones in mining environments is one way in which data pertaining to the state of a site in various industries can be remotely collected. This paper proposes a combined system that employs a 6-bands multispectral image capturing camera mounted on an Unmanned Aerial Vehicle (UAV) drone, Spectral Angle Mapping (SAM), as well as Artificial Intelligence (AI). Depth possessing multispectral data were captured at different flight elevations. This was in an attempt to find the best elevation where remote identification of magnetite iron sands via the UAV drone specialized in collecting spectral information at a minimum accuracy of +/? 16 nm was possible. Data were analyzed via SAM to deduce the cosine similarity thresholds at each elevation. Using these thresholds, AI algorithms specialized in classifying imagery data were trained and tested to find the best performing model at classifying magnetite iron sand. Considering the post flight logs, the spatial area coverage of 338 m2, a global classification accuracy of 99.7%, as well the per-class precision of 99.4%, the 20 m flight elevation outputs presented the best performance ratios overall. Thus, the positive outputs of this study suggest viability in a variety of mining and mineral engineering practices.
DS202205-0718
2022
Skuzovatov, S.Y., Shatsky, V.S., Wang, Q., Ragozin, A.L.,Kostrovitsky, S.T.Multiple tectonomagmatic reactivation of the unexposed basement in the northern Siberian craton: from Paleoproterozoic orogeny to Phanerozoic kimberlite magmatism.International Geology Review, Vol. 64, 8, pp. 1119-1138.Russia, Siberiakimberlite magmatism

Abstract: Zircon xenocrysts from two diamond-barren kimberlite pipes (Leningrad and Ruslovaya) in the West Ukukit kimberlite field opened a ‘window’ to the buried crustal basement in the northern Siberian craton. Zircon U-Pb ages reveal a close affinity of the basement of the Khapchan belt to the Archaean Anabar province and a significant tectonomagmatic reworking in the Paleoproterozoic (~2.1-1.8 Ga) due to collision between the Anabar province and the Olenek province. The West Ukukit kimberlite field experienced multiple tectonomagmatic reactivation from ~670 to 144 Ma, which can be attributed to interaction of the deep crust with mantle-derived melts. Hf isotope composition of zircon xenocrysts reveals significant addition of juvenile material into the crust during the Paleoproterozoic orogeny in diamond-barren kimberlite fields, which is different from the reworking crust in the southern Yakutia diamondiferous kimberlite fields. Eruption of the Leningrad and Ruslovaya pipes were constrained as the Late Jurassic, much later than the well-known Late Silurian-Earth Devonian kimberlites in the West Ukukit kimberlite field. A NE-trending, >2000 km long kimberlite corridor is proposed to account for a prolonged lithospheric channel for episodic eruption of kimberlites in the Siberian craton. The diamond storage in the lithosphere beneath the West Ukukit kimberlite field may have been largely reduced by the Paleoproterozoic orogeny and Phanerozoic reworking.
DS202201-0041
2021
Smith, E.Exploration implications of isotopically heavy iron in large gem type IIa diamonds.GAC/MAC Meeting UWO, 1p. Abstract p. 279.Africa, LesothoCLIPPIR - Letseng

Abstract: Large, high-quality type IIa diamonds such as the Cullinan and the Koh-i-Noor are among the most elusive of mined gem diamonds. These are called CLIPPIR diamonds, an acronym reflecting the distinguishing physical characteristics of this variety of diamonds (Cullinan-like, Large, Inclusion Poor, Pure, Irregular, Resorbed) [1]. There is currently no reliable method to predict the occurrence of CLIPPIR diamonds in a deposit, which remains a hurdle for exploration and mining [2]. Mineral inclusions reveal that these are sublithospheric diamonds [1], which explains why their occurrence is effectively independent from more common eclogitic and peridotitic lithospheric diamonds and their associated indicator minerals. More recently, an analysis of iron isotopes in the metallic inclusions sometimes found in CLIPPIR diamonds has provided additional insight into their formation, which may provide clues for exploration. Three measurements of metallic Fe-Ni-C-S inclusions from two diamonds from the Letseng mine, Lesotho reveal remarkably heavy iron isotopic compositions, ?56Fe = 0.79-0.90‰ [3]. These measurements lie far outside the range of known mantle compositions (near 0‰) or expected reaction products at depth. Instead, the heavy signature is ascribed to subducted iron sourced from magnetite and/or Fe-Ni alloys precipitated during seafloor serpentinization of oceanic peridotite. These metallic inclusions provide physical evidence that traces serpentinite subduction into the mantle transition zone. This finding is a step toward a genetic model for CLIPPIR diamonds. Their formation requires input from deeply subducted serpentinized peridotite. Furthermore, this input may come specifically from cold subducting slabs, whose serpentinized mantle portions can bypass the shallow sub-arc dehydration activity and instead transport serpentinite-derived components such as hydrous minerals and iron-rich phases to the transition zone/uppermost lower mantle [4]. The results suggest that geochemical signatures related to deeply subducted serpentinites may eventually provide a basis for targeting CLIPPIR diamonds in volcanic deposits at surface.
DS202205-0719
2022
Sokol, A.G., Kruk, A.N., Persikov, E.S.Dissolution of peridotite in a volatile-rich carbonate melt as a mechanism of the formation of kimberlite-like melts ( experimental constraints).Doklady Earth Science, Vol. 503, 2, pp. 157-163.Globalkimberlite magmatism

Abstract: In the experiments at 3.0-6.3 GPa and 1200-1350°C, it is found that under P-T parameters close to the conditions in ascending kimberlite magma, the carbonate melt enriched in potassium and volatiles is able to dissolve effectively the entire amount of xenogenic peridotite material that can potentially transport. As a result of this process, the melt is enriched in SiO2 (up to 30 wt %) and is transformed from carbonate to a kimberlite-like one. In the range of parameters studied, due to the high solubility of CO2 in the melt and the appearance of magnesite, an equilibrium fluid phase is not formed in the system. The interaction realized in the experiments may be the most important factor at the initial stage of magma evolution. The calculations performed in this work show that even after the dissolution of 30-50 wt % of lherzolite, the volatile-rich carbonate-silicate melt has a high degree of depolymerization (the ratio of the number of nonbridging oxygen atoms to the number of tetrahedrally coordinated ions (100NBO/T from 250 to 390) remains low-viscous (0.3-32.6 Pa s) and able to ascend to the surface rapidly. The obtained data indicate that immiscibility occurs between the potassium-rich carbonate-silicate and highly silicate melts only at 5.5 GPa and 1350°C and is likely to have a minor impact on the evolution of magma.
DS202204-0536
2022
Sokol, K., Finch, A.A., Hutchison, W., Cloutier, J., Borst, A.M., Humphreys, M.C.S.Quantifying metasomatic high-field-strength and rare-earth element transport from alkaline magmas.Geology, Vol. 50, 3, pp. 305-310.Europe, Greenlandalkaline

Abstract: Alkaline igneous rocks host many global high-field-strength element (HFSE) and rare-earth element (REE) deposits. While HFSEs are commonly assumed to be immobile in hydrothermal systems, transport by late-stage hydrothermal fluids associated with alkaline magmas is reported. However, the magnitude of the flux and the conditions are poorly constrained and yet essential to understanding the formation of REE-HFSE ores. We examined the alteration of country rocks (“fenitization”) accompanying the emplacement of a syenite magma at Illerfissalik in Greenland, through analysis of changes in rock chemistry, mineralogy, and texture. Our novel geochemical maps show a 400-m-wide intrusion aureole, within which we observed typically tenfold increases in the concentrations of many elements, including HFSEs. Textures suggest both pervasive and structurally hosted fluid flow, with initial reaction occurring with the protolith's quartz cement, leading to increased permeability and enhancing chemical interaction with a mixed Ca-K-Na fenitizing fluid. We estimated the HFSE masses transferred from the syenite to the fenite by this fluid and found ~43 Mt of REEs were mobilized (~12% of the syenite-fenite system total rare-earth-oxide [TREO] budget), a mass comparable to the tonnages of some of the world's largest HFSE resources. We argue that fenite can yield crucial information about the tipping points in magma evolution because retention and/or loss of volatile-bonded alkali and HFSEs are key factors in the development of magmatic zirconosilicate-hosted HFSE ores (e.g., Kringlerne, at Ilímaussaq), or the formation of the syenite-hosted Nb-Ta-REE (Motzfeldt-type) roof-zone deposits.
DS202203-0366
2021
Soonthorntantikul, W., Atikarnsakul, U., Vertriest, W.Blue sapphires from Mogok, Myanmar: a gemological review.Gems & Gemology, Vol. 57, pp. 292-317.Asia, Myanmarsapphire

Abstract: Burmese sapphires are among the most coveted colored gemstones in the world. The historical importance of this source and the fine quality of its high-grade material contribute to the legendary status of these gems. Since Mogok is such a long-known source, there are many classic studies available, but modern analytical data are often missing or not up to current standards. This article summarizes the characteristics of Burmese sapphires, including standard gemological properties, inclusion observations, and spectroscopic and trace element analyses. This information was collected from hundreds of blue sapphires that GIA's field gemologists sampled while visiting different mining regions in Mogok over the past decade. Our observations indicate that these sapphires show a wide range of blue color intensities but very consistent inclusion scenes. Trace element chemistry did not show any significant differences between various regions apart from a wider range of Fe concentrations in sapphires from north of Mogok. Rare observations such as orange fluorescence and unusual FTIR spectra can be attributed to the chemical compositions of the sapphires.
DS202202-0217
2022
Sparks, R.S.J., Blundym J.D., Cashman, K.V., Jackson, M., Rust, A., Wilson, C.J.N.Large silicic magma bodies and very large magnitude explosive eruptions. *** not specific to diamondsBulletin of Volcanology, Vol. 84, 8, 6p. PdfMantlemagmatism

Abstract: Over the last 20 years, new concepts have emerged into understanding the processes that lead to build up to large silicic explosive eruptions based on integration of geophysical, geochemical, petrological, geochronological and dynamical modelling. Silicic melts are generated within magma systems extending throughout the crust by segregation from mushy zones. Segregated melt layers become unstable and can assemble into ephemeral upper crustal magma chambers rapidly prior to eruption. In the next 10 years, we can expect major advances in dynamical models as well as in analytical and geophysical methods, which need to be underpinned in field research.
DS202205-0720
2022
Srivastava, R.K., Guarino, V., Melluso, L.Early Cretaceous ultramafic-alkaline-carbonatite magmatism in the Shilong Plateau-Mikir Hills, northeastern India - a synthesis.Mineralogy and Petrology, 10.1007/s00710-022-00777-z 20p. PdfIndiadeposit - Shilong Plateau

Abstract: A comprehensive mineralogical, geochemical and isotopic review of six ultramafic-alkaline-carbonatite magmatic intrusions of the Shillong Plateau (Sung Valley, Jasra, Swangkre-Rongjeng, and Mawpyut) and Mikir Hills (Samchampi-Samteran and Barpung) is presented here, using the published data. These intrusions emplaced ca. 115-102 Ma ago, thus are significantly younger than the tholeiitic flood basalts erupted in Rajmahal-Sylhet province (ca. 118-115 Ma). The intrusive lithologies vary from ultramafic (dunites, clinopyroxenites, melilitolites) to mafic (ijolites, gabbros sensu lato, shonkinites), to felsic (syenites, nepheline syenites) and carbonatites (mostly calcite-rich varieties). The volcanic-subvolcanic facies (lamprophyres, phonolites) are not abundant. The range of chemical compositions of the magmatic phases in the various assemblages is notable; the intrusive rocks are thus the result of crystallization of magmas from variably evolved, independent liquid-lines-of descent, generally of alkaline/strongly alkaline lineages and sodic-to-potassic in affinity. The large variations of the Sr-Nd isotopic ratios of the silicate intrusive rocks (sensu lato) suggest a role of shallow-level crustal contamination during their formation. The carbonatites of the Sung Valley and Samchampi-Samteran have different isotope ratios than the associated silicate rocks, have some isotopic affinity with the Group I tholeiitic basalts of Rajmahal Traps and have an ultimate genesis in a carbonate-bearing lithospheric mantle.
DS202201-0042
2021
Stachel, T., Grutter, H.Are peridotitic diamond substrates distinct from diamond-free cratonic peridotites?GAC/MAC Meeting UWO, 1p. Abstract p. 286.Globalperidotites

Abstract: The principal distinction between diamond substrates and the cratonic mantle roots as sampled by garnet peridotite xenoliths is the much higher proportion of harzburgite (-dunite) to lherzolite (-wehrlite) in the former (~85:15 %) compared to the latter (18:82 %). Dunitic mineralogies are common diamond substrates (~38%) but rarely documented in xenoliths (~2 %). Using mineral Mg# as an indicator of source depletion through melt extraction again documents the more depleted character of diamond substrates relative to the cratonic garnet-peridotite xenolith record. On a like-for-like paragenesis level, however, olivine inside and outside of diamond has statistically indistinguishable means in Mg#. This observation implies: (1) that the major element composition of inclusions is imposed largely by the substrate and not by the diamond forming medium and (2) that widespread Fe-rich metasomatism of the lithospheric mantle did not occur subsequent to diamond formation (Paleoarchean to Mesoproterozoic). The latter conclusion precludes neither localized metasomatic shifts in Mg#, nor metasomatism by small melt fractions/fluids subsequent to diamond formation, as such events have low fluid/rock ratios and hence limited impact on bulk rock Mg#. A distinctive feature of inclusions relative to xenolith minerals is the higher Cr/Al of garnet and chromite in diamond. Higher Cr/Al for inclusions is not limited to the harzburgitic-dunitic paragenesis, but also occurs among lherzolitic inclusions. This suggests that the almost exclusive restriction of Cr2O3 contents >13 wt% to inclusion garnets is not a consequence of higher degrees of primary melt depletion being restricted to, or preferentially preserved, in diamond substrates. Instead, the very high Cr contents in a subset of inclusions likely relate to the pressure and temperature dependence of the distribution of Cr between garnet and spinel. Experiments showed inclusion-like high Cr/Al for coexisting Cr-pyrope and Cr-spinel in harzburgite at high pressures and temperatures (>5 GPa and >1200 °C; Girnis and Brey 1999). High Cr/Al inclusion compositions thus likely reflect some diamond growth occurring over a wide range of temperatures, elevated above a cratonic geotherm during high-temperature thermal perturbations. Na and Ti are sensitive indicators of mantle metasomatism. Enrichment of Na and Ti in both inclusion and xenolith minerals is most prominent in the lherzolitic paragenesis and very intense Ti-rich metasomatism is almost entirely restricted to lherzolite xenoliths that resided at temperatures >1130 °C, i.e. above the hydrous solidus. Since equilibration temperatures of >1130 °C are common also for inclusions, the near absence of intense Ti-metasomatism in inclusions likely relates to either a diamond unfriendly character of such metasomatism or an increase in Ti-metasomatic intensity or frequency subsequent to principally Archean-Mesoproterozoic formation of peridotitic diamonds.
DS202205-0721
2022
Stefano, C.J., Betts, J.H.The Ekati and Diavik diamond mines, Lac de Gras, Northwest Territories. Diamond photosMineralogical Record, Vol. 53, 2, pp. 243-259.Canada, Northwest TerritoriesDeposit - Ekati, Diavik
DS202203-0367
2021
Stoppa, F.Evolution and involution of carbonatite thoughts. Kamafugites ( kasilite melilitites)Elements, Vol. 17, pp. 303-304.Europe, Italyhistory

Abstract: During my doctoral studies, in the late 1980s, I realised that the Italian kamafugites (kalsilite melilitites) had to be related to carbonatite magmatism. I started a detailed study of the kamafugitic sites, and I explored remote areas deep in Italy’s Apennine mountains. When I found the Polino carbonatite, I put a few drops of acid on it, and the rock reacted. I have a vivid memory of my heart beating faster. I had found it! My fellow geologists were somewhat sceptical, but the late Professor Giorgio Marinelli (1922-1993) encouraged me and predicted many new carbonatite discoveries. He was right. Overcoming my Latin temperament, I focused on the concept that carbonatites, however unusual as rocks, cannot be dismissed as simple geological oddities but require detailed and comprehensive study. I am fond of all the history that marked my latest 40 years of life, and it reminds me of the many friends and mentors that I have had, especially when I was a young researcher. Sadly, some of them are no longer with us. I am so grateful to them, and I consider it a life-changing experience to have met them
DS202204-0537
2022
Su, J-H., Zhao, X-F., Li, X-C., Hu, W., Chen. W., Slezak, P.Unmixing of REE-Nb enriched carbonatites after incremental fractionation of alkaline magmas in the Shixiongdong complex, central China.Lithos, Vol. 416-417, 18p. 106651ChinaREE
DS202204-0538
2022
Takayuk, ilshii., Ohtani, E., Shatskiy, A.Aluminum and hydrogen partitioning between bridgmanite and high-pressure hydrous phases: implications for water storage in lower mantle.Earth and Planetary Science Letters, Vol. 583, 8p. 117441Mantlebridgmanite

Abstract: We clarified the phase relations of MgSiO3-Al2O3-H2O system under the uppermost lower-mantle conditions and the partitioning of aluminum and hydrogen between bridgmanite and hydrous minerals of hydrous phase ?-H solid solution and aluminous hydrous phase D. Bridgmanite coexists with hydrous phase D and ?-H at 25-28 GPa and 1000-1100 °C. Hydrous phase D becomes unstable above 1200 °C, while hydrous phase ?-H remains up to 1400 °C in the pressure range. Aluminum is strongly partitioned to both aluminous phases D and ?-H resulting in alumina depletion in bridgmanite. Fourier transform infrared spectroscopy indicates that bridgmanite contains undetectable water when coexisting with these hydrous phases, showing strong hydrogen partitioning into hydrous phases, such as phases D and ?-H. The depletion of alumina in bridgmanite modified the phase relations significantly in hydrated slabs descending into the lower mantle, i.e., the pressures of the garnet-bridgmanite and post-perovskite transformations are lowered under the wet conditions where these hydrous phases coexist. The dry nature of bridgmanite coexisting with hydrous phases suggests that the major water carriers in the lower mantle are hydrous phases. Bridgmanite cannot be the water reservoir at least in the upper part of the lower mantle and could provide dry rheology of the wet slabs in the lower mantle.
DS202201-0043
2022
Tamblyn, R., Hasterok, D., Hand, M. , Gard, M.Mantle heating at ca. 2 Ga by continental insulation: evidence from granites and eclogites ** not specific to diamonds.Geology, Vol. 50, 1 pp. 91-95.Mantlethermometry
DS202202-0218
2022
Tamblyn, R., Hasterok, D., Hand, M., Gard, M.Mantle heating at ca 2 Ga by continental insulation: evidence from granites and eclogites.Geology, Vol. 50, 1, pp. 91-96.Mantleeclogites

Abstract: Igneous and metamorphic rocks contain the mineralogical and geochemical record of thermally driven processes on Earth. The generally accepted thermal budget of the mantle indicates a steady cooling trend since the Archean. The geological record, however, indicates this simple cooling model may not hold true. Subduction-related eclogites substantially emerge in the rock record from 2.1 Ga to 1.8 Ga, indicating that average mantle thermal conditions cooled below a critical threshold for widespread eclogite preservation. Following this period, eclogite disappeared again until ca. 1.1 Ga. Coincident with the transient emergence of eclogite, global granite chemistry recorded a decrease in Sr and Eu and increases in yttrium and heavy rare earth element (HREE) concentrations. These changes are most simply explained by warming of the thermal regime associated with granite genesis. We suggest that warming was caused by increased continental insulation of the mantle at this time. Ultimately, secular cooling of the mantle overcame insulation, allowing the second emergence and preservation of eclogite from ca. 1.1 Ga until present.
DS202202-0219
2022
Tan, W., Qin, X., Liu, J., Zhou, M-F., He, H., Yang, C.Y., Huang, J., Zhu, J., Yao, Y., Cudahy, T.Feasibility of visible short-wave infrared reflectance spectroscopy to characterize regolith-hosted rare earth element mineralization.Economic Geology, Vol. 117, 3, pp. 485-494.Chinadeposit - Renju

Abstract: Regolith-hosted rare earth element (REE) deposits predominate global resources of heavy REEs. Regoliths are underlain by various types of igneous rocks and do not always host economically valuable deposits. Thus a feasible and convenient method is desired to identify REE mineralization in a particular regolith. This study presents a detailed visible short-wave infrared reflectance (VSWIR) spectroscopic study of the Renju regolith-hosted REE deposit, South China, to provide diagnostic parameters for targeting REE orebodies in regoliths. The results show that the spectral parameters, M794_2nd and M800_2nd, derived from the VSWIR absorption of Nd3+ at approximately 800 nm, can be effectively used to estimate the total REE concentrations in regolith profiles. M1396_2nd/M1910_2nd ratios can serve as proxies to evaluate weathering intensities in a regolith. Abrupt changes of specific spectral features related to mineral abundances, chemical compositions, and weathering intensities can be correlated with variations of protolith that formed a regolith. These VSWIR proxies are robust and can be used for exploration of regolith-hosted REE deposits.
DS202202-0220
2022
Tappe, S., Shaikh, A.M., Wilson, A.H., Stracke, A.Evolution of ultrapotassic volcanism on the Kaapvaal craton: deepening the orangeite versus lamproite debate.Geological Society of London Special Publication 513, pp. 17-44.Africa, South Africalamproites

Abstract: Orangeites are a significant source of diamonds, yet ambiguity surrounds their status among groups of mantle-derived potassic rocks. This study reports mineralogical and geochemical data for a c. 140 Ma orangeite dyke swarm that intersects the Bushveld Complex on the Kaapvaal craton in South Africa. The dykes comprise distinctive petrographic varieties that are linked principally by olivine fractionation, with the most evolved members containing minor amounts of primary carbonate, sanidine and andradite garnet in the groundmass. Although abundant groundmass phlogopite and clinopyroxene have compositions that are similar to those of cratonic lamproites, these phases show notable Ti-depletion, which we consider a hallmark feature of type orangeites from the Kaapvaal craton. Ti-depletion is also characteristic of bulk rock compositions and is associated with strongly depleted Th-U-Nb-Ta contents at high Cs-Rb-Ba-K concentrations. The resultant high large ion lithophile element/high field strength element ratios of orangeites suggest that mantle source enrichment occurred by metasomatic processes in the proximity of ancient subduction zones. The Bushveld-intersecting orangeite dykes have strongly enriched Sr-Nd-Hf isotopic compositions (initial 87Sr/86Sr = 0.70701-0.70741; ?Nd = ?10.6 to ?5.8; ?Hf = ?14.4 to ?2.5), similar to those of other orangeites from across South Africa. Combined with the strong Ti-Nb-Ta depletion, this ubiquitous isotopic feature points to the involvement of ancient metasomatized mantle lithosphere in the origin of Kaapvaal craton orangeites, where K-rich metasomes imparted a ‘fossil’ subduction geochemical signature. Previous geochronology studies identified ancient K-enrichment events within the Kaapvaal cratonic mantle lithosphere, possibly associated with collisional tectonics during the 1.2-1.1 Ga Namaqua-Natal orogeny of the Rodinia supercontinent cycle. It therefore seems permissible that the cratonic mantle root was preconditioned for ultrapotassic magma production by tectonomagmatic events that occurred along convergent plate margins during the Proterozoic. However, reactivation of the K-rich metasomes had to await establishment of an extensional tectonic regime, such as that during the Mesozoic breakup of Gondwana, which was accompanied by widespread (1000 × 750 km) small-volume orangeite volcanism between 200 and 110 Ma. Although similarities exist between orangeites and lamproites, these and other potassic rocks are sufficiently distinct in their compositions such that different magma formation processes must be considered. In addition to new investigations of the geodynamic triggers of K-rich ultramafic magmatism, future research should more stringently evaluate the relative roles of redox effects and volatile components such as H2O-CO2-F in the petrogeneses of these potentially diamondiferous alkaline rocks.
DS202205-0722
2022
Tech BullionA never before seen mineral transported from deep Earth. Davemaoite see prev. Ref . In archives Tschauner 2021techbullion.com, techbullion.com/a-never-before-seen-mineral-transported-from-deep-earth Mar. 1, 2p.Mantlemineralogy

Abstract: The Earth’s mantle is 1,800 miles deep and accounts for around 84 percent of the planet’s volume. The stratum of largely solid rock, on the other hand, is characterized by high heat and crushing pressure, making it a challenge to be analyzed by geologists. Instead, they investigate the minerals and rocks that are brought to the surface by volcanic eruptions. According to a research study published last week in the journal Science, a team of scientists has identified a new mineral trapped within a diamond. The mineral was given the name davemaoite by the researchers after the well-known geophysicist Ho-Kwang (Dave) Mao. The mineral, calcium silicate perovskite, formed more than 400 miles down and gives geologists a view into the lower mantle’s chemical makeup, according to Live Science’s Harry Baker. These tiny black specks found in an African mine diamond are being hailed as a vital component of the deep earth, uncovered in nature for the first time after decades of seeking.
DS202203-0368
2021
Timmerman, S., Spivak, A.V., Jones, A.P.Carbonatitic melts and their role in diamond formation in the deep earth.Elements, Vol. 17, pp. 321-326.Mantlediamond genesis

Abstract: Carbonatitic high-density fluids and carbonate mineral inclusions in lithospheric and sub-lithospheric diamonds reveal comparable compositions to crustal carbonatites and, thus, support the presence of carbon-atitic melts to depths of at least the mantle transition zone (~410-660 km depth). Diamonds and high pressure-high temperature (HP-HT) experiments confirm the stability of lower mantle carbonates. Experiments also show that carbonate melts have extremely low viscosity in the upper mantle. Hence, carbonatitic melts may participate in the deep (mantle) carbon cycle and be highly effective metasomatic agents. Deep carbon in the upper mantle can be mobilized by metasomatic carbonatitic melts, which may have become increasingly volumetrically significant since the onset of carbonate subduction (~3 Ga) to the present day.
DS202205-0723
2022
Tovey, M., Giuliani, A., Phillips, D., Nowicki, T., Pearson, D.G., Fedorchouk, Y., Russell, J.K.Controls on the emplacement style of coherent kimberlites in the Lac de Gras Field, Canada.Journal of Petrology, 10.1093/petrology/egac028/6553928 24p. pdf Canada, Northwest Territoriesdeposit - Lac de Gras

Abstract: In the Lac de Gras (LDG) kimberlite field, Northwest Territories, Canada, coherent kimberlites (CKs) occur as tabular dykes, pipe-shaped diatremes, and irregular bodies without well-defined geometries. Combining the morphology of CK bodies with the occurrence of fragmented olivine microcrysts allows distinction of four CK types at LDG: (1) dykes with no broken olivine; (2) CK without well-defined but probable sheet geometry and no broken olivine; (3) pipe-filling CK (pfCK) with abundant broken olivine and (4) pfCK with no broken olivine. These features suggest an intrusive origin for type 1 and, probably, type 2 CK; a high-energy extrusive emplacement for CK type 3 and a low-energy intrusive or extrusive emplacement for the CK type 4. Here, we compare petrographic and whole-rock, olivine and spinel compositional data for high-energy extrusive pfCK, low-energy pfCK and intrusive CK units to understand the factors controlling their variable emplacement styles. Extrusive CK contain more abundant groundmass phlogopite and monticellite, lower carbonate/silicate mineral abundance ratios and significantly lower dolomite and pleonaste-spinel abundances compared to intrusive CK. This indicates greater CO2 loss and higher H2O/CO2 in the melt phase for the extrusive CK during emplacement. Lower incompatible element concentrations in the extrusive CKs and different chromite Ti# and olivine rim Mg# indicate derivation from distinct primitive melt compositions. The extrusive CK feature higher ?Ndi and marginally higher ?Hfi compositions than the intrusive CK, pointing to derivation from distinct sources. These findings strongly imply that distinct primary melt compositions were largely responsible for the differences in emplacement styles of CK at LDG. Low-energy pfCKs have similar olivine rim Mg#, chromite Ti# and, hence, primitive melt compositions to the high-energy extrusive CK samples. Their marginally different emplacement styles may depend on local factors, such as changing stress regimes, or slightly different volatile concentrations. Both types of pfCK might reflect the waning stages of volcanic sequences resulting from the eruption of a segregated magma column that started with pipe excavation and the explosive emplacement of gas-rich magma (volcaniclastic kimberlite), followed by the less energetic emplacement of melt-rich magma (pfCK). This hypothesis underscores different primary melt compositions for dyke vs pipe-forming (and filling) kimberlites and hence a fundamental primary melt control on the explosivity of kimberlites.
DS202201-0044
2021
Toyama, C., Sumino, H., Okabe, N., Ishikawa, A., Yamamoto, J., Kaneoka, I., Muramatsu, Y.Halogen heterogeneity in the subcontinental lithospheric mantle revealed by I/Br ratios in kimberlites and their mantle xenoliths from South Africa, Greenland, China, Siberia, Canada and Brazil.American Mineralogist, Vol. 106, pp. 1890-1899.Africa, South Africa, Europe, Greenland, China, Russia, Siberia, Canada, South America, Brazilsubduction, metasomatism

Abstract: To investigate halogen heterogeneity in the subcontinental lithospheric mantle (SCLM), we measured the concentrations of Cl, Br, and I in kimberlites and their mantle xenoliths from South Africa, Greenland, China, Siberia, Canada, and Brazil. The samples can be classified into two groups based on halogen ratios: a high-I/Br group (South Africa, Greenland, Brazil, and Canada) and a low-I/Br group (China and Siberia). The halogen compositions were examined with the indices of crustal contamination using Sr and Nd isotopes and incompatible trace elements. The results indicate that the difference between the two groups was not due to different degrees of crustal contamination but from the contributions of different mantle sources. The low-I/Br group has a similar halogen composition to seawater-influenced materials such as fluids in altered oceanic basalts and eclogites and fluids associated with halite precipitation from seawater. We conclude that the halogens of the high-I/Br group are most likely derived from a SCLM source metasomatized by a fluid derived from subducted serpentinite, whereas those of the low-I/Br group are derived from a SCLM source metasomatized by a fluid derived from seawater-altered oceanic crust. The SCLM beneath Siberia and China could be an important reservoir of subducted, seawater-derived halogens, while such role of SCLM beneath South Africa, Greenland, Canada, and Brazil seems limited.
DS202205-0724
2022
Tshiningayamwe, M., Bolhar, R., Nex, P.A.M., Ueckermann, H., Chang, Q.An apatite trace element and Sr-Nd isotope geochemical study of syenites and carbonatite, exemplified by the Epembe alkaline-carbonatite complex, Namibia.Lithos, 10.1016/j.lihos.2022. 106699 45p. PdfAfrica, Namibiadeposit - Epembe

Abstract: The Epembe Alkaline Carbonatite Complex (EACC) in northwestern Namibia was emplaced along a fault zone into medium- to high-grade Palaeoproterozoic basement rocks of the Epupa Metamorphic Complex (EMC), and extends over a distance of 9 km in a south-easterly direction with a width of 1 km. Nepheline syenite with minor syenite constitute the main lithologies, cross-cut by a calcite?carbonatite dyke. Apatite grains from one syenite, six nepheline syenite and five carbonatite samples were studied using cathodoluminescence (CL) imaging, trace element and Sr-Nd isotope compositions as well as U-Pb geochronology. Syenite-hosted apatite is homogenous in CL and contains the highest concentration of REE (9189-44,100 ppm) with light rare-earth element (LREE) enrichment (LaN/YbN = 4-91) relative to heavy (H) REE consistent with a magmatic origin. Negative Eu anomalies (Eu/Eu* = 0.4-0.9) in syenite apatite are attributed to the formation of apatite in an evolved mantle-derived melt associated with plagioclase fractionation. Nepheline syenite and carbonatite-hosted apatite is also commonly homogeneous in CL, while core-rim zoning and patchy textures are observed occasionally. Both texturally homogeneous and core-rim zoned apatite are enriched in LREE (LaN/YbN = 24-9) relative to HREE, consistent with a magmatic origin. Core-rim zoned apatite is characterized by rim-ward increase in REE concentrations, which can be attributed to mineral fractionation. Patchy apatite is depleted in Na, Y and REE, particularly the LREE (LaN/YbN = 4-19) relative to other nepheline syenite apatite, reflecting interaction with fluids (metasomatism). The strontium isotope composition of metasomatic apatite and magmatic apatite is indistinct suggesting a magmatic origin of the alteration fluids. No Eu anomalies (Eu/Eu* = 1) in chondrite-normalized REE patterns are observed in any apatite hosted by nepheline syenite and carbonatite. An LA-ICPMS U-Pb age of 1216 ± 11 Ma (MSWD = 4.3, 2 SE) for apatite constrains emplacement of the syenite, while magmatic nepheline syenite apatite ages are 1193 ± 14 Ma, 1197 ± 17 Ma and 1194 ± 16 Ma (MSWDs <4.0, 2 SE). The Sr and Nd isotopic composition of apatite in syenite (87Sr/86Sr(i) = 0.7035-0.7048; ?Nd(t) = +2.5 to +3.2), nepheline syenites (87Sr/86Sr(i) = 0.7031-0.7037; ?Nd(t) = +1.5 to +4.4) and carbonatite (87Sr/86Sr(i) = 0.7031-0.7033; ?Nd(t) = 0 to +3.3) overlap, pointing to a common but heterogeneous source, located in the sub-lithospheric mantle.
DS202204-0539
2022
Turner, S.J., Langmuir, C.H.Sediment and ocean crust both melt at subduction zones.Earth and Planetary Science Letters, Vol. 584, 13p. 117424Mantlesubduction

Abstract: Hydrous arc magmas are produced when water-bearing materials from subducted oceanic plates are transported to the mantle beneath volcanic arcs, though the mechanism of mass transport remains debated. The geochemical characteristics of the slab component have important implications for the thermal structures of down-going plates and the fluxes of elements into the deep mantle. If slab temperatures are low, then elemental fluxes from the slab will be carried in a dilute fluid. If temperatures are high, the slab may melt instead. While a long-standing paradigm for arc volcanism has been that sediments melt and ocean crust dehydrates, a growing body of evidence from arc geochemistry and experimental petrology suggests both sediment and ocean crust melt. The low solubility of many elements in aqueous fluids prevents them from making a substantial contribution to arc mass-balance. Constraints from Sr concentrations and 87Sr/86Sr ratios require a large flux of Sr from the ocean crust, which is only possible if the crust melts. H2O/Sr ratios of arc volcanics are also inconsistent with slab fluids. These conclusions are supported by thermo-mechanical models indicating that slab temperatures exceed the hydrous solidus for both ocean crust and sediments. Examination of experimental data shows a likely strong effect of oxygen fugacity on residual phases during slab melting. Arc data are best explained if the ocean crust melts beneath all arcs under oxidizing conditions somewhere between FMQ and NNO+2. Experimental constraints on sediments also require melting and that sediment melt compositions depend on bulk composition as well as temperature. If these experiments serve as analogs to sediment melting beneath arcs, then sediment bulk compositions are a necessary input for any rare earth element-based slab thermometer. We present compositions for ocean crust partial melts and partition coefficients for sediment melting based on existing experiments, physical models, and arc data, that can be used in geochemical models of arc volcanism.
DS202204-0540
2022
Van Rythoven, A.D., Schulze, D.J., Stern, R.A., Lai, M, Y.Composition of diamond from the 95-2 pipe, Lake Timiskaming kimberlite cluster, Superior craton, Canada.The Canadian Mineralogist, Vol. 60, pp. 67-90. pdfCanada, Ontariocathodluminenescence

Abstract: Forty-one samples of diamond from the Jurassic 95-2 kimberlite pipe in the Lake Timiskaming Kimberlite Cluster, Superior Craton, Canada, were imaged using cathodoluminescence and analyzed by secondary ion mass spectrometry and Fourier-transform infrared absorbance spectrometry to determine carbon stable isotope composition, total nitrogen abundance, and nitrogen aggregation state. The carbon isotope compositions results (?13CVPDB) range from -9.11 to -3.57‰, with a mean value of -5.8‰. Intra-stone variation is small (maximum ?2.2‰, and in most individual diamond samples <1‰). Nitrogen contents range from 0.5 to 2040 ppm (mean of 483 ppm). The greatest range of values in a single stone is 825 ppm. The samples are poorly aggregated in terms of nitrogen. The samples are mostly type IaA or IaAB, with a few bordering on type Ib. Diamond growth was episodic, with nitrogen behaving highly compatibly (i.e., D = [N]diamond/[N]fluid >> 1). Precipitation was likely from a carbonate-rich fluid in a peridotitic (lherzolitic) environment within the mantle of the central Superior Craton. This generation of diamond growth is very similar to those reported from the Jurassic age Victor and U2 pipes of the Attawapiskat Kimberlite Cluster, and distinct from a possibly much older (>1.1 Ga) generation of diamond reported in other older host rocks (T1, Wawa, Lynx, and Renard). This older generation of diamond at these other localities is also predominantly of the peridotitic (harzburgitic) paragenesis but contains far less nitrogen (although typically more aggregated as B centers) and has higher ?13CVPDB. The younger generation of diamond formed after mantle heating during formation of the Mid-Continental Rift (ca. 1.1 Ga) destroyed any proximal prior generation(s) of diamond. Igneous activity after 1.1 Ga subsequently refertilized the cratonic mantle to a lherzolitic paragenesis in which the younger generation precipitated.
DS202201-0045
2021
Vanneste, T.Blood, Sweat and Earth: The struggle for control over the world's diamonds through history.Reaktion Books, London UK, isbn 978-1789144352GlobalBook - notice

Abstract: Blood, Sweat and Earth is a hard-hitting historical exposé of the diamond industry, focusing on the exploitation of workers and the environment, the monopolization of uncut diamonds, and how little this has changed over time. It describes the use of forced labor and political oppression by Indian sultans, Portuguese colonizers in Brazil, and Western industrialists in many parts of Africa - as well as the hoarding of diamonds to maintain high prices, from the English East India Company to De Beers. While recent discoveries of diamond deposits in Siberia, Canada, and Australia have brought an end to monopolization, the book shows that advances in the production of synthetic diamonds have not yet been able to eradicate the exploitation caused by the world’s unquenchable thirst for sparkle.
DS202205-0725
2021
Vasilev, E., Kriulina, G.Y., Garanin, V.K.Spectroscopy of diamonds from the M.V. Lomonosov deposit.Geology of Ore deposits, Vol. 63, pp. 668-684. pdfRussiadeposit - Lomonosov

Abstract: Diamond crystals from the M.V. Lomonosov deposit (Archangelsk oblast, Russia) were studied by luminescence and infrared spectroscopy. Three groups of crystals were distinguished according to their morphology, thermal history, and photoluminescence. The structural diversity of yellow cuboids typical for the deposit is demonstrated. New photoluminescence systems among the low-temperature cuboid crystals are observed.
DS202204-0541
2022
Vasilev, E.A., Kriulina, G.Yu., Garanin, V.K.Spectroscopy of diamond from the M.V. Lomonosov deposit.Geology of Ore Deposits, Vol. 63, 7, pp. 668-674.Russia, Kola Peninsuladeposit - Lomonosov

Abstract: Diamond crystals from the M.V. Lomonosov deposit (Archangelsk oblast, Russia) were studied by luminescence and infrared spectroscopy. Three groups of crystals were distinguished according to their morphology, thermal history, and photoluminescence. The structural diversity of yellow cuboids typical for the deposit is demonstrated. New photoluminescence systems among the low-temperature cuboid crystals are observed.
DS202205-0726
2022
Veglio, C., Lawley, C.J.M., Kjarsgaard, B., Petts, D., Pearson, G., Jackson, S.E.Olivine xenocrysts reveal carbonated mid-lithosphere in the northern Slave craton.Lithos, 10.1016/j.lithos.2022.106633, 14p. PdfCanada, Northwest Territoriesolivine

Abstract: The cold, rigid, and melt-depleted mantle underlying Archean cratons plays an important role in the preservation of the overlying continental crust and is one of the main sources of diamonds. However, with the possible exception of rare earth elements (REE) and platinum group-elements (PGE), the concentrations and host mineral phases for many other critical trace elements within lithospheric mantle remain very poorly understood. Here we address that knowledge gap, presenting new electron microprobe and laser-ablation inductively-coupled-plasma mass-spectrometry results for a suite of mantle xenoliths (n = 12) and olivine xenocrysts (n = 376) from the Jericho, Muskox, and Voyageur kimberlites (northern Slave craton, Canada). Low-temperature (<1000 °C) harzburgite xenoliths and olivine xenocrysts suggest that the shallowest portions of the garnet-bearing mantle (?160 km) underlying the northern Slave craton is chemically depleted and becomes increasing re-fertilized from 160 to 200 km. High-temperature (>1000 °C) garnet and clinopyroxene crystals with Ti/Eu ratios > > 1000, and olivine xenocrysts suggest that interaction with ultramafic silicate melts is the most likely mechanism to re-fertilize melt-depleted peridotite with incompatible elements toward the base of the lithosphere (~200 km). In contrast, lower temperature garnet and clinopyroxene with Ti/Eu ratios <1000 are more likely related to metasomatism by carbonatitic melts and/or fluids. Carbonatitic metasomatism is also interpreted as the preferred explanation for the trend of Nb (4 ppm)- and Ta (185 ppb)-rich concentrations of olivine xenocrysts sampled from mid-lithosphere depths (~140 km). With the exception of a few elements that substitute into the olivine crystal structure during sub-solidus re-equilibration (e.g., Ca, Cr, Cu, Na, Sc, V, Zn), most other olivine-hosted trace elements do not systematically vary with depth. Instead, we interpret olivine-hosted trace element concentrations that are significantly above the analytical detection and/or quantification limits to reflect trapped fluid (e.g., As, Mo, Sb, Sn), base-metal sulphide (e.g., Ag, Au, Bi, Pd, Pt, Se, Te), and other mineral inclusions (e.g., U, Th) rather than enrichments of these elements due to substitution reactions or analytical artefacts. We interpret that these inclusions occur in olivine throughout the garnet stability field, but are relatively rare. As a result, these trapped carbonatitic, proto-kimberlite, and/or other ultramafic silicate melts do not represent a significant source for the suite of trace elements that become enriched to economic levels in the crust.
DS202205-0727
2022
Viladkar, S.G., High-field strength elements in carbonatites of Siriwasan, Gujarat, India.Journal of Geological Society of India, Vol. 98, p. 440. 1p.Indiadeposit - Siriwasan
DS202203-0369
2022
Vladkar, S.G.Nb-bearing minerals in Sirwasan carbonatite, Chhota Udapur, Gujarat, India.Journal of the Geological Society of India, Vol. 98, 2, p. 285. (1p)Indiadeposit - Sirwasan
DS202204-0542
2022
Vladykin, N.V., Ashchepkov, I.V., Sotnikova, I.A., Medvedev, N.S.Lamproites of Kayla pipe and their mantle xenocrysts, SE Aldan shield, Russia: geochemistry and petrology.Jounral of Earth System Science, Vol. 131 81 doi.org/10/1007/s12040-022-01814-3 19p. PdfRussiadeposit - Kayla

Abstract: Origin of abundant alkaline and related lamproite massifs and dykes in Aldan shield have no explanation and the geochemistry of rocks and their xenocrysts is used for the explanation. Bulk-rock geochemistry, mineral chemistry data of the Kayla lamproites of Russia and mineral chemical data (trace and rare elements) of the mantle xenocrysts found in these lamproites was studied using ICP MS and electron microprobe analyses (EPMA). The trace element spectrum of Kayla tuffs and breccias show the similarity with the olivine lamproites and belong to the orogenic type according to Th-U-Nb systematics. Primitive mantle normalized trace element (TRE) spider diagrams show right-leaning patterns with the peaks in large ion lithophile elements Sr, Pb, U, and troughs in Ta, Nb suggesting melting of original peridotites mixed with the ancient EMI (according to Nd, Sr isotopes) source probably belonging to eclogites or lower crust. The age of the emplacement is 132-134 Ma, similar to the Chompolo lamprophyres and many other alkaline Aldan complexes. Thermo-barometric estimation from Cr-diopsides and chromites xenocrysts suggest the origin from the spinel-garnet transition in the lithospheric mantle region. The P-T estimates derived from low-Cr-clinopyroxene xenocrysts, and related to lamproites show a high heat flow of 90 mW/m2 due to interaction with the plume-related magma. The Cr-diopsides and chromites give 45 mW/m2 geotherm similar to regional heat flow. The chondrite normalized rare earth element (REE) pattern for chrome-diopsides is steeper, compared to the low-chrome varieties. Primitive mantle normalized spidergram of Cr-diopsides displays peaks for Sr, U, and Th, and deep troughs of Nd, Nb, Ta. REE. The trace element spider diagrams of both types of xenocrysts show that they were equilibrated with the lamproitic melts and reconstructed parental melts of low-Cr-clinopyroxene coincides with the lamproite spectrums.
DS202205-0728
2022
Voosen, P.The planet inside.Science, Vol. 376, 6588, pp. 18-22. 10.1126/wcience.abq2090MantleCore-mantle

Abstract: Earth’s magnetic field, nearly as old as the planet itself, protects life from damaging space radiation. But 565 million years ago, the field was sputtering, dropping to 10% of today’s strength, according to a recent discovery. Then, almost miraculously, over the course of just a few tens of millions of years, it regained its strength—just in time for the sudden profusion of complex multicellular life known as the Cambrian explosion. What could have caused the rapid revival? Increasingly, scientists believe it was the birth of Earth’s inner core, a sphere of solid iron that sits within the molten outer core, where churning metal generates the planet’s magnetic field. Once the inner core was born, possibly 4 billion years after the planet itself, its treelike growth—accreting a few millimeters per year at its surface—would have turbocharged motions in the outer core, reviving the faltering magnetic field and renewing the protective shield for life. “The inner core regenerated Earth’s magnetic field at a really interesting time in evolution,” says John Tarduno, a geophysicist at the University of Rochester. “What would have happened if it didn’t form?” Just why and how the inner core was born at that moment is one of many lingering puzzles about the Pluto-size orb 5000 kilo meters underfoot. “The inner core is a planet within a planet,” says Hrvoje Tkal?i?, a seismologist at Australian National University (ANU)—with its own topography, its own spin rate, its own structure. “It’s beneath our feet and yet we still don’t understand some big questions,” Tkal?i? says. But researchers are beginning to chip away at those questions. Using the rare seismic waves from earthquakes or nuclear tests that penetrate or reflect off the inner core, seismologists have discovered it spins independently from the rest of the planet. Armed with complex computer models, theorists have predicted the structure and weird behavior of iron alloys crushed by the weight of the world. And experimentalists are close to confirming some of those predictions in the lab by re-creating the extreme temperatures and pressures of the inner core. Arwen Deuss, a geophysicist at Utrecht University, feels a sense of anticipation that may resemble the mood in the 1960s, when researchers were observing seafloor spreading and on the cusp of discovering plate tectonics, the theory that makes sense of Earth’s surface. “We have all these observations now,” she says. It’s simply a matter of putting them all together.
DS202205-0729
2022
Wang, C., Zhang, Z., Giuliani, A., Cai, R., Cheng, Z., Liu, J.New insights into the mantle source of a large igneous province from highly siderophile element and Sr-Nd-Os isotope compositions of carbonate-rich ultramafic lamprophyres.Geochimica et Cosmochimica Acta, Vol. 326, pp. 77-96.Chinaallikites

Abstract: Despite being volumetrically minor components, carbonate-rich ultramafic magmas like aillikites represent good candidates to investigate the compositional variations in plume and/or lithospheric mantle sources because they represent low-degree melts which preferentially sample highly fusible components including recycled crustal material. To gain new insights into the composition of the plume-related magmas and, more broadly, the petrogenesis of ultramafic lamprophyres, we have undertaken the first comprehensive study of bulk rock and mineral (olivine and Ti-magnetite) highly siderophile element (HSE) abundances and Re-Os isotopes combined with in situ major-, trace-element and Sr-Nd isotope analyses of apatite and perovskite from the Permian Wajilitag aillikites of the Tarim large igneous province, China. The Wajilitag aillikites have high PPGE (Pt and Pd) contents relative to IPGE (Os, Ir and Ru), which can be ascribed to low-degree partial melting and/or fractionation of olivine and laurite. Measured 187Os/188Os ratios are moderately to highly radiogenic (0.186-0.313) with age-corrected ?Os values up to +113. In situ Sr and Nd isotope analyses of apatite phenocrysts (87Sr/86Sr(i) = 0.70349-0.70384; ?Nd(i) = +1.3 to +4.9) and fresh perovskite grains (87Sr/86Sr(i) = 0.70340-0.70390; ?Nd(i) = +1.3 to +3.8) exhibit limited variability both within and across samples from different aillikite dykes and the only volcanic pipe in the area. These Nd isotopic values resemble those from bulk-rock samples (?Nd(i) = +1.9 to +5.2), whereas Sr in apatite and perovskite extends to marginally less radiogenic values than the bulk-rock compositions (87Sr/86Sr(i) = 0.70362-0.70432). The moderately depleted Sr-Nd isotope compositions of magmatic apatite and perovskite, and the previously reported mantle-like C isotope values of these samples suggest that the aillikites and their carbon probably derived from a sub-lithospheric (plume) source with minimal contribution of deeply subducted material. Conversely, the radiogenic Os isotope compositions of the Tarim aillikites and separated minerals require some contribution from recycled crustal material in the plume source. Mass balance calculations suggest that the radiogenic Os isotopes and moderately depleted Sr-Nd isotopes can be reproduced by less than one third of eclogite component addition to a moderately depleted mantle source. We conclude that the combination of complementary isotopic systems can enlighten contributions from different components to mantle-derived magmas and, in this case, clarifies the occurrence of carbon-free subducted oceanic crust in the Tarim plume.
DS202202-0221
2021
Wang, S., Tkalcic, H.Shear-wave anisotropy in the Earth's inner core.Geophysical Research Letters, Vol. 48, e2021GLo94784 Mantlegeophysics -seismics

Abstract: Earth's inner core (IC) anisotropy-the directional dependence of seismic wave speed in the IC-contains essential information of deep Earth's structure and dynamics. It results from a preferred alignment of iron crystals related to the formation and post-formation dynamics of the IC. Many studies have investigated the IC anisotropy observed for compressional waves. In contrast, possible anisotropy for the inner-core shear waves remains elusive. This study presents a new class of inner-core shear-wave anisotropy observations based on recent advances in earthquake coda-correlation wavefield. We find that the coda-correlation feature I2-J, sensitive to the inner-core shear-wave speed, exhibits variable timing and amplitude for sampling the IC in different directions. Quantitatively, inner-core shear waves travel faster for at least ?5 s in directions oblique to the Earth's rotation axis than directions parallel to the equatorial plane. The simplest and most plausible explanation for our observations is the inner-core shear-wave anisotropy with a strength of ?0.8% or higher. We can rule out at least one of the body-centered-cubic iron models in the IC, although the other models are not distinguishable.
DS202205-0730
2021
Wang, W., Sueno, S,m Yurimoto, H., Takahashi, E.Geochemical study of eclogitic mineral inclusions from Chinese diamonds.Researchgate Chapter, 8p. PdfChinadiamond inclusions

Abstract: Major and trace element geochemistry of eclogitic mineral inclusions from Chinese diamonds are reported in this study, for the first time. Bulk major element compositions of mantle eclogite, estimated from diamond inclusions, are very close to that of MORB. All the analyzed samples exhibit evident positive Eu anomalies. Estimated bulk trace element compositions of mantle eclogite are generally parallel to that of MORB, but with deviations like enrichment in LILE and depletion in HFSE. It is proposed that the formation of mantle eclogite could be closely related to recycling of ancient oceanic crust. Other processes like (1) metasomatism by incompatible trace element rich melts; or (2) remelting and interaction with mantle peridotite, may also be involved. Coexisting of olivine with eclogitic mineral inclusions in a same diamond host, and evident trace element variations in some mineral inclusions show that some diamonds were formed by disequilibrium growth.
DS202204-0543
2022
Wang, W., Vidale, J.E.An initial map of fine-scale heterogeneity in the Earth's inner core. *** not specific to diamondsNature Geoscience, Vol. 15, pp. 240-244.United States, Asia, South Americageophysics - seismics

Abstract: The seismological properties of Earth’s inner core are key to understanding its composition, dynamics and growth history. Within the inner core, fine-scale heterogeneity has previously been identified from backscattering of high-frequency compressional waves. Here we use historical earthquake and explosion data from the Large Aperture Seismic Array, USA, between 1969 and 1975 to build a 3D map of heterogeneity from the inner-core boundary to 500?km depth and determine the geographical distribution of the scatterers across the 40% of the inner core that is visible to the array. Our model has two regions of strong scattering, one beneath eastern Asia and the other beneath South America, both located where past local surveys have identified scattering. We suggest that these loci of strong, fine-scale heterogeneities may be related to random alignments of small, inner-core crystals due to fast freezing. These areas, which have been identified as having high attenuation and lie beneath colder areas of the core-mantle boundary, potentially provide constraints on the dynamics of the inner core and the motions in the outer core, with downwelling in the mantle and outer core possibly associated with strong scattering and inner-core heterogeneity.
DS202202-0222
2022
Wang, X., Zhao, D., Xia, S., Li, J.Mantle structure and flow beneath the central western US: constraints from anisotropic tomography.Tectonophysics, Vol. 822, 229180, 11p. PdfUnited Statestomography

Abstract: To investigate lateral and depth variations of seismic anisotropy beneath the central-western United States, we determined a detailed 3-D model of P-wave anisotropic tomography by inverting a large number of arrival-time data of local and teleseismic events. Our results reveal significant azimuthal anisotropies in the crust and lithosphere, which are associated with ancient orogenic collisional and magmatic activities. As depth increases, the fast-velocity direction (FVD) pattern becomes gradually trended and small features fade away. There is a boundary in the FVD distribution, which separates the tectonically active region in the west from the stable cratonic region in the east. Frozen-in anisotropy with a NW-SE FVD is preserved in the thick Wyoming cratonic lithosphere that exhibits as a high-velocity (high-V) anomaly to a depth of ~250 km. In the asthenosphere beneath the western thin lithosphere, FVDs are generally parallel with the absolute motion direction of the North American plate due to shearing between the plate and the asthenosphere. In the deeper areas, the subducted and fragmented slab exhibiting as high-V anomalies leads to slab-related mantle flows. These results indicate that seismic anisotropies exist in both the lithosphere and asthenosphere with different geodynamic mechanisms and it is feasible to link the P-wave azimuthal anisotropy to lithospheric deformations, fossil anisotropy in the lithosphere, and flows in the asthenosphere.
DS202205-0731
2022
Wang, Z., Kusky, T.M., Wang, L.Long-lasting viscous drainage of eclogites from the cratonic lithospheric mantle after Archean subduction stacking.Geology , Vol. 50, 5, pp.583-587.Mantleeclogites

Abstract: The origin of early continental lithosphere is enigmatic. Characteristics of eclogitic components in the cratonic lithospheric mantle (CLM) indicate that some CLM was likely constructed by stacking of subducted oceanic lithosphere in the Archean. However, the dynamic process of converting high-density, eclogite-bearing subducted oceanic lithosphere to buoyant CLM remains unclear. We investigate this process through numerical modeling and show that some subducted and stacked eclogites can be segregated into the asthenosphere through an episodic viscous drainage process lasting billions of years. This process increases the chemical buoyancy of the CLM, stabilizes the CLM, and promotes the preservation and redistribution of the eclogites in the CLM, explaining the current status of early subduction relicts in the CLM revealed by geophysical and petrological studies. Our results also demonstrate that the subduction stacking hypothesis does not conflict with the longevity of CLM.
DS202203-0370
2022
Wang, Ze-Zhou, Liu, S,-A., Rudnick, R.L., Haggerty, R.S.Zinc isotope evidence for carbonate alteration of oceanic crustal protoliths of cratonic eclogites,Earth and Planetary Science Letters, Vol. 580, 11p. PdfMantleeclogites

Abstract: Zinc isotopic compositions (ZnJMC-Lyon) of low-MgO (<13 wt.%) and high-MgO (>16 wt.%) eclogites from the Koidu kimberlite complex, Sierra Leone, West African Craton, help constrain the origins of cratonic eclogites. The Zn of low-MgO eclogites range from MORB-like to significantly higher values (0.21‰ to 0.75‰), and correlate inversely with Zn concentrations. Since marine carbonates are characterized by higher Zn and lower Zn concentration than basaltic rocks, the low-MgO eclogites are suggested to originate from altered oceanic crustal protoliths that underwent isotopic exchange with carbonates within the crust during subduction. Compared to low-MgO eclogites, all but one of the high-MgO eclogites also have high Zn (0.35‰ to 0.95‰), but they have lower Zn concentrations and Zn/Fe ratios, both of which are negatively correlated with MgO contents. These features point to formation of high-MgO eclogites via metasomatic overprinting of low-MgO eclogites through addition of secondary clinopyroxenes crystallized from infiltrating ultramafic melts. Thus, both low-MgO and high-MgO eclogites bear the imprint of subducted carbonate-bearing oceanic crust. Our study shows that the distinctively high-Zn signatures of marine carbonates can be retained in deeply subducted oceanic crust that may contribute to mantle sources of intraplate alkali basalts with elevated Zn and Zn/Fe. Therefore, Zn isotopes provide a viable means to trace carbonate recycling in the mantle.
DS202202-0223
2021
Watremez, L., Leroy, S., d'Acremont, E., Roche, V., Evain, M., Lepretre, A., Verrier, F., Aslanian, D., Dias, N., Afilhado, A., Schnurle, P., Castilla, R., Despinois, F., Moulin, M. The Limpopo magma-rich transform margin, south Mozambique - pt. 1 Insights from deep-structure seismic imaging.Tectonics, e2021TC006915Africa, Mozambiquegeophysics -seismics

Abstract: A variety of structures results from the interplay of evolving far-field forces, plate kinematics, and magmatic activity during continental break-up. The east Limpopo transform margin, offshore northern Mozambique, formed as Africa and Antarctica separated during the mid-Jurassic period break-up of the Gondwana supercontinent. The nature of the crust onshore has been discussed for decades in an effort to resolve issues with plate kinematic models. Two seismic refraction profiles with coincident multichannel seismic reflection profiles allow us to interpret the seismic velocity structures across the margin, both onshore and offshore. These seismic profiles allow us to (a) delineate the major regional crustal domains; (b) identify widespread indications of magmatic activity; and (c) map crustal structure and geometry of this magma-rich transform margin. Careful examination of the profiles allows us to make the following observations and interpretations: (a) on land, continental crust is overlain by a >10-km thick volcano-sedimentary wedge related to an early rifting stage, (b) offshore, thick oceanic crust formed due to intense magmatic activity, and between the two (c) a 50-60-km wide transform zone where the crustal structures are affected by intense magmatic activity and faulting. The prominent presence of intrusive and extrusive igneous units may be attributed to the combination of a deep-seated melting anomaly and a trans-tensional fault zone running through thinned lithosphere that allowed melt to reach the surface. A comparison of the crustal thinning along other transform margins shows a probable dependence with the thermal and/or tectonic history of the lithosphere.
DS202204-0544
2022
Weng, Q., YanZurevinski, S., Wu, D.g, W-B., Niu, H-C., Li, N-B., Mitchell, R.H.Formation of the Maoniuping giant REE deposit: constraints from mineralogy and in situ bastnasite U-Pb geochronology.American Mineralogist, Vol. 107, pp. 282-293. pdfChinadeposit - Maoiuping REE

Abstract: The time and processes of hydrothermal mineralization are long-standing problems in geology. This work addresses these questions with reference to the Maoniuping giant rare earth elements (REE) deposit (southwest China), which has rare earth oxides (REO) reserves of 3.17 million tons with an average grade of 2.95 wt%. Bastnäsite is the dominant economic mineral, occurring as four distinct paragenetic types in the Maoniuping syenite-carbonatite complex: (1) primary euhedral bastnäsite (type-A) in syenite, with isolated melt inclusions; (2) macro-crystalline tabular euhedral bastnäsite (type-B) in pegmatitic dikes, with a diverse variety of fluid inclusions; (3) fine-grained, anhedral veinlet-disseminated bastnäsite (type-C) in syenite; and (4) coarse-grained anhedral bastnäsite (type-D) in carbonatite dikes, occurring as veinlets or interstitial to calcite, fluorite, and barite. From the paragenetic and compositional variations, it is inferred that type-A bastnäsite is of primary magmatic origin, whereas the other three types have characteristics of hydrothermal origins. In situ LA-ICP-MS U-Pb geochronology of the four types of bastnäsite results in lower intercept ages of 28.2 ± 0.5 Ma (n = 95, MSWD = 5.10), 27.8 ± 0.4 Ma (n = 43, MSWD = 0.73), 26.8 ± 0.7 Ma (n = 50, MSWD = 0.83), and 25.8 ± 0.7 Ma (n = 55, MSWD = 1.70), respectively, which are consistent with the weighted average 206Pb/238U and 208Pb/232Th ages by 207Pb-correction method. Compositional variations of clinopyroxene and apatite from the associated syenite, pegmatitic and carbonatitic dikes indicate a genetic relationship of the Maoniuping alkaline complex. The compositions of clinopyroxene range from Ae44-67Di14-18Hd17-41 in pegmatitic dikes, Ae43-66Di6-20Hd21-38 in carbonatitic dikes to Ae68-90Di0-3Hd10-30 in syenite. Apatites in the pegmatitic and carbonatitic dikes have similar compositions with higher F, total REE, and Sr, and lower CaO contents than those in the syenite, which suggests a cogenetic origin for the associated pegmatite and carbonatite. Clinopyroxene and apatite compositions suggest that the pegmatitic melt might differentiate directly from the initial carbonatitic melt rather than the syenitic magma. The bastnäsite U-Pb geochronology and minerals data indicate continuous magmatic-hydrothermal evolution for the REE mineralization in the Maoniuping alkaline complex.
DS202201-0046
2021
Wolf, J., Evans, D.A.D.Reconciling supercontinent cycle models with ancient subduction zones.Earth and Planetary Science Letters, in press available 8p. PdfMantlesubduction

Abstract: Long-term patterns of mantle convection are illustrated by the locations of large low-shear-velocity provinces (LLSVPs) in the lowermost mantle, as well as an enclosing girdle of subduction zones. These structures, stable since Pangea's breakup, have been proposed to provide an absolute reference frame to anchor plate motions in deep time. Simple conceptual models of the supercontinent cycle (introversion, extroversion, orthoversion) predict differing loci of global subduction zones and inferred LLSVPs. We develop a tool to statistically compare idealized supercontinent cycle models with paleolatitude distributions of global subduction zones from paleogeographic reconstructions. We find that subduction zone locations younger than 250 Ma are moderately well described by an idealized girdle around the LLSVPs, but more robust conceptual models must take into account a Tethyan locus or “arm” within the girdle. Between 540 and 250 Ma, such an orthogonal arm is not needed to generate robust correlations with paleogeography; but the global subduction girdle is found to rotate progressively by approximately 90°. Our results suggest that planetary degree-two mantle structures are long-lived but not eternal: they reorganize their absolute locations from one supercontinent cycle to the next.
DS202202-0224
2022
Wolf, J., Evans, D.A.D.Reconciling supercontinent cycle models with ancient subduction zones.Earth and planetary Science Letters, Vol. 578, 117293, 8p.Pangeasubduction

Abstract: Long-term patterns of mantle convection are illustrated by the locations of large low-shear-velocity provinces (LLSVPs) in the lowermost mantle, as well as an enclosing girdle of subduction zones. These structures, stable since Pangea's breakup, have been proposed to provide an absolute reference frame to anchor plate motions in deep time. Simple conceptual models of the supercontinent cycle (introversion, extroversion, orthoversion) predict differing loci of global subduction zones and inferred LLSVPs. We develop a tool to statistically compare idealized supercontinent cycle models with paleolatitude distributions of global subduction zones from paleogeographic reconstructions. We find that subduction zone locations younger than 250 Ma are moderately well described by an idealized girdle around the LLSVPs, but more robust conceptual models must take into account a Tethyan locus or “arm” within the girdle. Between 540 and 250 Ma, such an orthogonal arm is not needed to generate robust correlations with paleogeography; but the global subduction girdle is found to rotate progressively by approximately 90°. Our results suggest that planetary degree-two mantle structures are long-lived but not eternal: they reorganize their absolute locations from one supercontinent cycle to the next.
DS202203-0371
2021
Woolley, A.R.Rembrances of carbonatites past.Elements, Vol. 17, pp. 367-368.Globalcarbonatite

Abstract: As I was finishing my PhD thesis on the Borralan alkaline complex in Scotland, my professor, Basil King, who published the first account of the Napak carbonatite occurrence in Uganda, proposed that I should apply for a NERC fellowship to investigate the fenites associated with carbonatites of the Chilwa Province in Malawi (Fig. 1). After a successful application, I duly flew out to Malawi and spent three months building an extensive collection of fenites from the very large metasomatic aureoles around the carbonatites of Chilwa Island, Tundulu, and Kangankunde. Back at Bedford College (University of London, UK) I had been working on my fenites for about a year when Brian Sturt, a lecturer in the department, told me that at a council meeting of the Mineralogical Society of Great Britain and Ireland the previous day he had been told by Frank Claringbull that he, Claringbull, was looking for a petrologist to work in the Department of Mineralogy at the British Museum (Natural History), now called the Natural History Museum. I arranged to see Claringbull, was interviewed, and was fortunate enough to be appointed as a petrologist in the department.
DS202205-0732
2022
Wu, H., Zhu, W., Ge, R.Evidence for carbonatite derived from the Earth's crust: the late Paleoproterozoic carbonate-rich magmatic rocks in the southeast Tarim Craton, northwest China.Precambrian Research, Vol. 369, 106425 20p.Chinacarbonatite

Abstract: Carbonatites are generally accepted as derived from the mantle, whereas viewpoint of carbonatitic melt formed at crust level is considered marginal. Here we document large-scale (?17?km2) igneous carbonate-rich rocks in the southeast Tarim Craton that were formed within the crust. These rocks exhibit clear intrusive contact with the wall-rocks and contain diverse xenolith, indicating an igneous origin. Zircon U-Pb dating reveals that they were emplaced at ca. 1.94-1.92 and 1.87-1.86?Ga, respectively. ?18O values in zircons (5.7-13.7‰) are higher than those crystallized in equilibrium with mantle melt. Total REE content is 1-2 magnitude lower than that of mantle carbonatite and shows weak fractionation of HREE. REE modeling reveals that the samples cannot be produced by partial melting of carbonated MORB at mantle conditions. The studied samples have positive ?13CV-PDB values (4.2-15.7‰), which are distinct from the mantle carbonatite but comparable to sedimentary carbonates. C-O-Sr-Nd isotope modelling indicates that the compositions of the studied samples cannot be produced by evolution of mantle carbonatite. Integrating these lines of evidence, we conclude that the studied carbonate-rich magmatic rocks were derived from partial melting of impure marble at crustal level via fluid-present melting. These carbonatites probably represent the initial magmatic record of tectonic extension of the late Paleoproterozoic collisional orogenic belt in the southern margin of the Tarim craton. The positive carbon excursion recorded by the high ?13CV-PDB values probably corresponds to the global Paleoproterozoic Lomagundi-Jatuli event. Our study implies that partial melting of sedimentary carbonates is more common than previously thought, which has significant impacts on crust rheology and global carbon cycling
DS202205-0733
2022
Xiang, L., Zheng, J., Zhai, M.Archean to Paleoproterozoic crustal evolution of the southern Yangtze block ( south China): U-Pb age and Hf-isotope of zircon xenocrysts from the Paleozoic diamondiferous kimberlites.Precambrian Research, Vol. 374, 106651, 17p.Chinadeposit - Maping

Abstract: Crustal zircon xenocrysts from mantle-derived magmatic rocks have the potential to probe the deep crust. Here we present integrated U-Pb dating and Hf-isotope analyses of zircons from a Paleozoic diamondiferous kimberlite dike in the Maping area of Zhenyuan County (southeastern Guizhou Province), with implications for the tectonothermal evolution of unexposed continental crust beneath the southern Yangtze Block, South China. All zircons (n = 236) show a wide range of U-Pb ages between Mesoarchean and middle Carboniferous. Among them, 96 zircons with 90-110% concordance yield concordant ages from 2942 ± 8 Ma to 342 ± 2 Ma, and form major age peaks at ?2.9 Ga, ?2.6 Ga and ?2.0 Ga. The overwhelming majority of zircons are dominated by Mesoarchean-Paleoproterozoic U-Pb ages regardless of their concordance degrees. The zircon populations mainly consist of magmatic zircons, with minor metamorphic grains (Th/U < 0.10). The youngest magmatic zircon (Th/U = 0.43) with a well concordant 206Pb/238U age of 342 ± 2 Ma (M1-16) is interpreted as the maximum emplacement age of the Maping diamondiferous kimberlites. Most zircons with pre-eruption ages are considered to be xenocrysts, and they may be derived from the deep-seated continental crust through which kimberlite host magmas have passed. Their U-Pb ages and Hf isotopic compositions suggest the possible existence of a highly evolved Archean basement beneath the southern Yangtze Block, South China, which is much older than its known surface rocks. A lot of magmatic zircon xenocrysts reveal complex Precambrian crustal evolution in the southern Yangtze Block. These processes involved the important growth of continental crust at 2.6-2.5 Ga, and in the meantime, crustal reworking could be intermittently proceeding at 3.0-2.6 Ga. In addition, a group of xenocrystic zircons are identified to be of metamorphic origin, indicating that the proposed Archean basement beneath the southern Yangtze Block likely experienced a metamorphic event around 2.0 Ga. This geologically significant episode is consistent with the well-developed coeval metamorphism in other places of the Yangtze Block (e.g., Kongling Terrane), which has been considered to link to the assembly of the Paleoproterozoic Nuna/Columbia supercontinent. Our zircon data implies that the unexposed Archean basement beneath the southern Yangtze Block was affected by multiple thermal activities.
DS202204-0545
2022
Xu, C., Inoue, T., Gao, J., Noda, M., Kakizawa, S.Melting phase relation of Fe-bearing phase D up to the uppermost lower mantle.American Mineralogist, Vol. 107, 19p.Mantlemelting

Abstract: Dense hydrous magnesium silicates (DHMSs) are considered important water carriers in the deep Earth. Due to the significant effect of Fe on the stability of DHMSs, Fe-bearing Phase D (PhD) deserves much attention. However, few experiments have been conducted to determine the stability of PhD in different bulk compositions. In this study, we provide experimental constraints for the stability of PhD in the AlOOH-FeOOH-Mg1.11Si1.89O6H2.22 system between 18 and 25 GPa at 1000-1600 °C, corresponding to the P-T conditions of the mantle transition zone and uppermost lower mantle. Fe3+-bearing PhD was synthesized from the FeOOH-Mg1.11Si1.89O6H2.22 binary system with two different Fe3+ contents. The resultant Al,Fe3+-bearing compositions are close to analog specimens of the fully oxidized mid-ocean ridge basalt (MORB) and pyrolite in the AlOOH-FeOOH-Mg1.11Si1.89O6H2.22 ternary system. The substitution mechanism of Fe is shown to be dependent on pressure, and Fe3+ occupies both Mg and Si sites in PhD at pressures below 21 GPa. In contrast, Fe3+ only occupies Si site at pressures exceeding 21 GPa. The presence of Fe3+ results in a slight reduction in the thermal stability field of PhD in the FeOOH-Mg1.11Si1.89O6H2.22 system in comparison to Mg-bearing, Fe-free PhD. In contrast, Al,Fe3+-bearing PhD is more stable than Mg-bearing PhD in both MORB and pyrolite compositions. In this regard, Al,Fe3+-bearing PhD could act as a long-term water reservoir during subduction processes to the deep mantle.
DS202201-0047
2021
Xu, Y., Pearson, G., Harris, G., Kopylova, M., Liu, J.Age and provenance of the lithospheric mantle beneath the Chidliak kimberlite province, southern Baffin Island: implications for the evolution of the North Atlantic craton.GAC/MAC Meeting UWO, 1p. Abstract p. 312.Canada, Baffin Islanddeposit - Chidliak

Abstract: A suite of peridotite xenoliths from the Chidliak kimberlite province provides an ideal opportunity to assess the age of the mantle lithosphere beneath the eastern Hall Peninsula Block (EHPB) in southern Baffin Island, Nunavut and to provide constraints on the lithospheric architecture of this region. The new dataset comprises highly siderophile element (HSE) abundances and Re-Os isotopic compositions for 32 peridotite xenoliths sampled from four Late Jurassic-Early Cretaceous kimberlite pipes (CH-1, -6, -7, and -44). These peridotites represent strongly depleted mantle residues, with bulk-rock and olivine chemistry denoting melt extraction extents of up to 40%. The vast majority of samples show PPGE (Pt and Pd) depletion relative to IPGE (Os, Ir, and Ru) ((Pt/Ir)N: 0.10-0.96, median = 0.57; (Pd/Ir)N: 0.03-0.79, median = 0.24), coupled with mostly unradiogenic Os isotopic compositions (187Os/188Os = 0.1084-0.1170). These peridotites display strong correlations between 187Os/188Os and melt depletion indicators (such as olivine Mg number and bulk-rock Al2O3, (Pd/Ir)N), suggesting that an ancient (~2.8 Ga) melt depletion event governed the formation of the Chidliak lithosphere. The prominent mode of TRDerupt model ages at ca. 2.8 Ga matches the main crust-building ages of the EHPB, demonstrating temporal crust-mantle coupled in the Meso-Neoarchean. These ancient melt-depletion ages are present throughout the depth of the ~ 200 km thick lithospheric mantle column beneath Chidliak. The Meso-Neoarchean formation age of the EHPB mantle broadly coincides with the timing of stabilization of the lithospheric mantle beneath the Greenlandic portion of the North Atlantic Craton (NAC). This, along with the similarity in modal mineralogy, chemical composition and evolutionary history, indicates that the EHPB, southern Baffin Island was once -contiguous with the Greenlandic NAC. The mantle lithosphere beneath both the EHPB and the NAC show a similar metasomatic history, modified by multiple pulses of metasomatism. These multiple metasomatic events combined to weaken and thin the lithospheric mantle, culminating in the formation of the Labrador Sea and Davis Strait separating the EHPB from the Greenlandic NAC in the Paleocene.
DS202202-0225
2022
Yakovlev, D.A., Kostrovistsky, S.I., Fosu, B.R., Ashchepkov, I.V.Diamondiferous kimberlites from recently explored Upper Muna field ( Siberian craton): petrology, mineralogy and geochemistry insights,Geological Society of London Special Publication 513, pp. 71-102.Russia, Siberiadeposit - Muna

Abstract: Petrographic, geochemical and mineralogical characteristics of diamond deposits from the Upper Muna field have been investigated. Geochemically, diamondiferous kimberlites from Upper Muna belong to the most widespread Fe-Mg-rich rocks in the Yakutian kimberlite province (average FeOtotal = 8.4 wt%, MgO = 32.36 wt%, TiO2 = 1.6 wt%). Striking mineralogical features of Upper Muna kimberlites are: (1) abundance of monticellite and perovskite in the groundmass; (2) rare occurrence of Mg-ilmenite; (3) abundance of phlogopite megacrysts (up to 8 cm across); and (4) coexistence of low-Cr (0.1-4 wt% Cr2O3, with 0.8-1.2 wt% TiO2) and high-Cr (3-8 wt% Cr2O3, with 0.1-0.6 wt% TiO2) garnet megacrysts with contrasting rare earth element patterns. The compositional features of groundmass minerals, the relatively low CaO and CO2 contents in kimberlites and few deuteric alteration in Upper Muna kimberlites suggest high-temperature melt crystallization during pipe emplacement. Based on the compositional data of garnet and Cr-diopside from megacrysts and peridotites, we suggest a poor Cr dunite-harzburgitic and lherzolitic mantle source beneath the Upper Muna field where Cr-diopside crystallized within a wide pressure and temperature range (40-65 kbar and 900-1350°?). The mineral geochemistry, trace element distribution and Sr-Nd isotope variations of Upper Muna kimberlites are typical for group I kimberlites and reflect a deep-seated asthenospheric (convective mantle) source for the kimberlites.
DS202203-0373
2022
Yakovlev, D.A., Kostrovistsky, S.I., Fosu, B.R., Ashchepkov, I.V.Diamondiferous kimberlites from recently explored Upper Muna field ( Siberian craton): petrology, mineralogy and geochemistry insights,Geological Society of London Special Publication 513, pp. 71-102.Russia, Siberiadeposit - Muna

Abstract: Petrographic, geochemical and mineralogical characteristics of diamond deposits from the Upper Muna field have been investigated. Geochemically, diamondiferous kimberlites from Upper Muna belong to the most widespread Fe-Mg-rich rocks in the Yakutian kimberlite province (average FeOtotal = 8.4 wt%, MgO = 32.36 wt%, TiO2 = 1.6 wt%). Striking mineralogical features of Upper Muna kimberlites are: (1) abundance of monticellite and perovskite in the groundmass; (2) rare occurrence of Mg-ilmenite; (3) abundance of phlogopite megacrysts (up to 8 cm across); and (4) coexistence of low-Cr (0.1-4 wt% Cr2O3, with 0.8-1.2 wt% TiO2) and high-Cr (3-8 wt% Cr2O3, with 0.1-0.6 wt% TiO2) garnet megacrysts with contrasting rare earth element patterns. The compositional features of groundmass minerals, the relatively low CaO and CO2 contents in kimberlites and few deuteric alteration in Upper Muna kimberlites suggest high-temperature melt crystallization during pipe emplacement. Based on the compositional data of garnet and Cr-diopside from megacrysts and peridotites, we suggest a poor Cr dunite-harzburgitic and lherzolitic mantle source beneath the Upper Muna field where Cr-diopside crystallized within a wide pressure and temperature range (40-65 kbar and 900-1350°?). The mineral geochemistry, trace element distribution and Sr-Nd isotope variations of Upper Muna kimberlites are typical for group I kimberlites and reflect a deep-seated asthenospheric (convective mantle) source for the kimberlites.
DS202205-0734
2022
Yang, W-B., Niu, H-C., Li, N-B., Hollings, P., Zurevinski, S., Mitchell, R.H.Scavenging and release of REE and HFSE by alkali amphiboles during Na-metasomatism in magmatic-hydrothermal systems.Fundamental Research , 10.1016/j.fmre.2022.04.004 34p. PdfMantleREE

Abstract: Exploitable or potentially exploitable deposits of critical metals, such as rare-earth (REE) and high-field-strength elements (HFSE), are commonly associated with alkaline or peralkaline igneous rocks. However, the origin, transport and concentration of these metals in peralkaline systems remains poorly understood. This study presents the results of a mineralogical and geochemical investigation of the Na-metasomatism of alkali amphiboles from a barren peralkaline granite pluton in NE China, to assess the remobilization and redistribution of REE and HFSE during magmatic-hydrothermal evolution. Alkali amphiboles from the peralkaline granites show evolutionary trends from calcic through sodic-calcic to sodic compositions, with increasing REE and HFSE concentrations as a function of increasing Na-index (Na#, defined as molar Na/(Na+Ca) ratios). The Na-amphiboles (i.e., arfvedsonite) can be subsequently altered, or breakdown, to form Na-clinopyroxene (i.e., aegirine) during late- or post-magmatic alteration. Representative compositions analyzed by in-situ LA-ICPMS show that the alkali amphiboles have high and variable REE (1295-2218 ppm) and HFSE (4194-16,862 ppm) contents, suggesting that these critical metals can be scavenged by alkali amphiboles. Compared to amphiboles, the early replacement aegirine (Aeg-I, Na#?=?0.91-0.94) has notably lower REE (577-797) and HFSE (4351-5621) contents. In contrast, the late hydrothermal aegirine (Aeg-II, Na#?=?0.92-0.96) has significantly lower REE (127-205 ppm) and HFSE (6.43-72.2 ppm) contents. Given that the increasing Na# from alkali amphibole to aegirine likely resulted from Na-metasomatism, a scavenging-release model can explain the remobilization of REE and HFSE in peralkaline granitic systems. The scavenging and release of REE and HFSE by alkali amphiboles during Na-metasomatism provides key insights into the genesis of globally significant REE and HFSE deposits. The Na-index of alkali amphibole-aegirine might be useful as a geochemical indicator in the exploration for these critical-metals.
DS202203-0372
2021
Yaxley, G.M., Kjarsgaard, B.A., Jaques, A.L.Evolution of carbonatite magmas in the upper mantle and crust.Elements, Vol. 17, pp. 315-320.Mantlecarbonatite

Abstract: Carbonatites are the most silica-poor magmas known and are amongst Earth’s most enigmatic igneous rocks. They crystallise to rocks dominated by the carbonate minerals calcite and dolomite. We review models for carbonatite petrogenesis, including direct partial melting of mantle lithologies, exsolution from silica-undersaturated alkali silicate melts, or direct fractionation of carbonated silicate melts to carbonate-rich residual melts. We also briefly discuss carbonatite-mantle wall-rock reactions and other processes at mid- to upper crustal depths, including fenitisation, overprinting by carbohydrothermal fluids, and reaction between carbonatite melt and crustal lithologies.
DS202202-0226
2021
Yin, J.N., Song, X.A review of major rare earth element and yttrium deposits in China.Australian Journal of Earth Sciences, Vol.1, pp. 1-25. pdfChinaREE

Abstract: Rare earth element and yttrium (REY) deposits are important strategic resources widely used in high-tech applications, such as solar cells and wind turbines. This paper summarises the temporal-spatial characteristics and genesis of REY deposits in China classified as alkaline carbonatite, ion-adsorption, placer, sedimentary metamorphism, marine sedimentary phosphorite and coal-hosted REY types. This study focuses on alkaline carbonatite and ion-adsorption deposits, because of their importance in terms of both exploitation and global reserves. The general characteristics, genesis, and enrichment of these REY deposit types are summarised, and eight districts have been identified as having prospectivity for REY, based on geological and geochemical data. An overview of these districts is presented, together with a detailed investigation of four important districts in terms of geological settings, mineralisation, regional deposit models and metallogenic prospect. KEY POINTS: 1) REY deposits in China can be classified as alkaline carbonatite, ion-adsorption, placer, sedimentary metamorphism and marine sedimentary phosphorite and coal-hosted REY types. 2) Ion-adsorption REY in the weathering profile of granitic rocks is strongly controlled by the resistance to weathering, climate, topography and layers of weathering crust. 3) Carbonatite and alkaline rocks are major hosts for REYs and commonly have high concentrations of REY-bearing accessory minerals. 4) Eight districts have been identified as having prospectivity for REY in China.
DS202204-0546
2022
Yoo, K., Park, I. Recovery of rare earth metals from nickel metal hydride batteries of electric vehicles.MDPI, Vol. 12, 1 , 11p.GlobalREE

Abstract: Nickel metal hydride (NiMH) batteries are extensively used in the manufacturing of portable electronic devices as well as electric vehicles due to their specific properties including high energy density, precise volume, resistance to overcharge, etc. These NiMH batteries contain significant amounts of rare earth metals (REMs) along with Co and Ni which are discarded due to illegal dumping and improper recycling practices. In view of their strategic, economic, and industrial importance, and to mitigate the demand and supply gap of REMs and the limited availability of natural resources, it is necessary to explore secondary resources of REMs. Therefore, the present paper reports a feasible hydrometallurgical process flowsheet for the recovery of REMs and valuable metals from spent NiMH batteries. More than 90% dissolution of REMs (Nd, Ce and La) was achieved using 2 M H2SO4 at 75 C in 60 min in the presence of 10% H2O2 (v/v). From the obtained leach liquor, the REMs, such as Nd and Ce, were recovered using 10% PC88A diluted in kerosene at eq. pH 1.5 and O/A ratio 1/1 in two stages of counter current extraction. La of 99% purity was selectively precipitated from the leach liquor in the pH range of 1.5 to 2.0, leaving Cu, Ni and Co in the filtrate. Further, Cu and Ni were extracted with LIX 84 at equilibrium pH 2.5 and 5, leaving Co in the raffinate. The developed process flow sheet is feasible and has potential for industrial exploitation after scale-up/pilot trails.
DS202205-0735
2022
Yu, X., Liu, F., Long, Z-Y.Li, H.B., Wang, H., Yu, X-Y.Color genesis of brown diamond from the Mengyin kimberlite, China.Crystals, March 23p.Chinadeposit - Mengyin

Abstract: The Mengyin diamondiferous kimberlite cluster in Shandong province is one of the three major sources of natural diamond in China, where many brown diamonds are mined, but the genesis of their color is still controversial. In this paper, studies including microscopic examination, optical properties of orthogonal polarization, low temperature photoluminescence spectra, infrared spectra, Raman spectra, ultraviolet-visible absorption spectra, luminescence of cathodoluminescence, and transmission electron microscopy have been carried out on the uncut brown diamonds and their slice samples to constrain on the color genesis of brown diamond from the Mengyin deposit. The results show that the brown color is dominantly caused by plastic deformation, and some samples are also caused by non-deformation-related defects and inclusions.
DS202202-0227
2022
Zakharov, V.S., Lubina, N.V., Stepanova, A.V., Gerya, T.V.Simultaneous intruding of mafic and felsic magmas into the extending continental crust caused by mantle plume underplating: 2D magmatic-thermomechanical modeling and implications for the Paleoproterozoic Karelian cratonTectonophysics, Vol. 822, 229173, 13p. PdfEuropemagmatism

Abstract: Available data suggest that the breakup of the Neoarchean Kenorland supercontinent at 2.5-2.4 Ga was likely triggered by a large mantle plume upwelling that caused significant magmatism. Here, we present 2D high-resolution magmatic-thermomechanical numerical models of extension of the continental crust underplated by a hot mantle plume material. Using this model, it is demonstrated that mantle plume underplating generates a large amount of mafic melt by decompression melting. This melt penetrates into the extending continental crust along normal faults thereby forming multiple generations of mafic dyke-like intrusions along normal faults. In case of extension velocity of 0.2-1 cm/yr, lower crustal heating and hot mafic melt emplacement may cause partial melting of the continental crust that can generate significant volume of felsic melts. This in turn triggers emplacement of felsic intrusions that temporarily and spatially associate with the mafic dyke-like intrusions. The modeling results agree well with geological data from the Karelian Craton and provide possible explanation for the observed association of Paleoproterozoic mafic dykes and felsic intrusions which formed in a relatively short time interval (up to 20 Myrs) in the early stages of the supercontinent breakup.
DS202205-0736
2022
Zelenski, M., Plyasunov, A.V., Kamenetsky, V.S., Nikolai, N., Mateev, D.V., Korneeva, A.High-temperature water-olivine interaction and hydrogen liberation in the subarc mantle.Contributions to Mineralogy and Petrology, Vol. 177, 4. 10.1007/s00410-022-01910-zMantlewater

Abstract: Oxidized fluids in the subduction zone may convert polyvalent elements in the mantle to their higher valence states. The most abundant polyvalent element in the mantle is Fe, a significant part of which is contained in olivine as Fe2+. Results of the study of arc mantle xenoliths, in lab high-pressure-high-temperature experiments, and thermodynamic modeling have shown that at pressures of?~?50-2000 MPa and temperatures of 1000-1250 °C, well above the serpentine stability field, Fe2+ from olivine reacts with free aqueous fluid according to the following simplified reaction: 3Fe2SiO4?+?2H2O???3SiO2?+?2Fe3O4?+?2H2. The resulting ferric iron is preserved in spinel of a certain composition, (Mg,Fe2+)Fe3+2O4, whereas new high-Mg olivine, with magnesium number up to 96 in natural samples and 99.9 in experiments, forms in the reaction zone. SiO2 produced in the reaction either dissolves in the fluid or, with a small amount of water, reacts with olivine to form orthopyroxene as follows: (Mg,Fe)2SiO4?+?SiO2?=?(Mg,Fe)2Si2O6. The released H2 may decrease the oxidation state of polyvalent elements present in the fluid (e.g., S4+, S6+). Traces of high-temperature water-olivine interaction appear as swarms of fluid-spinel inclusions and are ubiquitous in olivine from ultramafic arc xenoliths. The described process is similar to serpentinization but occurs at higher pressure and temperature conditions and yields different reaction products. The reducing capacity of olivine is relatively low; however, given the large volume of mantle (and crustal) peridotites, the overall effect may be significant.
DS202204-0547
2022
Zhang, W., Mei, T., li, B., Yang, L., Du, S., Miao, Y., Chu, H.Effect of current density and agitation modes on the structural and corrosion behavior of Ni/diamond composite coatings. Nanoparticles ( nickel)Journal of Materials Research and Technology, Vol. 12, pp. 1473-1485.Chinananodiamonds

Abstract: In this work, Ni/diamond composite coatings have been synthesized by electrodeposition in direct current mode. The effects of mechanical and ultrasonic agitations on the microstructural, surface characteristics and electrochemical properties have been comparatively investigated by various methods. Results show that diamond nanoparticles have been evenly dispersed in Ni metallic matrix, which could reinforce their performances. The coatings prepared under ultrasonic and mechanical agitation both exhibit compact, dense and hill-valley like morphology with pyramid-like nickel crystallite grains. The relative texture coefficient (RTC) values show that the preferred orientation of the Ni/diamond coating was (200) texture. From 3 to 5 A dm?2, the crystallite sizes of ultrasonic conditions were 59.2-81.7 nm, which were smaller than 76.3-83.2 nm of magnetic agitations. The average roughness (Ra = 78.9-133 nm) of ultrasonic-assisted coatings were lower than 103-139 nm of magnetic conditions. The mechanism of the co-electrodeposition process was proposed. Electrochemical impedance spectroscopy (EIS) results illustrate that the ultrasonic-assisted electrodeposited Ni/diamond coating has better corrosion resistance than that prepared under mechanical stirring conditions. The Ni/diamond composite coatings could be applied as protective materials in harsh mediums.
DS202202-0228
2022
Zhao, L., Tyler, I.M., Gorczk, W., Murdie, R.E., Gessner, K., Lu, Y., Smithies, H., Lia, T., Yang, J., Zhan, A., Wan, B., Sun, B., Yuan, H.Seismic evidence of two cryptic sutures in northwestern Australia: implications for the style of subduction during the Paleoproterozoic assembly of Columbia.Earth and planetary Science Letters, Vol. 579, 117343, 11p. PdfAustraliageophysics- seismics

Abstract: Plate tectonics, including rifting, subduction, and collision processes, was likely to have been different in the past due to the secular cooling of the Earth. The northeastern part of the West Australian Craton (WAC) has a complex Archean and Paleoproterozoic tectonic history; therefore, it provides an opportunity to study how subduction and collision processes evolved during the emergence of plate tectonics, particularly regarding the assembly of Earth's first supercontinent, Columbia. Because the northeastern boundary of the WAC and the southwestern boundary of the North Australian Craton (NAC) are covered by the Phanerozoic Canning Basin, the regional tectonic evolution has remained enigmatic, including how many tectonic elements were assembled and what may have driven rifting and subsequent collision events. Here, we use new passive-source seismic modeling to identify a seismically distinct segment of the lithosphere, the Percival Lakes Province, which lies east of the Pilbara Craton and is separated by two previously unknown southeast-trending lithosphere scale Paleoproterozoic sutures. We interpret that the northeastern suture, separates the Percival Lakes Province from the NAC, records the amalgamation of the WAC with the NAC. The southwestern suture separates the PLP from the reworked northeastern margin of the Pilbara Craton, including the East Pilbara Terrane and the Rudall Province. A significant upper mantle dipping structure was identified in the southwestern suture, and we interpret it to be a relic of subduction that records a previously unknown Paleoproterozoic collision that pre-dated the amalgamation of the WAC and NAC. By comparing our findings with previously documented dipping features, we show that the Paleoproterozoic collisions are seismically distinguishable from their Phanerozoic counterparts.
DS202202-0229
2022
Zhou, W-Y., Zhang, J.S., Huang, Q., Lai, X., Chen, B., Dera, P., Schmandte, B.High pressure-temperature single crystal elasticity of ringwoodite: implications for detecting the 520 discontinuity and metastable ringwoodite at depths greater than 660 km.Earth and planetary Science Letters, Vol. 579, 117359, 11p. PdfMantleringwoodite

Abstract: The 520 km discontinuity (the 520) and the 660 km discontinuity (the 660) are primarily caused by the wadsleyite to ringwoodite and ringwoodite to bridgmanite + ferropericlase phase transitions, respectively. Global seismic studies show significant regional variations of the 520, which are likely due to chemical and thermal heterogeneities in the Mantle Transition Zone (MTZ). However, the effects of chemical composition and temperature on the detectability of the 520 are unclear. Additionally, it remains unknown whether the possibly existing metastable ringwoodite in the core of the cold and fast subducting slabs could create a detectable seismic signature near the top of the lower mantle. Our understanding of both issues is hindered by the lack of single-crystal elasticity measurements of ringwoodite at simultaneous high pressure-temperature (P-T) conditions. In this study, we measured the single-crystal elasticity of an anhydrous Fe-bearing ringwoodite up to 32 GPa and 700 K by Brillouin spectroscopy, and then modeled the composition-dependent elastic properties of ringwoodite to calculate the compositional effects on the velocity jumps at the 520. We found that opposite to the effect of Fe, water enhances the Vp (P-wave velocity) jump, yet decreases the Vs (S-wave velocity) jump of the 520 across the wadsleyite to ringwoodite transition. Higher temperature increases both Vp and Vs contrasts across the 520. At depths between 660-700 km in the lower mantle, the existence of metastable ringwoodite may only result in ?1-2% low velocity anomaly, which is seismically difficult to resolve. The low velocity anomaly caused by metastable ringwoodite increases to 5-7% at 750 km depth due to the weak pressure dependence of Vs in ringwoodite at lower mantle conditions, but whether it is seismically detectable depends on the extension of the regions in subducted slabs that are sufficiently cold to host metastable ringwoodite.
DS202202-0230
2022
Zhu, R-Z, Ni, P., Wang, G-g., Ding, J-v., Kang, N.Temperature and oxygen state of kimberlite magma from the North China craton and their implication for diamond survival. Name change from Fuxian in Mengyin fieldsMineralium Deposita, Vol. 57, pp. 301-318. pdfChinadeposit - Wafangdiam

Abstract: The grade and morphological character of kimberlite-hosted diamonds were compared to crystallization temperature (T) and oxygen fugacity ( f O 2 ) estimated from groundmass spinels in six kimberlite pipes in the North China Craton (NCC). Crystallization temperatures calculated at an assumed pressure of 1 GPa are in the range of 1037-1395 °C, with a mean of 1182 °C. At these temperatures, the estimated f O 2 varies from 1.2 to 3.1 log units below the nickel-nickel oxide (NNO) buffer. Generally, individual kimberlite pipe shows a small variation of the T (50-100 °C) and f O 2 (0.4-0.6 log units), whereas different kimberlite pipes present great changes of T and f O 2 which can be up to 300 °C and 2 units respectively. The f O 2 of kimberlite magma shows a strong negative correlation with the diamond grade of kimberlite, suggesting that the f O 2 plays an important role in diamond resorption, whereas the T shows no relationship with the diamond grade, indicating the T plays no role in diamond resorption. The conditions of kimberlite crystallization ( f O 2 ) can be a useful parameter in evaluating diamond survival in diamond exploration.
DS202201-0048
2021
Zinchenko, V.N., Ivanov, A.S., Ashepkov, I.V.Composition of the diamond indicator minerals on the Mitchell chart - criteria of CLIPPIR diamonds in kimberlites and conditions of their mantle crystallization.Acta Geologica Sinica, Vol. 95, 1, pp. 121-124.Russiaindicator minerals
DS202204-0548
2022
Zou, Z., Wang, Z., Foley, S., Xu, R., Geng, X., Liu, Y-N., Liu, Y., Hu, Z.Origin of low-MgO primitive intraplate alkaline basalts from partial melting of carbonate-bearing eclogite sources. Hannuoba Geochimica et Cosmochimica Acta, in press available, 53p.Chinaeclogite

Abstract: Alkaline basalts occur widely in intraplate settings and carbonate-bearing mantle sources such as carbonated peridotites are increasingly regarded to play a key role in their formation. Carbonated eclogites, most likely the products of subducted carbonate-bearing altered oceanic crust, are probable alternative ingredients in the mantle sources of many intraplate alkaline basalts, highlighting the importance of the subduction-driven deep carbon cycle. However, this widely proposed hypothesis remains enigmatic because the recognition of low-MgO primitive alkaline basalts predicted by experiments is scarce. Here we show that Cenozoic continental intraplate alkaline basalts occurring above the stagnant oceanic slab in the mantle transition zone beneath the Hannuoba region, eastern China, display geochemical features consistent with their origin as low-degree partial melts of carbonate-bearing eclogites. Their MgO contents correlate positively with CaO, Ba/Th and Ti/Eu, but negatively with Dy/Yb and ?Nd. Remarkably, the most primitive alkaline basalts are characterized by low MgO (<5.25 wt.%), low heavy rare earth elements and Sc contents, low CaO/Al2O3 (<0.41), low Ti/Eu (<3380), but Dy/Yb (>7.1) higher than those of ocean island basalts (OIBs). These features cannot be ascribed to differentiation from high-MgO alkaline basalts because significant amounts of crystallization of clinopyroxene and garnet did not occur during ascent. Differentiation also cannot account for the correlations of time-integrated Sr-Nd isotopes with MgO, Dy/Yb and Ba/Th. Instead, the linear correlations mainly reflect strong interaction between ascending primitive alkaline melts and the lithospheric mantle. The compositions of primitive alkaline basalts reflect the key control of garnet and clinopyroxene in the mantle residue (eclogites), and the Ti, Zr and Hf anomalies further indicate the critical effect of carbonates in the eclogite source. Partial melting of the carbonate-bearing eclogites likely occurred in the uppermost asthenosphere. The production of alkaline basalts with low MgO contents by partial melting of carbonate-bearing eclogite below the peridotite solidus in an intraplate setting has been overlooked and the magmas were instead often considered to be highly evolved. Recycled altered oceanic crust thus may not only cause metasomatism of the deep mantle but may also serve as a direct source of mafic melts. These results on natural rocks support the experiment-based model for subducted altered oceanic crustal material and also indicate its diverse fate in the mantle.
 
 

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