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The Sheahan Diamond Literature Reference Compilation - Scientific and Media Articles based on Major Keyword - Rare Earths
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 announcements called 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 Keyword Index
Sheahan Diamond Literature Reference Compilation - Scientific Articles by Author for all years
Each article reference in the SDLRC is tagged with one or more key words assigned by Pat Sheahan to highlight the main topics of the article. In an effort to make it easier for users to track down articles related to a specific topic, KRO has extracted these key words and developed a list of major key words presented in this Key Word Index to which individual key words used in the article reference have been assigned. In most of the individual Key Word Reports the references are in crhonological order, though in some such as Deposits the order is first by key word and then chronological. Only articles classified as "technical" (mainly scientific journal articles) and "media" (independent media articles) are included in the Key Word Index. References that were added in the most recent monthly update are highlighted in yellow.
Rare Earths have no direct relevance to diamonds but they do tend to be concentrated in intrusions called carbonatites or syenites, but they are indirectly related because of the shared question of how rare earth enriched intrusions do evolve and end up at the earth's surface. The abundance of rare earth related scientific articles in the SDLRC can be construed as a cheeky reminder from Pat Sheahan to her diamond pals that diamonds aren't everything.
Geochemical and petrographic investigation of the genesis of the cancrinite-syenite niobium bearing carbonatite complex of Lueske Kivu Northeastern Zaire.*G
Ph.D. Thesis University of Berlin (in German), 330p
Compositional variation of some rare earth minerals from the Fen complex(telemark, southeast Norway): implications for the mobility of rare earths in a carbonatite system
Mineralogical Magazine, Vol. 50, No. 357, September pp. 503-509
Trace element charactertistics of the Strange Lake Zirconium, Yttrium, Niobium,and Berylium rare earth elements (REE) mineralization and the host peralkaline granite
Geological Association of Canada (GAC) Annual Meeting, Vol. 11, p. 102. (abstract.)
Quebec, Labrador
Rare earth, Zirconium, Berylium, REE, yttrium, Carbonatite, Alkaline rock
Niobium and zirconium in alkaline olivine basalts and alkaline basaltoids of the Baikal-Mongolian regions as criteria for estimating their distrib. In mantle source
Soviet Geology and Geophysics, Vol. 30, No. 2, pp. 62-68
Coupled substitutions involving REEs and Sodium and Silicon in apatites in Alkaline rocks from the Ilimaussaqintrusion, South Greenland, and the petrol.implication
American Mineralogist, Vol. 74, No. 7 and 8, July-August pp. 896-901
A reappraisal of the geology and geochemistry of the Zr-Y-Nb-Be and rare earth elements (REE)mineralized Strange Lake peralkalinepluton, Quebec-Labrador
Geological Association of Canada (GAC)/Mineralogical Association of Canada (MAC) Vancouver 90 Program with Abstracts, Held May 16-18, Vol. 15, p. A12. Abstract
The role of hydrothermal processes in the granite-hosted Zirconium, Yttrium, rare earth elements (REE) deposit at Strange Lake Quebec, Labrador- evidence from fluid inclusions-comment
Geochimica et Cosmochimica Acta, Vol. 55, No. 11, pp. 3443-3447
Chao, E.C.T., Back, J.M., Minkin, J.A., en Yinchen
Host rock controlled epigenetic, hydrothermal metasomatic origin of the Bayan Obo rare earth elements (REE)-iron-Nb ore deposit, Inner Mongolia, P.R.C.
light rare earth element (LREE) distribution in accessory minerals from southwest Ugand an xenoliths and their kamafugite hosts: an electron microprobe study
Rare earth Minerals: chemistry, origin and ore deposits, International Geological Correlation Programme (IGCP) Project, pp. 73-75. abstract
iron-copper-rare earth elements (REE) deposits in Middle Proterozoic rocks of the Midcontinent region of the United States..are they Olympic Dam-type deposits?
The Gangue, Geological Association of Canada (GAC)/Mineral Deposits Newsletter, No. 42, April pp. 1-4
Hidden gems in the NURE data: placer exploration potential for gold, PGM, rare earth elements (REE) and other metals in the Arctic coastal plain and Foothills Province, Alaska
Reacyion relationships in the Bayan Obo rare earth elements (REE) niobium deposit, Inner Mongolia: implications for stability rare earth elements (REE)
Contributions to Mineralogy and Petrology, Vol. 134, No. 2-3, pp. 294-310.
China, Mongolia
Carbonates, phosphates, rare earths, Deposit - Bayan Obo
Condie, K.C., Cox, J., O'Reilly, S.Y., Griffin, W.L., Kerrich, R.
Definition of high field strength and rare elements in mantle and lower crustal xenoliths from the SE United States: the role of grain boundary phases.
Geochimica et Cosmochimica Acta, Vol. 68, 19, pp. 3919-3942.
Dampare, S.B., Asiedu, D.K., Osea, S., Nyarko, B.J.B., Banoeng-Yakubo, B.
Determination of rare earth elements by neutron activation analysis in altered ultramafic rocks from the Akwatia district of Birim Diamondiferous field.
Journal of Radioanalytical and Nuclear Chemistry , Vol. 265, 1, pp. 101-106.
Application of rare element composition of garnet and clinopyroxene from peridotite xenoliths ( Udachnaya kimberlite) for modeling of primitive mantle melting
Deep Seated Magmatism, magmatism sources and the problem of plumes., pp. 148-162.
Yang, K-F, Fan, H-R., Santosh, M., Hu, F-F., Wang, K-Y.
Mesoproterozoic carbonatitic magmatism in the Bayan Obo deposit, Inner Mongolia, North China: constraints for the mechanism of super accumulation of rare earth elements.
Yang, K-F., Fan, H-R., Santosh, M., Hu, F-F., Wang, K-Y.
Mesoproterozoic mafic and carbonatitic dykes from the northern margin of the North Chin a craton: implications for the fin al breakup of Columbia supercontinent.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 231-240.
Technology
Rare earths
Abstract: Biogeochemical exploration is an effective but underutilized method for delineating covered mineralization. Plants are capable of accumulating rare earth elements (REEs) in their tissue, and ferns (pteridophytes) are especially adept because they are one of the most primitive land plants, therefore lack the barrier mechanisms developed by more evolved plants. The Norra Kärr Alkaline Complex, located in southern Sweden approximately 300km southwest of Stockholm, is a peralkaline nepheline syenite enriched in heavy rare earth elements (HREEs). The deposit, roughly 300m wide, 1300m long, and overlain by up to 4 m of Quaternary sediments, has been well-defined by diamond drilling. The inferred REE mineral resource, over 60 million tonnes averaging 0.54% Total Rare Earth Oxide (TREO), is dominantly hosted within the pegmatitic “grennaite” unit, a eudialyte-catapleiite-aegerine nepheline syenite. Vegetation and soil samples were collected from the surficial environment above Norra Kärr to address four key questions: which plant species is the most effective biogeochemical exploration medium; what are the annual and seasonal REE variations in that plant; how do the REEs move through the soil profile; and into which part of the plant are they concentrated. Athyrium filix-femina (lady fern) has the highest concentration of LREEs and HREEs (up to 125.17ppm Ce and 1.03ppm Dy) in its dry leaves; however, there is better contrast between background and anomalous areas in Dryopteris filix-mas (wood fern), which makes it the preferred biogeochemical sampling medium. The REE content in all fern species was shown to decrease from root > frond > stem, and chondrite normalized REE patterns within the plant displayed preferential fractionation of the LREEs in the fronds relative to the roots. Samples collected from an area directly overlying the deposit had up to five times greater HREE content (0.74ppm Dy) in August than the same plants did in June (0.14ppm Dy). The elevated REE content and distinct contrast to background demonstrate that biogeochemical sampling is an effective method for REE exploration in this environment.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov 13-14 2015, pp. 5-12.
Global
Rare earths
Abstract: Rare earth elements (REE), as defi ned by the International Union of Pure and Applied Chemistry (IUPAC), include yttrium (Y), scandium (Sc), and the lanthanides, comprising lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). In the scientifi c community, subdivisions into light (LREE) and heavy (HREE) categories are based on electron confi guration. In this context, LREE include La, Ce, Pr, Nd, Pm, Sm, Eu, and Gd and HREE include Y, Tb, Dy, Ho, Er, Tm, Yb, and Lu (Connelly et al., 2005). Industry commonly refers to LREE as lanthanides from La to Sm, and HREE as lanthanides from Eu to Lu, plus Y (Simandl, 2014). World mine production of rare earth oxides (REO) for 2014 is estimated at approximately 117,000 tonnes, including Y2O3, which accounts for 7000 tonnes of the total (Gambogi, 2015a, b). In 2014, the main producing countries for REE less Y were China, with 86% of worldwide production (Gambogi, 2015a), the United States, India, Australia, Russia, and Thailand (Fig. 1).
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 211-218.
Technology
Rare earths
Abstract: Quantitative Evaluation of Materials by Scanning electron microscopy (QEMSCAN®) was used to assess carbonatite indicator minerals in fl uvial sediments from the drainage area of the Aley carbonatite, in north-central British Columbia. QEMSCAN® is a viable method for rapid detection and characterization of carbonatite indicator minerals with minimal processing other than dry sieving. Stream sediments from directly above, and up to 11 km downstream, of the carbonatite deposit were selected for this indicator mineral study. The geology of the Aley carbonatite is described by Mäder (1986), Kressal et al. (2010), McLeish (2013), Mackay and Simandl (2014), and Chakhmouradian et al. (2015). Traditional indicator mineral exploration methods use the 0.25-2.0 mm size fraction of unconsolidated sediments (Averill, 2001, 2014; McCurdy, 2006, 2009; McClenaghan, 2011, 2014). Indicator minerals are detectable by QEMSCAN® at particle sizes smaller than those used for hand picking (<0.25 mm). Pre-concentration (typically by shaker table) is used before heavy liquid separation, isodynamic magnetic separation, optical identifi cation using a binocular microscope, and hand picking (McClenaghan, 2011). Following additional sieving, the 0.5-1 and 1-2 mm fractions are hand picked for indicator minerals while the 0.25-0.5 mm fraction is subjected to paramagnetic separation before hand picking (Averill, 2001; McClenaghan, 2011). Hand picking indicator minerals focuses on monomineralic grains, and composite grains may be lost during processing. Composite grains are diffi cult and time consuming to hand pick and characterize using optical and Scanning Electron Microscopy (SEM) methods. A single grain mount can take 6-12 hours to chemically analyse (Layton- Matthews et al., 2014). Detailed sample analysis using the QEMSCAN® Particle Mineral Analysis routine allows for 5-6 samples to be analyzed per day. When only mineral identifi cation and mineral concentrations and counts are required, the use of a Bulk Mineral Analysis routine reduces the analysis time from ~4 hours to ~30 minutes per sample.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 251-264.
Technology
Rare earths
Abstract: Fluorite (CaF2) belongs to the isometric system, with a cubic, face-centred lattice. Fluorite commonly forms cubes or octahedrons, less commonly dodecahedrons and, rarely, tetrahexahedrons, trapezohedrons, trisoctahedrons, hexoctahedrons, and botyroidal forms. Fluorite is transparent to translucent, and has vitreous luster. It occurs in a variety of colours including purple, green, blue, or yellow, however it can also be colourless, and can exhibit colour zoning, (Staebler et al., 2006). Fluorite from many localities is fl uorescent (Verbeek, 2006). Fluorite density varies from 3.0-3.6 g/cm3, depending to a large extent on inclusions and impurities in the crystal lattice (Staebler et al., 2006), and its hardness is 4 on Mohs scale (Berry et al., 1983). Many single fl uorite crystals display sector zoning, refl ecting preferential substitution and incorporation of trace elements along successive crystal surfaces (Bosce and Rakovan, 2001). The Ca2+ ion in the fl uorite crystal structure can be substituted by Li+, Na+, K+, Mg2+, Mn2+, Fe2+,3+, Zn2+, Sr2+, Y3+, Zr4+, Ba2+, lanthanides ions, Pb2+, Th4+, and U4+ ions (Bailey et al., 1974; Bill and Calas, 1978, Gagnon et al., 2003; Schwinn and Markl, 2005; Xu et al., 2012; Deng et al., 2014). Concentrations of these impurities do not exceed 1% (Deer, 1965) except in yttrofl uorite (Ca,Y)F2-2.33 and cerfl uorite (Ca,Ce)F2-2.33 (Sverdrup, 1968). Fluorite occurs in a variety of rocks, as an accessory and as a gangue mineral in many metalliferous deposits and, in exceptional cases, as the main ore constituent of economic deposits (Simandl, 2009). Good examples of fl uorite mines are Las Cuevas, Encantada-Buenavista (Mexico); St. Lawrence pluton-related veins and the Rock Candy Mine (Canada); El Hamman veins (Morocco) and LeBurc Montroc -Le Moulinal and Trebas deposits (France) as documented by Ruiz et al. (1980), Grogan and Montgomery (1975), González-Partida et al. (2003), Munoz et al. (2005), and Fulton III and Miller (2006). Fluorite also commonly occurs adjacent to or within carbonatites and alkaline complexes (Kogut et al., 1998; Hagni,1999; Alvin et al., 2004; Xu et al., 2004; Salvi and Williams-Jones, 2006); Mississippi Valley-type (MVT) Pb- Zn-F-Ba deposits; F-Ba-(Pb-Zn) veins (Grogan and Bradbury, 1967 and 1968; Baxter et al., 1973; Kesler et al., 1989; Cardellach et al., 2002; Levresse et al., 2006); hydrothermal Fe (±Au, ±Cu) and rare earth element (REE) deposits (Borrok et al., 1998; Andrade et al., 1999; Fourie, 2000); precious metal concentrations (Hill et al., 2000); fl uorite/metal-bearing skarns (Lu et al., 2003); Sn-polymetallic greissen-type deposits (Bettencourt et al., 2005); and zeolitic rocks and uranium deposits (Sheppard and Mumpton, 1984; Cunningham et al., 1998; Min et al., 2005). Ore deposit studies that document the trace element distribution in fl uorite are provided by Möller et al. (1976), Bau et al. (2003), Gagnon et al. (2003), Schwinn and Markl (2005), and Deng et al. (2014). The benchmark paper by Möller et al. (1976) identifi ed variations in the chemical composition of fl uorites according their origin (sedimentary, hydrothermal, or pegmatitic). Recently, Makin et al. (2014) compiled trace-element compositions of fl uorite from MVT, fl uorite-barite veins, peralkaline-related, and carbonatite-related deposits. They showed that fl uorite from MVT and carbonatite deposits can be distinguished through trace element concentrations, and that the REE concentration of fl uorite from veins is largely independent of the composition of the host rock. Based on the physical and chemical properties of fl uorite, its association with a variety of deposit types, and previous studies, it is possible that fl uorite can be used as a proximal indicator mineral to explore for a variety of deposit types. Unfortunately, the compilation by Makin et al. (2014) contained chemical analyses performed at different laboratories using different analytical techniques (including laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), electron microprobe, neutron activation, and ICP-MS), and precision and accuracy varied accordingly. As an orientation survey, herein we present data from fi ve deposits, with two samples from the Rock Candy deposit (British Columbia), and one sample from each of Kootenay Florence (British Columbia), Eaglet (British Columbia), Eldor (Quebec), and Hastie quarry (Illinois) deposits (Table 1). The main objectives of this study are to: 1) assess variations in chemical composition of fl uorite in the samples and deposit types; 2) evaluate relations between analyses made using laser ablation-inductively coupled plasma mass spectrometry on individual grains [LA-ICP-MS(IG)], and those made using laser ablation-inductively coupled plasma mass spectrometry on fused beads [LA-ICP-MS(FB)] and X-ray fl uorescence (XRF); 3) test the use of stoichiometric Ca content as an internal fl uorite standard, such has been done by Gagnon et al. (2003) and Schwinn and Markl, (2005); 4) select the elements that are commonly present in concentrations above the lower limit of detection of LA-ICP-MS and available for constructing discrimination diagrams; 5) consider if our results agree with the preliminary discrimination diagrams of Makin et al. (2014).
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 109-118.
Canada, Labrador
Rare earths
Abstract: The Foxtrot rare earth element (REE) deposit is hosted by peralkaline volcanic rocks, primarily pantellerite and commendite fl ows and ash-fl ow tuffs, of the Fox Harbour Volcanic belt in southeast Labrador, near the coastal community of St Lewis (Fig. 1). Search Minerals personnel discovered the deposit in 2010 as a result of a REE exploration program in southeast Labrador. Exploration diamond drilling in late 2010, 2011, and early 2012, totalling 72 diamond-drill holes and 18,855 metres, outlined a Dy-Nd-Y-Tb deposit of 9.2 million tonnes indicated resource (cut-off 130 ppm Dy), grading 189 ppm Dy, 1442 ppm Nd and 1040 ppm Y, and, 5.2 million tonnes inferred resource, grading 176 ppm Dy, 1233 ppm Nd, and 974 ppm Y (Table 1; Srivastava et al., 2012, 2013). A smaller highgrade resource (HGC) was also defi ned (Table 1) and was the subject of a Preliminary Economic Assessment (Srivastava et al., 2013). The Foxtrot deposit and the Fox Harbour Volcanic belt have been the target of continued REE exploration and the subject of engineering and metallurgical studies (Srivastava et al., 2012, 2013; Search Minerals 2014, 2015b) to evaluate the possibility of developing a REE mine at Foxtrot and a REE processing plant in the St. Lewis area (Fig. 1). Herein we outline the geology and mineralization of the Foxtrot REE deposit and develop a preliminary exploration model for REE mineralization in the Fox Harbour Volcanic belt and related belts in southeast Labrador.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 265-
Canada, Quebec
Rare earths
Abstract: Rare earth elements (REE) are strategic metals vital to global economic growth because they are used in a wide range of high-technology industries (e.g., energy, transport, and telecommunications; Walters et al., 2011). The world production and reserves are mainly owned by China. In 2008, the Chinese government introduced export quotas on rare metals, which led to a global search for new sources of REE. Québec has substantial REE resources (Simandl et al., 2012), which may contribute to future production. Gosselin et al. (2003) and Boily and Gosselin (2004) inventoried rare metals (REE, Zr, Nb, Ta, Be, and Li) occurrences and deposits in Québec and, based mainly on lithological association, subdivided them into seven types: 1) deposits associated with peraluminous granitic complexes; 2) deposits associated with carbonatite complexes; 3) deposits associated with peralkaline complexes; 4) deposits associated with placers and paleoplacers; 5) iron oxide, Cu, REE, and U deposits; 6) deposits associated with granitic pegmatites, migmatites, and peraluminous to metaluminous granites; and 7) deposits associated with calc-silicate and metasomatized rocks or skarns. Herein we review REE mineralization in the province, adopting a more genetic scheme based on the classifi cation of Walters et al. (2011). The REE occurrences and deposits are subdivided into primary deposits, formed by magmatic and/ or hydrothermal processes, and secondary deposits, formed by sedimentary processes and leaching. Primary deposits are then subdivided into four types: 1) carbonatite complex-associated; 2) peralkaline igneous rock-associated; 3) REE-bearing Iron- Oxide-Copper-Gold (IOCG) deposits; and 4) hyperaluminous/ metaluminous granitic pegmatite-, granite-, and migmatiteassociated deposits, and skarns. Secondary deposits are subdivided into two deposit types: 1) placers and paleoplacers and 2) REE-bearing ion-adsorption clays.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 97-108.
Europe, Sweden
Rare earths
Abstract: The Norra Kärr peralkaline complex is about 300 km southwest of Stockholm in southern Sweden (Fig. 1). As the only heavy REE deposit in the European Union, Norra Kärr is signifi cant for the security of future REE, zirconium (Zr) and hafnium (Hf) supply (European Commission’s European Rare Earths Competency Network; ERECON, 2015). The project is well serviced by power and other infrastructure that will allow year-round mining and processing. A four-lane highway links Scandinavia to mainland Europe and passes with 1km of Norra Kärr. The skill-rich cities of Linköping and Jönköping, lie within daily commuting distances from Norra Kärr. A rail line that passes within 30 km of the site may be used to transport feed stocks and products. If Norra Kärr is developed, European REE users will no longer require substantial material stockpiles to deal with market uncertainties.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 199-210.
Technology
Rare earths
Abstract: For decades, gamma ray spectrometry has been used worldwide to map rocks and locate mineralization in diverse geological settings (Shives et al., 1997). The method is particularly well suited to rare metal and REE (rare earth element) exploration because primary host rocks are enriched in incompatible elements known as LILE (large-ion lithophile elements K, Rb, Cs, Sr, Ba) and HSFE (high fi eld strength elements Zr, Nb, Hf, REEs, Th, U and Ta). As a result, the ores of REEs are commonly radioactive because host rocks, orebearing minerals, or associated accessory minerals may contain trace to anomalous concentrations of radioactive elements K, U and Th. These radioactive elements provide a useful and direct exploration vectors. Gamma ray data are often collected simultaneously with magnetic, electromagnetic, and gravity data in multisensor surveys. The objective of this extended abstract is to emphasize the importance of gamma ray spectrometry as a primary exploration tool for rare metal deposits. Case histories presented herein illustrate radioactive element and magnetic signatures associated with diverse rare metal deposit types in different geological settings. Canadian examples include: Cantley, Quebec (Quinnville and Templeton carbonatites); Oka, Quebec (carbonatite); Bancroft, Ontario (pegmatites); Allan Lake, Ontario (a blind carbonatite discovery); Nechalacho, Northwest Territories (previously called Thor Lake; altered ultra-alkaline layered complex); Strange Lake, Quebec (peralkaline granite, pegmatite); and one each from British Columbia and Labrador. Also presented are examples from Greenland, Norway, and Mozambique.
Symposium on critical and strategic materials, British Columbia Geological Survey Paper 2015-3, held Nov. 13-14, pp. 193-198.
Technology
Rare earths
Abstract: Geochemical exploration for Nb, Ta, Zr and rare earth element (REE) mineralization associated with carbonatite, pegmatite, and peralkaline intrusions presents unique challenges and opportunities. The challenges are mainly due to the tendency of these elements, as High Field Strength Elements (HFSE), to be relatively immobile in surface environments in addition to commonly forming minerals that are resistant to weathering. In addition, many of the host minerals are resistant to routine exploration geochemistry digestions, which are typically aimed at dissolving soluble oxides or extracting more labile ionic forms (Reimann et al., 2014). Opportunities arise because host rocks typically represent relatively rare end products of the magmatic processes that generate peralkaline magmas including, at the far end of the spectrum, carbonatites. Hence host rocks are relatively easy to identify geochemically and commonly defi ne classic lithological zoning (e.g., Modreski et al., 1995). In addition, many of the minerals that contain these elements are resistant to weathering, mechanically durable, have relatively high densities, and have the have the potential to form heavy mineral concentrates when released by weathering. This is particularly so for Zr, Nb, and Ta, which form primary minerals such as tantalite (Ta Nb), pyrochlore (Nb), coltan (Ta Nb), columbianite (Ta Nb), dysanalite-perovskite (Nb) and zircon (Zr). In contrast, the REE are mobile in the weathering environment and commonly re-locate from primary carbonate and phosphate minerals (e.g., synchysite, monazite, xenotime, bastnäsite, allanite) to secondary phosphate minerals such as churchite (Lottermoser, 1990) and gorceixite (Mariano, 1989).
Abstract: The layered agpaitic nepheline syenites (kakortokites) of the Ilímaussaq complex, South Greenland, host voluminous accumulations of eudialyte-group minerals (EGM). These complex Na-Ca-zirconosilicates contain economically attractive levels of Zr, Nb and rare-earth elements (REE), but have commonly undergone extensive autometasomatic/hydrothermal alteration to a variety of secondary mineral assemblages. Three EGM alteration assemblages are recognized, characterized by the secondary zirconosilicates catapleiite, zircon and gittinsite. Theoretical petrogenetic grid models are constructed to assess mineral stabilities in terms of component activities in the late-stage melts and fluids. Widespread alteration of EGM to catapleiite records an overall increase in water activity, and reflects interaction of EGM with late-magmatic Na-, Cl- and F-rich aqueous fluids at the final stages of kakortokite crystallization. Localized alteration of EGM and catapleiite to the rare Ca-Zr silicate gittinsite, previously unidentified at Ilímaussaq, requires an increase in CaO activity and suggests post-magmatic interaction with Ca-Sr bearing aqueous fluids. The pseudomorphic replacement of EGM in the kakortokites was not found to be associated with significant remobilization of the primary Zr, Nb and REE mineralization, regardless of the high concentrations of potential transporting ligands such as F and Cl. We infer that the immobile behaviour essentially reflects the neutral to basic character of the late-magmatic fluids, in which REE-F compounds are insoluble and remobilization of REE as Cl complexes is inhibited by precipitation of nacareniobsite-(Ce) and various Ca-REE silicates. A subsequent decrease in F- activity would furthermore restrict the mobility of Zr as hydroxyl-fluoride complexes, and promote precipitation of the secondary zirconosilicates within the confines of the replaced EGM domains.
American Mineralogist, Vol. 101, 5, pp. 1129-1134.
Technology
Bastanesite
Abstract: Bastnaesite, [RE-CO3-OH/F] (RE = rare earth) is one of the major sources of rare earth elements found in commercial deposits at Mountain Pass, California, Bayan Obo, China, and elsewhere. Synthetic forms of bastnaesite have been explored for applications including optical devices and phosphors. Determination of thermodynamic properties of these phases is critical for understanding their origin, mining, and processing. We report the first experimental determination of formation enthalpies of several OH and F bastnaesites based on high-temperature oxide melt solution calorimetry of well-characterized synthetic samples. The formation enthalpies from binary oxides and fluorides for all the bastnaesite samples are highly exothermic, consistent with their stability in the garnet zone of the Earth’s crust. Fluoride bastnaesite, which is more abundant in nature than its hydroxide counterpart, is thermodynamically more stable. For both OH and F bastnaesite, the enthalpy of formation becomes more negative with increasing ionic radius of the RE3+ cation. This periodic trend is also observed among rare earth phosphates and several other rare earth ternary oxides. For a given RE, the formation enthalpies from binary oxides are more negative for orthophosphates than for bastnaesites, supporting the argument that monazite could have formed by reaction of bastnaesite and apatite at high temperature. The difference in formation enthalpy of monazite and bastnaesite provides insight into energetics of such reactions along the rare earth series.
Abstract: Rare earth mineralization in the Bear Lodge alkaline complex (BLAC) is mainly associated with an anastomosing network of carbonatite dikes and veins, and their oxidized equivalents. Bear Lodge carbonatites are LREE-dominant, with some peripheral zones enriched in HREEs. We describe the unique chemistry and mineralogy one such peripheral zone, the Cole HFSE(+HREE) Occurrence (CHO), located ~2 km from the main carbonatite intrusions. The CHO consists of anatase, xenotime-(Y), brockite, fluorite, zircon, and K-feldspar, and contains up to 44.88% TiO2, 3.12% Nb2O5, 6.52% Y2O3, 0.80% Dy2O3, 2.63% ThO2, 6.0% P2O5, and 3.73% F. Electron microprobe analyses of xenotime-(Y) overgrowths on zircon show that oscillatory zoning is a result of variable Th and Ca content. Cheralite-type substitution, whereby Th and Ca are incorporated at the expense of REEs, is predominant over the more commonly observed thorite-type substitution in xenotime-(Y). Th/Ca-rich domains are highly beam sensitive and accompanied by high-F concentrations and low-microprobe oxide totals, suggesting cheralite-type substitution is more easily accommodated in fluorinated and hydrated/hydroxylated xenotime-(Y). Analyses of xenotime-(Y) and brockite show evidence of Embedded Image substitution for Embedded Image with patches of an undefined Ca-Th-Y-Ln phosphovanadate solid-solution composition within brockite clusters. Fluorite from the CHO is HREE-enriched with an average Y/Ho ratio of 33.2, while other generations of fluorite throughout the BLAC are LREE-enriched with Y/Ho ratios of 58.6-102.5. HFSE(+HREE) mineralization occurs at the interface between alkaline silicate intrusions and the first outward occurrence of calcareous Paleozoic sedimentary rocks, which may be local sources of P, Ti, V, Zr, and Y. U-Pb zircon ages determined by LA-ICP-MS reveal two definitive 207Pb/206Pb populations at 2.60-2.75 and 1.83-1.88 Ga, consistent with derivation from adjacent sandstones and Archean granite. Therefore, Zr and Hf are concentrated by a physical process independent of the Ti/Nb-enriched fluid composition responsible for anatase crystallization. The CHO exemplifies the extreme fluid compositions possible after protracted LREE-rich crystal fractionation and subsequent fluid exsolution in carbonatite-fluid systems. We suggest that the anatase+xenotime-(Y)+brockite+fluorite assemblage precipitated from highly fractionated, low-temperature (<200 °C), F-rich fluids temporally related to carbonatite emplacement, but after significant fractionation of ancylite and Ca-REE fluorocarbonates. Low-temperature aqueous conditions are supported by the presence of fine-grained anatase as the sole Ti-oxide mineral, concentrically banded botryoidal fluorite textures, and presumed hydration of phosphate minerals. Fluid interaction with Ca-rich lithologies is known to initiate fluorite crystallization which may cause destabilization of (HREE,Ti,Nb)-fluoride complexes and precipitation of REE+Th phosphates and Nb-anatase, a model valuable to the exploration for economic concentrations of HREEs, Ti, and Nb.
Geochimica et Cosmochimica Acta, Vol. 191, pp. 187-202.
Australia
Jack Hills REE
Abstract: Despite the robust nature of zircon in most crustal and surface environments, chemical alteration, especially associated with radiation damaged regions, can affect its geochemistry. This consideration is especially important when drawing inferences from the detrital record where the original rock context is missing. Typically, alteration is qualitatively diagnosed through inspection of zircon REE patterns and the style of zoning shown by cathodoluminescence imaging, since fluid-mediated alteration often causes a flat, high LREE pattern. Due to the much lower abundance of LREE in zircon relative both to other crustal materials and to the other REE, disturbance to the LREE pattern is the most likely first sign of disruption to zircon trace element contents. Using a database of 378 (148 new) trace element and 801 (201 new) oxygen isotope measurements on zircons from Jack Hills, Western Australia, we propose a quantitative framework for assessing chemical contamination and exchange with fluids in this population. The Light Rare Earth Element Index is scaled on the relative abundance of light to middle REE, or LREE-I = (Dy/Nd) + (Dy/Sm). LREE-I values vary systematically with other known contaminants (e.g., Fe, P) more faithfully than other suggested proxies for zircon alteration (Sm/La, various absolute concentrations of LREEs) and can be used to distinguish primary compositions when textural evidence for alteration is ambiguous. We find that zircon oxygen isotopes do not vary systematically with placement on or off cracks or with degree of LREE-related chemical alteration, suggesting an essentially primary signature. By omitting zircons affected by LREE-related alteration or contamination by mineral inclusions, we present the best estimate for the primary igneous geochemistry of the Jack Hills zircons. This approach increases the available dataset by allowing for discrimination of on-crack analyses (and analyses with ambiguous or no information on spot placement or zircon internal structures) that do not show evidence for chemical alteration. It distinguishes between altered and unaltered samples in ambiguous cases (e.g., relatively high Ti), identifying small groups with potentially differing provenance from the main Jack Hills population. Finally, filtering of the population using the LREE-I helps to more certainly define primary correlations among trace element variables, potentially relatable to magmatic compositional evolution.
Journal of Physical Chemistry, 10.1002/ chemv.201600068
Technology
Rare earths
Abstract: Scientists in the U.S. have provided a new understanding of the structure and crystal properties of the main mineral source of rare earth metals, bastnäsites. They are fluoro-carbonate minerals which contain ytterbium, lanthanum, and cerium, among other elements. The researchers used powder X-ray diffraction (XRD) and density functional theory (DFT) to reveal details of the minerals' structure and interfacial energy. The work could help in the design of new reagents for selective binding to mineral interfaces and could improve the recovery of rare metals by froth flotation, which is the major stage of ore beneficiation. Increasing flotation concentrate grades makes the subsequent leaching and rare earth separations more efficient and economic. Rare earth elements are increasingly important in modern technology - for electronics, catalysis, possible future quantum devices, and especially for clean energy applications like wind and solar energy, energy-efficient lighting, and electric vehicles. For example, neodymium and praseodymium are used in strong permanent magnets, lanthanum and cerium are used in batteries, metal alloys, petroleum refining, and catalysis, and ytterbium is a common material in phosphors for displays and in high-tech ceramics. These elements, which are defined as the fifteen lanthanides, as well as scandium and yttrium, are commonly found in the same ores. Despite what their name suggests, they are not actually rare, but they are difficult and costly to refine. As such, it is crucial that scientists and technologists optimize ore beneficiation to provide an enriched feedstock for the subsequent efficient extraction of these elements from the mined mineral ores in which they are found.
Abstract: This paper is an updated overview, including many new data, of what is known about Italian alkaline-carbonatite complexes, plus a new description of a carbothermal residua-related district, and its potential for mineral deposits. The Italian carbonatite occurrences can be divided into two belts. The first is a 350 km long and 75 km wide belt along the Apennines mountain range mainly with primary extrusive carbonatites generally from monogenic volcanoes and from the Vulture volcanic complex; the second belt is 60 km long and 20 km wide in the Northern Latium region in which carbothermal residua carbonatites and fluorite mineralisation deposited by high-temperature fluids rich in CO2, SO2 and fluorine are occurring in caldera volcanoes. Several of the raw materials, such as Light Rare Earth Elements, vanadium, niobium, zirconium, fluorite and phosphate are identified as critical as well as other commodities, occur in Italian carbonatites and alkaline rocks. At the Pianciano quarry (Bracciano) fluorite-rich ore (fluor-ore = fluorite in a mineralised gangue) is actually exploited as flux for cement, but Rare Earth Elements (+ V) could be a notable by-product (300,000 metric tonnes, equivalent to 4.2% of European resources). Pyrochlore, monazite, apatite, and britholite bearing subvolcanic rocks in ejecta from the Vulture volcano are of a near-economic grade, but their geological constraints are not known. A conceptual framework of combined geological and geochemical data improves the general understanding of this regional magmatic system, aimed at laying the foundations of a future geological model disclosing unrecognised potential exploration targets. However, this paper is not intended for direct use by the exploration industry; rather it is principally aimed at mineralogists and petrologists who could develop strategies for the identification of unexposed or unrecognised deposits.
Abstract: This paper reviews the available information on the geology, mineralogy, and resources of the significant rare earth element (REE) deposits and occurrences in the Murmansk Region, northwest Russia. The region has one of the largest endowments of REE in the world, primarily the light REE (LREE); however, most of the deposits are of potential economic interest for the REE, only as by-products of other mining activity, because of the relatively low REE grade. The measured and indicated REE2O3 resources of all deposits in the region total 22.4, and 36.2 million tonnes, respectively. The most important resources occur in (1) the currently mined Khibiny titanite-apatite deposits, and (2) the Lovozero loparite-eudialyte deposit. The Kovdor baddeleyite-apatite-magnetite deposit is a potentially important resource of scandium. These deposits all have polymetallic ores, i.e., REE would be a by-product of P, Ti, and Al mining at Khibiny, Fe, Zr, Ta, and Nb mining at Lovozero, and Fe and Ti mining at Afrikanda. The Keivy block has potential for heavy REE exploitation in the peralkaline granite-hosted Yumperuaiv and Large Pedestal Zr-REE deposits and the nepheline syenite-hosted Sakharyok Zr-REE deposit. With the exception of the Afrikanda perovskite-magnetite deposit (LREE in perovskite) and the Kovdor baddeleyite-apatite-magnetite deposit (scandium in baddelyite), carbonatite-bearing complexes of the Murmansk Region appear to have limited potential for REE by-products. The sound transport, energy, and mining infrastructure of the region are important factors that will help ensure future production of the REE.
Abstract: The paper presents detailed geochemical data on the rocks of the Zashikhinsky Massif and mineralogical-geochemical characteristics of the ores of the eponymous deposit. The rare-metal granites are divided into three facies varieties on the basis of the degree of differentiation and ore potential: early facies represented by microcline-albite granites with arfvedsonite, middle facies represented by leucocratic albite-microcline granites, and late (most ore-bearing) facies represented by quartz-albite granites grading into albitites. Microprobe data were obtained on major minerals accumulating trace elements in the rocks and ores. All facies of the rare-metal granites, including the rocks of the fluorite-rare-metal vein, define single compositional trends in the plots of paired correlations of rock-forming and trace elements. In addition, they also show similar REE patterns and spidergrams. The latter, however, differ in the depth of anomalies of some elements. Obtained geological, petrographic, and geochemical data suggest a magmatic genesis of the rocks of different composition and their derivation from a single magma during its differentiation. On the basis of all characteristics, the Zashikhinskoe deposit is estimated as one of the largest tantalum rare-metal deposits of alkaline-granite type in Russia.
International Geology Review, Vol. 58, 15, pp. 1940-1950.
China
Rare earths
Abstract: Carbonatites are characterized by the highest concentration of rare earth elements (REEs) of any igneous rock and are therefore good targets for REE exploration. Supergene, hydrothermal, and magmatic REE deposits associated with carbonatites have been widely studied. REE enrichment related to fluorapatite metasomatism in Fengzhen carbonatites in the North China block is reported in this study. REE minerals (monazite, britholite, and Ca-REE-fluorocarbonates) associated with barite and quartz formed as inclusions within the fluorapatite and externally on its surface. Monazite, allanite, barite, and quartz occur as rim grains on the edges of the fluorapatite. Zoned fluorapatite was observed and showed varying chemical composition. Based on back-scattered electron imaging, the dark domains with mineral inclusions contain lower Si (0.3-0.6 wt.% SiO2) and light REE (LREE) [0.36-1.54 wt.% (Y+LREE)2O3] contents than inclusion-poor areas [0.7-1 wt.% SiO2; 2.16-4.51 wt.% (Y + LREE)2O3]. This indicates a dissolution-re-precipitation texture. Different types of monazites were distinguished by their chemical compositions. Monazite inclusions have lower La2O3contents (~13 wt.%) and La/Ndcn (~3) ratios than those (18-26 wt.% and 10-14 for La2O3 and La/Ndcn, respectively) growing externally on the fluorapatite. REE enrichment in the metasomatic fluorapatites is related to different stages of carbonatitic liquids. The early carbonatite-exsolved fluids metasomatized the fluorapatites to form REE mineral inclusions. The late carbonatitic fluids from carbonatite magmas that underwent strong fractional crystallization were enriched in REEs, Al, and Fe and metasomatized the fluorapatites to produce allanite and monazite rim grains.
Geostandards and Geoanalytical Research, in press available
Technology
REE mass fractions
Abstract: Olivine offers huge, largely untapped, potential for improving our understanding of magmatic and metasomatic processes. In particular, a wealth of information is contained in rare earth element (REE) mass fractions, which are well studied in other minerals. However, REE data for olivine are scarce, reflecting the difficulty associated with determining mass fractions in the low ng g?1 range and with controlling the effects of LREE contamination. We report an analytical procedure for measuring REEs in olivine using laser ablation quadrupole-ICP-MS that achieved limits of determination (LOD) at sub-ng g?1 levels and biases of ~ 5-10%. Empirical partition coefficients (D values) calculated using the new olivine compositions agree with experimental values, indicating that the measured REEs are structurally bound in the olivine crystal lattice, rather than residing in micro-inclusions. We conducted an initial survey of REE contents of olivine from mantle, metamorphic, magmatic and meteorite samples. REE mass fractions vary from 0.1 to double-digit ng g?1 levels. Heavy REEs vary from low mass fractions in meteoritic samples, through variably enriched peridotitic olivine to high mass fractions in magmatic olivines, with fayalitic olivines showing the highest levels. The variable enrichment in HREEs demonstrates that olivine REE patterns have petrological utility.
Abstract: The Strange Lake peralkaline complex is one of the world's largest deposits of yttrium, heavy rare-earth elements, and zirconium. The Precambrian intrusive body of peralkaline granitic rocks in central Labrador is extensively mineralized but mineralogically complex. It is a pleasure to acknowledge John Jambor's important contributions to the understanding of the unusual and varied mineralization. He was first to identify and characterize the potentially economic minerals: gittinsite, widespread at Strange Lake but otherwise an uncommon zirconosilicate, and the unusual acid-soluble zircon, which are the main sources of Strange Lake zirconium. He also identified the previously unknown mineral gerenite-(Y), and provided better characterization of kainosite-(Y) and of the complex gadolinite-datolite species which, collectively, account for most of the yttrium and heavy rare-earths. In all, his identification and characterization of these minerals were invaluable to understanding of the peralkaline complex, particularly the late-stage alteration that affected it and generated its economically important minerals, making them amenable to effective metallurgical processes.
Reviews in Economic Geology, Vol. 18, 365p. $ 72. CD/pdf/print
Global
Book - rare earth
Abstract: This special volume provides a comprehensive review of the current state of knowledge for rare earth and critical elements in ore deposits. The first six chapters are devoted to rare earth elements (REEs) because of the unprecedented interest in these elements during the past several years. The following eight chapters describe critical elements in a number of important ore deposit types. These chapters include a description of the deposit type, major deposits, critical element mineralogy and geochemistry, processes controlling ore-grade enrichment, and exploration guides. This volume represents an important contribution to our understanding of where, how, and why individual critical elements occur and should be of use to both geoscientists and public policy analysts.
Reviews in Economic Geology, Vol. 18, pp. 115-136.
China
REE deposits
Abstract: China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite-related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.
Abstract: The crystal structure of the cubic modification of the natural mineral loparite has been studied for the first time by the methods of the X-ray diffraction analysis (?MoK ? radiation, 105 independent reflections with I > 3?(I), R = 0.041 in the anisotropic approximation). The structure belongs to the perovskite type (ABO 3) with the double period of the cubic unit cell, a = 7.767(1) Å (sp. gr. Pn3m; Z = 2 for the composition (Ca,Na,Ce)(Na,Ce)3(Ti,Nb)2Ti2O12. Period doubling is explained by ordering of cations both in the A and the B positions.
Abstract: Baddeleyite has been recognized as a key mineral to determine the crystallization age of silica-undersaturated igneous rocks. Here we report a new occurrence of baddeleyite identified from REE-Nb-Th-rich carbonatite in the world's largest REE deposit, Bayan Obo, in the North China Craton (China). U-Th-Pb dating of three baddeleyite samples yields crystallization ages of 310–270 Ma with the best estimated crystallization age of ca. 280 Ma. These ages are significantly younger than the ca. 1300 Ma Bayan Obo carbonatites, but broadly coeval to nearby Permian granitoids intruding into the carbonatites. Hence, the Bayan Obo baddeleyite did not crystallize from the carbonatitic magma that led to the formation of the Bayan Obo carbonatites and related REE-Nb-Th deposit. Instead, it crystallized from hydrothermal fluids and/or a reaction involving zircon and dolomite during contact metamorphism related to the Permian granitoid emplacement. This is in agreement with the results of electron microprobe analysis that show humite inclusions in baddeleyite, since humite is a typical magnesian skarn mineral and occurs in close proximity to the intrusive contacts between carbonatites and granitoids. Our results show that baddeleyite can be used for dating hydrothermal and contact metamorphic processes.
Abstract: A growing number of studies have suggested that hydrothermal remobilization is crucial for the formation of carbonatite-hosted rare earth element (REE) deposits [1-3]. The Ashram REE deposit, hosted by the Paleoproterozoic Eldor Carbonatite Complex [4], is an example of a REE deposit formed mainly due to hydrothermal processes in magnesio- and ferro-carbonatite. The REE minerals in the Ashram deposit, monazite-(Ce), bastnäsite-(Ce), xenotime- (Y) and minor aeschynite-(Y), are secondary, and were precipitated from hydrothermal fluids. They occur mainly as disseminations, in breccia matrices and veins, and as vug fillings. Hydrothermal apatite and fluorite are also present in appreciable quantities in REE-mineralized zones. Monazite- (Ce) was the earliest REE mineral to form, and was followed by xenotime-(Y) and bastnäsite-(Ce). The compositions of the main REE minerals vary with location in the deposit, particularly in respect to their Nd2O3 and ThO2 contents. Two generations of monazite-(Ce) have been distinguished on the basis of their Nd content. Early, low-Nd monazite-(Ce) formed by replacing apatite through the substitution of 3REE3+ for 5Ca2+ + F- ; low-Nd apatite is LREE-enriched compared to apatite. In contrast, the later high-Nd generation, which has a chondrite-normalized REE profile almost perfectly parallel to that of the apatite, is interpreted to have formed by dissolving the Ca2+ and F- of the apatite and reconstituting the REE and phosphate as monazite-(Ce): Ca4.94REE0.060(PO4)3F = 0.060REEPO4 + F- + 4.94Ca2+ + 2.94PO4 3- Bastnäsite-(Ce) developed as a replacement of monazite- (Ce) through ligand exchange (F- and CO3 2- for PO4 3- ), while preserving the original REE chemistry. A combination of magmatic zone-refinement and hydrothermal remobilization, involving a chloride-bearing fluid, contributed to the formation of a carbonatite-hosted REE deposit.
Natural Resources Research, in press available, 16p.
Global
rare earths
Abstract: The rare earth elements (REE) have attracted much attention in recent years, being viewed as critical metals because of China’s domination of their supply chain. This is despite the fact that REE enrichments are known to exist in a wide range of settings, and have been the subject of much recent exploration. Although the REE are often referred to as a single group, in practice each individual element has a specific set of end-uses, and so demand varies between them. Future demand growth to 2026 is likely to be mainly linked to the use of NdFeB magnets, particularly in hybrid and electric vehicles and wind turbines, and in erbium-doped glass fiber for communications. Supply of lanthanum and cerium is forecast to exceed demand. There are several different types of natural (primary) REE resources, including those formed by high-temperature geological processes (carbonatites, alkaline rocks, vein and skarn deposits) and those formed by low-temperature processes (placers, laterites, bauxites and ion-adsorption clays). In this paper, we consider the balance of the individual REE in each deposit type and how that matches demand, and look at some of the issues associated with developing these deposits. This assessment and overview indicate that while each type of REE deposit has different advantages and disadvantages, light rare earth-enriched ion adsorption types appear to have the best match to future REE needs. Production of REE as by-products from, for example, bauxite or phosphate, is potentially the most rapid way to produce additional REE. There are still significant technical and economic challenges to be overcome to create substantial REE supply chains outside China.
Abstract: Most critical raw materials, such as the rare-earth elements (REEs), are starting products in long manufacturing supply chains. Unlike most consumers, geoscientists can become involved in responsible sourcing, including best environmental and social practices, because geology is related to environmental impact factors such as energy requirements, resource efficiency, radioactivity and the amount of rock mined. The energy and material inputs and the emissions and waste from mining and processing can be quantified, and studies for REEs show little difference between ‘hard rocks’, such as carbonatites, and easily leachable ion-adsorption clays. The reason is the similarity in the embodied energy in the chemicals used for leaching, dissolution and separation.
Rare earth element applications, market outlook and Indian perspectives.
Carbonatite-alkaline rocks and associated mineral deposits , Dec. 8-11, abstract p.41-42.
India
rare earths
Abstract: Rare earth elements (REE) are a group of seventeen chemical elements that occur together in the periodic table. The group consists of yttrium and the 15 lanthanide elements (lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium). Promethium does not occur in nature because it is highly and the only lanthanide which has no stable (or even long-lived) isotopes. The most stable isotope of the element is Promethium-145, a half-life of 17.7 years. Due to its very less half-life most of the Promethium might have exhausted within first 10,000 years of formation of Earth. Scandium is found in most rare earth element deposits and is sometimes classified as a rare earth element. The rare earth elements are all metals, and the group is often referred to as the "rare earth metals." These metals have many similar properties, and that often causes them to be found together in geologic deposits. They are also referred to as "rare earth oxides" because many of them are typically sold as oxide compounds. The rare earths elements are classified into two groups; Cerium Group and Yttrium group, the former consists of light rare earths ( Sc, La, Ce, Nd, Pr, Pm, Sm and Eu ). The later is composed of (Y, Gd,Tb, Dy, Ho, Er, Tm, Yb and Lu). In nature the minerals of cerium group are different then the Yttrium group. The most common light rare earth minerals are monazite and bastnasite and for the heavy rare earth element the mineral is xenotime. Rare earth elements are not as "rare" as their name implies. Thulium and lutetium are the two least abundant rare earth elements - but they each have an average crustal abundance that is nearly 200 times greater than the crustal abundance of gold. However, these metals are very difficult to mine because it is unusual to find them in concentrations high enough for economical extraction. The most abundant rare earth elements are cerium, yttrium, lanthanum and neodymium. They have average crustal abundances that are similar to commonly used industrial metals such as chromium, nickel, zinc, molybdenum, tin, tungsten, and lead. Again, they are rarely found in extractable levels. Because of their unique magnetic, luminescent, and electrochemical properties, these elements help make many technologies perform with reduced weight, emissions, and energy consumption, and give them greater efficiency, performance, miniaturization, speed, durability, and thermal stability. Rare earth-enabled products and technologies help to fuel global economic growth, maintain high standards of living, and save lives. Rare earth elements are used extensively in aerospace and defense, health care, clean energy, electronics, transportation and vehicles, catalysts, polishing industry etc. Global resources of rare earths are about 120 Mt, China tops with 44 Mt, Vietnam and Brazil both 22Mt each, Russia 18 Mt, India 6.9 Mt, Australia 3.4 Mt, USA 1.4 Mt, Greenland 1.5 Mt, Malawi, 0.136 Mt, South Africa 0.86 Mt. The major producers today are China and Australia. China producing about 105,000 tons and Australia, 14000 tons, Russia, 3000 tons, India, 1700 tons, Brazil, 1100 tons, Thailand 800 tons, Malaysia, 300 tons( based on 2016 data). In 2016, excess global supply caused prices for many rare-earth compounds and metals to decline, and China continued to dominate the global supply. In China, the rare-earth mining production quota for 2016 was set at 105,000 tons, unchanged from 2015.The major reason of price decline was the illegal mining of rare earths in China which cause pollution and other financial losses. Now China is clamping down on mining as part of a campaign to tackle pollution and tighten control of its massive industrial complex. Various measures to curb production have already driven up prices of aluminum, steel, and now rare earths. Praseodymium-neodymium oxide, a raw material for the metal, has almost doubled this year, Neodymium surged by nearly a third in August alone and is up 81 percent in 2017. Demand for some rare earths may exceed supply in the second half after the crackdown on illegal mines. The global demand for automobiles, consumer electronics, energy-efficient lighting, permanent magnets and catalysts is expected to rise rapidly over the next decade. Rare earth magnet demand is expected to increase, as is the demand for rechargeable batteries. New developments in medical technology are expected to increase the use of surgical lasers, magnetic resonance imaging, and positron emission tomography scintillation detectors. Rare earth elements are heavily used in all of these industries, so the demand for them should remain high. So far EVs and renewable energy from clean technology point of view are concerned the rare earths join with niche metals including lithium and cobalt as beneficiaries of rapid growth in the electric vehicle industry and in renewable energy in the form of permanent magnets used in gearless turbines. By 2020, the REE demand in EVs will increase from 2000 tons per year to 7000 tons per year in 2020 and 12000 tons by 2024. In India, Indian Rare Earth Ltd is planning to produce 10,000 tons REO per year. The carbonatite hosted REE deposit with non-monazite sources has also been identified in Barmer district of Rajasthan.
Journal of Geochemical Exploration, Vol. 188, pp. 194-215.
Canada, Northwest Territories
rare earths
Abstract: The Canadian Nechalacho rare metal deposit (Thor Lake, Northwest Territories) contains one of the of the world's largest high-grade resources of rare earth elements (REE) and a large niobium (Nb) resource (Avalon Rare Metals Inc., 2013). The deposit formed mainly by magmatic accumulation of eudialyte (a complex REE-Nb-zirconosilicate) at the top of a > 1.1 km deep and ~2 km diameter layered nepheline-sodalite syenite intrusion, the Nechalacho Layered Suite. The strongest enrichment of REE and Nb is contained in the eudialyte cumulates of the Basal Zone layer. However, a strong hydrothermal overprint modified the eudialyte cumulate layers and their host rocks to produce a variety of hydrothermal silicates and REE-Nb minerals. The primary objective of this study is to evaluate the spatial distribution of the alteration minerals and identify possible mineral zoning.
Abstract: Granites and pegmatites in the Strange Lake pluton underwent extreme enrichment in high field strength elements (HFSE), including the rare earth elements (REE). Much of this enrichment took place in the most altered rocks, and is expressed as secondary minerals, showing that hydrothermal fluids played an important role in HFSE concentration. Vasyukova et al. (2016) reconstructed a P-T-X path for the evolution of these fluids and provided evidence that hydrothermal activity was initiated by exsolution of fluid during crystallisation of border zone pegmatites (at ~450-500?°C and 1.1?kbar). This early fluid comprised a high salinity (25?wt% NaCl) aqueous phase and a CH4?+?H2 gas. During cooling, the gas was gradually oxidised, first to higher hydrocarbons (e.g., C2H6, C3H8), and then to CO2, and the salinity decreased to 4?wt% (~250-300?°C), before increasing to 19?wt%, due to fluid-rock interaction (~150?°C). Here, we present crush-leach fluid inclusion data on the concentrations of the REE and major ligands at different stages of the evolution of the fluid. The chondrite-normalised REE profile of the fluid evolved from light REE (La-Nd)-enriched at high temperature (~400?°C, Stages 1-2a) to middle REE (Sm-Er)-enriched at 360 to 250?°C (Stages 2b-3) and strongly heavy REE (Tm-Lu)-enriched at low temperature (150?°C, Stage 5). These changes in the REE distribution were accompanied by changes in the concentrations of major ligands, i.e., Cl? was the dominant ligand in Stages 1, 2, 4 and 5, whereas HCO3? was dominant in Stage 3. Alteration of arfvedsonite to aegirine and/or hematite contributed strongly to the mobilisation of the REE. This alteration released middle REE (MREE) and heavy REE (HREE), which either partitioned into the fluid or precipitated directly as bastnäsite-(Ce), ferri-allanite-(Ce) or gadolinite-(Y). Replacement of primary fluorbritholite-(Ce), which crystallised from an immiscible fluoride melt and altered to bastnäsite-(Ce), was also important in mobilising the REE (MREE). This paper presents the first report of the distribution of the REE in an evolving hydrothermal fluid. Using this distribution, in conjunction with information on the changing physicochemical conditions, the study identifies the sources of REE enrichment, reconstructs the path of REE concentration, and evaluates the REE mineralising capacity of the fluid. Finally, this information is integrated into a predictive model for REE mobilisation applicable not only to Strange Lake but any REE ore-forming system, in which hydrothermal processes were important.
Abstract: Rare earth element (REE) orebodies are typically associated with alkaline igneous rocks or develop as placer or laterite deposits. Here, we describe an economically important heavy (H)REE mineralization type that is entirely hydrothermal in origin with no demonstrable links to magmatism. The mineralization occurs as numerous xenotime-rich vein and breccia orebodies across a large area of northern Australia but particularly close to a regional unconformity between Archean metasedimentary rocks of the Browns Range Metamorphics and overlying Proterozoic sandstones of the Birrindudu Group. The deposits formed at 1.65 to 1.61 Ga along steeply dipping faults; there is no known local igneous activity at this time. Depletion of HREEs in the Browns Range Metamorphics, together with the similar nonradiogenic Nd isotope composition of the orebodies and the Browns Range Metamorphics, indicates that ore metals were leached directly from the Browns Range metasedimentary rocks. We propose an ore genesis model that involves fluid leaching HREEs from the Browns Range Metamorphics and subsequently mixing with P-bearing acidic fluid from the overlying sandstones in fault zones near the unconformity. The union of P and HREEs via fluid mixing in a low-Ca environment triggered extensive xenotime precipitation. This mineralization is unlike that of any other class of REE ore deposit but has a similar setting to unconformity-related U deposits of Australia and Canada, so we assign it the label “unconformity-related REE.” Further discoveries of this REE mineralization type are expected near regional unconformities within Proterozoic intracontinental sedimentary basins across the globe.
Abstract: Security of supply of “hi-tech” raw materials (including the rare earth elements (REE) and some high-field-strength elements (HFSEs)) is a concern for the European Union. Exploration and research projects mostly focus on deposit- to outcrop-scale description of carbonatite- and alkaline igneous-associated REE-HFSE mineralization. The REE-HFSE mineral system concept and approach are at a nascent stage, so developed further here. However, before applying the mineral system approach to a chosen REE-HFSE metallogenic province its mineral system extent first needs defining and mapping. This shifts a mineral system project’s foundation from the mineral system concept to a province’s mineral system extent. The mapped extent is required to investigate systematically the pathways and potential trap locations along which the REE-HFSE mass may be distributed. A workflow is presented to standardize the 4-D definition of a REE-HFSE mineral system at province-scale: (a) Identify and hierarchically organize a mineral system’s genetically related sub-divisions and deposits, (b) map its known and possible maximum extents, (c) name it, (d) discern its size (known mineral endowment), and (e) assess the favorability of the critical components to prioritize further investigations. The workflow is designed to generate process-based perspective and improve predictive targeting effectiveness along under-evaluated plays of any mineral system, for the future risking, comparing and ranking of REE-HFSE provinces and plays.
Abstract: The role of magmatic differentiation is considered for the formation of the Ulan-Tologoi Ta-Nb-Zr deposit (northwestern Mongolia) related to the eponymous alkali granite pluton. Data are presented on the structure of the pluton, the composition of its rocks, and distribution of rare metal mineralization. The ores of the pluton include alkali granites with contents of ore elements exceeding the normative threshold for Ta (>100 ppm). The rare metal mineralization includes pyrochlore, columbite, zircon, bastnaesite, monazite, and thorite, which are typical of all alkali-salic rocks; however, their amount varies depending on the REE content of the rocks. The pluton was formed ~298 Ma ago under the influence of a mantle-crustal melt source.
Abstract: Granites and pegmatites in the Strange Lake pluton underwent extreme enrichment in high field strength elements (HFSE), including the rare earth elements (REE). Much of this enrichment took place in the most altered rocks, and is expressed as secondary minerals, showing that hydrothermal fluids played an important role in HFSE concentration. Vasyukova et al. (2016) reconstructed a P-T-X path for the evolution of these fluids and provided evidence that hydrothermal activity was initiated by exsolution of fluid during crystallisation of border zone pegmatites (at ~450-500?°C and 1.1?kbar). This early fluid comprised a high salinity (25?wt% NaCl) aqueous phase and a CH4?+?H2 gas. During cooling, the gas was gradually oxidised, first to higher hydrocarbons (e.g., C2H6, C3H8), and then to CO2, and the salinity decreased to 4?wt% (~250-300?°C), before increasing to 19?wt%, due to fluid-rock interaction (~150?°C). Here, we present crush-leach fluid inclusion data on the concentrations of the REE and major ligands at different stages of the evolution of the fluid. The chondrite-normalised REE profile of the fluid evolved from light REE (La-Nd)-enriched at high temperature (~400?°C, Stages 1-2a) to middle REE (Sm-Er)-enriched at 360 to 250?°C (Stages 2b-3) and strongly heavy REE (Tm-Lu)-enriched at low temperature (150?°C, Stage 5). These changes in the REE distribution were accompanied by changes in the concentrations of major ligands, i.e., Cl? was the dominant ligand in Stages 1, 2, 4 and 5, whereas HCO3? was dominant in Stage 3. Alteration of arfvedsonite to aegirine and/or hematite contributed strongly to the mobilisation of the REE. This alteration released middle REE (MREE) and heavy REE (HREE), which either partitioned into the fluid or precipitated directly as bastnäsite-(Ce), ferri-allanite-(Ce) or gadolinite-(Y). Replacement of primary fluorbritholite-(Ce), which crystallised from an immiscible fluoride melt and altered to bastnäsite-(Ce), was also important in mobilising the REE (MREE). This paper presents the first report of the distribution of the REE in an evolving hydrothermal fluid. Using this distribution, in conjunction with information on the changing physicochemical conditions, the study identifies the sources of REE enrichment, reconstructs the path of REE concentration, and evaluates the REE mineralising capacity of the fluid. Finally, this information is integrated into a predictive model for REE mobilisation applicable not only to Strange Lake but any REE ore-forming system, in which hydrothermal processes were important.
Abstract: The Gakara Rare Earth Elements (REE) deposit is one of the world’s highest grade REE deposits, likely linked to a carbonatitic magmatic-hydrothermal activity. It is located near Lake Tanganyika in Burundi, along the western branch of the East African Rift. Field observations suggest that the mineralized veins formed in the upper crust. Previous structures inherited from the Kibaran orogeny may have been reused during the mineralizing event. The paragenetic sequence and the geochronological data show that the Gakara mineralization occurred in successive stages in a continuous hydrothermal history. The primary mineralization in bastnaesite was followed by an alteration stage into monazite. The U-Th-Pb ages obtained on bastnaesite (602 ± 7 Ma) and on monazite (589 ± 8 Ma) belong to the Pan-African cycle. The emplacement of the Gakara REE mineralization most likely took place during a pre-collisional event in the Pan-African belt, probably in an extensional context.
Abstract: Rare earth elements (REE) include the lanthanide series elements (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) plus Sc and Y. Currently these metals have become very critical to several modern technologies ranging from cell phones and televisions to LED light bulbs and wind turbines. This article summarizes the occurrence of these metals in the Earth's crust, their mineralogy, different types of deposits both on land and oceans from the standpoint of the new data with more examples from the Indian subcontinent. In addition to their utility to understand the formation of the major Earth reservoirs, multi-faceted updates on the applications of REE in agriculture and medicine including new emerging ones are presented. Environmental hazards including human health issues due to REE mining and large-scale dumping of e-waste containing significant concentrations of REE are summarized. New strategies for the future supply of REE including recent developments in the extraction of REE from coal fired ash and recycling from e-waste are presented. Recent developments in individual REE separation technologies in both metallurgical and recycling operations have been highlighted. An outline of the analytical methods for their precise and accurate determinations required in all these studies, such as, X-ray fluorescence spectrometry (XRF), laser induced breakdown spectroscopy (LIBS), instrumental neutron activation analysis (INAA), inductively coupled plasma optical emission spectrometry (ICP-OES), glow discharge mass spectrometry (GD-MS), inductively coupled plasma mass spectrometry (including ICP-MS, ICP-TOF-MS, HR-ICP-MS with laser ablation as well as solution nebulization) and other instrumental techniques, in different types of materials are presented.
Abstract: Recent exploration work in South Morocco revealed the occurrence of several carbonatite bodies, including the Paleoproterozoic Gleibat Lafhouda magnesiocarbonatite and its associated iron oxide mineralization, recognized here as iron-oxide-apatite (IOA) deposit type. The Gleibat Lafhouda intrusion is hosted by Archean gneiss and schist and not visibly associated with alkaline rocks. Metasomatized micaceous rocks occur locally at the margins of the carbonatite outcrop and were identified as glimmerite fenite type. Rare earth element (REE) and Nb mineralization is mainly linked to the associated IOA mineralization and is represented by monazite-(Ce) and columbite-(Fe) as major ore minerals. The IOA mineralization mainly consists of magnetite and hematite that usually contain large apatite crystals, quartz and some dolomite. Monazite-(Ce) is closely associated with fluorapatite and occurs as inclusions within the altered parts of apatite and along cracks or as separate phases near apatite. Monazite shows no zonation patterns and very low Th contents (<0.4?wt%), which would be beneficial for commercial extraction of the REE and which indicates monazite formation from apatite as a result of hydrothermal volatile-rich fluids. Similar monazite-apatite mineralization and chemistry also occurs at depth within the carbonatite, although the outcropping carbonatite is barren, suggesting an irregular REE ore distribution within the carbonatite body. The barren carbonatite contains some tiny unidentified secondary Nb-Ta-U phases, synchysite and monazite. Niobium mineralization is commonly represented by anhedral minerals of columbite-(Fe) which occur closely associated with magnetite-hematite and host up to 78?wt% Nb2O5, 7?wt% Ta2O5 and 1.6?wt% Sc2O3. This association may suggest that columbite-(Fe) precipitated by an interaction of Nb-rich fluids with pre-existing Fe-rich minerals or as pseudomorphs after pre-existing Nb minerals like pyrochlore. Our results most strongly suggest that the studied mineralization is economically important and warrants both, further research and exploration with the ultimate goal of mineral extraction.
Abstract: There are a number of peralkaline granitic plutons, which show significant enrichment in the REE and, in some cases, host REE deposits; the grades of the deposits represent the final enrichment in the REE. Thus, it is important to understand how this enrichment occurs and by which processes, in order to develop tools for discovering other similar deposits. The best way to reconstruct the REE composition of an evolving magma is by analysing melt inclusions, i.e., the tiny samples of magma trapped at different stages of its evolution. Such inclusions, however, are rarely preserved and difficult to analyse. Another way to reconstruct the REE composition of an evolving magma is to analyse the REE composition of the minerals crystallising from this magma at different stages in its evolution. This, however, requires that the REE mineral-melt partition coefficients be known. Here we present a model for the calculation of arfvedsonite-melt REE partition coefficients, based on data from the Strange Lake pluton (Canada). The model employs the lattice strain theory, which derives mineral-melt partition coefficients from the values of the ideal partition coefficient (D0), the ideal radius (r0) and the elastic response (EM) of the mineral. There are two sites in arfvedsonite into which the REE partition, namely the M4 site, which is preferred by the light REE and the M2 site, which is preferred by the heavy REE. Partition coefficients for both sites were modelled. Significantly, values of D0, r0 and EM for the M4 site vary linearly with the Ca content of the arfvedsonite, whereas for the M2 site these parameters vary linearly with the temperature of arfvedsonite crystallisation. Using these two relationships, a set of equations was derived, which enables the calculation of arfvedsonite-melt REE partition coefficients for any arfvedsonite for which the Ca content and crystallisation temperature are known. This model was tested on a peralkaline granitic pegmatite from the Amis complex (Namibia), for which data on the composition of the amphibole and corresponding magma (melt inclusions) have been reported. The model successfully predicts the concentrations of the various REE in the Amis magma, thereby providing confidence that it can be used to trace the REE content of evolving granitic magmas in other plutons.
Journal of Geochemical Exploration, Vol. 204, pp. 270-288.
Europe, Spain
REE
Abstract: Gran Canaria is a hotspot-derived, intraplate, oceanic island, comprising a variety of alkaline felsic magmatic rocks (i.e. phonolites, trachytes, rhyolites and syenites). These rocks are enriched in rare-earth elements (REE) in relation to the mean concentration in the Earth's crust and they are subsequently mobilised and redistributed in the soil profile. From a set of 57 samples of felsic rocks and 12 samples from three paleosol profiles, we assess the concentration and mobility of REE. In the saprolite that developed over the rhyolites, we identified REE-bearing minerals such as primary monazite-(Ce), as well as secondary phases associated with the edaphic weathering, such as rhabdophane-(Ce) and LREE oxides. The averaged concentration of REE in the alkaline bedrock varies from trachytes (449?mg?kg?1), to rhyolites (588?mg?kg?1) and to phonolites (1036?mg?kg?1). REE are slightly enriched in saprolites developed on trachyte (498?mg?kg?1), rhyolite (601?mg?kg?1) and phonolite (1171?mg?kg?1) bedrocks. However, B-horizons of paleosols from trachytes and phonolites showed REE depletion (436 and 994?mg?kg?1, respectively), whereas a marked enrichment was found in soils developed on rhyolites (1584?mg?kg?1). According to our results, REE resources on Gran Canaria are significant, especially in Miocene alkaline felsic magmatic rocks (declining stage) and their associated paleosols. We estimate a total material volume of approximately 1000?km3 with REE concentrations of 672?±?296?mg?kg?1, yttrium contents of 57?±?30?mg?kg?1, and light and heavy REE ratios (LREE/HREE) of 17?±?6. This mineralisation can be considered as bulk tonnage and low-grade ore REE deposits but it remains necessary to develop detailed mineral exploration on selected insular zones in the future, without undermining environmental and socioeconomic interests.
Canadian Journal of Earth Science, Vol. 56, pp. 957-969.
Canada, Quebec, Labrador
REE
Abstract: A study of rare metal indicator minerals and glacial dispersal was carried out at the Strange Lake Zr?-?Y?-?heavy rare earth element deposit in northern Quebec and Labrador, Canada. The heavy mineral (>3.2 specific gravity) and mid-density (3.0-3.2 specific gravity) nonferromagnetic fractions of mineralized bedrock from the deposit and till up to 50 km down ice of the deposit were examined to determine the potential of using rare earth element and high fileld strength element indicator minerals for exploration. The deposit contains oxide, silicate, phosphate, and carbonate indicator minerals, some of which (cerianite, uraninite, fluorapatite, rhabdophane, thorianite, danburite, and aeschynite) have not been reported in previous bedrock studies of Strange Lake. Indicator minerals that could be useful in the exploration for similar deposits include Zr silicates (zircon, secondary gittinsite (CaZrSi2O7), and other hydrated Zr±Y±Ca silicates), pyrochlore ((Na,Ca)2Nb2O6(OH,F)), and thorite (Th(SiO4))/thorianite (ThO2) as well as rare earth element minerals monazite ((La,Ce,Y,Th)PO4), chevkinite ((Ce,La,Ca,Th)4(Fe,Mg)2(Ti,Fe)3Si4O22), parisite (Ca(Ce,La)2(CO3)3F2), bastnaesite (Ce(CO3)F), kainosite (Ca2(Y,Ce)2Si4O12(CO3)•H2O), and allanite ((Ce,Ca,Y)2(Al,Fe)3(SiO4)3(OH)). Rare metal indicator minerals can be added to the expanding list of indicator minerals that can be recovered from surficial sediments and used to explore for a broad range of deposit types and commodities that already include diamonds and precious, base, and strategic metals.
Abstract: For the past two decades, Zimbabwe has experienced a pervasive economic collapse. Most of the challenges were caused by policy inconsistencies, bad policy choices, economic mismanagement and political instability. This led to deindustrialization with a sharp decline in manufacturing and agriculture productivity and output, which consequently caused a sharp increase in unemployment and poverty. Although it is not fully developed, the mining industry in Zimbabwe presents an opportunity for economic stimulation that may lead to economic recovery, but requires broad-based economic reforms. This paper presents the findings of a review, and benchmarking of Zimbabwe's policies, which affect mining investment, inclusive economic growth and human development. The policies were benchmarked and compared to similar policies of Botswana, Namibia and South Africa using the Natural Resources Benchmarking Charter Framework. The outcomes of the review and benchmarking process were taken into consideration when coming up with policy suggestions that are meant to economically transform Zimbabwe, which at the same time brings sustained human development. The work reported in this paper is part of an MSc research study in the School of Mining Engineering at the University of the Witwatersrand.
Abstract: Although REE (lanthanides + Sc + Y) mineralization in alkaline silicate systems is commonly accompanied with Zr mineralization worldwide, our understanding of the relationship between Zr and REE mineralization is still incomplete. The Baerzhe deposit in Northeastern China is a reservoir of REE, Nb, Zr, and Be linked to the formation of an Early Cretaceous, silica-saturated, alkaline intrusive complex. In this study, we use in situ laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) analyses of zircon and monazite crystals to constrain the relationship between Zr and REE mineralization at Baerzhe. Three groups of zircon are identified and are differentiated based upon textural observations and compositional characteristics. Type Ia zircons display well-developed oscillatory zoning. Type Ib zircons are darker in cathodoluminescence images and have more irregular zoning and resorption features than type Ia zircons. In addition, type Ib zircons can locally occur as overgrowths on type Ia zircons. Type II zircons contain irregular but translucent cores and rims with oscillatory zoning that are murky brown in color and occur in aggregates. Textural features and compositional data suggest that types Ia and Ib zircon crystallized at the magmatic stage, with type Ia being least-altered and type Ib being strongly altered. Type II zircons, on the other hand, precipitated during the magmatic to magmatichydrothermal transition. Whereas the magnitude of the Eu anomaly is moderate in the barren alkaline granite, both magmatic and deuteric zircon exhibit pronounced negative anomalies. Such features are difficult to explain exclusively by feldspar fractionation and could indicate the presence of fluid induced modification of the rocks. Monazite crystals occur mostly through replacement of zircon and sodic amphibole; monazite clusters are also present. Textural and compositional evidence suggests that monazite at Baerzhe is hydrothermal. Types Ia and Ib magmatic zircon yield 207Pb-corrected 206Pb/238U ages of 127.2 ± 1.3 and 125.4 ± 0.7 Ma, respectively. Type II deuteric zircon precipitated at 124.9 ± 0.6 Ma. The chronological data suggest that the magmatic stage of the highly evolved Baerzhe alkaline granite lasted less than two million years. Hydrothermal monazite records a REE mineralization event at 122.8 ± 0.6 Ma, approximately 1 or 2 million years after Zr mineralization. We therefore propose a model in which parental magmas of the Baerzhe pluton underwent extensive magmatic differentiation while residual melts interacted with aqueous hydrothermal fluids. Deuteric zircon precipitated from a hydrosilicate liquid, and subsequent REE mineralization, exemplified by hydrothermal monazite, correlates with hydrothermal metasomatic alteration that postdated the hydrosilicate liquid event. Such interplay between magmatic and hydrothermal processes resulted in the formation of discrete Zr and REE mineralization at Baerzhe.
Geostandards and Geoanalltical Research, Vol. 43, 3, pp. 543-565.
China, Europe, Sweden, Asia, Mongolia, United States, Africa, Malawi, Madagascar
REE
Abstract: Bastnäsite is the end member of a large group of carbonate-fluoride minerals with the common formula (REE) CO3F•CaCO3. This group is generally widespread and, despite never occurring in large quantities, represents the major economic light rare earth element (LREE) mineral in deposits related to carbonatite and alkaline intrusions. Since bastnäsite is easily altered and commonly contains inclusions of earlier?crystallised minerals, in situ analysis is considered the most suitable method to measure its U?Th?Pb and Sr?Nd isotopic compositions. Electron probe microanalysis and laser ablation (multi?collector) inductively coupled plasma?mass spectrometry of forty?six bastnäsite samples from LREE deposits in China, Pakistan, Sweden, Mongolia, USA, Malawi and Madagascar indicate that this mineral typically has high Th and LREE and moderate U and Sr contents. Analysis of an in?house bastnäsite reference material (K?9) demonstrated that precise and accurate U?Th?Pb ages could be obtained after common Pb correction. Moreover, the Th?Pb age with its high precision is preferable to the U?Pb age because most bastnäsites have relatively high Th rather than U contents. These results will have significant implications for understanding the genesis of endogenous ore deposits and formation processes related to metallogenic geochronology research.
Abstract: Clinopyroxene is a key fractionating phase in alkaline magmatic systems, but its impact on metal enrichment processes, and the formation of REE + HFSE mineralisation in particular, is not well understood. To constrain the control of clinopyroxene on REE + HFSE behaviour in sodic (per)alkaline magmas, a series of internally heated pressure vessel experiments was performed to determine clinopyroxene-melt element partitioning systematics. Synthetic tephriphonolite to phonolite compositions were run H2O-saturated at 200?MPa, 650-825?C with oxygen fugacity buffered to log f O2 ? ?QFM + 1 or log f O2 ? ?QFM +5. Clinopyroxene-glass pairs from basanitic to phonolitic fall deposits from Tenerife, Canary Islands, were also measured to complement our experimentally-derived data set. The REE partition coefficients are 0.3-53, typically 2-6, with minima for high-aegirine clinopyroxene. Diopside-rich clinopyroxenes (Aeg5-25) prefer the MREE and have high REE partition coefficients (DEuup to 53, DSmup to 47). As clinopyroxene becomes more Na- and less Ca-rich (Aeg25-50), REE incorporation becomes less favourable, and both the VIM1 and VIIIM2 sites expand (to 0.79 Å and 1.12 Å), increasing DLREE/DMREE. Above Aeg50 both M sites shrink slightly and HREE (VIri? 0.9 Å ? Y) partition strongly onto the VIM1 site, consistent with a reduced charge penalty for REE3+ ? Fe3+ substitution. Our data, complemented with an extensive literature database, constrain an empirical model that predicts trace element partition coefficients between clinopyroxene and silicate melt using only mineral major element compositions, temperature and pressure as input. The model is calibrated for use over a wide compositional range and can be used to interrogate clinopyroxene from a variety of natural systems to determine the trace element concentrations in their source melts, or to forward model the trace element evolution of tholeiitic mafic to evolved peralkaline magmatic systems.
Abstract: Detailed studies on U?Pb ages and Hf isotope have been carried out in zircons from a carbonatite dyke associated with the Bayan Obo giant REE?Nb?Fe deposit, northern margin of the North China Craton (NCC), which provide insights into the plate tectonic in Paleoproterozoic. Analyses of small amounts of zircons extracted from a large sample of the Wu carbonatite dyke have yielded two ages of late Archaean and late Paleoproterozoic (with mean 207Pb/206Pb ages of 2521±25 Ma and 1921±14 Ma, respectively). Mineral inclusions in the zircon identified by Raman spectroscopy are all silicate minerals, and none of the zircon grains has the extremely high Th/U characteristic of carbonatite, which are consistent with crystallization of the zircon from silicate, and the zircon is suggested to be derived from trapped basement complex. Hf isotopes in the zircon from the studied carbonatite are different from grain to grain, suggesting the zircons were not all formed in one single process. Majority of ?Hf(t) values are compatible with ancient crustal sources with limited juvenile component. The Hf data and their TDM2 values also suggest a juvenile continental growth in Paleoproterozoic during the period of 1940-1957 Ma. Our data demonstrate the major crustal growth during the Paleoproterozoic in the northern margin of the NCC, coeval with the assembly of the supercontinent Columbia, and provide insights into the plate tectonic of the NCC in Paleoproterozoic.
Abstract: Sulfur-bearing monazite-(Ce) occurs in silicified carbonatite at Eureka, Namibia, forming rims up to ~0.5 mm thick on earlier-formed monazite-(Ce) megacrysts. We present X-ray photoelectron spectroscopy data demonstrating that sulfur is accommodated predominantly in monazite-(Ce) as sulfate, via a clino-anhydrite-type coupled substitution mechanism. Minor sulfide and sulfite peaks in the X-ray photoelectron spectra, however, also indicate that more complex substitution mechanisms incorporating S2 and S4+ are possible. Incorporation of S6+ through clino-anhydrite-type substitution results in an excess of M2+ cations, which previous workers have suggested is accommodated by auxiliary substitution of OH for O2. However, Raman data show no indication of OH, and instead we suggest charge imbalance is accommodated through F substituting for O2. The accommodation of S in the monazite-(Ce) results in considerable structural distortion that may account for relatively high contents of ions with radii beyond those normally found in monazite-(Ce), such as the heavy rare earth elements, Mo, Zr and V. In contrast to S-bearing monazite-(Ce) in other carbonatites, S-bearing monazite-(Ce) at Eureka formed via a dissolutionprecipitation mechanism during prolonged weathering, with S derived from an aeolian source. While large S-bearing monazite-(Ce) grains are likely to be rare in the geological record, formation of secondary S-bearing monazite-(Ce) in these conditions may be a feasible mineral for dating palaeo-weathering horizons.
Abstract: Trace elements play a significant role in interpretation of different processes in the deep Earth. However, the systematics of interphase rare-earth element (REE) partitioning under the conditions of the uppermost lower mantle are poorly understood. We performed high-pressure experiments to study the phase relations in key solid-phase reactions CaMgSi2O6 = CaSiO3-perovskite + MgSiO3-bridgmanite and (Mg,Fe)2SiO4-ringwoodite = (Mg,Fe)SiO3-bridgmanite + (Mg,Fe)O with addition of 1 wt % of REE oxides. Atomistic modeling was used to obtain more accurate quantitative estimates of the interphase REE partitioning and displayed the ideal model for the high-pressure minerals. HREE (Er, Tm, Yb, and Lu) are mostly accumulated in bridgmanite, while LREE are predominantly redistributed into CaSiO3. On the basis of the results of experiments and atomistic modeling, REE in bridgmanite are clearly divided into two groups (from La to Gd and from Gd to Lu). Interphase REE partition coefficients in solid-state reactions were calculated at 21.5 and 24 GPa for the first time. The new data are applicable for interpretation of the trace-element composition of the lower mantle inclusions in natural diamonds from kimberlite; the experimentally determined effect of pressure on the interphase (bridgmanite/CaSiO3-perovskite) REE partition coefficients can be a potential qualitative geobarometer for mineral inclusions in super-deep diamonds.
Abstract: This study reports major, trace, rare earth and platinum group element compositions of lava flows from the Vempalle Formation of Cuddapah Basin through an integrated petrological and geochemical approach to address mantle conditions, magma generation processes and tectonic regimes involved in their formation. Six flows have been identified on the basis of morphological features and systematic three-tier arrangement of vesicular-entablature-colonnade zones. Petrographically, the studied flows are porphyritic basalts with plagioclase and clinopyroxene representing dominant phenocrystal phases. Major and trace element characteristics reflect moderate magmatic differentiation and fractional crystallization of tholeiitic magmas. Chondrite-normalized REE patterns corroborate pronounced LREE/HREE fractionation with LREE enrichment over MREE and HREE. Primitive mantle normalized trace element abundances are marked by LILE-LREE enrichment with relative HFSE depletion collectively conforming to intraplate magmatism with contributions from sub-continental lithospheric mantle (SCLM) and extensive melt-crust interaction. PGE compositions of Vempalle lavas attest to early sulphur-saturated nature of magmas with pronounced sulphide fractionation, while PPGE enrichment over IPGE and higher Pd/Ir ratios accord to the role of a metasomatized lithospheric mantle in the genesis of the lava flows. HFSE-REE-PGE systematics invoke heterogeneous mantle sources comprising depleted asthenospheric MORB type components combined with plume type melts. HFSE-REE variations account for polybaric melting at variable depths ranging from garnet to spinel lherzolite compositional domains of mantle. Intraplate tectonic setting for the Vempalle flows with P-MORB affinity is further substantiated by (i) their origin from a rising mantle plume trapping depleted asthenospheric MORB mantle during ascent, (ii) interaction between plume-derived melts and SCLM, (iii) their rift-controlled intrabasinal emplacement through Archean-Proterozoic cratonic blocks in a subduction-unrelated ocean-continent transition zone (OCTZ). The present study is significant in light of the evolution of Cuddapah basin in the global tectonic framework in terms of its association with Antarctica, plume incubation, lithospheric melting and thinning, asthenospheric infiltration collectively affecting the rifted margin of eastern Dharwar Craton and serving as precursors to supercontinent disintegration.
Abstract: Rare earth elements (REEs) including fifteen lanthanides, yttrium and scandium are found in more than 250 minerals, worldwide. REEs are used in various high-tech applications across various industries, such as electrical and electronics, automotive, renewable energy, medical and defence. Therefore, the demand for REEs in the global market is increasing day by day due to the surging demand from various sectors, such as emerging economies, green technology and R&D sectors. Rare earth (RE) deposits are classified on the basis of their genetic associations, mineralogy and form of occurrences. The Bayan Obo, Mountain Pass, Mount Weld and China’s ion adsorption clays are the major RE deposits/mines in the world to date and their genesis, chronology and mineralogy are discussed in this review. In addition, there are other RE deposits, which are currently being mined or in the feasibility or exploration stages. Most of the RE resources, production, processing and supply are concentrated in the Asia-Pacific region. In this regard, China holds the dominancy in the RE industry by producing more than 90% of the current rare earth requirements. Thus, REEs are used as a powerful tool by China in trade wars against other countries, especially against USA in 2019. However, overwhelming challenges in conventional RE explorations and mining make secondary RE resources, such as electric and electronic waste (e-waste) and mine tailings as promising resources in the future. Due to the supply risk of REEs and the monopoly of the REEs market, REEs recycling is currently considered as an effective method to alleviate market fluctuations. However, economical and sustainable processing techniques are yet to be established to exploit REEs via recycling. Moreover, there are growing ecological concerns along with social resistance towards the RE industry. To overcome these issues, the RE industry needs to be assessed to maintain long-term social sustainability by fostering the United Nations sustainable development goals (SDGs).
Journal of the Geological Society of India, Vol. 95, pp. 464-474.
India, global
REE
Abstract: The RM (Li, Be, Ti, Zr, Nb, Ta, Th and U) and REE (Light Rare Earths and Heavy Rare Earths including Yttrium) are strategic and critical for sustaining a variety of industries such as nuclear, defence, information technology (IT) and green energy options (wind, solar, electric vehicles and others). The 2010 ‘Rare Earth’ crisis of the world, following China’s monopoly with over 80% share and export restrictions in the REE market, led to an exploration boom for REE all over the world including India. This led to a substantial increase in REE mineral resources (98 Mt of contained REO in 2015) outside China located in Canada (38 Mt), Greenland (39 Mt) and Africa (10.3 Mt) that represents a fivefold increase in resources (c.f. Paulick and Machacek, 2017). As per the 2019, USGS commodity survey, the world reserves of REE have been estimated at 120 Mt in countries such as China (44Mt), Brazil (22Mt), Vietnam (22 Mt), Russia (12 Mt), India (6.9 Mt) and others (13 Mt). At present world resources of RM and REE are adequate to cater the demands of the different industries. The constraints, however, appear to be not technical but mainly environmental and social issues.
Abstract: Mantle xenoliths were found in alkaline basalts of Tokinsky Stanovik (TSt) in the Dzhugdzhur-Stanovoy superterrane (DS) and Vitim plateau (VP) in the Barguzin-Vitim superterrane (BV) (Stanovoy suture area) at junction of the Central Asian Orogenic Belt (CAOB) and the Siberian craton (SC). Xenoliths from TSt basalts are represented by spinel lherzolites, harzburgites, wehrlites; while VP basalts frequently contain spinel-garnet and garnet peridotites lherzolites, and pyroxenites. Xenoliths in kimberlites of the Siberian craton are mainly represented by garnet-bearing lherzolites with abundant eclogite xenoliths (age of 2.7-3.1 Ga), which were not found in mantle of superterranes. The Re-Os determinations point to the Early Archean age of peridotites and eclogites from mantle beneath the Siberian craton. The major and trace (rare-earth and high-filed strength) elements and Nd-Sr-Os composition were analyzed in the peridotites (predominant rocks) of lithospheric mantle at junction of the Central Asian Orogenic Belt and Siberian Craton. The degree of rock depletion in CaO and Al2O3 and enrichment in MgO relative to the primitive mantle in the peridotites of the Dzhugdzhur-Stanovoy superterrane is close to that of the Siberian craton. The peridotites of the Barguzin-Vitim superterrane are characterized by much lower degree of depletion and have mainly a primitive composition. Mantle melting degree reaches up to 45-50% in the Siberian Craton and Dzhugdzhur-Stanovoy superterrane, and is less than 25% in the Barguzin-Vitim terrane. The mantle peridotites of the craton as compared to those of adjacent superterranes are enriched in Ba, Rb, Th, Nb, and Ta and depleted in Y and REE from Sm to Lu. However, all studied peridotites are characterized by mainly superchondritic values of Nb/Ta (>17.4), Zr/Hf (>36.1), Nb/Y (>0.158), and Zr/Y (>2.474). The Nb/Y ratio is predominantly >1.0 in SC peridotites and < 1.0 in the superterrane peridotites. The Nd and Sr isotopic compositions in the latter correspond to those of oceanic basalts. The 187Os/188Os ratio is low (0.108-0.115) in the peridotites of the Siberian Craton and > 0.115 but usually lower than 0.1296 (primitive upper mantle value) in the peridotites of the Dzhugdzhur-Stanovoy and Barguzin-Vitim superterranes. Thus, the geochemical and isotopic composition of peridotites indicates different compositions and types of mantle beneath the Siberian craton and adjacent superterranes of the Central Asian Orogenic Belt in the Early Archean, prior to the formation of 2.7-3.1 Ga eclogites in the cratonic mantle.
SEG Reviews In Economic Geology Chapter 6, Vol. 18, pp. 115-136.
China
REE
Abstract: China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite- related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.
Abstract: The rare earth elements (REEs) consist of the 15 lantha-nide elements (La to Lu). Because of the increasing application of REEs and yttrium (REY) in high-and green-tech industries, the demand for the REY is projected to increase in the future. Rare earth elements are relatively abundant in the Earth's crust, but discovered, minable concentrations are less common than for most other ore types. Bastnaesite and monazite are the main mineral source of REEs in the world. Bastnaesite-hosted deposits in China and the United States Abstract China has been the world's leading rare earth element (REE) and yttrium producer for more than 20 years and hosts a variety of deposit types. Carbonatite-related REE deposits are the most significant REE deposit type, with REY (REE and yttrium)-bearing clay deposits, or ion adsorption-type deposits, being the primary source of the world's heavy REEs. Other REY resources in China include those hosted in placers, alkaline granites, pegmatites, and hydrothermal veins, as well as in additional deposit types in which REEs may be recovered as by-product commodities. Carbonatite-related REE deposits in China provide nearly all the light REE production in the world. Two giant deposits are currently being mined in China: Bayan Obo and Maoniuping. The carbonatite-related REE deposits in China occur along the margins of Archean-Paleoproterozoic blocks, including the northern , southern, and eastern margins of the North China craton, and the western margin of the Yangtze craton. The carbonatites were emplaced in continental rifts (e.g., Bayan Obo) or translithospheric strike-slip faults (e.g., Maoniuping) along reactivated craton margins. The craton margins provide the first-order control for carbonatite-related REE resources. Four REE metallogenic belts, including the Proterozoic Langshan-Bayan Obo, late Paleozoic-early Mesozoic eastern Qinling-Dabie, late Mesozoic Chishan-Laiwu-Zibo, and Cenozoic Mianning-Dechang belts, occur along cratonic margins. Geologic and geochemical data demonstrate that the carbonatites in these belts originated from mantle sources that had been previously enriched, most likely by recycled marine sediments through subduction zones during the assembly of continental blocks. Although the generation of carbonatite magma is debated, a plausible mechanism is by liquid immiscibility between silicate and carbonate melts. This process would further enrich REEs in the carbonatite end member during the evolution of mantle-derived magma. The emplacement of carbonatite magma in the upper crust, channeled by translithospheric faults in extensional environments, leads to a rapid decompression of the magma and consequently exsolution of a hydrothermal fluid phase. The fluid is characterized by high temperature (600°-850°C), high pressure (up to 350 MPa), and enrichment in sulfate, CO2, K, Na, Ca, Sr, Ba, and REEs. Immiscibility of sulfate melts from the aqueous fluid, and phase separation between CO2 and water may take place upon fluid cooling. Although both sulfate and chloride have been called upon as important ligands in hydrothermal REE transport, results of our studies suggest that sulfate is more important. The exsolution of a sulfate melt from the primary carbonatite fluid would lead to a significant decrease of the sulfate activity in the fluid and trigger REE precipitation. The subsequent unmixing between CO2 and water may also play an important role in REE precipitation. Because of the substantial ability of the primary carbonatite fluid to contain REEs, a large-volume magma chamber or huge fluid flux are not necessary for the formation of a giant REE deposit. A dense carbonatite fluid and rapid evolution hinder long distance fluid transportation and distal mineralization. Thus, carbonatite-related alteration and mineralization occur in or proximal to carbonatite dikes and sills, and this is observed in all carbonatite-related REE deposits in China. Ion adsorption-type REE deposits are primarily located in the South China block and are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits. Hydro-thermal alteration by fluids exsolved from late Mesozoic granites or related alkaline rocks (e.g., syenite) may have enriched the parent rocks in REEs, particularly the heavy REEs. Furthermore, this alteration process led to the transformation of some primary REE minerals to secondary REE minerals that are more readily broken down during subsequent weathering. During the weathering process, the REEs are released from parent rocks and adsorbed onto kaolinite and halloysite in the weathering profile, and further enriched by the loss of other material to form the ion adsorption-type REE deposits. A warm and humid climate and a low-relief landscape are important characteristics for development of ion adsorption REE deposits.
Cimen, O., Corcoran, L., Kuebler, C., Simonetti, S.S., Simonetti, A.
Geochemical, stable ( O, C, and B) and radiogenic ( Sr, Nd, Pb) isotopic data from the Eskisehir-Kizulxaoren ( NW-Anatolia) and the Malatya-Kuluncak ( E- central Anatolia) F-REE-Th deposits, Turkey: implications for nature of carbonate-hosted mineralizati
Turkish Journal of Earth Sciences, Vol. 29, doe:10.3906/yer-2001-7 18p. Pdf
Abstract: Australia is host to a diverse range of rare earth element (REE) ore deposits, and therefore is well placed to be a major supplier of REE into the future. This paper presents a review of the geology and tectonic setting of Australia's hard-rock REE resources. The deposits can be classified into four groups: 1. Carbonatite associated; 2. Peralkaline/alkaline volcanic associated; 3. Unconformity related, and; 4. Skarns and iron-oxide?copper?gold (IOCG) related. With the exception of the unconformity related deposits, all of these deposit groups are directly or indirectly related to continental alkaline magmatism. Extensive fractional crystallisation and/or igneous accumulation of REE minerals were essential ore-forming processes for carbonatite-associated and peralkaline/alkaline volcanic-associated deposits, while hydrothermal transport and concentration of REE sourced from basement rocks was responsible for producing ore in unconformity-related, skarns and, potentially, IOCG deposits. The economic potential of many deposits has also been enhanced by supergene alteration processes. All of Australia's REE deposits formed in an intracontinental setting in association with crustal-scale fault zones or structures that acted as transport conduits for ore-forming magmas or fluids. Most deposits formed in the Mesoproterozoic under conditions of relative tectonic quiescence. There is little evidence for the involvement of mantle plumes, with the exception of the Cenozoic peralkaline volcanic systems of eastern Australia, and possibly the IOCG deposits. Instead, ore productive magmas were generated by melting of previously-enriched mantle lithosphere in response to disruption of the lithosphere-asthenophere boundary due to fault activation. REE minerals in many deposits also record episodes of recrystallisation/resetting due to far-field effects of orogenic activity that may significantly postdate primary ore formation. Therefore, REE orebodies can be effective recorders of intracontinental deformation events. In general, Australia's inventory of REE deposits is similar to the global record. Globally, the Mesoproterozoic appears to be a particularly productive time period for forming REE orebodies due to favourable conditions for generating ore-fertile magmas and favourable preservation potential due to a general lack of aggressive continental recycling (i.e., active plate tectonics).
Abstract: The rare earth element (REE) mineralization of Gakara (Burundi) has first been discovered in 1936 and has periodically been the subject of geological studies, at times when the exploitation of bastnäsite-(Ce) and monazite-(Ce) was economically interesting. This study focuses on the establishment of a mineral paragenesis for Gakara, with special attention to the REE-bearing phases, to understand the formation history of the deposit. The paragenesis can be subdivided into 3 stages: primary ore deposition, brecciation stage and supergene alteration. Evidence for fenitization processes (i.e. pinkish-red cathodoluminescence of K-feldpar, brecciation stage) and the strong enrichment of light REEs in bastnäsite and monazite substantiate the hypothesis of a structurally controlled hydrothermal mineralization with a strong carbonatitic affinity. This likely confirms the association of the Gakara REE deposit with the Neoproterozoic alignment of alkaline complexes and carbonatites along the present-day Western Rift. It suggests a direct link with a - currently unidentified - carbonatitic body at depth, possibly derived from a predominantly metasomatized lithospheric mantle.
Abstract: Rare-earth elements play a crucial role in modern technologies and are necessary for a transition to a green economy. Potentially economic deposits of these elements are typically hosted in minerals such as monazite, bastnäsite, and eudialyte (a complex Na-Ca-Fe-Zr silicate mineral with Cl), making these prime targets for geological research. Globally, rare-earth mineral deposits commonly show evidence of polyphase development and mineralisation processes, which need to be better understood to improve exploration strategies. The Norra Kärr alkaline complex (Sweden) contains a globally significant deposit of rare-earth elements, hosted in the mineral eudialyte. In this study, we focussed on eudialyte crystals in undeformed, cross-cutting pegmatoid veins from Norra Kärr. In order to determine their age, we refined an established micromilling method to enable sampling of minerals rich in rare-earth elements for precise analysis of major and trace elements, Nd isotope ratios, and Sm-Nd geochronology down to a scale of <200??m. Mineral samples were subjected to detailed textural and chemical characterisation by backscattered electron imaging and laser ablation inductively coupled plasma mass spectrometry, by which precise and accurate Sm/Nd ratios were determined to steer subsequent micromill sampling for small-aliquot Sm-Nd isotope analysis by isotope dilution thermal ionisation mass spectrometry. Given enough internal spread in Sm/Nd ratios, reliable Sm-Nd isochrons can be derived from discrete textural domains within a single crystal. This provided an age of 1.144?±?0.053?Ga (95% confidence); approximately 350?million?years younger than the magmatic intrusion of the alkaline complex (ca. 1.49?Ga). Primary compositional sector and oscillatory zoning in these eudialyte crystals shows core-to-rim enrichment in rare-earth elements and significant fractionation of K/Rb, Y/Ho, Zr/Hf, and Nb/Ta, which we attribute to crystallisation under influence of complexing ligands in a confined volume. We argue that these mineralised pegmatoid veins formed by low-temperature (<550?°C) partial melting of the agpaitic host rock during an early Sveconorwegian (Grenvillian) metamorphic overprinting event. Given the challenge of directly dating rare-earth ore minerals by conventional methods, modification of rare-earth mineral deposits may be more widespread than already assumed, which shows the importance of investigations that date the rare-earth minerals themselves.
Abstract: The newly-discovered supergiant Huayangchuan uranium (U)-polymetallic deposit is situated in the Qinling Orogen, Central China. The deposit contains economic endowments of U, Nb, Pb, Se, Sr, Ba and REEs, some of which (e.g., U, Se, and Sr) reaching super-large scale. Pyrochlore, allanite, monazite, barite-celestite and galena are the major ore minerals at Huayangchuan. Uranium is mainly hosted in the primary mineral of pyrochlore, and the mineralization is mainly hosted in or associated with carbonatite dikes. According to the mineral assemblages and crosscutting relationships, the alteration/mineralization at Huayangchuan comprises four stages, i.e., pegmatite REE mineralization (I), main mineralization (II), skarn mineralization (III) and post-ore alteration (IV). Coarse-grained euhedral allanite is the main Stage I REE mineral, and the pegmatite-hosted REE mineralization (ca. 1.8 Ga) occurs mostly in the shallow-level of northwestern Huayangchuan, corresponding to the Paleoproterozoic Xiong'er Group volcanic rocks (1.80-1.75 Ga) in the southern margin of North China Block. Carbonatite-hosted Stage II mineralization contributes to the majority of U-Nb-REE-Ba-Sr resources, and is controlled by the Huayangchuan Fault. Stage II mineralization can be further divided into the sulfate mineralization (barite-celestite) (II-A), alkali-rich U mineralization (aegirine-augite + pyrochlore + uraninite + uranothorite) (II-B) and REE (allanite + monazite + chevkinite)-U (pyrochlore + uraninite) mineralization (II-C) substages. Stage II mineralization may have occurred during the Late Triassic Mianlue Ocean closure. Skarn mineralization contributed to the majority of Pb and minor U-REE (uraninite-allanite) resources at Huayangchuan, and is spatially associated with the Late Cretaceous-Early Jurassic (Yanshanian) Huashan and Laoniushan granites. We suggested that hydrothermal fluids derived from the Laoniushan and Huashan granites may have reacted with the Triassic carbonatites, and formed the Huayangchuan Pb skarn mineralization. The mantle-derived Triassic carbonatites may have been fertilized by the U-rich subducting oceanic sediments, and were further enriched through reacting with the Proterozoic U-REE-rich pegmatite wallrocks at Huayangchuan. Ore-forming elements were likely transported in metal complexes (F?, and ), and deposited with the dilution of the complex concentration. This may have formed the distinct vertical mineralization zoning, i.e., sodic fenite-related alkali-U mineralization at depths and potassic fenite-related REE-U mineralization at shallow level.
Mineralogical Magazine, doi.10.1180/mgm.2020.70 11p. Pdf
Mantle
REE
Abstract: The line connecting rare earth elements (REE) in chondrite-normalised plots can be represented by a smooth polynomial function using ? shape coefficients as described by O'Neill (2016). In this study, computationally generated ? combinations are used to construct artificial chondrite-normalised REE patterns that encompass most REE patterns likely to occur in natural materials. The dominant REE per pattern is identified, which would lead to its inclusion in a hypothetical mineral suffix, had this mineral contained essential REE. Furthermore, negative Ce and Y anomalies, common in natural minerals, are considered in the modelled REE patterns to investigate the effect of their exclusion on the relative abundance of the remainder REE. The dominant REE in a mineral results from distinct pattern shapes requiring specific fractionation processes, thus providing information on its genesis. Minerals dominated by heavy lanthanides are rare or non-existent, even though the present analysis shows that REE patterns dominated by Gd, Dy, Er and Yb are geologically plausible. This discrepancy is caused by the inclusion of Y, which dominates heavy REE budgets, in mineral name suffixes. The focus on Y obscures heavy lanthanide mineral diversity and can lead to various fractionation processes to be overlooked. Samarium dominant minerals are known, even though deemed unlikely by the computational model, suggesting additional fractionation processes that are not well described by ? shape coefficients. Positive Eu anomalies only need to be moderate in minerals depleted in the light REE for Eu to be the dominant REE, thus identifying candidate rocks in which the first Eu dominant mineral might be found. Here, I present an online tool, called ALambdaR that allows interactive control of ? shape coefficients and visualisation of resulting REE patterns.
Science Advances, Vol. 6, 11p. 10.1126/sciadv.abb6570 pdf
Global
carbonatites, REE
Abstract: Carbonatites and associated rocks are the main source of rare earth elements (REEs), metals essential to modern technologies. REE mineralization occurs in hydrothermal assemblages within or near carbonatites, suggesting aqueous transport of REE. We conducted experiments from 1200°C and 1.5 GPa to 200°C and 0.2 GPa using light (La) and heavy (Dy) REE, crystallizing fluorapatite intergrown with calcite through dolomite to ankerite. All experiments contained solutions with anions previously thought to mobilize REE (chloride, fluoride, and carbonate), but REEs were extensively soluble only when alkalis were present. Dysprosium was more soluble than lanthanum when alkali complexed. Addition of silica either traps REE in early crystallizing apatite or negates solubility increases by immobilizing alkalis in silicates. Anionic species such as halogens and carbonates are not sufficient for REE mobility. Additional complexing with alkalis is required for substantial REE transport in and around carbonatites as a precursor for economic grade-mineralization.
Abstract: The Bayan Obo deposit is a world-class Fe-REE-Nb deposit, and its reserves of rare earth element (REE) resources rank the first over the world. In the face of the current situation of insufficient utilization rate of rare earth resources and scarcity of middle-heavy rare earth elements (M?HREE) resources, the Bayan Obo deposit with such a huge amount of M?HREE cannot be underestimated. In this paper, the occurrence characteristics of M?HREE in different types of iron ore in the Bayan Obo main ore body are studied by using field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS) and advanced mineral identification and characterisation system (AMICS), and the enrichment mechanism is also discussed. The results show that both Sm and Y are the most abundant M?HREE in each type of iron ore in the main ore body, and the content of M?HREE accounts for 1.41%-5.57% of total REE, among which the content of M?HREE in aegirine type Nb-REE-Fe ore (824.47 ppm) and fluorite type Nb-REE-Fe ore (794.82 ppm) are higher, and the content of M?HREE in massive type Nb-REE-Fe ore is lower (318.49 ppm). The main minerals containing M?HREE are bastnasite, parisite, Huanghoite, monazite, aeschynite and fergusonite, among which the content of M?HREE in fergusonite and aeschynite are the highest. According to the characteristics of mineral paragenetic association of REE in this ore district, it is believed that the REE migrates mainly in many different forms of complexes. Heavy rare earth elements (HREE) mainly experienced carbonatite magmatism stage, sodium-fluorine metasomatism stage and late vein mineralization stage, and finally got enrichment.
Abstract: China is the world’s leading rare earth element (REE) producer and hosts a variety of deposit types. Carbonatite- related REE deposits, the most significant deposit type, include two giant deposits presently being mined in China, Bayan Obo and Maoniuping, the first and third largest deposits of this type in the world, respectively. The carbonatite-related deposits host the majority of China’s REE resource and are the primary supplier of the world’s light REE. The REE-bearing clay deposits, or ion adsorption-type deposits, are second in importance and are the main source in China for heavy REE resources. Other REE resources include those within monazite or xenotime placers, beach placers, alkaline granites, pegmatites, and hydrothermal veins, as well as some additional deposit types in which REE are recovered as by-products. Carbonatite-related REE deposits in China occur along craton margins, both in rifts (e.g., Bayan Obo) and in reactivated transpressional margins (e.g., Maoniuping). They comprise those along the northern, eastern, and southern margins of the North China block, and along the western margin of the Yangtze block. Major structural features along the craton margins provide first-order controls for REE-related Proterozoic to Cenozoic carbonatite alkaline complexes; these are emplaced in continental margin rifts or strike-slip faults. The ion adsorption-type REE deposits, mainly situated in the South China block, are genetically linked to the weathering of granite and, less commonly, volcanic rocks and lamprophyres. Indosinian (early Mesozoic) and Yanshanian (late Mesozoic) granites are the most important parent rocks for these REE deposits, although Caledonian (early Paleozoic) granites are also of local importance. The primary REE enrichment is hosted in various mineral phases in the igneous rocks and, during the weathering process, the REE are released and adsorbed by clay minerals in the weathering profile. Currently, these REE-rich clays are primarily mined from open-pit operations in southern China. The complex geologic evolution of China’s Precambrian blocks, particularly the long-term subduction of ocean crust below the North and South China blocks, enabled recycling of REE-rich pelagic sediments into mantle lithosphere. This resulted in the REE-enriched nature of the mantle below the Precambrian cratons, which were reactivated and thus essentially decratonized during various tectonic episodes throughout the Proterozoic and Phanerozoic. Deep fault zones within and along the edges of the blocks, including continental rifts and strike-slip faults, provided pathways for upwelling of mantle material.
MDPI Minerals, Vol. 10, 965 doi:103390/min10110965, 26p. Pdf
China
carbonatite, REE
Abstract: The rare earth elements (REEs) have unique and diverse properties that make them function as an “industrial vitamin” and thus, many countries consider them as strategically important resources. China, responsible for more than 60% of the world’s REE production, is one of the REE-rich countries in the world. Most REE (especially light rare earth elements (LREE)) deposits are closely related to carbonatite in China. Such a type of deposit may also contain appreciable amounts of industrially critical metals, such as Nb, Th and Sc. According to the genesis, the carbonatite-related REE deposits can be divided into three types: primary magmatic type, hydrothermal type and carbonatite weathering-crust type. This paper provides an overview of the carbonatite-related endogenetic REE deposits, i.e., primary magmatic type and hydrothermal type. The carbonatite-related endogenetic REE deposits are mainly distributed in continental margin depression or rift belts, e.g., Bayan Obo REE-Nb-Fe deposit, and orogenic belts on the margin of craton such as the Miaoya Nb-REE deposit. The genesis of carbonatite-related endogenetic REE deposits is still debated. It is generally believed that the carbonatite magma is originated from the low-degree partial melting of the mantle. During the evolution process, the carbonatite rocks or dykes rich in REE were formed through the immiscibility of carbonate-silicate magma and fractional crystallization of carbonate minerals from carbonatite magma. The ore-forming elements are mainly sourced from primitive mantle, with possible contribution of crustal materials that carry a large amount of REE. In the magmatic-hydrothermal system, REEs migrate in the form of complexes, and precipitate corresponding to changes of temperature, pressure, pH and composition of the fluids. A simple magmatic evolution process cannot ensure massive enrichment of REE to economic values. Fractional crystallization of carbonate minerals and immiscibility of melts and hydrothermal fluids in the hydrothermal evolution stage play an important role in upgrading the REE mineralization. Future work of experimental petrology will be fundamental to understand the partitioning behaviors of REE in magmatic-hydrothermal system through simulation of the metallogenic geological environment. Applying "comparative metallogeny" methods to investigate both REE fertile and barren carbonatites will enhance the understanding of factors controlling the fertility.
Mineralogy and Petrology, Vol. 115, 19p. Doi.org/101007 /s00710-020- 00723-x pdf
South America, Colombia
REE
Abstract: A multi-methodological study was conducted in order to provide further insight into the structural and compositional complexity of rare earth element (REE) fluorcarbonates, with particular attention to their correct assignment to a mineral species. Polycrystals from La Pita Mine, Municipality de Maripí, Boyacá Department, Colombia, show syntaxic intergrowth of parisite-(Ce) with röntgenite-(Ce) and a phase which is assigned to B3S4 (i.e., bastnäsite-3-synchisite-4; still unnamed) fluorcarbonate. Transmission electron microscope (TEM) images reveal well-ordered stacking patterns of two monoclinic polytypes of parisite-(Ce) as well as heavily disordered layer sequences with varying lattice fringe spacings. The crystal structure refinement from single crystal X-ray diffraction data - impeded by twinning, complex stacking patterns, sequential and compositional faults - indicates that the dominant parisite-(Ce) polytype M1 has space group Cc. Parisite-(Ce), the B3S4 phase and röntgenite-(Ce) show different BSE intensities from high to low. Raman spectroscopic analyses of parisite-(Ce), the B3S4 phase and röntgenite-(Ce) reveal different intensity ratios of the three symmetric CO3 stretching bands at around 1100 cm?1. We propose to non-destructively differentiate parisite-(Ce) and röntgenite-(Ce) by their 1092 cm?1 / 1081 cm?1 ?1(CO3) band height ratio.
Turkish Journal of Earth Sciences, Vol. 29, pp. 798-814. pdf
Europe, Turkey
REE
Abstract: In Turkey, the largest fluorine (F)-rare earth element (REE)-thorium (Th) deposits are located within the Eski?ehir-K?z?lcaören (north-western Anatolia) and the Malatya-Kuluncak (east-central Anatolia) regions, and these are associated with Oligocene extensional alkaline volcanic and Late Cretecaous-Early Paleocene postcollisional intrusive rocks, respectively. In the K?z?lcaören region, the basement units include the Triassic Karakaya Complex and the Late Cretaceous oceanic units (Neotethyan suture) that are cut and overlain by phonolite and carbonatite intrusions and lava flows. In the Kuluncak region, the plutonic rocks are mainly composed of syenite, quartz syenite, and rare monzonite, and these cut the late-Cretaceous Karap?nar limestone, which hosts the F-REE-Th mineralization in contact zones. A carbonatite sample from the K?z?lcaören region displays both a total rare earth element (TREE) concentration (4795 ppm) and ?11B (-6.83‰) isotope composition consistent with mantle-derived carbonatite; whereas it is characterized by heavier ?13C (+1.43‰) and ?18O (+20.23‰) isotope signatures compared to those for carbonatites worldwide. In contrast, the carbonates which host the F-REE-Th mineralization in the Kuluncak region are characterized by lower TREE concentrations (5.13 to 55.88 ppm), and heavier ?13C (-0.14 to -0.75‰), ?18O (+27.36 to +30.61‰), and ?11B (+5.38 to +6.89‰) isotope ratios compared to mantle-derived carbonatites. Moreover, the combined initial 87Sr/86Sr (0.70584 to 0.70759) and 143Nd/144Nd (0.512238 to 0.512571) isotope ratios for samples investigated here are distinct and much more radiogenic compared to those for carbonatites worldwide, and therefore indicate significant crustal input and/or hydrothermal metasomatic-related alteration. Overall, stable and radiogenic isotope data suggest that the host carbonate rocks for the F-REE-Th mineralization in both the K?z?lcaören and the Kuluncak regions consist of hydrothermally metasomatized carbonatite and limestone, respectively. The mineralization in the K?z?lcaören region may potentially be related to carbonatite magmatism, whereas the mineralization in the Kuluncak region, which most likely formed through interactions between the plutonic rocks and surrounding limestone at contact metamorphism zone, involved hydrothermal/magmatic fluids associated with extensive postcollisional magmatism.
Geochemistry International, Vol. 59, pp. 92-98. pdf
Russia
REE
Abstract: This paper reports the results of the first study of pyroxenes from the deepest zones of the Lovozero deposit. The geochemical and mineralogical study of these rocks is of great scientific interest, as they are the least differentiated rocks and provide insight into the composition of a parental magma. According to microprobe analysis, clinopyroxenes evolve from early diopside-hedenbergite-augite to later alkaline aegirine-augite species. Upsection, the contents of Na, Fe3+ and Ti increase, while Mg, Ca, Fe2+, and Zr decrease. Thus, isomorphic substitution in pyroxenes of the lower zone follows the scheme (Ca, Mg, Fe2+, Zr) ? (Na, Fe3+, Ti).
Abstract: A review of the compositional features of Tunisia, Algeria, and Morocco phosphorites is proposed in order to assess and compare the paleoenvironmental conditions that promoted the deposit formation as well as provide information about their economic perspective in light of growing worldwide demand. Since these deposits share a very similar chemical and mineralogical composition, the attention was focused on the geochemistry of rare earth elements (REEs) and mostly on ?REEs, Ce and Eu anomalies, and (La/Yb) and (La/Gd) normalized ratios. The REEs distributions reveal several differences between deposits from different locations, suggesting mostly that the Tunisian and Algerian phosphorites probably were part of the same depositional system. There, sub-reducing to sub-oxic conditions and a major REEs adsorption by early diagenesis were recorded. Conversely, in the Moroccan basins, sub-oxic to oxic environments and a minor diagenetic alteration occurred, which was likely due to a different seawater supply. Moreover, the drastic environmental changes associated to the Paleocene-Eocene Thermal Maximum event probably influenced the composition of Northern African phosphorites that accumulated the highest REEs amounts during that span of time. Based on the REEs concentrations, and considering the outlook coefficient of REE composition (Koutl) and the percentage of critical elements in ?REEs (REEdef), the studied deposits can be considered as promising to highly promising REE ores and could represent a profitable alternative source for critical REEs.
Geology of Ore Deposits, Vol. 62, 8, pp. 754-763. pdf
Russia, Kola Peninsula
REE
Abstract: This paper presents the results of the first geological, isotope, geochemical, and mineralogical study of carbonatite veins that were previously unknown in the Soustov pluton. The studied veins are similar in the Sm-Nd isotope composition and model age to the host rocks, which implies a common formation processs. High contents of light lanthanides, Sr, and Nb in carbonatite veins were measured. These elements are concentrated in bastnäsite, strontianite, monazite, and pyrochlore. These data significantly enlarge our concepts of the geochemical and ore specialization of the massif.
Abstract: Rare metals including Lithium (Li), Beryllium (Be), Rubidium (Rb), Cesium (Cs), Zirconium (Zr), Hafnium (Hf), Niobium (Nb), Tantalum (Ta), Tungsten (W) and Tin (Sn) are important critical mineral resources. In China, rare metal mineral deposits are spatially distributed mainly in the Altay and Southern Great Xingán Range regions in the Central Asian orogenic belt; in the Middle Qilian, South Qinling and East Qinling mountains regions in the Qilian-Qinling-Dabie orogenic belt; in the Western Sichuan and Bailongshan-Dahongliutan regions in the Kunlun-Songpan-Garze orogenic belt, and in the Northeastern Jiangxi, Northwestern Jiangxi, and Southern Hunan regions in South China. Major ore?forming epochs include Indosinian (mostly 200-240 Ma, in particular in western China) and the Yanshanian (mostly 120-160 Ma, in particular in South China). In addition, Bayan Obo, Inner Mongolia, northeastern China, with a complex formation history, hosts the largest REE and Nb deposits in China. There are six major rare metal mineral deposit types in China: Highly fractionated granite; Pegmatite; Alkaline granite; Carbonatite and alkaline rock; Volcanic; and Hydrothermal types. Two further types, namely the Leptynite type and Breccia pipe type, have recently been discovered in China, and are represented by the Yushishan Nb-Ta- (Zr-Hf-REE) and the Weilasituo Li-Rb-Sn-W-Zn-Pb deposits. Several most important controlling factors for rare metal mineral deposits are discussed, including geochemical behaviors and sources of the rare metals, highly evolved magmatic fractionation, and structural controls such as the metamorphic core complex setting, with a revised conceptual model for the latter.
Contributions to Mineralogy and Petrology, 176, 19p. Pdf
Mantle
REE
Abstract: Clinopyroxene and orthopyroxene are the two major repositories of rare earth elements (REE) in spinel peridotites. Most geochemical studies of REE in mantle samples focus on clinopyroxene. Recent advances in in situ trace element analysis has made it possible to measure REE abundance in orthopyroxene. The purpose of this study is to determine what additional information one can learn about mantle processes from REE abundances in orthopyroxene coexisting with clinopyroxene in residual spinel peridotites. To address this question, we select a group of spinel peridotite xenoliths (9 samples) and a group of abyssal peridotites (12 samples) that are considered residues of mantle melting and that have major element and REE compositions in the two pyroxenes reported in the literature. We use a disequilibrium double-porosity melting model and the Markov chain Monte Carlo method to invert melting parameters from REE abundance in the bulk sample. We then use a subsolidus reequilibration model to calculate REE redistribution between cpx and opx at the extent of melting inferred from the bulk REE data and at the closure temperature of REE in the two pyroxenes. We compare the calculated results with those observed in clinopyroxene and orthopyroxene in the selected peridotitic samples. Results from our two-step melting followed by subsolidus reequilibration modeling show that it is more reliable to deduce melting parameters from REE abundance in the bulk peridotite than in clinopyroxene. We do not recommend the use of REE in clinopyroxene alone to infer the degree of melting experienced by the mantle xenolith, as HREE in clinopyroxene in the xenolith are reset by subsolidus reequilibration. In general, LREE in orthopyroxene and HREE in clinopyroxene are more susceptible to subsolidus redistribution. The extent of redistribution depends on the modes of clinopyroxene and orthopyroxene in the sample and thermal history experienced by the peridotite. By modeling subsolidus redistribution of REE between orthopyroxene and clinopyroxene after melting, we show that it is possible to discriminate mineral mode of the starting mantle and cooling rate experienced by the peridotitic sample. We conclude that endmembers of the depleted MORB mantle and the primitive mantle are not homogeneous in mineral mode. A modally heterogeneous peridotitic starting mantle provides a simple explanation for the large variations of mineral mode observed in mantle xenoliths and abyssal peridotites. Finally, by using different starting mantle compositions in our simulations, we show that composition of the primitive mantle is more suitable for modeling REE depletion in cratonic mantle xenoliths than the composition of the depleted MORB mantle.
Mineralium Deposita, 10.1007/s00126-020-01026-z 20p. Pdf
Australia
REE
Abstract: The Yangibana rare earth element (REE) district consists of multiple mineral deposits/prospects hosted within the Mesoproterozoic Gifford Creek Carbonatite Complex (GCCC), Western Australia, which comprises a range of rock types including calcite carbonatite, dolomite carbonatite, ankerite-siderite carbonatite, magnetite-biotite dykes, silica-rich alkaline veins, fenite, glimmerites and what have historically been called “ironstones”. The dykes/sills were emplaced during a period of extension and/or transtension, likely utilising existing structures. The Yangibana REE deposits/prospects are located along many of these structures, particularly along the prominent Bald Hill Lineament. The primary ore mineral at Yangibana is monazite, which is contained within ankerite-siderite carbonatite, magnetite-biotite dykes and ironstone units. The ironstones comprise boxwork-textured Fe oxides/hydroxides, quartz, chalcedony and minor monazite and subordinate rhabdophane. Carbonate mineral-shaped cavities in ironstone, fenite and glimmerite alteration mantling the ironstone units, and ankerite-siderite carbonatite dykes altering to ironstone-like assemblages in drill core indicate that the ironstones are derived from ankerite-siderite carbonatite. This premise is further supported by similar bulk-rock Nd isotope composition of ironstone and other alkaline igneous rocks of the GCCC. Mass balance evaluation shows that the ironstones can be derived from the ankerite-siderite carbonatites via significant mass removal, which has resulted in passive REE concentration by ~?2 to ~?10 times. This mass removal and ore tenor upgrade is attributed to extensive carbonate breakdown and weathering of ankerite-siderite carbonatite by near-surface meteoric water. Monazite from the ironstones has strong positive and negative correlations between Pr and Nd, and Nd and La, respectively. These relationships are reflected in the bulk-rock drill assays, which display substantial variation in the La/Nd throughout the GCCC. The changes in La/Nd are attributed to variations in primary magmatic composition, shifts in the magmatic-hydrothermal systems related to CO2 versus water-dominated fluid phases, and changes in temperature.
Ore Geology Reviews, doi.org/10.1016/j.oregeorev.2021.104310, 50p. Pdf
China
carbonatite, REE
Abstract: The Huayangchuan deposit in the North Qinling alkaline province of Central China is a unique carbonatite-hosted giant U-Nb-REE polymetallic deposit. The mineralization is characterized by the presence of betafite, monazite, and allanite as the main ore minerals, but also exhibit relatively high budgets of heavy rare earth elements (HREE = Gd-Lu and Y). The origin of carbonatites has long been controversial, thus hindering our understanding of the genesis of the deposit. Here, we conducted an in-situ trace elemental, Sr-Nd isotopic, and bulk C-O isotopic analyses of multi-type calcites in the deposit. Two principal types (Cal-I and Cal-II), including three sub-types (Cal-I-1, Cal-I-2 and Cal-I-3) of calcites were identified based on crosscutting relationships and calcite textures. Texturally, Cal-I calcites in carbonatites display cumulates with the grain size decreasing from early coarse- (Cal-I-1) to medium- (Cal-I-2) and late fine-grained (Cal-I-3), whereas Cal-II calcites coexist with zeolite displaying zeolite-calcite veinlets. Geochemically, Cal-I calcites contain relatively high REE(Y) (151-2296 ppm), Sr (4947-9566 ppm) and Na (28.6-390 ppm) contents, characterized by right- to left-inclined flat distribution patterns [(La/Yb)N=0.2-4.2] with enrichment of HREE(Y) (136-774 ppm), whereas Cal-II calcites display low REE, Sr and undetectable Na contents, characterized by a right-inclined distribution pattern [(La/Yb)N=13.5, n=16]. The U-Nb-REE mineralization, accompanied with intense and extensive fenitization and biotitization, is mainly associated with the Cal-I-3 calcites which show flat to relatively left-inclined flat REE distribution patterns [(La/Yb)N=0.2-1.0]. Isotopic results show that Cal-I calcites with mantle signatures are primarily igneous in origin, whereas Cal-II are hydrothermal, postdating the U-Nb-REE mineralization. Cal-I calcites (Cal-I-1, Cal-I-2 and Cal-I-3) from mineralized and unmineralized carbonatites, displayed regular changes in REE, Na and Sr contents, but similar trace element distribution patterns and Sr-Nd-C-O isotopic signatures, indicating that these carbonatites originated from the same enriched mantle (EM1) source by low-degree partial melting of HREE-rich carbonated eclogites related to recycled marine sediments. The combination of trace elements and Sr-Nd isotopic composition of calcites further revealed that these carbonatites have undergone highly differentiated evolution. Such differentiation is conducive to the enrichment of ore-forming elements (U-Nb-REE) in the late magmatic-hydrothermal stages owing to extensive ore-forming fluids exsolved from carbonatitic melts. The massive precipitation of the U-Nb-REE minerals from ore-forming hydrothermal fluids may have been triggered by intense fluid-rock reactions indicated by extensive and intense fenitization and biotitization. Therefore, the Huayangchuan carbonatite-related U-Nb-REE deposit may have formed by a combination of processes involving recycled U-Nb-REE-rich marine sediments in the source, differentiation of the produced carbonatitic magmas, and subsequent exsolution of U-Nb-REE-rich fluids that precipitated ore minerals through reactions with wall rocks under the transitional tectonic regime from compression to extension at the end of Late Triassic.
Ore Geology Reviews, doi.org/10.1016/ j.oregeorev. 2021.104308 59p. Pdf
South America, Brazil
REE
Abstract: In the Morro dos Seis Lagos Nb (Ti, REE) deposit (MSLD), Amazonas state, Brazil, there are four types of REE mineralization: primary, associated to siderite carbonatite; supergene, associated to laterite profile; and sedimentary (detrital and authigenic). The mineralogical and geochemical evolutions of the REE in these domains are integrated into a comprehensible metallogenic model. The main primary ore in the core siderite carbonatite is 52 m thick with 1.47 wt% REE2O3 mainly in monazite-(Ce) and bastnäsite. However, considering the entire section intersected in the core siderite carbonatite, the average grade drops to 0.7 wt% REE2O3 mainly contained in thorbastnasite. In the border siderite carbonatite, the REE mineralization is hydrothermal [rhabdophane-(Ce) and REE-rich gorceixite]. The LREE and phosphates are concentrated at the reworked laterites from where the HREE were leached. With the advance of lateritization, pyrochlore was completely decomposed. The final secondary Ce-pyrochlore was progressively enriched in Ce4+ with loss in REE3+, resulting in the breakdown of the structure and release Ce under strongly oxidizing conditions (high Ce4+/Ce3+) thus forming extremely pure cerianite-(Ce). This mineral occurs intercalated with goethite bands in the lower part of the weathering profile, represented by the brown laterite, and forms intergrowth with hollandite in the manganiferous laterite, formed in a more alkaline environment closer to the water table. The brown laterite has 1.30 wt% REE2O3, the manganese laterite has 1.54 wt% REE2O3, of which 1.42 wt% is Ce2O3. Tectonic and karstic processes over the carbonatite formed several sedimentary basins. In the Esperança Basin, the sedimentary record (233 m thick) shows the whole evolution of the MSLD. The base of the basin (layer 5) is formed by abundant carbonatite fragments, have florencite-(Ce) mineralization with 1.07 wt% REE2O3; layer 4 is formed by carbonatite fragments interbedded with clayey bed; layer 3 is a rhythmite deposited in a lacustrine environment, with clasts of ferruginous materials related to early stages of carbonatite alteration; layer 2 is made up by clays, is rich in organic matter, has authigenic florencite-(Ce), florencite-(La) and base metals. This layer marks the inversion of the relief and the input into the basin of REE leached from the upper laterites, carried by the groundwater flow; layer 1 was formed by the oxidation of the upper part of layer 2. Layers 1 + 2 have 73 m thick and average of 1.72 wt% REE2O3.
Abstract: Apatite is a ubiquitous mineral in carbonatites, and incorporates a variety of trace elements including rare earth elements (REEs). In this study, the textural and chemical variations of apatite were examined in order to trace the magmatic and hydrothermal petrogenesis of three carbonatite-related REE deposits: Shaxiongdong, Miaoya, and Bayan Obo. Various apatite textures were revealed by cathodoluminescence and back-scattered electron imaging. Magmatic apatite, which occurs predominantly in samples from Shaxiongdong, is euhedral, and commonly shows oscillatory or growth zonation with a yellow-green luminescent core and a violet luminescent rim. Euhedral to subhedral metasomatic apatite from Miaoya and Bayan Obo has a turbid texture, with the majority of grains associated with exsolved monazite. Hydrothermal apatite from Bayan Obo, typically occurring as aggregates in close association with fluorite and barite, is anhedral, with green or light violet luminescence. The different apatite textures are characterised by distinct trace element compositions. Magmatic apatite contains the highest concentrations of Mn (avg. 457 ppm) and Sr (avg. 18,285 ppm) and is characterised by a steeply inclined REE chondrite-normalised pattern. Metasomatic apatite, which has undergone in situ dissolution-reprecipitation, contains lower Mn (avg. 272 ppm) and Sr (avg. 9945 ppm) concentrations. It is characterised by highly variable REE trends with an La/SmN ratio varying from 0.13 to 5.61, and lower average La/YbN, La/SmN, and Sr/Y ratios (46, 2.2, and 18, respectively) than magmatic apatite. Hydrothermal apatite that was precipitated from a fluid is characterised by convex upward chondrite-normalised REE distributions with the lowest La/YbN, La/SmN, and Sr/Y ratios (13, 0.69, and 5.8, respectively). The average concentrations of Mn and Sr in this apatite are 270 and 6610 ppm, respectively. There are no Eu anomalies (Eu/Eu* = 0.97) in the chondrite-normalised REE plots for any of the analysed apatite samples. The combined textural and compositional variations of apatite in the three deposits reflect diverse magmatic and hydrothermal processes, including: 1) mineral fractionation contributing to core-rim zoning within the Shaxiongdong magmatic apatite; 2) dissolution-reprecipitation inducing monazite precipitation in Miaoya and Bayan Obo metasomatic apatite; and 3) coprecipitation with fluorite and barite from fluids generating the Bayan Obo hydrothermal apatite. A compilation of published apatite compositions from other rock types demonstrates that trace element compositions of apatite can be used to differentiate crystallisation environments and differentiate apatite from other rock types. Apatite from carbonatite has high Sr, REEs, La/YbN, Th/U, and Sr/Y, and no Eu anomaly, compared with apatite from igneous silicate rocks (except ultramafic rocks), and iron-oxide copper gold (IOCG) or iron-oxide apatite (IOA) deposits.
Ore Geology Reviews, doi.org/10.1016/j.oregeorev.2021.104284 11p. Pdf
China
REE
Abstract: The carbonatites in the southern margin of the North China Craton are distinguishable by containing abundant quartz and are closely spatially associated with Mo-(REE) deposits. Unveiling the nature of ore-forming fluids is key to understand the genesis of these Mo-(REE) deposits and to explore their potential genetic relationships with the quartz-rich carbonatites, but such issues were currently not convincingly addressed. Here, we provide detailed petrographic, microthermometric and LA-ICP-MS analyses of the fluid inclusions hosted in the primary quartz from the carbonatites in the Huangshuian Mo-(REE) deposit which is the largest Mo-(REE) one in the region, containing 0.4 million tons of Mo metal with REEs as the major by-product. Our results show that the fluid inclusions in the quartz of the carbonatites are two- and three-phase CO2-bearing types with high homogenization temperatures (average at 396 °C) and low salinities (average at 3.88 wt% NaCl equiv). The LA-ICP-MS analyses of these inclusions reveal that the primary fluids contain high concentrations of La, Ce, Pr, Nd, Sr, and Ba, similar to typical carbonatite-related fluids. In addition, they are characterized by high Y, Cu, Pb, and Zn. Such a metal association is broadly consistent with the mineral assemblages of the Huangshuian Mo-(REE) deposit, such as the widespread barite, bastnäsite, xenotime, chalcopyrite, galena, and sphalerite, strongly supporting the close genetic relation of the deposit with the quartz-rich carbonatites. Although the concentrations of Mo are extremely low in these inclusions (below the detect limit), it was constrained to be gradually enriched in evolved fluids. Considering that the recorded fluids in quartz represent earliest generation of fluids exsolved from carbonatite magmas, our new results highlight that quantifying metal budgets of fluid inclusions could be a robust way to evaluate fertility of carbonatites that are widespread in the southern margin of the North China Craton.
Abstract: A study of radiogenic (Sr, Nd) and stable (C, O) isotopic data for rare earth carbonatites from the Petyayan-Vara field of the Devonian Vuoriyarvi alkaline-ultrabasic massif is presented. The cumulative evidence indicates that the primary igneous rocks of the Petyayan-Vara area are burbankite-bearing magnesiocarbonatites having isotopic signatures of the depleted mantle (?Nd365Ma = 5.0, 87Sr/86Sr(i) = 0.7031, ?13C ca. -4‰, and ?18O ca. 11‰). Interaction of the primary carbonatite melt with the host silicate rocks produced high-Ti carbonatites with a mantle ?13C (ca. -4‰) and isotopically heavy ?18O (ca. 20‰). These rocks trapped K, Na, Mg, CO2, and rare earth elements (REEs) (mainly heavy REEs) from the melt and Si, Al, Fe, Ti, and P from the host rocks. Early post-magmatic exposure of burbankite-bearing carbonatites to a mixture of fluids of crustal and orthomagmatic carbonatite origin caused redistribution of REEs, Ba, and Sr and formation of REE-rich carbonatites with abundant ancylite mineralization. This effect did not disturb the Smsingle bondNd system but induced radiogenic Sr accumulation and a change in C and O isotopic composition towards heavier values. Later, but most likely before denudation, the Petyayan-Vara rocks underwent another metasomatic event involving crustal fluids infiltrating through fracture systems. This event triggered formation of bastnäsite-rich carbonatites with fewer REEs at the expense of ancylite-rich carbonatites, and changed all the isotopic systems in the affected rocks. This model successfully accounts for the evolution of all the carbonatite varieties discovered to date in the Petyayan-Vara field.
Abstract: Carbonatites and related alkaline rocks host most REE resources. Phosphate minerals, e.g., apatite and monazite, commonly occur as the main REE-host in carbonatites and have been used for tracing magmatic and mineralization processes. Many carbonatite intrusions undergo metamorphic and/or metasomatic modification after emplacement; however, the effects of such secondary events are controversial. In this study, the Miaoya and Shaxiongdong carbonatite-alkaline complexes, in the South Qinling Belt of Central China, are selected to unravel their magmatic and hydrothermal remobilization histories. Both the complexes are accompanied by Nb-REE mineralization and contain apatite and monazite-(Ce) as the major REE carriers. Apatite grains from the two complexes commonly show typical replacement textures related to fluid metasomatism, due to coupled dissolution-reprecipitation. The altered apatite domains, which contain abundant monazite-(Ce) inclusions or are locally surrounded by fine-grained monazite-(Ce), have average REE concentrations lower than primary apatite. These monazite-(Ce) inclusions and fine-grained monazite-(Ce) grains are proposed to have formed by the leaching REE from primary apatite grains during fluid metasomatism. A second type of monazite-(Ce), not spatially associated with apatite, shows porous textures and zoning under BSE imaging. Spot analyses of these monazite-(Ce) grains have variable U-Th-Pb ages of 210-410 Ma and show a peak age of 230 Ma, which is significantly younger than the emplacement age (440-430 Ma) but is roughly synchronous with a regionally metamorphic event related to the collision between the North China Craton and Yangtze Block along the Mianlue suture. However, in situ LA-MC-ICP-MS analyses of those grains show that they have initial Nd values same as those of magmatic apatite and whole rock. We suggest these monazite-(Ce) grains crystallized from the early Silurian carbonatites and have been partially or fully modified during a Triassic metamorphic event, partially resetting U-Pb ages over a wide range. Mass-balance calculations, based on mass proportions and the REE contents of monazite-(Ce) and apatite, demonstrate that the quantity of metasomatized early Silurian monazite-(Ce) is far higher than the proportion of monazite-(Ce) resulting from the metasomatic alteration of the apatite. Therefore, Triassic metamorphic events largely reset the U-Th-Pb isotopic system of the primary monazite-(Ce) and apatite but only had limited or local effects on REE remobilization in the carbonatite-alkaline complexes in the South Qinling Belt. Such scenarios may be widely applicable for other carbonatite and hydrothermal systems.
Ph.d. thesis University of Gootenberg Sweden, 105p. Pdf
Europe, Sweden
REE
Abstract: The Norra Kärr alkaline complex in southern Sweden (58°06’N, 14°34’E) is a classic occurrence of agpaitic rocks, which contains a large mineral deposit of rare-earth elements (REE), Zr, and Nb. The complex consists of different varieties of agpaitic peralkaline nepheline syenite that are defined by the occurrence of Na-rich Zr-Ti silicate minerals that contain volatiles F and Cl, including members of the rinkite, catapleiite, and eudialyte groups. The eudialyte-group minerals in Norra Kärr contain different ratios of light to heavy REE across the lithological domains. The magmatic age of the alkaline complex, which is poor in common chronometric minerals, was determined at 1.49 ± 0.01 Ga (2?) by U-Pb dating of zircon that formed during alkali metasomatism (fenitisation) of the surrounding 1.8 Ga granite. The 176Hf/177Hf isotopic ratio of this metasomatic zircon is different from Hf isotopes in the granite, but is identical with the Hf isotope composition of Lu-poor eudialyte from the alkaline complex. The relatively highly radiogenic composition of the Hf isotopes is consistent with a mantle source for the agpaitic magma. New radiometric dating methods were developed. These allow precise in situ measurements of isotope ratios of the Rb-Sr and K-Ca as well as Sm-Nd systems in K-rich and Nd-rich minerals, respectively. Three varieties of alkaline rocks in Sweden were dated by the in situ Rb-Sr method. Biotite Rb-Sr cooling ages in the region east of Norra Kärr are approximately coeval with the emplacement of the alkaline rocks. The complex has been affected by metamorphic overprinting. The foliated and folded fine-grained nepheline syenite is frequently cross-cut by coarse-grained eudialyte- rich pegmatoids. One eudialyte crystal with primary zoning from a pegmatoid was pre-characterised by SEM BSE imaging and in situ chemical analysis by LA-ICP-MS, including full REE composition and precise Sm/Nd ratios. Sampling at a resolution of <200 ?m by micromill provided a sufficient Nd aliquot for routine high-precision ID- TIMS Sm-Nd isotope analysis. Eudialyte crystal growth was dated at 1144 ± 53 Ma (2?) in the undeformed pegmatoid vein, about 350 million years after the magmatic event. The pegmatoid is suggested to have formed by low-temperature partial melting of the peralkaline nepheline syenite host at the margin of Sveconorwegian orogeny. The agpaitic rocks were produced from a magma that formed by extensive fractional crystallisation of an alkali basaltic parental magma. The concentrations of highly enriched incompatible elements in the most differentiated nepheline syenite may indicate 98 % crystallisation of the parental magma.
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.
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.
Journal of African Earth Science, Vol. 186, 104434, 12p. Pdf
Africa, Zimbabwe
REE
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.
Australian Journal of Earth Sciences, Vol.1, pp. 1-25. pdf
China
REE
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.
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.-
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.-
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.
Fundamental Research , 10.1016/j.fmre.2022.04.004 34p. Pdf
Mantle
REE
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.
