Rare Earth Element Deposits Research Articles

Meifuite, A New Ferrous Phyllosilicate Mineral With Modulated Tetrahedral Sheets Similar to Minnesotaite

AbstractA new ferrous phyllosilicate, meifuite, has been discovered in the Yinachang Fe-Cu-REE (rare-earth element) deposit in China. The structural formula, calculated using averaged electron probe microanalysis (EPMA) results, is K0.72Na0.20(Fe5.56Mg0.31Mn0.13)Σ6.00(Si6.95Al1.04)Σ7.99O18.84(OH)4.84 Cl1.33, with an ideal formula of KFe6(AlSi7)O19(OH)4Cl2. The structure of meifuite has a P1¯ space group symmetry, with unit-cell parameters of a = 22.7773(13) Å, b = 9.5553(5) Å, c =14.3282(8) Å, α = 99.258(4)°, β = 136.750(3)°, γ = 89.899(4)°, Z = 2, and V = 2077.9(2) Å3. Meifuite has a strip-modulated 2:1 layer (T–O–T) structure similar to that of minnesotaite. About 1/8 of the tetrahedra in the T sheet are occupied by Al instead of Si, and the interlayer cavities are partially occupied by K and Na. Some of the OH sites in the octahedral sheet in the layer structure are fully or partially substituted by Cl, which is apparently the primary reason for the meifuite structure being more stable than stilpnomelane, the most common ferrous layer silicate mineral found at similar temperature and pressure conditions. An updated, more accurate structure model of minnesotaite is also provided for comparison with the meifuite structure. The mineral is named after Meifu Zhou in honor of his outstanding contributions to the field of economic geology.

Petrology of weathering materials developed on granites in Biou area, North-Cameroon: implication for rare-earth elements (REE) exploration in semi-arid regions

Due to the increasing demand resulting from the use of REE in many fields of human life, a weathering profile developed on granites in the semi-arid region of Biou area (North-Cameroon) has been characterized for rare-earth elements (REE) exploration. The mineralogical compositions of weathered materials were revealed by X-ray diffraction (XRD). X-ray Fluorescence (XRF) and Inductively Coupled Plasmas-Mass Spectrometry (ICP-MS) have been used to determine the geochemical composition of granites and the overlying weathered materials. The S-type and peraluminous granites are constituted by quartz, orthoclase, microcline, plagioclase, biotite, muscovite, pyroxene and opaque minerals. Accessory minerals are probably responsible for the interesting contents in REE + Y and some trace elements (e.g., Zr, Zn, Ba, Rb). The weathering profile show from the bottom to the top: (i) saprolitic horizons; (ii) lower loose clayey horizon; (iii) iron duricrust horizon; (iv) upper loose clayey horizon; (v) and organo-mineral horizon. Some weathered rock fragments remain in the loose clayey and organo-mineral horizons. The mineralogical composition of the weathering materials is dominated by illite, muscovite and feldspar. The low weathering degree of the materials is justified by the climatic and reducing conditions. The large ion lithophiles and ferromagnesian elements (Mg, Fe, V, Cu, Co, Cs Cr, Ni, Sc and Li) which are supposed to be mobile are so much accumulated in the weathering materials. REE show very low degree of fractionation in weathering profile due probably to the lack of good drainage. The whole weathering materials shows high REE + Y contents as its parent rock. Geochemical mass balance and enrichment factor reveal that REE, especially light REE, are so much enriched in the iron duricrust horizon (ion-adsorption REE deposit type). Some heavy REE are also enriched in the lower loose clayey horizon. This first survey has revealed that the weathering materials developed on granites in Biou area are favorable for further REE exploration.

Organic and inorganic compounds as corrosion inhibitors to reduce galvanic effect for the hybrid structure AA2024-CFPR

The effect of the galvanic corrosion process taking place between aluminium alloy (AA2024-T3) and carbon fiber reinforced plastic (CFRP) immersed in 0.05 M NaCl was studied using organic and inorganic compounds as corrosion inhibitors. Electrochemical approaches such as electrochemical noise analysis (ENA) and electrochemical impedance spectroscopy (EIS) were carried out to evaluate efficiencies of 1,2,4-triazole (C2H3N3) and cerium nitrate hexahydrate (Ce(NO3)3·6H2O) as corrosion inhibitors. The highest efficiency was reached for Ce(NO3)3.6H2O, with some improvement observed by adding C2H3N3 in a mixed inhibitor solution. The noise resistance (Rn) and polarization resistance (Rp) values calculated from ENA and EIS data showed almost identical behavior with different magni­tudes but similar trends. Adsorption isotherm models estimated with fractional surface coverage (q) parameter were fitted better to Langmuir model for C2H3N3 and Temkin model for Ce(NO3)3·6H2O. The calculated values of Gibbs free energy suggested physi­sorption and chemisorption as spontaneous interactions between a metal surface and both inhibitors. Energy-dispersive X-ray spectroscopy (EDS) was carried out before and after immersing AA2024-T3 in the electrolyte, identifying rich zones in copper with cerium deposited over it and confirming the presence of rare-earth oxide deposition and oxide film products. The EDS analysis for CFRP revealed the deposition of Ce and Al particles over its surface after immersion in the electrolyte, especially in the areas rich in carbon.

Geochemical and REE mineralogical characteristics of the Zhaibei Granite in Jiangxi Province, southern China, and a model for the genesis of ion-adsorption REE deposits

The Zhaibei Granite in Jiangxi Province, southern China, hosts an ion-adsorption light rare earth element (LREE) deposit. Recently, heavy REE (HREE) ores have also been reported from weathered crusts of the granitic rocks. In this study, petrological, geochemical, and mineralogical characteristics of the Zhaibei pluton were analysed to establish the genesis of this REE deposit. The pluton contains coarse-grained biotite syenogranite and minor hornblende–biotite–quartz monzonite in its central zone, medium-grained biotite syenogranite in its transitional zone, and fine-grained muscovitic alkali-feldspar granite and porphyritic muscovitic biotite–alkali-feldspar granite together with monzogranite porphyry intrusions in its marginal zone. The REE minerals include titanite, allanite, monazite, bastnasite, and thorite-(Y) in the central zone, allanite, monazite, xenotime, bastnasite, and thorite-(Y) in the transitional zone, and synchysite-(Y), thorite-(Y), and xenotime in the marginal zone. The SiO2 content increases from 62 to 77 wt% from the centre to the margin, whereas the Al2O3, TiO2, MgO, FeO, and CaO contents decrease. In addition, the size of the negative Eu anomaly and HREE content increase, accompanied by decreases in Co, Zr, Hf, Sr, and Ba and increases in Rb, Cs, Nb, and Sn. These observations indicate that the Zhaibei Granite might have been formed by crystallisation differentiation of magma. The granitic pluton was also influenced by reactions with late-magmatic F-, CO2–, and REE-rich fluids that altered magmatic minerals and crystallised as REE-fluorocarbonates and thorite. The hydrothermal REE minerals constitute ∼ 40% of the total REEs in the bedrock and are the major supplier of ion-exchangeable REEs in the ores of the Zhaibei deposit. LREE-rich ores may have been derived from the LREE-rich granitic rocks, which contain bastnasite, titanite, and allanite, whereas HREE-rich ores were sourced mainly from the HREE-rich granites, which contain synchysite-(Y) and thorite-(Y). Furthermore, REE ores with enrichment in both HREEs and LREEs were probably sourced from the monzogranite porphyry bedrock, which contains bastnasite-(Y), bastnasite, allanite, and thorite-(Y).

Visible/near infrared reflectance (VNIR) spectral features of ion-exchangeable Rare earth elements hosted by clay minerals: Potential use for exploration of regolith-hosted REE deposits

Regolith-hosted ion-exchangeable rare earth element (REE) mineralization in South China dominate the global source of heavy REEs. The lack of studies on spectral features of ion-exchangeable REEs limits the application of visible/near infrared reflectance (VNIR, 350–2500 nm) spectroscopy for rapid identification of regolith-hosted REE deposits in prospective areas. This paper presents a systematic study on VNIR spectral features of ion-exchangeable REEs hosted by a series of synthetic REE-adsorbed clay minerals and natural regolith samples. The results show that ion-exchangeable Nd3+, Dy3+, Ho3+, Er3+ and Tm3+ display diagnostic absorption features at the bands of 730–870, 805, 641, 652, and 684 nm. Specifically, the Nd3+ related absorption bands of regolith samples at ~800 nm show a shoulder at ~802 nm that are distinguishable from unweathered primary REE(−bearing) minerals. The maxima of second derivative curves derived from the Nd3+ absorption at ~802 nm, M802_2nd, can be used to quantify variations of ion-exchangeable REEs in regoliths. Nevertheless, the absorption features of REE3+ ions could be subdued due to an overlapping problem caused by the broad absorption bands of Fe-oxides in the range of 700–900 nm. The obtained VNIR spectra of ion-exchangeable REEs provide critical supplement to spectral library for REE-bearing minerals. This study demonstrates that field-based VNIR spectroscopy can be deployed as a powerful tool for regional and deposit-scale exploration of regolith-hosted ion-exchangeable REE resources.

Subducted sediment contributions to REE deposits recorded by alkaline mafic dikes in the Lizhuang REE deposit, Panxi area, southwest China

Carbonatite-associated rare earth element (REE) deposits are the most important source of REEs worldwide. Recycled subducted sediments are critical for REE mineralization, but it remains unclear how the subducted sediments contribute to the REE mineralization. This study presents new whole-rock and apatite geochemical data for alkaline mafic dikes from the Lizhuang REE deposit, southwest China. These alkaline mafic dikes were emplaced at ca. 28.4 Ma (monazite U-Pb age), broadly coeval with the carbonatite–syenite complex and REE mineralization in the Lizhuang REE deposit. The alkaline mafic dikes have enriched Sr-Nd-Pb isotopic compositions, and variable Ba/Th and La/Sm ratios, demonstrate they were derived from an enriched mantle source, which had been modified by both slab-derived fluids and sediment melts. The apatite grains in the alkaline mafic dikes have distinctive geochemical features in their irregular cores (apatite A) and rim overgrowths (apatite B). Apatite A has low REE contents (18.6–161 ppm) and apatite B has high REE contents (1869–4288 ppm). The different REE contents in these apatites could have been caused by the addition of REE-rich carbonatitic melts at lower crustal depths. We propose that the REE-rich carbonatitic melts could be formed by melting of a sediment-rich mantle source, and that collision between India–Asia triggered the melting.

Three‐Dimensional Electrical Resistivity Characterization of Mountain Pass, California and Surrounding Region

AbstractThe Sulphide Queen carbonatite deposit at Mountain Pass in southeast California is a world class rare earth element (REE) resource. This study images electrical resistivity structure of the REE deposit and surrounding area to characterize resources under cover. An east‐west elongated grid (35 × 15 km) of 65 wideband magnetotelluric stations spanning from eastern Shadow Valley to eastern Ivanpah Valley were collected and modeled in three‐dimensions (3‐D). Gravity, aeromagnetic, and geologic data are used to inform interpretation of structures in the resistivity model, including the following observations. Shadow Valley is filled with conductive sediment that locally dips southward to a depth of 1 km. The Kingston Range‐Halloran Hills detachment fault dips westward at ∼15 degrees. The REE deposit is a moderate low resistivity zone dipping southwest to a possible depth of ∼1 km, and is bounded by the North and South faults and bisected by the Middle fault. Ivanpah Dry Lake is underlain by a north striking southward dipping sedimentary basin. Two possible zones of mineralization are observed in Ivanpah Valley, one along the western edge of Ivanpah Dry Lake and one on the western edge of valley along a new inferred fault. The brittle‐ductile transition is imaged at ∼10 km below mean sea level. No deep electrically conductive structures are imaged to be related to the REE deposit likely due to the complex geologic history of the Mojave terrane. Future studies should regional target Proterozoic rocks and search within for geophysical signatures similar to Mountain Pass.

The sequential REE (Rare Earth Elements) extraction of weathered crusts of granitoids from Sibolga, Indonesia

Indonesia needs a proven technology for REE extraction to build a national REE industry. Monazite that has been recovered from placer deposits at Bangka-Belitung areas is the most potential REE source. In the future, ion adsorption type will be another potential source of REE deposits. This paper describes the sequential REE extraction of the weathered crusts of granitoids from Sibolga using sequential extraction ICP-MS analysis is applied to determine bulk samples mineralogical compositions and REE content. The total REE (∑REE) content of weathered crusts of granitoids from Sibuluhan Sihaporas A ranges from 265 to 479 ppm, while the amount of ∑REE leached by sequential extraction range from 151 to 263 ppm, and the percentage of adsorbed ∑REE ranges from 55 to 74%. In comparison, Sibuluhan Sihaporas B ranges from 302 to 634 ppm, 82 to 198 ppm, and 28 to 44%, respectively. ∑REE content of weathered granitoids crusts from Sarudik ranges from 135 to 219 ppm, while that SREE leached by sequential extraction range from 21 to 82 ppm, and percentage of adsorbed ∑REE range from 11 to 50 %, while that Sibolga Julu ranges from 191 to 304 ppm, 111 to 138 ppm, and 27 to 44%.

Normative indexes calibrated by automated mineralogy to model a rare earth deposit

The Bull Hill open pit mine is a planned rare earth element (REE) development of the Bear Lodge REE resource in northeast Wyoming, United States of America. It contains 16.3 Mt of ore at 3.05 wt. % total rare earth oxide as fully oxidized (OX) and partially oxidized (OxCa) carbonatite in a variety of REE mineral modes and textures.The establishment of a mineralogical model based on quantitative mineralogical data enables the use of geochemical indexes for selected mineral abundances. The indexes are calculated from assays and are used to augment mineralogical data for the purpose of 3D modeling of mineral variation throughout the resource. These models allow for the estimation of lateral and vertical variations in mineralogy throughout the proposed Bull Hill and Whitetail pits, and into adjacent areas.The Bull Hill resource has a variable assemblage of ore minerals. The model shows that the REE mineralogy over the main dyke zone is dominated by REE-fluorocarbonates, with a significant cerianite component at shallower levels. Locally, adjacent and distal lower-grade zones can be REE-phosphate-dominant. Shallower zones tend to have a greater proportion of REE-phosphates as well. With increasing depth, ancylite becomes an important constituent of the REE mineral assemblage. The Whitetail resource is strongly REE-fluorocarbonate-dominant, with some significant zones of cerianite at shallower levels. At depth the deposit is also fluorocarbonate dominant, with decreasing cerianite and slightly increasing ancylite. Phosphates are a minor component of Whitetail ore mineralization, and phosphorous concentrations at Whitetail are generally lower.The Bull Hill deposit is more weathered (lateritized) with a higher proportion of OX ore and, as a consequence, has a higher clay content and lower abundance of calcite, whereas the Whitetail deposit has a greater component of OxCa. Iron- and Mn-oxide phases (Fe3+ and Mn3+/4+) are more prevalent near the surface in both resources, owing to supergene oxidation during weathering. Bull Hill ore is higher in Mn concentrations than Whitetail. This is reflected by a greater proportion of Mn-oxides and/or Mn-bearing carbonate gangue phases. Clay content is higher near the surface in both deposits. At Bull Hill, the clay content of the main dyke zone is lower than that of the ore zones in the western and southeastern parts of the pit. At Whitetail, clay content is lower and more sporadic than at Bull Hill, and is concentrated in the central to southern parts of the pit. Silicification of ore is common in the upper central-north and northwestern parts of the Whitetail pit, whereas the Bull Hill pit has some significant ore silicification toward its northwest corner and in patches along the main dyke zone, especially towards the southern pit edge.These variations in ore and gangue mineralogy make it likely that, for a given mineral processing circuit, costs and/or REE recoveries may vary from bench to bench over the life expectancy of the mine. Accurate modeling of mineralogical variations allows for the early identification of anomalous areas in order to enable more efficient mining and mineral processing.

Complex REE systematics of carbonatites and weathering products from uniquely rich Mount Weld REE deposit, Western Australia

Carbonatite intrusive complexes are important hosts for Rare Earth Elements (REE) deposits and are commonly affected by surficial weathering processes. Mount Weld REE deposit of Western Australia is one of the world’s richest REE deposits and here we present whole-rock and REE mineral geochemical data on compositions of primary and weathered carbonatites. The REE concentrations in magmatic carbonatites at Mount Weld vary by two orders of magnitude, suggesting a significant role of magmatic processes in REE enrichment in the carbonatite complex. The Th-Pb age 2056±67 (2σ) Ma of monazite-(Ce) from the carbonatite obtained by in situ LA-ICP-MS analyses confirm Paleoproterozoic age of the mineralization. The regolith samples preserve a detailed record of evolution from carbonatite to products of intensive weathering. The silica-cemented regolith (silcrete) contains monazite-(Ce) and apatite chemically identical to their carbonatite-hosted equivalents. The high-REE regolith containing 51.8 wt% ∑REE2O3 has some of the highest REE concentrations found to date, negative Ce anomaly and contains lithogenic monazite within matrix of florencite-(Ce) and rhabdophane-(Nd) and rhabdophane-(Nd) tubes resembling casts of plant material. The pronounced negative Ce anomalies in the ferruginous cap rock (ferricrete) and the high-REE regolith indicate intensive weathering, where Ce4+ was preferential removed relative to the REE3+. The presence of paleo-plants in the high-REE regolith implicates bio-assisted processes involved in the extreme REE fractionation. The diverse REE enrichment processes, which occurred in supergene environment of Mount Weld, have implications for the understanding of the genesis of REE deposits worldwide.

Impact of freeze-thaw on the behaviour of flotation tailings from a rare earth deposit

The Ashram Rare Earth and Fluorspar Deposit, located in northern Quebec (Canada), contains a potential carbonatite-type rock source of rare earth elements (REE). A pilot scale pre-concentration of REE minerals produced flotation tailings. A kinetic leach column study was performed to evaluate the behaviour of these tailings in a northern context (i.e. freeze-thaw cycles). The tailings were exposed to 12 cycles (over 1 year) of leaching with deionized water under two different conditions. The first column, CW (water column), was stored at 5 °C for the duration of the experiment, while the second column, CFT (freeze-thaw column), was subjected to freeze-thaw cycling. A comparison with Quebec environmental guidelines showed that the tailings were not acid generating but deemed leachable for Cd, Pb, Zn and Mn. Leachate analysis for the CW (water column) showed that the behaviour of Ba, Ca, Sr and Mn appeared similar. These elements could originate from the dissolution of calcite [CaCO3], dolomite [CaMg(CO3)2], dolomite-Fe [Ca(Mg,Fe2+)(CO3)2] or ankerite [Ca(Fe2+,Mg,Mn)(CO3)2]. Mg, F and Si could originate from the dissolution of biotite [K2(Mg,Fe2+)6-4(Fe3+,Al,Ti)0-2(Si6-5Al2-3O20)(OH,F)2]. The release of these elements would, however, appear to come from separate minerals. The presence of fluorine in the leachate could come from the dissolution of fluorite [CaF2], apatite [Ca5(PO4)3(O,H,F,Cl)] or bastnaesite [(La,Ce)CO3F]. Mg could come from the dissolution of carbonate minerals such as magnesite [MgCO3]. Despite high Fe content (98,620 mg/kg) in the initial flotation tailings, Fe was not present in the leachate, probably because of potential precipitation in the form of iron oxides/hydroxides. Despite being only slightly soluble (<0.001% mobilized), some heavy REE (HREE), Er, Yb, Lu and Sc, have a distinct leaching behaviour compared to other REE. Overall, the freeze-thaw cycles only decreased the mobility of some elements (e.g. Ca, Ba, Sr and Mn) and, thus, the potential for environmental contamination from the tested REE tailings.

FEASIBILITY OF VISIBLE SHORT-WAVE INFRARED REFLECTANCE SPECTROSCOPY TO CHARACTERIZE REGOLITH-HOSTED RARE EARTH ELEMENT MINERALIZATION

Abstract Regolith-hosted rare earth element (REE) deposits predominate global resources of heavy REEs. Regoliths are underlain by various types of igneous rocks and do not always host economically valuable deposits. Thus a feasible and convenient method is desired to identify REE mineralization in a particular regolith. This study presents a detailed visible short-wave infrared reflectance (VSWIR) spectroscopic study of the Renju regolith-hosted REE deposit, South China, to provide diagnostic parameters for targeting REE orebodies in regoliths. The results show that the spectral parameters, M794_2nd and M800_2nd, derived from the VSWIR absorption of Nd3+ at approximately 800 nm, can be effectively used to estimate the total REE concentrations in regolith profiles. M1396_2nd/M1910_2nd ratios can serve as proxies to evaluate weathering intensities in a regolith. Abrupt changes of specific spectral features related to mineral abundances, chemical compositions, and weathering intensities can be correlated with variations of protolith that formed a regolith. These VSWIR proxies are robust and can be used for exploration of regolith-hosted REE deposits.

Melt–Fluid and Fluid–Fluid Immiscibility in a Na2SO4–SiO2–H2O System and Implications for the Formation of Rare Earth Deposits

AbstractLiquid–liquid immiscibility has crucial influences on geological processes, such as magma degassing and formation of ore deposits. Sulfate, as an important component, associates with many kinds of deposits. Two types of immiscibility, including (i) fluid–melt immiscibility between an aqueous solution and a sulfate melt, and (ii) fluid–fluid immiscibility between two aqueous fluids with different sulfate concentrations, have been identified for sulfate–water systems. In this study, we investigated the immiscibility behaviors of a sulfate‐ and quartz‐saturated Na2SO4–SiO2–H2O system at elevated temperature, to explore the phase relationships involving both types of immiscibility. The fluid–melt immiscibility appeared first when the Na2SO4–SiO2–H2O sample was heated to ∼270°C, and then fluid–fluid immiscibility emerged while the sample was further heated to ∼450°C. At this stage, the coexistence of one water‐saturated sulfate melt and two aqueous fluids with distinct sulfate concentrations was observed. The three immiscible phases remain stable over a wide pressure–temperature range, and the appearance temperature of the fluid–fluid immiscibility increases with the increased pressure. Considering that sulfate components occur extensively in carbonatite‐related deposits, the fluid–fluid immiscibility can result in significant sulfate fractionation and provides implications for understanding the formation of carbonatite‐related rare earth deposits.

Formation of Rare Earth Deposits in Carbonatites

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.

Mineralogical characteristics and Sr–Nd–Pb isotopic compositions of banded REE ores in the Bayan Obo deposit, Inner Mongolia, China: Implications for their formation and origin

Rare earth elements (REEs) are a focus of current research due to their importance in a wide range of industries and technologies. Bayan Obo in China is the largest REE deposit in the world. Although some studies have investigated the banded REE ores in the Bayan Obo deposit, the origin and formation processes of the ores are unclear. In this study, we used X-ray powder diffraction, electron microprobe, laser ablation–inductively coupled plasma–mass spectrometry, and mass spectrometry methods to investigate the mineral assemblages and geochemical characteristics of minerals in banded ores in the Bayan Obo REE deposit. Based on petrographic observations, the early minerals that precipitated were alkali- and Fe-rich silicates, such as aegirine–augite and arfvedsonite, followed by bastnäsite, fluorite, barite, calcite, and monazite in the late stage. The REE minerals in the banded REE ores are mainly monazite, bastnäsite, and parisite (1–10 vol%) that overprinted gangue minerals, suggesting that REE mineralization occurred during the late hydrothermal stage. The sequence of mineral formation and their evolution caused progressive enrichment in REEs, F, Sr, and Ba. For example, fluorite in the banded REE ores has high concentrations of Sr (252–1910 ppm), Ba (1040–8230 ppm), and light REEs (1001–16,079 ppm), but is depleted in Nb and Ta. The bastnäsite is enriched in Sr (885–4046 ppm), Ba (1073–80,809 ppm), and ΣREEs (99,631–158,227 ppm). The fluorite, arfvedsonite, and bastnäsite in the banded REE ores have ɛNd(t) values of −3.68–1.78, −5.54, and 0.05, and initial (87Sr/86Sr)i (ISr) ratios of 0.70352–0.70478, 0.70620, and 0.70346, respectively. Based on these data, and the regional geological setting and Pb isotope data, it is proposed that fluorite and bastnäsite crystallized from ferrocarbonatite and fine-grained dolomite, and the REE source was a mixture of HIMU mantle and global marine sediments. We also suggest that the carbonatite- or dolomite-hosting ores in Bayan Obo formed by melting of the subcontinental lithospheric mantle, which might have been previously metasomatized by REE- and CO2-rich fluids derived from subducted marine sediments.

Behaviour of flotation tailings from a rare earth element deposit at high salinity

Various rare earth element (REE) deposits hosted by carbonatite complexes have been identified in southern (Montviel, Niobec) and northern Quebec (Eldor deposit). During the winter in Quebec, the use of road salts to facilitate transportation on the mine site and/or avoid water freezing during mine operation may be necessary. The sources of salinity can be diverse on a mine site: process water, precipitation, alteration of minerals in the soil. Thus, tailings may come in contact with these salts and react. The purpose of the present study was to evaluate the impact of salinity on the behaviour of flotation tailings (Eldor deposit), i.e. the mobility of the elements contained in the tailings under these conditions and the environmental risks involved. For this purpose, leaching column tests were developed. The solutions were deionized water (CW column), NaCl (25 g/L; CS1 column) and CaCl2 (25 g/L; CS2 column). The leachate analysis revealed that the divalent cations (Ba, Cd, Mg, Mn, Sr, and Zn) are more mobile in the presence of CaCl2 (CaCl2 > NaCl > deionized water). The mobility of these elements appears to be governed by the competition with Ca2+ for tailings sorption sites. U and Sc are most mobile in the presence of salts regardless of the applied salt solution, i.e. CaCl2 = NaCl > deionized water. The formation of soluble chloride complexes with these elements could therefore be the cause of this phenomenon. For S, the leaching solution has no impact on its mobility. In conclusion, the presence of salts would tend to increase the mobility of divalent cations present in these residues and enhance their contamination potential. Modeling using PHREEQC software allowed comparison of these results with post-dismantling mineralogical characterization. Both methods showed: (i) total dissolution of fluorite [CaF2], galena [PbS], richterite [Na(CaNa(Mg,Fe2+)5[Si8O22](OH)] and Ba silicate; (ii) precipitation of iron oxides/hydroxides and silicate minerals. However, the modeling was unable to predict the behaviour of carbonate minerals. Further modeling tests involving kinetics should be considered in a future study.

Zr-Rich Eudialyte from the Lovozero Peralkaline Massif, Kola Peninsula, Russia

The Lovozero peralkaline massif (Kola Peninsula, Russia) has several deposits of Zr, Nb, Ta and rare earth elements (REE) associated with eudialyte-group minerals (EGM). Eudialyte from the Alluaiv Mt. often forms zonal grains with central parts enriched in Zr (more than 3 apfu) and marginal zones enriched in REEs. The detailed study of the chemical composition (294 microprobe analyses) of EGMs from the drill cores of the Mt. Alluaiv-Mt. Kedykvyrpakhk deposits reveal more than 70% Zr-enriched samples. Single-crystal X-ray diffraction (XRD) was performed separately for the Zr-rich (4.17 Zr apfu) core and the REE-rich (0.54 REE apfu) marginal zone. It was found that extra Zr incorporates into the octahedral M1A site, where it replaces Ca, leading to the symmetry lowering from R3¯m to R32. We demonstrated that the incorporation of extra Zr into EGMs makes the calculation of the eudialyte formula on the basis of Si + Al + Zr + Ti + Hf + Nb + Ta + W = 29 apfu inappropriate.

The Autistic Brain Can Process Local but Not Global Emotional Information in Faces and Music

Tieshan complex body (TCB) is located in Zhenghe County on the border of Zhejiang and Fujian, covering an area of about 5.7 km2. Tieshan complex body (TCB) is the most developed metasomatised area in the southeast of China, which was misunderstood as a syenite intrusion.Much Study has carried on at Shizigang in the southwest of the TCB. The alkali metasomatites are composed of feldspar, pyroxene, amphibole, biotite and melanite et al. Potassic feldspars in Complex body have four kinds of forms and can be separated into three stages: (1) one in facial alkali alteration and one in alkali alteration with melanites, (2) one in light alkali feldspar veins, and (3) one in dark alkali feldspar veins and.Pyroxenes had three kinds of forms: some in breccias, some in feldspar and some accompanied with amphiboles. Amphiboles had two kinds of forms: in breccias and scatter in feldspars in the veins, its mineral compositions are composed of basaltic hornblende, ferrous pargasite, actinolite and ferroactinolite, all belong to calcic amphibole subgroup. Biotites are scattered in breccias and in the veins or which is the product of metasomatised pyroxenes. The compositions of biotites show low-Ti and Fe, but high-Mg, which were the thermal products of a higher oxygen fugacity. Melanites occurred as layers and belts, which were metasomatised by feldspars and epidotes and amphiboles and carbonates and sericites and diopsides, their ingredients are solid solution series between andradite and Grossular and reflect the melanites were formed in the relative oxidative, alkaline environment.X-ray powder diffraction and infrared spectrum analyses of K-feldspar from early alkali feldspar provide degrees of ordering of 0.71–0.80, structural parameters of 1.27–1.61, triclinicities of 0.23–0.29, T1 (o) + T1 (m) of 0.86–0.90 degrees of ordering of 0.67–0.88 from late K-feldspar, its structural parameters of 1.10–1.91, triclinicities of 0.30–0.70, T1 (o) + T1(m) of 0.84–0.93. Both two kinds of alkali feldspars are microcline, most adularia. Their structure temperatures vary from 200 to 370 °C which are the highest temperatures at which K-feldspars were formed. Thus, it is concluded the K-feldspars in Tieshan is originated from thermal fluid, and the fluid was potassium-rich and a little rich in sodium at the later stage.The 39Ar-40Ar age of feldspars shows 118.68 ± 7.70 Ma and 114.61 ± 6.74 Ma, which represent the ages of early stage facial alkali alteration and late stage dark alkali feldspar veins respectively. It is obvious that an original granites were formed at about 250 to 255 Ma, but all the rocks were considered to be strongly metasomatised by alkali fluid later, most occurred during 108–126 Ma in Yanshanism. Metasomatism of the TCB reflected that complex history of the region. The metasomatised rocks include fenite and amphibole feldsparite. Fenite, especially apatite-rich fenite is associated with REE mineralization, which is helpful to understand the mechanism of a large scale of rare earth deposits in the region.

Utopian Romantic Social Belief Recognition, Recognition, and Practice Self-Generation Mechanism

Tieshan complex body (TCB) is located in Zhenghe County on the border of Zhejiang and Fujian, covering an area of about 5.7 km2. Tieshan complex body (TCB) is the most developed metasomatised area in the southeast of China, which was misunderstood as a syenite intrusion.Much Study has carried on at Shizigang in the southwest of the TCB. The alkali metasomatites are composed of feldspar, pyroxene, amphibole, biotite and melanite et al. Potassic feldspars in Complex body have four kinds of forms and can be separated into three stages: (1) one in facial alkali alteration and one in alkali alteration with melanites, (2) one in light alkali feldspar veins, and (3) one in dark alkali feldspar veins and.Pyroxenes had three kinds of forms: some in breccias, some in feldspar and some accompanied with amphiboles. Amphiboles had two kinds of forms: in breccias and scatter in feldspars in the veins, its mineral compositions are composed of basaltic hornblende, ferrous pargasite, actinolite and ferroactinolite, all belong to calcic amphibole subgroup. Biotites are scattered in breccias and in the veins or which is the product of metasomatised pyroxenes. The compositions of biotites show low-Ti and Fe, but high-Mg, which were the thermal products of a higher oxygen fugacity. Melanites occurred as layers and belts, which were metasomatised by feldspars and epidotes and amphiboles and carbonates and sericites and diopsides, their ingredients are solid solution series between andradite and Grossular and reflect the melanites were formed in the relative oxidative, alkaline environment.X-ray powder diffraction and infrared spectrum analyses of K-feldspar from early alkali feldspar provide degrees of ordering of 0.71–0.80, structural parameters of 1.27–1.61, triclinicities of 0.23–0.29, T1 (o) + T1 (m) of 0.86–0.90 degrees of ordering of 0.67–0.88 from late K-feldspar, its structural parameters of 1.10–1.91, triclinicities of 0.30–0.70, T1 (o) + T1(m) of 0.84–0.93. Both two kinds of alkali feldspars are microcline, most adularia. Their structure temperatures vary from 200 to 370 °C which are the highest temperatures at which K-feldspars were formed. Thus, it is concluded the K-feldspars in Tieshan is originated from thermal fluid, and the fluid was potassium-rich and a little rich in sodium at the later stage.The 39Ar-40Ar age of feldspars shows 118.68 ± 7.70 Ma and 114.61 ± 6.74 Ma, which represent the ages of early stage facial alkali alteration and late stage dark alkali feldspar veins respectively. It is obvious that an original granites were formed at about 250 to 255 Ma, but all the rocks were considered to be strongly metasomatised by alkali fluid later, most occurred during 108–126 Ma in Yanshanism. Metasomatism of the TCB reflected that complex history of the region. The metasomatised rocks include fenite and amphibole feldsparite. Fenite, especially apatite-rich fenite is associated with REE mineralization, which is helpful to understand the mechanism of a large scale of rare earth deposits in the region.

Carbonatites and Alkaline Igneous Rocks in Post-Collisional Settings: Storehouses of Rare Earth Elements

The rare earth elements (REE) are critical raw materials for much of modern technology, particularly renewable energy infrastructure and electric vehicles that are vital for the energy transition. Many of the world’s largest REE deposits occur in alkaline rocks and carbonatites, which are found in intracontinental, rift-related settings, and also in syn- to post-collisional settings. Post-collisional settings host significant REE deposits, such as those of the Mianning-Dechang belt in China. This paper reviews REE mineralization in syn- to post-collisional alkaline-carbonatite complexes worldwide, in order to demonstrate some of the key physical and chemical features of these deposits. We use three examples, in Scotland, Namibia, and Turkey, to illustrate the structure of these systems. We review published geochemical data and use these to build up a broad model for the REE mineral system in post-collisional alkaline-carbonatite complexes. It is evident that immiscibility of carbonate-rich magmas and fluids plays an important part in generating mineralization in these settings, with REE, Ba and F partitioning into the carbonate-rich phase. The most significant REE mineralization in post-collisional alkaline-carbonatite complexes occurs in shallow-level, carbothermal or carbonatite intrusions, but deeper carbonatite bodies and associated alteration zones may also have REE enrichment.