Rare Metal Resources Research Articles

Indicator element selection and lithological mapping using deep learning methods in the Dahongliutan area, NW China

Rare metal resources are extensively used in the emerging energy field, making the security and sustainability of rare metal supply chains critical issues. Pegmatite-type rare metal deposits are a significant source of rare metal resources. Geochemistry is one of the most direct and effective methods of mineral exploration. In this study, whole-rock geochemical data from the Akesayi region, located in the Western Kunlun area of China, were used to identify the indicative elements of pegmatite automatically. Based on the stream sediment geochemical data, various deep learning models have been employed to achieve automatic lithological identification of the area. The results indicate that a novel interpretable model using SHapley Additive exPlanations (SHAP) and eXtreme Gradient Boosting (XGBoost) was employed to select indicative elements for the pegmatite in the Akesayi region, identifying Ta and Rb as key elements. The state-of-the-art application of deep-learning algorithms for lithological mapping has proven to be highly effective. Among the four approaches, the ensemble strategy integrating 1D convolutional neural networks, 2D3D convolutional neural networks, and dual-branch neural networks yields the best lithological mapping results. This approach resulted in a total classification accuracy of 90.422 %, an average accuracy of 90.502 %, a Kappa coefficient of 89.643 %, and a user accuracy of 65.530 % for the pegmatite lithological unit. These results demonstrate that the proposed model can provide robust technical support for the exploration of rare metal pegmatites in regions with challenging natural conditions and limited research.

Geochemistry of Middle Jurassic Coals from the Dananhu Mine, Xinjiang: Emphasis on Sediment Source and Control Factors of Critical Metals

In recent years, coal-type critical metal deposits have become a research hotspot in coal geology. As a major coal-accumulating basin in the Xinjiang area, the Turpan-Hami Basin contains abundant coal resources and has the potential to become a large coal-type critical metal deposit. However, previous studies on the enrichment characteristics of critical metal elements in coal are few and need further research. Based on SEM-EDS, XRF, and ICP-MS experiments, this study investigates the coal petrology, mineralogy, and geochemistry of the No. 22 coal of the Xishanyao Formation from the Dananhu Coal Mine, Xinjiang, to identify the sediment source, depositional environment, and controlling factors of the critical metal elements of the No. 22 coal. The results showed that the Dananhu coals are characterized by a low ash yield, low total sulfur content, high volatile yield, and high inertinite proportions. Quartz, kaolinite, and illite are the main minerals in the coal. Compared with the world’s low-rank coals, Ni, Co, Mo, and Ta are slightly enriched, Li, Rb, Cs, Ba, Tl, Bi, and Ge are depleted, and the concentrations of other trace elements are comparable to the average values of the world’s low-rank coals. The REY of the Dannanhu coals exhibited high fractionation, with its enrichment patterns characterized by the H-type and M-H-type. Although most of the critical metals are not enriched in the Dannanhu coals, the Ga, Zr (Hf), and Nb (Ta) concentrations in the coal ash of the Dannanhu coals have reached the economic cut-off grade and have the potential to be a substitute for rare metal resources. The terrigenous detrital sources of the Dannanhu coals mainly come from the Paleozoic dacite, andesite, and a small amount of granite from the Harik Mountain and Eastern Bogda Mountain in the Turpan-Hami Basin. The Dannanhu coals are generally in a dry and hot depositional environment, with high salinity and weak reduction-oxidation. The low source input and weak reduction-oxidation environment have resulted in low concentrations of critical metal of the No. 22 coal from the Dananhu Coal Mine.

Multiple-pulse magmatic intrusion and fluid metasomatism in Mesozoic Qianlishan rare metal granite, South China: Records from apatite geochemistry

South China block contains abundant rare metal resources that have widely been considered to be associated with highly evolved granitic magmatism and related fluid metasomatism. Here we perform detailed geochemical analyses on apatite and bulk rock from the ore-bearing granites (equigranular zinnwaldite granite) and ore-barren granites (porphyritic biotite granite and granitic dyke) at Qianlishan pluton, South China, to decipher the respective roles of magmatic and fluid processes and further understand the petrogenesis of rare metal granite (RMG). Apatites from both granite types are F-rich, displaying heterogeneous textures and large compositional variations in Cl, Sr, rare earth elements (REEs), Ga, Th, and U. Relative to the ore-barren granite, the apatites from ore-bearing granite contain lower Sr but higher ∑REE, Th + U and Ga, reflecting more evolved features. The oscillatory compositional zonation and bimodal O-Nd isotopic compositions in apatite from the ore-barren granite indicate multiple-pulse intrusion instead of other open-system processes such as magma mixing and/or crustal assimilation during magmatic evolution, while the additional occurrence of monazite and lower δ18O (< 8‰) in half of the apatite crystals from the ore-bearing granite require further influence of hydrothermal metasomatism. In combination with their high W + Sn concentrations and La tetrad effect in chondrite-normalized REE patterns, the ore-bearing granite experienced extensive metasomatism, during which the fluids in equilibrium with the metasomatic apatite were likely magmatic in origin. We therefore suggest that multiple-pulse magmatic intrusion and fluid metasomatism are two predominant factors during the formation of highly evolved RMG, such as the Qianlishan pluton in South China. Our results demonstrates that apatite geochemistry can be a potential approach to monitoring the magmatic evolution and fluid metasomatism during rare metal mineralization.

Environmental impacts of shallow water mining in the Baltic Sea

The discovery of rare metal resources in international waters has raised seabed mining claims for large areas of the bottom. There is abundant scientific evidence of major negative consequences for the maritime environment, such as the destruction of natural landforms and the fauna that depend on them, as well as the production of enormous silt plumes that disrupt aquatic life. This study investigated the environmental risks of seabed mining for metal resources in the Baltic Sea using a combination of hydrodynamic, particle-tracking, and sediment-transport models. The models were applied for ten years i.e., 2000-2009 under prevailing conditions to simulate seabed mining operations. The focus was on sediment concentration near the seabed and its spread. The mean background concentrations were low with small seasonal bed-level variations throughout the Baltic Sea Basin. Late summer and early autumn periods were the most active. Seabed mining significantly alters the dynamics of sediment suspensions and bed level variations. The concentrations increase unsustainably to high levels, posing a serious threat to the ecological health of the Baltic Sea. The Gotland basins in the Baltic Sea are the most susceptible to mining. The bed level variations will be ten-fold, exposing the highly contaminated sediments at the seabed to the flow. In less than a year, 30-60% of the total particles released in each basin reached the thermocline layers. This study suggests that seabed mining in the Baltic Sea is not sustainable.

Mechanism of Tungsten Recovery from Spent Cemented Carbide by Molten Salt Electrodeposition

The accumulation of spent carbide (YG8), not only pollutes the environment but also causes waste of tungsten, cobalt and other rare metal resources. To better address this issue, we proposed a combined electrochemical separation process of low-temperature aqueous solution and high-temperature molten salt for tungsten and cobalt. H&lt;sub&gt;2&lt;/sub&gt;WO&lt;sub&gt;4&lt;/sub&gt; was obtained from spent carbide in an aqueous solution, and we calcined it to obtain WO&lt;sub&gt;3&lt;/sub&gt;, which was used as a raw material to obtain tungsten by using molten salt electrodeposition. The influence of the current efficiency and the electrochemical behavior of the discharge precipitation of W(VI) were also studied. The calcination results showed that the morphology of WO&lt;sub&gt;3&lt;/sub&gt; was regular and there were no other impurities. The maximum current efficiency of 82.91% was achieved in a series of electrodeposition experiments. According to XRD and SEM analysis, the recovered product was high purity tungsten, which belongs to the simple cubic crystal system. In the W(VI) reduction mechanism experiments, the electrochemical process of W(VI) in NaCl-Na&lt;sub&gt;2&lt;/sub&gt;WO&lt;sub&gt;4&lt;/sub&gt;-WO&lt;sub&gt;3&lt;/sub&gt; molten salt was investigated using linear scanning voltammetry (LSV) and chronoamperometry in a three-electrode system. The LSV showed that W(VI) was reduced at the cathode in two steps and the electrode reaction was controlled by diffusion. The fitting results of chronoamperometry showed that the nucleation mechanism of W(VI) was an instantaneous nucleation mode, and the diffusion coefficient was 7.379×10&lt;sup&gt;−10&lt;/sup&gt; cm&lt;sup&gt;2&lt;/sup&gt;·s&lt;sup&gt;−1&lt;/sup&gt;.

Effective delineation of rare metal-bearing granites from remote sensing data using machine learning methods: A case study from the Umm Naggat Area, Central Eastern Desert, Egypt

Albitized granite (ABG) is considered as one of the most significant hosts of rare metals (RMs). Consequently, adequate recognition of ABG through proper lithological discrimination highly increases the targeting of rare metal resources. In order to delineate outcrops of ABG from satellite data, our study integrates eight image enhancement techniques, including optimum index factor, false color composites, band rationing, relative band depth, independent component analysis, principal component analysis, decorrelation stretch, minimum noise fraction transform, and spectral indices ratios, for the interpretation of ASTER and Sentinel-2 (S2) datasets. This integrated approach allows the effective discrimination of AGB outcrops in the Umm Naggat area, Central Eastern Desert, Egypt. The interpretation maps derived from these integrated image processing techniques were systematically verified in the field and formed the base for the feature selection process (i.e., training and testing data delineation) of different lithologies supported by the support vector machine algorithm (SVM). In order to produce a high‐quality lithological interpretation map, SVM was applied to Sentinel-2, ASTER, and combined ASTER-S2 datasets. The fused ASTER-S2 classification properly delineates ABG, as verified by our field investigations and confirmed by previous geological maps. Furthermore, comprehensive structural analysis (lineaments extraction and their density map) and hydrothermal alteration detection were performed to check the spatial association between the distribution of ABG, higher density zones, and highly altered areas, that in turn, could shed light on new potentially mineralized zones and proposed exploration targets. Our study reveals new ABG occurrences mainly situated in the southern and southwestern parts of the study area, and it confirms the location of known mineralized zones in the northern part of the Umm Naggat region. The distribution of ABG and its spatial correlation with alteration and high structural density zones suggest that rare‐metal mineralization is mostly structurally controlled (NW, NNW, NNE, and N-S), demonstrating the higher possibility of metasomatic enrichment of rare-metals within the study area. Our study provides an updated geological map of the study area based on the SVM‐supported interpretation of ASTER-S2 data. Importantly, the results reveal a high exploration potential for rare‐metal mineralization at Umm Naggat and defining new anomalies for follow‐up work by geochemical soil surveys.

Electrochemical Mechanism of the Preparation of High-Purity Indium by Electrodeposition.

Indium is a crucial material and is widely used in high-tech industries, and electrodeposition is an efficient method to recover rare metal resources. In this work, the electrochemical behavior of In3+ was investigated by using different electrochemical methods in electrolytes containing sodium and indium sulfate. Cyclic voltammetry (CV), chronoamperometry (CA), and alternating current impedance (EIS) techniques were used to investigate the reduction reaction of In3+ and the electrocrystallization mechanism of indium in the indium sulfate system. The cyclic voltammetry results showed that the electrodeposition process is irreversible. The average charge transfer coefficient a of In3+ was calculated to be 0.116 from the relationship between the cathodic peak potential and the half-peak potential, and the H+ discharge occurred at a higher negative potential of In3+. The nucleation mechanism of indium electrodeposition was analyzed by chronoamperometry. The mechanism of indium at potential steps of −0.3 to −0.6 V was close to diffusion-controlled instantaneous nucleation with a diffusion coefficient of 7.31 × 10−9 cm2 s−1. The EIS results demonstrated that the reduction process of In3+ is subject to a diffusion-controlled step when pH = 2.5 and the applied potential was −0.5 V. SEM and XRD techniques indicated that the cathodic products deposited on the titanium electrode have excellent cleanliness and purity.

Mineralogical Characteristic and Beneficiation Evaluation of a Ta-Nb-Li-Rb Deposit

In order to rationally develop and utilize a Ta–Nb–Li–Rb rare metal deposit in Jiangxi Province, the mineralogical characteristics of the ore, such as chemical composition, mineral composition, modes of occurrence of major elements, and dissemination characteristics of major minerals, were investigated in detail based on optical microscopy analysis, chemical analysis, X-ray diffraction analysis, artificial panning, mineral liberation analysis, and electron probe microanalysis. The results reveal that the main useful elements in the ore are tantalum, niobium, lithium, and rubidium. Niobium and tantalum are mainly found in the mineral form of columbite. Columbite has particle sizes ranging from 0.5 mm to 0.012 mm, with the most common sizes being 0.3 to 0.044 mm. Intergranular dispersion accounts for 73.92% of the embedding in columbite, whereas inclusions account for 26.08%. Lithium is found mostly in zinnwaldite, while rubidium is found primarily in feldspar and zinnwaldite, both in a homogenous distribution. The beneficiation evaluation of this ore was conducted based on the mineralogical characteristic, and it indicates that the tantalum-niobium–lithium–rubidium rare metal resources, as well as the feldspar and quartz non-metallic resources in the ore, can be effectively and comprehensively recovered using gravity, magnetic, and flotation separation methods. A staged grinding and separating process was adopted which could produce tantalum–niobium mineral concentrates (18.34% Ta2O5 at a recovery of 47.65% and 41.33% Nb2O5 at a recovery of 69.96%), zinnwaldite concentrate (2.41% Li2O and 0.80% Rb2O at a recovery of 81.82%) and other concentrates such as cassiterite, topaz, galena, sphalerite, and feldspar. This study provides suggestions for the rational development and utilization of the deposit and provides a reasonable level of recovery prediction.

Mineral prospectivity mapping based on wavelet neural network and Monte Carlo simulations in the Nanling W-Sn metallogenic province

The Nanling Range in South China is endowed with abundant W-Sn and other important rare metal resources associated with granitic intrusions, but the rate of new major mineral discoveries has been drastically diminished over the last decades. Data-driven mineral prospectivity mapping (MPM) using machine learning is emerging as a powerful tool in support of mineral exploration targeting at regional or camp scale. However, MPM based on supervised learning faces some general problems, notably including subtle information obscured in exploration data and imbalanced training samples. In this paper, we proposed a novel ensemble scheme for MPM using wavelet neural network (WNN) and Monte Carlo simulation (MCs) to address the forementioned issues. Specifically, the purpose of using WNN based on multiscale wavelet analysis is to capture weak or hidden (geophysical and geochemical) information caused by concealed ore deposits, while an undersampling MCs (UMCs) algorithm is employed to assess uncertainties caused by data imbalance and lessen its impact on MPM. Subtle (weak and mixing) information related to concealed mineralization, including geophysical and geochemical anomalies, were extracted using wavelet analysis at first, and then a dozen of predictive evidences was integrated based on WNN using UMCs for producing a W-Sn perspectivity map. The results suggest that WNN has a higher prediction accuracy (∼90%) in comparison to the artificial neural network (ANN) (∼85%). Moreover, the improved AUC value (∼0.9) of WNN based on UMCs compared to the classic ANN (∼0.82) and WNN (∼0.85) suggests that the proposed ensemble algorithm improves the geological generalization of machine learning. Revisiting WNN predictions by uncertainties produced more sharply focused exploration targets of W-Sn deposits (covering ∼5% of the study area). The resulting predictive map provides important clues of W-Sn deposit occurrences which could guide and stimulate future mineral exploration in the Nanling Range.

RECOGNITION OF A 600-KM-LONG LATE TRIASSIC RARE METAL (Li-Rb-Be-Nb-Ta) PEGMATITE BELT IN THE WESTERN KUNLUN OROGENIC BELT, WESTERN CHINA

AbstractThe rising demand of strategic metals, especially lithium, necessitates discovery of new resources to meet the global supply chain. Recently, several pegmatite-hosted rare metal (Li-Rb-Be-Nb-Ta) deposits have been discovered in the Western Kunlun orogenic belt, making it a new world-class rare metal resource (estimated ~7 Mt Li2O and 0.16 Mt BeO). Understanding the metallogenesis of this belt is critical to further evaluate the rare metal potential. In this study, columbite-tantalite (coltan) and monazite from rare metal pegmatites and zircon from potential parental granites were collected from five representative rare metal pegmatite deposits in the western, middle, and eastern parts of the Western Kunlun orogenic belt for U-Pb geochronology. The results indicate that despite the distances of the sampling localities in different parts of the Western Kunlun orogenic belt, the ages of pegmatite-hosted rare metal mineralization fall in a narrow range of ca. 208–204 Ma. These rare metal pegmatites are temporally and spatially related to adjacent postorogenic granites emplaced following the closure of the Paleo-Tethys Ocean. The compositional characteristics of K-feldspar, biotite, and muscovite of the granites and pegmatites, along with regional mineralogical and textural zonation of the pegmatites, suggest that the rare metal pegmatites were derived from the volumetrically much more important, highly fractionated granitic intrusions. We propose that, in combination with the data from previous studies, the 218–204 Ma interval represents a newly recognized rare metal metallogenic period linked with granitic intrusions in the Western Kunlun orogenic belt, revealing a 600-km-long late Triassic rare metal pegmatite belt composed of multiple ore fields formed in a similar metallogenic setting. These results emphasize the importance of identifying fertile, Late Triassic to Early Jurassic granitic intrusions for rare metal pegmatite exploration. Furthermore, combined with recent studies on the Songpan-Ganzi rare metal pegmatite belt along the eastern segment of the Paleo-Tethys, this study further highlights the great potential of rare metal resources in this global tectonic zone.

Multielement biogeochemistry and lithium isotopic composition of the dominant plants at the Jiajika mine, western Sichuan, China - The largest hard rock-type lithium mine in Asia

To comprehensively study the multielement and Li isotope geochemistry at the largest hard rock-type lithium (Li) mine in Asia, a large number of root and shoot (77 sets and 154 pieces) samples of the dominant plants were collected at the Jiajika mine for the first time. The concentrations of 37 trace elements (Li, Be, Nb, Ta, Rb, Cs, Sr, Zr, Hf, Sn, U, Cd, As, Pb, Cu, Cr, Zn, Mn, Co, Ni, Mo, W, Y, and La series without Pm) in 154 plant samples were determined via inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, Li isotopic compositions were determined for 9 groups of soil-root-shoot samples via multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed that 1) the dominant plants from mining-related areas had markedly higher mineralization-related element (Li, Be, Nb, Ta, Rb, Cs, Sr, Zr, Hf, Co, Ni, Mo, W, Sn, and U) and rare earth element (REE) (except for Tm and Lu) concentrations than those from non-mining-activity areas; 2) the Cr concentrations of 60 shoot samples exceeded the Chinese hygienic standard for pasture forage by 1.054–19.74 times; 3) based on the BTF (biological translocation factor) values of trace elements, the translocation of trace elements, excluding Ta, Rb, Cs, Sr, Zr, and Cd, was restrained in tailing-affected areas. Furthermore, the excessive accumulation of 31 trace elements (except for Ta, Cs, Sn, U, Cd, and Zn) in the roots could also inhibit the root-shoot translocation of corresponding trace elements; and 4) the δ7Li ranges of the roots, shoots, and corresponding soils of the dominant plants at the Jiajika mine were approximately −6.12 to −0.84‰, approximately −4.84 to 2.02‰, and approximately −5.34 to 3.42‰, respectively. Compared with the roots, the shoots of rhododendron plants showed obvious enrichment in 7Li. The results of this study have some implications: high concentrations of 15 mineralization-related elements and 13 REEs in plants could be regarded as plant indicators of rare metal resources; the Cr concentrations in plants should be given more attention and closely monitored in the future to ensure forage safety; and the mechanism of Li isotope fractionation in plants may be controlled by ambient temperature, but further study and verification are needed.

Prospect for expansion and replenishment of rare metal resources and reserves in Eastern Kazakhstan

The main rare metal-bearing structures in Eastern Kazakhstan are granitoid belts formed in the Hercynian cycle of tectogenesis in the post-collisional (orogenic) geodynamic environment of the Permian time and confined to the continental blocks of siallitic high-level. The geotectonic position of the Kalba&ndash;Narym rare metal granitoid belt in the geological structure of the Greater Altai is considered. The known rare-metal pegmatite deposits (Ta, Nb, Be, Li, etc.) are spatially and genetically related to Kalba granites (P1). The richest ore-bearing are granite massifs formed in the mobile tectonic environment and under unbalanced P&ndash;T conditions. The distribution of rare alkalis in granitoids of the Hercynian evolutionary series is given. The forecast estimate of prospects is associated with the study of hidden granite massifs on the northwestern flank of the belt, identified based on the geological and geophysical data. The forecasting criteria are the intensive alteration of the above-intrusive zone (granitization, greisenization, silicification), direct signs of tin&ndash;tungsten mineralization on ground surface, identification of ongonite-like dikes and rare metal minerals in metasomatites from the results of electron microscopy. The estimation of the prospects of nontraditional tin&ndash;lithium&ndash;tantalum mineralization associated with albitized and greisenized granites is given. It is recommended to undertake deep mineralogical mapping of the closed reserved areas. The further geological exploration should be aimed at expansion of mineral resources and reserves for rare metal production.The study was supported by the Committee of Science of the Ministry of Education and Science of the Republic of Kazakhstan, Contract No. 120 dated 1 June 2020, Registration No. 0120RK00135, and Grant IRN AR08856325.

Promotional effect of embedded Ni NPs in alginate-based carbon toward Pd NPs efficiency for high-concentration p-nitrophenol reduction

Noble metal-based catalytic material with maximum utilization is of prime attraction for conserving rare metal resources. Herein, highly dispersion Ni nanoparticles (NPs)-modified N-doped mesoporous carbon material (Ni-N@C) was fabricated by pyrolysis of Ni2+/Histidine cross-linked alginate hydrogels. In a step forward, the obtained Ni-N@C nanocatalyst was treated by the solution of Pd2+, and tiny amount of Pd NPs were deposited on the surface of Ni via the reducibility of Ni to achieve the high dispersion of precious metals material. In the degradation of highly-concentration p-nitrophenol, the catalyst presents excellent performance which could completely degrade pollutants within a very short period. It was demonstrated that pre-embedded Ni NPs could not only increase the efficiency of Pd NPs but also endow the facile separation characteristic to the catalyst. Besides, the catalyst maintained favorable catalytic capacity even after five reaction cycles. In brief, this work may provide novel guidance for the maximum utilization of noble metal-modified mesoporous N-doped carbon-supported catalysts in practical applications of industrial and the treatment highly-concentration p-nitrophenol.

Enrichment of REE and HFSE during the magmatic-hydrothermal evolution of the Baerzhe alkaline granite, NE China: Implications for rare metal mineralization

The Baerzhe Cretaceous (123.7 ± 0.9 Ma) peralkaline pluton underwent extensive fractional crystallization and extreme enrichment in incompatible elements including rare earth elements (REE) and the high field strength elements (HFSE). It is one of the largest resources of rare metals in China, containing approximately 100 million tons of ore with an average grade of 1.84 wt% ZrO2, 1.00 wt% REE2O3 (34% heavy rare-earth oxides), and 0.26 wt% Nb2O5. Zr, REE and Nb are mainly hosted by hydrothermal minerals, such as zircon, hingganite-(Y), monazite-(Ce), polycrase, pyrochlore, fergusonite and columbite. An integrated investigation of field geology, mineral textures and compositions of minerals and host granites was carried out to examine the evolution of the Baerzhe pluton and the roles of magmatic and hydrothermal processes in concentrating REE and HFSE. Most minerals in the intensively altered subsolvus granite show secondary textures or replaced pseudomorphs, such as the replacement of arfvedsonite by aegirine, zircon dissolution and reprecipitation, and the replacement of monazite-(Ce) and polycrase-(Y) by hingganite-(Y). Compositions of the key economic minerals and changes with respect to these alteration stages reveal evidence that hydrothermal alteration played a role in the mineralization of the pluton. In-situ analyses and element mappings suggest that large volume of metals were remobilized and redistributed during hydrothermal replacement, such as the replacing of monazite-(Ce) and polycrase by hingganite-(Y). It is suggested that subsolidus re-equilibration and hydrothermal alteration, in addition to magmatic fractionation, is critical for further concentrating REE and HSFE in peralkaline granitic systems.

The igneous petrogenesis and rare metal potential of the peralkaline volcanic complex of the southern Peak Range, Central Queensland, Australia

The Oligocene Peak Range Volcanics (PRV) of central Queensland have intruded through, and erupted onto, Permian sedimentary rocks of the Bowen Basin above what is likely to be a lithospheric-scale suture zone. The southern PRV consists of domes and flows of augite (bearing) trachyte, hornblende trachyte, hornblende rhyolite, arfvedsonite rhyolite and aegirine rhyolite. The aegirine rhyolite bodies represent the most evolved rock types, with peralkaline index (molar Na + K/A) values of >1.3 and extreme enrichment in trace elements, including the rare metals Zr, Hf, Nb, Ta, and REE. Clarrys Dome, one of three aegirine rhyolite domes, features a late stage magmatic agpaitic assemblage of dalyite (K2ZrSi6O15), a eudialyte-like mineral and aegirine, which is variably replaced and overprinted by secondary REE carbonates and Zr silicates.Major and trace element geochemistry are used to show that the suite of PRV rock types represent a fractionation sequence from the least evolved augite trachytes to the most evolved aegirine rhyolites. This rock type range can be modelled by extended alkali-feldspar-dominated fractional crystallisation of an alkali basalt parental melt at a shallow crustal levels. Initial εNd values across the range of rock types are between +3 to +4, which is consistent with a common mantle source. Thus, the extreme trace element enrichment and high peralkalinity of the aegirine rhyolites is the product of the extended fractionation of a melt formed by low-degree partial melting of a mildly depleted mantle source. The secondary ore mineral assemblage and REE redistribution observed in the core of Clarrys Dome is interpreted to be due to a combination of hydrothermal alteration by fluids derived from subjacent devolatilising magma bodies, and late-stage weathering.The extreme enrichment of rare metals in the aegirine rhyolite bodies in the southern PRV support their potential to represent low grade, but large tonnage (100 s of Mt) resources of rare metals. Clear evidence of hydrothermal alteration across the region also raised the potential that higher grade rare metal mineralisation produced by hydrothermal activity may exist in the region.

Comparison of method and performance in tantalum coating prepared by molten salt electroplating and glow infiltration

Tantalum as a rare refractory metal is mainly used for temperature-resistant and wear-resistant surfaces of rocket engines and aerospace structures. In this paper, two preparation methods of metal tantalum coating were discussed, and the performance testing and application of the coating were studied. The results show the thickness of tantalum coating (S-Ta coating) formed by glow infiltration method is about 12 μm, the grain growth of coating is compact and the bonding strength with the matrix is about 65 N. The thickness and bonding strength of the S-Ta coating are better than those of the tantalum coating (D-Ta coating) obtained by molten salt electroplating method. The two coatings mainly exist in α-Ta phase and the crystal plane (211) preferred orientation appears. Compared with the matrix, the wear resistance and friction reduction of two coatings are obviously improved at room temperature. The friction coefficient is further reduced by 42% and 57%, and the wear rates are 2.65 × 10−4 and 2.45 × 10−4 mm3/N·m respectively, with the combination of tantalum and oxygen to form a self-lubricating oxide (Ta2O5) at 600 °C. Tantalum can be used as high temperature protective coating material to achieve sustainable development of rare metal resources by reducing costs and improving performance.

Dual Control of Depositional Facies on Uranium Mineralization in Coal‐bearing Series: Examples from the Tuanyushan Area of the Northern Qaidam Basin, NW China

AbstractThe uranium deposits in the Tuanyushan area of northern Qaidam Basin commonly occur in coal‐bearing series. To decipher the U‐enrichment mechanism and controlling factors in this area, a database of 72 drill cores, including 56 well‐logs and 3 sampling wells, was examined for sedimentology and geochemistry in relation to uranium concentrations. The results show that coal‐bearing series can influence uranium mineralization from two aspects, i.e., spatial distribution and dynamic control. Five types of uranium‐bearing rocks are recognized, mainly occurring in the braided river and braided delta sedimentary facies, among which sandstones near the coals are the most important. The lithological associations of sandstone‐type uranium deposits can be classified into three subtypes, termed as U‐coal type, coal‐U‐coal type, and coal‐U type, respectively. The coal and fine siliciclastic rocks in the coal‐bearing series confined the U‐rich fluid flow and uranium accumulation in the sandstone near them. Thus, the coal‐bearing series can provide good accommodations for uranium mineralization. Coals and organic matters in the coal‐bearing series may have served as reducing agents and absorbing barriers. Methane is deemed to be the main acidolysis hydrocarbon in the U‐bearing beds, which shows a positive correlation with U‐content in the sandstones in the coal‐bearing series. Additionally, the δ13C in the carbonate cements of the U‐bearing sandstones indicates that the organic matters, associated with the coal around the sandstones, were involved in the carbonation, one important component of alteration in the Tuanyushan area. Recognition of the dual control of coal‐bearing series on the uranium mineralization is significant for the development of coal circular economy, environmental protection during coal utilization and the security of national rare metal resources.

Detection Technology of Metal Elements in Crude Oil and Prospect of Utilization of Metal Resources

There are many kinds of metals in crude oil. The rare metals are essential metals for the development of atomic energy, aviation and space, national defense construction, electronic computer, high point scientific instruments and so on. Although the resources of rare metals are abundant in China, but for a long time, china supplies 90% of the world's rare metals at a relatively low price, the reserves of rare metal resources are declining at an alarming rate. By 2020, only 6 of the 45 major minerals could meet the needs of China. Through the establishment of metal element detection technology in crude oil, the crude oil of Toutai Oil Field in China is determined, and there are rich rare metal elements in the crude oil. For example, the rare-earth metal content is 62.61 micrograms per kilogram, the rare light metals is 78.4 micrograms per kilogram, and the rare refractory metals is 290.47 micrograms per kilogram, etc. Although the research on the prospect of comprehensive utilization of rare metals in crude oil is late in China, the extraction of rare metals from crude oil has a broad prospect.

Bottlenecks in rare metal supply and the importance of recycling – a Japanese perspective

ABSTRACTRare metals are less common metals that are generally perceived to be scarce. The media often presents one-track thinking on the depletion of mineral resources. Despite this common notion, the supply of most rare metals – including rare earth metals (REMs) – in terms of the amount of minerals available in known deposits is not a serious problem. Key factors that determine the supply of rare metals are the costs of mining and smelting, and related environmental destruction. These are the major practical constraints, rather than the amount of mineral deposits in the earth. When extracting rare metals from recycled feed material, harmful wastes generated from natural ore processing can be avoided. This is the primary advantage of the cyclical use of rare metal resources. In this article, bottlenecks of rare metal supply, and the importance of recycling, are discussed, using REMs as an example.

Research progress in biohydrometallurgy of rare metals and heavy nonferrous metals with an emphasis on China

In the past decade, progress in the field of biohydrometallurgy had been significant. A total of 17 novel biomining microorganisms were discovered, and eight copper heap bioleaching plants and 11 gold biooxidation plants were established or expanded. In this review, it was summarized the physiological properties of the newly isolated biomining microorganisms and three novel microbial ecological methods for studying microbial community dynamics and structure. In addition, biohydrometallurgy research on rare metals such as uranium, molybdenum, tellurium, germanium, indium, and secondary rare metal resources, as well as heavy nonferrous metals such as copper, nickel, cobalt, and gold has been reviewed, with an emphasis on China. In future, further studies on bioleaching of chalcopyrite, rare metals, secondary resources from waste, and environmental pollution caused by resource utilization are necessary. Zijinshan heap bioleaching plant restarted operation in 2012 with capacity of 30,000 ton·year−1. The average copper grade is 0.308 %. The ore particle size is 40 mm accounting for 80 %. The heap height is 8 m. The solution pH is controlled at 1.5–1.7, and redox potential is maintained at 730–760 mV. After 185 days leaching, copper leaching rate of more than 76 % and iron leaching rate of <6 % are achieved.