From mantle to critical zone: A review of large and giant sized deposits of the rare earth elements

This is the final version. Available from Elsevier via the DOI in this record.The rare earth elements are unusual when defining giant-sized ore deposits, as resources are often quoted as total rare earth oxide, but the importance of a deposit may be related to the grade for individual, or a limited group of the elements. Taking the total REE resource, only one currently known deposit (Bayan Obo) would class as giant (>1.7 × 107 tonnes contained metal), but a range of others classify as large (>1.7 × 106 tonnes). With the exception of unclassified resource estimates from the Olympic Dam IOCG deposit, all of these deposits are related to alkaline igneous activity - either carbonatites or agpaitic nepheline syenites. The total resource in these deposits must relate to the scale of the primary igneous source, but the grade is a complex function of igneous source, magmatic crystallisation, hydrothermal modification and supergene enrichment during weathering. Isotopic data suggest that the sources conducive to the formation of large REE deposits are developed in subcontinental lithospheric mantle, enriched in trace elements either by plume activity, or by previous subduction. The reactivation of such enriched mantle domains in relatively restricted geographical areas may have played a role in the formation of some of the largest deposits (e.g. Bayan Obo). Hydrothermal activity involving fluids from magmatic to meteoric sources may result in the redistribution of the REE and increases in grade, depending on primary mineralogy and the availability of ligands. Weathering and supergene enrichment of carbonatite has played a role in the formation of the highest grade deposits at Mount Weld (Australia) and Tomtor (Russia). For the individual REE with the current highest economic value (Nd and the HREE), the boundaries for the large and giant size classes are two orders of magnitude lower, and deposits enriched in these metals (agpaitic systems, ion absorption deposits) may have significant economic impact in the near future.Natural Environment Research CouncilUniversity of Exete

From mantle to critical zone : a review of large and giant sized deposits of the rare earth elements

MS, AF and FW acknowledge the support of the NERC SoS:RARE consortium grant (NE/M011267/1). D. Kavecsanszki acknowledges the support of a postgraduate fellowship from the College of Engineering, Mathematics and Physical Sciences at the University of Exeter.The rare earth elements are unusual when defining giant-sized ore deposits, as resources are often quoted as total rare earth oxide, but the importance of a deposit may be related to the grade for individual, or a limited group of, the elements. Taking the total REE resource, only one currently known deposit (Bayan Obo) would class as giant (>1.7×107 tonnes contained metal), but a range of others classify as large (>1.7×106 tonnes). With the exception of unclassified resource estimates from the Olympic Dam IOCG deposit, all of these deposits are related to alkaline igneous activity – either carbonatites or agpaitic nepheline syenites. The total resource in these deposits must relate to the scale of the primary igneous source, but the grade is a complex function of igneous source, magmatic crystallisation, hydrothermal modification and supergene enrichment during weathering. Isotopic data suggest that the sources conducive to the formation of large REE deposits are developed in subcontinental lithospheric mantle, enriched in trace elements either by plume activity, or by previous subduction. The reactivation of such enriched mantle domains in relatively restricted geographical areas may have played a role in the formation of some of the largest deposits (e.g. Bayan Obo). Hydrothermal activity involving fluids from magmatic to meteoric sources may result in the redistribution of the REE and increases in grade, depending on primary mineralogy and the availability of ligands. Weathering and supergene enrichment of carbonatite has played a role in the formation of the highest grade deposits at Mount Weld (Australia) and Tomtor (Russia). For the individual REE with the current highest economic value (Nd and the HREE), the boundaries for the large and giant size classes are 2 orders of magnitude lower, and deposits enriched in these metals (agpaitic systems, ion absorption deposits) may have significant economic impact in the near future.Publisher PDFPeer reviewe

The origin of secondary heavy rare earth element enrichment in carbonatites: Constraints from the evolution of the Huanglongpu district, China

publisher: Elsevier articletitle: The origin of secondary heavy rare earth element enrichment in carbonatites: Constraints from the evolution of the Huanglongpu district, China journaltitle: Lithos articlelink: http://dx.doi.org/10.1016/j.lithos.2018.02.027 content_type: article copyright: © 2018 The Authors. Published by Elsevier B.V.Copyright: © 2018 Published by Elsevier B.V. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The file attached is the Published/publisher’s pdf version of the articl

Deducing the source and composition of rare earth mineralising fluids in carbonatites: insights from isotopic (C, O, 87Sr/86Sr) data from Kangankunde, Malawi

This is the final version of the article. Available from Springer Verlag via the DOI in this record.Carbonatites host some of the largest and highest grade rare earth element (REE) deposits but the composition and source of their REE-mineralising fluids remains enigmatic. Using C, O and 87Sr/86Sr isotope data together with major and trace element compositions for the REE-rich Kangankunde carbonatite (Malawi), we show that the commonly observed, dark brown, Fe-rich carbonatite that hosts REE minerals in many carbonatites is decoupled from the REE mineral assemblage. REE-rich ferroan dolomite carbonatites, containing 8–15 wt% REE2O3, comprise assemblages of monazite-(Ce), strontianite and baryte forming hexagonal pseudomorphs after probable burbankite. The 87Sr/86Sr values (0.70302–0.70307) affirm a carbonatitic origin for these pseudomorph-forming fluids. Carbon and oxygen isotope ratios of strontianite, representing the REE mineral assemblage, indicate equilibrium between these assemblages and a carbonatite-derived, deuteric fluid between 250 and 400 °C (δ18O + 3 to + 5‰VSMOW and δ13C − 3.5 to − 3.2‰VPDB). In contrast, dolomite in the same samples has similar δ13C values but much higher δ18O, corresponding to increasing degrees of exchange with low-temperature fluids (< 125 °C), causing exsolution of Fe oxides resulting in the dark colour of these rocks. REE-rich quartz rocks, which occur outside of the intrusion, have similar δ18O and 87Sr/86Sr to those of the main complex, indicating both are carbonatite-derived and, locally, REE mineralisation can extend up to 1.5 km away from the intrusion. Early, REE-poor apatite-bearing dolomite carbonatite (beforsite: δ18O + 7.7 to + 10.3‰ and δ13C −5.2 to −6.0‰; 87Sr/86Sr 0.70296–0.70298) is not directly linked with the REE mineralisation.This project was funded by the UK Natural Environment Research Council (NERC) SoS RARE project (NE/M011429/1) and by NIGL (NERC Isotope Geoscience Laboratory) Project number 20135

Zircon from the East Orebody of the Bayan Obo Fe–Nb–REE deposit, China, and SHRIMP ages for carbonatite-related magmatism and REE mineralization events

Extremely U-depleted

The Rare Earth Elements: demand, global resources, and challenges for resourcing future generations

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

Fluorescence microscope images of nuclear counterstains with Hoechst staining and TUNEL assay.

<p>Proliferation (blue color) and apoptosis (small green spots) of MG-63 cell samples cultured with 0, 1, 10 and 30 mM of TSP for 1, 3 and 4 days were illustrated.</p

Origin of carbonatites in the South Qinling orogen: Implications for crustal recycling and timing of collision between the South and North China Blocks

Most studies of compositional heterogeneities in the mantle, related to recycling of crustal sediments or delaminated subcontinental lithosphere, come from oceanic setting basalts. In this work, we present direct geochronological and geochemical evidence for the incorporation of recycled crustal materials in collision-related carbonatites of the South Qinling orogenic belt (SQ), which merges with the Lesser Qinling orogen (LQ) to separate the South and North China Blocks. The SQ carbonatites occur mainly as stock associated with syenites. The data presented here show that zircon from the syenites yields an age of 766 ± 25 Ma, which differs significantly from the age of primary monazite from the carbonatites (233.6 ± 1.7 Ma). The syenites contain lower initial 87Sr/86Sr and higher εNd values. This indicates that the carbonatites do not have genetically related with the silicate rocks, and were directly derived from a primary carbonate magma generated in the mantle. The carbonatites show a Sr–Nd isotopic signature similar to that of the chondritic uniform reservoir (CHUR), and parallel Sm–Nd model ages (TCHUR) of 190–300 Ma. However, the rocks have extremely variable Pb isotopic values straddling between the HIMU and EM1 mantle end-members. Most carbon and oxygen isotopic compositions of the SQ carbonatites plot outside the field for primary igneous carbonates. Their δ13C shows higher value than a ‘normal’ mantle, which implies an incorporation of recycled inorganic carbon. The carbonatites were emplaced close to the Mianlue suture, and followed the closure of the Mianlue ocean and Triassic collision of the South and North China Blocks.However, direct melting of the subducted Mianlue oceanic crust characterized by high εNd and low (EM1-like) 206Pb/204Pb values cannot explain the CHUR-like Nd signature and the Pb isotopic trend toward HIMU in the SQ carbonatites. We conclude that their parental magma was derived from a source incorporating the Mianlue oceanic crust mixed with an asthenospheric (or deeper) material characterized by high Pb and low Nd isotopic values. This material represents a deep-seated Proterozoic carbonate component recycled via mantle convection or localized upwelling. Notably, this model cannot explain the isotopic compositions of the Late Triassic (209–221 Ma) carbonatites in the LQ, characterized by a mantle-derived δ13C, but EM1-like Sr–Nd–Pb isotopic compositions. This signature is best explained in terms of delamination of the lower continental crust thickened during the collision of the South and North China Blocks, and partial incorporation of the delaminated material into the LQ mantle source. Modeling of the measured Sr–Nd–Pb isotopic variations suggests that the source of the LQ carbonatites could be produced by mixing of 80–85% of mantle material and 15–20% of delaminated lower continental crust. The emplacement of the SQ and LQ carbonatites marked a gradual transition from a compressional tectonic regime, brought about by the collision of the South and North China Blocks to intra-orogenic extension in the waning stages of the Triassic orogeny

Resolving the structural state of heavy rare earth elements in lateritic ion adsorption clays

Lateritic Ion Adsorption Deposits (IADs) are the world's dominant source for heavy rare earth elements (HREE: Gd-Lu), currently mostly mined from China. IADs in Brazil, Madagascar and South East Asia may provide alternative supply for HREE. However, the exact nature of REE in the IADs is unclear; for example whether deposits elsewhere are directly analogous to the easily-leachable Chinese laterites, and whether the REE are truly adsorbed, structurally bound in clays or hosted in other mineral phases.This study compares economically mineralized IADs from the Zhaibei granite, China to prospective IADs developed on peralkaline igneous rocks from Madagascar. We use synchrotron X-Ray Fluorescence (SXRF) element mapping and X-ray Absorption Spectroscopy (XAS) to study the distribution and coordination state of light and heavy REE. We explore sites of adsorption to clays and the presence of HREE in other mineral phases. The Malagasy and Chinese laterites have kaolinite as the dominant REE-hosting clay phase, with minor halloysite. XAS data demonstrate that the REE occur as 8 to 9-coordinated outer-sphere basal surface complexes on kaolinite, rather than 5- or 6-coordinated edge complexes, or 6- or 8-coordinated interlayer complexes, thus confirming the truly adsorbed nature of REE in lateritic IAD's from both localities.</p