High Concentrations Of Rare Earth Elements Research Articles

Distribution, source and contamination of rare earth elements in sediments from lower reaches of the Xiangjiang River, China

Rare earth elements (REEs) are emerging micropollutants in aquatic environments. In this study, concentrations of REEs and major elements, and mineralogical compositions of sediments from lower reaches of the Xiangjiang River (China) were analyzed using ICP-MS technique. The results suggested that sediments were characterized by terrigenous compositions TiO2, SiO2, Al2O3, K2O, Na2O and P2O, and contained high concentrations of REEs with mean total REE concentrations (∑REE) of 318.7 mg/kg. REEs were moderately enriched in upper river sediments, and slightly or less enriched in downriver sediments. The normalized REE distribution pattern for sediments was characterized by flat shalelike and Eu depleted V-shape REE patterns, which indicated REEs in sediments were lithologically contributed from sedimentary rocks and granites distributed in the watershed respectively. REEs in sediments were hosted mainly in Fe–Mn oxides, and sulfide and organic matters that were characterized by middle REEs (MREE) enrichments relative to light REEs (LREE) and heavy REEs (HREE), and the distribution and differentiation of REEs in sediments were controlled by clays, Fe–Mn oxides, organic matters and finer grains; and also by accessory minerals (e.g., zircon) from granite. The distribution features of REEs in sediments and BCR extraction results suggested that the sediment REE enrichment resulted from additional REE input from anthropogenic sources, including those in discharges from sulfide-ore smelting industries at Zhuzhou city and from phosphate fertilizer plants at Xiangtan city along the river. Thus, sediments were contaminated with REEs in moderate degree in upper river area, and REE contamination was then formed by superimposing anthropogenic REEs on lithological residues. Finally, concentrations of Ce > 100 mg/kg, Gd > 8.12 mg/kg, ∑REE >274.9 mg/kg, ∑LREE >252.3 mg/kg and ∑HREE >28.8 mg/kg here were recommended as the REE contamination levels that represented as REE indices for identifying and rating REE contamination in this mining impacted river.

Geochronology, geochemistry, and Sr–Nd–C–O isotopic composition of the Qieganbulake carbonatites at the northeastern margin of the Tarim Craton, northwest China

Carbonatites are the predominant source of rare earth element (REE) resources globally, but their origins and petrogenesis remain unclear. Currently, >600 carbonatites have been found worldwide, but only a few (<14%) of these carbonatites contain REE deposits. Some carbonatites are rich in REEs but do not host high-grade REE deposits. The Qieganbulake carbonatites at the northeastern margin of the Tarim Craton, China, are ideal for investigating why some carbonatites do not host REE mineralization. We undertook a detailed petrographic, geochronological, and isotopic study of the Qieganbulake carbonatites. In previous studies, a carbonatite at Qieganbulake was dated to ca. 811 Ma. However, in this study, ages of ca. 926 Ma were obtained for phlogopite and baddeleyite in carbonatite dykes rather than pyroxenites or phlogopitelites-bearing carbonatite complex. Such ages of ca. 926 Ma are consistent with a previously published apatite U–Pb age. 40Ar/39Ar dating of phlogopite yielded a plateau age of 928 ± 17 Ma and secondary ion mass spectrometry U–Pb dating of baddeleyite yielded a concordia age of 926 ± 8 Ma, implying the carbonatite was emplaced at ca. 926 Ma. Laser ablation–inductively coupled plasma–mass spectrometry U–Pb dating of monazite yielded a 206Pb/238U intercept age of 811 ± 27 Ma, indicating that the main REE mineralization stage was coeval with later carbonatite emplacement at ca. 811 Ma. The studied Qieganbulake calcio-carbonatite samples are REE-rich (864–1495 ppm) and consist of calcite (62.18–93.92 vol%), apatite (1.10–24.82 vol%), dolomite (0.37–10.48 vol%), and lesser amounts of phlogopite, olivine, monazite, magnetite, and vermiculite. The calcite, apatite, and monazite (<1 vol%) have REE contents of 757–1111 ppm, 5127–11,556 ppm, and 45.35–59.88 wt%, respectively, and account for the high REE contents of the carbonatites (883–1539 ppm). The small amount of monazite in this carbonatite suggests it is a prospective rather than a confirmed ore deposit. Petrographic studies, oxygen values of 5.74 and 7.51 ‰ and characteristics of trace element for apatites with less monazite around suggest they have magmatic origin with less alteration. The 926 Ma Qieganbulake carbonatite has high Sr isotope ratios (0.70580–0.70639) and negative εNd(t) values (−7.6 to −11.8), indicative of an enriched mantle source. δ13CPDB and δ18OVSMOW values of the carbonatites vary from –3.3‰ to –4.1‰ and 9.7‰ to 12.0‰, respectively, indicative of a contribution from recycled crustal C that was probably derived from a subducted oceanic slab. Above characteristics of carbonatite with ∼926 Ma are different with those of carbonatite occurred at ∼811 Ma, suggesting two carbonatite emplacements in Qieganbulake. Based on our results and the regional geology, we infer that the 926 Ma Qieganbulake carbonatite was derived by partial melting of a subcontinental lithospheric mantle source that had been metasomatized by early Neoproterozoic subduction during circum-Rodinia subduction in the northern Tarim Craton. Early crystallization of apatite sequestered the REEs, resulting in limited REE mineralization. In addition, the limited hydrothermal alteration and ligands available, such as F− and SO42−, hindered REE transportation and precipitation.

CONSUMPTION OF MINE WATER BY WILD UNGULATES IN THE SOURCES OF THE USSURI RIVER, ON THE TERRITORY OF THE NATIONAL PARK «CALL OF THE TIGER»

Link for citation: Panichev A.M., Baranovskaya N.V., Aramilev V.V., Chekryzhov I.Yu., Vakh E.A., Vetoshkina A.V., Lutsenko T.N., Strepetov D.A. Consumption of mine water by wild ungulates in the sources of the Ussuri river, on the territory of the national park «Call of the tiger». Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 7, рр. 111-121. In Rus. The relevance of the study is determined by the need to clarify the reason for the use of mineralized water by wild animals, which is typical for many areas of the world. The new knowledge is closely related to the geophagy problem, the solution of which opens a wide prospect of fundamental research in the fields of landscape biogeochemistry, ecology and medicine. Purpose: to study chemical composition of the mineralized mine water in the lake located on the territory of the out-of-operation tin-polymetallic ores concentrator dump in the upper Ussuri river which is being consumed actively by wild ungulates; to reveal number of animal visitors to the lake during an annual cycle; to reveal the reason of mine water consumption. Objects: ungulates visiting the lake with mine water; lake water and bottom sediments. Methods: estimation of visitation of the mine lake by animals by means of photographic traps; chemical composition determination: inductively coupled plasma mass spectrometry (ICP-MS) (Agilent 7700x spectrometer, Agilent Techn., USA); atomic emission spectrometry (spectrometer iCAP 7600 Duo); ion chromatography (LC-20 ion-liquid chromatograph, Shimadzu, Japan). Results. It was revealed that animals come to the lake uniformly throughout the year, except for the winter period, when the water is covered by a thick layer of ice. In high concentrations trace elements were found, including both elements with high toxicity (Cd and Pb) exceeding MAC for drinking water from 20 to 80 times and essential elements such as Fe, Mn, Cu, Zn, Co, Cr, Ni, Se, Li, which concentration either does not exceed MPC or exceeds it insignificantly. The concentration of REE, especially of the light subgroup, is also very high. The reason for mine water consumption by animals, most likely, is the high concentration of rare-earth elements of the light subgroup in it.

Exploitation alters microbial community and its co-occurrence patterns in ionic rare earth mining sites

The exploitation of ion-adsorption rare earth elements (REEs) deposits results in serious ecological and environmental problems, which has attracted much attention. However, the influences of exploitation on the prokaryotic communities and their complex interactions remain poorly understood. In the present study, bacterial and archaeal communities, as well as ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), in and around REEs mining area were investigated through high throughput sequencing and quantitative polymerase chain reaction (qPCR). Our results indicated that mining soil was characterized by poor soil structure, nutrient deficiency, and high concentrations of residual REEs. Oligotrophic bacteria (e.g., Chloroflexi and Acidobacteriota) were dominant in unexploited soil and mining soil, while copiotrophic bacteria (Proteobacteria and Actinobacteriota) were more abundant in surrounding soil. Nutrient was the key factor affecting microbial variation and abundance in mining soil. The bacterial community was more sensitive to REEs, while the archaeal communities were relatively stable. As the key members for ammonia oxidation, AOA outnumbered AOB in all the soil types, and the former was significantly influenced by pH, nutrients, and TREEs in mining soil. The microbial co-occurrence network analysis demonstrated that exploitation significantly influenced topological properties, decreased the complexity, and resulted in a much unstable network, leading to a more fragile microbial ecosystem in mining areas. Notably, the abundance of keystone taxa decreased after exploitation, and oligotrophic groups (Chloroflexi) replaced copiotrophic groups (Proteobacteria and Actinobacteriota) as the key to rebuilt a co-occurrence network, suggesting potentially important roles in maintaining network stability. The current results are of great significance to the ecological risk assessment of REEs exploitation.

Geochemical Characteristics of Garnet from Zinc–Copper Ore Bodies in the Changpo–Tongkeng Deposit and Its Geological Significance

The Changpo–Tongkeng tin polymetallic deposit in Dachang, Guangxi, is a world-class, superlarge, polymetallic tin deposit consisting of lower skarn zinc–copper ore bodies and upper tin polymetallic ore bodies. Garnet is the main gangue mineral in the skarn zinc–copper ore bodies and has a granular texture. Based on hand specimens and microscopic observations, the existing garnet can be divided into two generations: an early generation (Grt I) and a late generation (Grt II). The results of electron probe microanalysis (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in situ microanalysis show that the contents of SiO2 and CaO in the garnets from the two generations present limited variations, while the FeOT and Al2O3 contents vary significantly, indicating the grossular–andradite solid solution series (Gro29–82And12–69). Compared with Grt I (Gro72And25), Grt II (Gro39And59) is Fe-enriched and oscillatory zoning is developed. The total rare earth element (REE) contents in the two generations of garnet are relatively low, showing light rare earth element (LREE) depletion and heavy rare earth element (HREE) enrichment patterns. Grt II has higher REE content than Grt I and exhibits significant negative Eu anomalies (δEu = 0.18–0.44). The contents and variation characteristics of the major and trace elements in the two generations of garnet suggest that there were variable redox conditions and water/rock ratios in the hydrothermal system during the crystallization process of garnet. In the early stage, skarnization was in a relatively closed and low-oxygen fugacity system, with hydrothermal diffusion metasomatism being dominant, forming homogeneous Grt I lacking well-developed zoning. In the late stage of skarnization, the oxygen fugacity of the ore-forming fluids increased, with infiltration metasomatism being dominant, forming Grt II with well-developed oscillatory zoning. The contents of Sn, As, W, In, and Ge in the garnets are relatively high and increase with the proportion of andradite. Sn in zinc–copper ore bodies mainly exists in the form of isomorphic substitution in garnet, which may be the main reason for the lack of tin ore bodies during the skarn stage. This paper compares the trace element contents in garnets from domestic skarn deposits. The results indicate that the Sn content and δEu in garnet can be used to evaluate the tin-forming potential of skarn deposits.

Large Difference in Nonlinear Optical Activity of Rare Earth Ion Substitution of Bi3+ in A3TeBO9 (A = Bi, La, Pr, Nd, Sm-Dy).

A series of oxides with high rare earth contents, RE3TeBO9 (RE = La, Pr, Nd, Sm-Dy), were synthesized, and they all crystallize in the noncentrosymmetric space group P63 resembling that of a previously reported Bi3TeBO9 (J. Am. Chem. Soc. 2016, 138, 14190-14193), which showed a very strong second harmonic generation (SHG) signal believed to come from all three structural units [BO3], [TeO6], and [BiO6]. Surprisingly, compared with the isostructural compound Bi3TeBO9, both theoretical calculations and powder SHG tests show that RE3TeBO9 has an abnormally small SHG effect (0.2 × KDP). Based on the group theory analysis, the possible reasons are attributed to the misalignments and lack of distortions of the [BO3], [TeO6], and [REO8] groups in the unit cell. The 21 symmetric operation (a subset operation of the 63-screw axis) of the [TeO6], [BO3], and [REO8] groups leads to complete cancellation of their contributions to the xy directions, while the absence of lone pair electrons in RE3+ and Te6+ results in small distortion in the c axis, hence small contributions to the SHG coefficients dijk involving the z axis. Diffuse reflectance spectra of RE3TeBO9 (RE = La, Pr, Nd, Sm-Dy) show typical absorption of different RE3+, and the similarity of their infrared spectra is due to the same crystal structure and same structural units of the [TeO6] and [BO3] groups. The strong fluorescence intensities of Eu3TeBO9 and Tb3TeBO9 show the characteristic emissions of Eu3+ and Tb3+, which may serve as luminescence materials with proper doping.

Microbialite Textures and Their Geochemical Characteristics of Middle Triassic Dolomites, Sichuan Basin, China

Microbialite textures, such as microbial mats and biofilms, were observed in the Middle Triassic dolomite in the Sichuan Basin, western China, using core examination, thin section petrography, scanning electron microscopy (SEM), and geochemical analyses. The dolomite texture, consisting of fibrous and spherulitic structures, is similar in morphology and size distribution to those observed in microbial culture experiments. Extracellular polymeric substances (EPS) were identified based on the occurrence of fibers forming a reticular pattern and nanometer-sized spheroids. The rare earth element (REE) and stable isotope (C, O, and Sr) compositions of the Middle Triassic dolomite were measured to determine their geochemical characteristics. Using seawater as a standard, the dolomitic microbialites (MD) exhibited significantly positive La and Eu anomalies and higher REE concentrations and (Nd/Yb)sn values than associated limestones, and these patterns are inferred to be related to initial complexation on organic ligands in the biofilm, as proposed by previous researchers. The ambient temperature during dolomite precipitation was estimated to be within the 23 °C to 50 °C range, as indicated by the δ18O values of the dolomite. This study suggests that various microbial effects can significantly affect diagenetic processes in the Middle Triassic dolomite.

Targeting ash generated from coal combustion as secondary source of rare earth elements

ABSTRACT The demand of Rare Earth Elements (REEs) has increased for the development of clean and green technologies. Conventional geological sources of REE are insufficient to overcome the high demand of REE; hence, the secondary resources are being actively explored. Coal ashes (CAs), a potentially hazardous material, is one of the best secondary sources containing high concentration of REE. The present study aims to explore the abundance of REE in coal and coal ash from different Thermal Power Stations (TPS). The mineralogy and surface morphology of all samples have been determined. The coals mostly consist of quartz and kaolinite, whereas CAs predominantly contain quartz and mullite. Both coal and CAs are dominated by LREE elements, followed by MREE and HREE. The outlook coefficient (C out) is close to “1” and the critical percentage (C p) is more than 30%. Coal ash from some of the TPS is identified as secondary source for REE. Fractionation study of REE from coal to CA is carried out to understand the feasibility of CA. A Pearson correlation has been plotted for individual REE elements with other parameters to understand the affinity of REE to different phases of CA.

Anomalous concentrations of rare earth elements in acid mine drainage and implications for rare earth resources from late Permian coal seams in northern Guizhou

Rare earth elements (REEs) have attracted much attention in recent decades due to their growing applications in high-tech industries. Coal and acid mine drainage (AMD) are considered promising alternative sources due to their high concentrations of REEs. Here, AMD with anomalous REEs concentrations was reported in a coal-mine area in northern Guizhou, China. The AMD had a total concentration as high as 22.3 mg/l, suggesting that regional coal seams may be enriched with REEs. Five segments from borehole samples, which contained coal, rocks from the roof and floor of the coal seam were collected from the coal mine site to investigate the abundance, enrichment, and occurrence of REE-bearing minerals. Elemental analysis showed that the REE contents in the coal, mudstone and limestone from the coal seam roof, and claystone from the floor (all dating to the late Permian) varied greatly, with averages of 388, 549, 60.1 mg/kg and 2030 mg/kg, respectively. Encouragingly, the REEs content in the claystone is over an order of magnitude higher than the average content reported in most other coal-based materials. The enrichment of REEs resources in regional coal seams is particularly associated with the contribution of REEs in the claystone that comprises the coal seam floor, rather than just the coal, as considered in previous studies. The minerals in these claystone samples were dominated by kaolinite, pyrite, quartz and anatase. Two types of REE-bearing minerals, bastnaesite and monazite, were detected in the claystone samples by SEM–EDS analysis, and they were found to be adsorbed by a large amount of clay minerals, mainly kaolinite. Additionally, the results of chemical sequential extraction also confirmed that the majority of the REEs in the claystone samples are mainly in their ion-exchangeable, metal oxide and acid-soluble forms, which are viable prospects for REE extraction. Therefore, the anomalous concentrations of REEs and most of them are in extractable phases, which demonstrates that the claystone from the floor of the late Permian coal seam should be a potential secondary source of REEs. Future studies will further consider the extraction model and the economic benefits of REEs from the floor claystone samples.

Source, environmental behavior and potential health risk of rare earth elements in Beijing urban park soils.

Rare earth elements (REEs) have been increasingly diffused to the environment due to their extensive use and application in industries, agriculture, and high-tech devices, which have been regarded as emerge pollutants. However, the study concerning REEs in urban soils is still limited. Therefore, the objectives of this study were to investigate the potential source and risk of REEs in urban environment. We analyzed the concentration and distribution of REEs in urban park soils, and performed a combination of micro geochemical method and random forest method to characterize the pollution sources of REEs. The results showed that the ΣREE concentrations in Beijing urban park soils ranged from 117.19 to 198.09mg/kg. Spatial distribution indicated that the high concentrations of REEs were mainly concentrated in the west of Beijing near an industrial area. The geochemical parameters, micro spherules and random forest results confirmed the anthropogenic pollution sources from industry and traffic. Risk assessment showed that the average daily doses of total REEs for children and adults were far below the reference threshold with values of 0.08 and 0.02µg/kg/day, respectively. Our study has exhibited that though the reconstruction of parks from abandoned industrial sites showed an accumulation of REEs, the health risk of REEs for human beings are negligible.

The Quality of Scutellaria baicalensis Georgi Is Effectively Affected by Lithology and Soil’s Rare Earth Elements (REEs) Concentration

The top-geoherb “Rehe Scutellaria baicalensis” was naturally distributed on Yanshan Mountain in Chengde city, Hebei Province, China. Exploring the influences of parent materials on the quality of the top-geoherbs in terms of micronutrient elements is of great significance for the protection of origin and for optimizing replanting patterns of Scutellaria baicalensis. In this study, three habitats of Scutellaria baicalensis with contrasting geopedological conditions, i.e., naturally grown habitats (NGHs), artificial planting habitats (APHs), and biomimetic cultivation habitats (BCHs), are taken as objects to probe the influences of parent materials on the quality of Scutellaria baicalensis in terms of rare earth elements (REEs) by testing on REEs concentrations in the weathering profiles, rhizosphere soil and growing Scutellaria baicalensis, as well as their flavonoid compound contents. Hornblende-gneiss was the parent rock in NGHs, whose protolith was femic volcanic rock. Loess was the parent rock in APHs and BCHs. REEs were more abundant in hornblende-gneiss than loess, and therefore, soils developed in NGHs contained higher REE concentrations than those in APHs, which was lower than BCHs after REE-rich micro-fertilizers application. The coefficient of variation (CV) of REEs concentrations in the rhizosphere soils of hornblende-gneiss was higher than that in loess. It possibly was attributed to the complicated minerals compositions and various minerals’ grain sizes of hornblende-gneiss, resulting in the variety of weathering intensity involving eluviation, leaching, adsorption, etc., as well as weathering productions, dominated by clay minerals and Fe-(hydro)oxide, and ultimately the remarkable differences in the migrations, enrichments and fractionations within REEs. The biological absorption coefficients (BACs) of REEs for Scutellaria baicalensis decreased in the order of NGHs &gt; APHs &gt; BCHs. Roots of Scutellaria baicalensis contained similar ΣREE in NGHs (2.02 mg·kg−1) and BCHs (2.04 mg·kg−1), which were higher than that in APHs (1.78 mg·kg−1). Soils developed in hornblende-gneiss were characterized by lower clay fraction content and overall alkalinity with a pH value of 8.06. The absorption and utilization efficiency of REEs for Scutellaria baicalensis in NGHs was higher than in APHs and BCHs. Flavonoid compounds, effective constituents of Scutelleria baicalensis, showed more accumulations in NGHs than APHs and BCHs, implying their optimal quality of Scutellaria baicalensis in NGHs. Flavonoid compounds were remarkably correlated with REEs in the roots, suggesting the influence of REEs concentrations on the quality of Scutellaria baicalensis. It can be concluded that high REEs and micronutrient element concentrations of hornblende-gneiss favored the synthesis and accumulation of flavonoid compounds in Scutellaria baicalensis after the activation of endocytosis induced by REEs.

Exploring rare earth mineral recovery through characterization of riebeckite type ore in Bayan Obo

The aim of this study was to characterize the riebeckite type rare earth ore found in the Bayan Obo deposit, in order to identify the distribution and occurrence of both rare earths and gangue species within the ore. Several analytical techniques were utilized to accomplish this, such as chemical analysis, quantitative XRD, a single polarizing microscope, and a mineral automatic analysis system. The analysis revealed that the primary rare earth minerals (REMs) in the ore were bastnaesite and monazite, with huanghoite, parisite, aeschynite, and fergusonite identified as secondary rare earth minerals. The main gangue species was magnetite, accompanied by smaller quantities of riebeckite and dolomite. The ore was rich in rare earth oxides, with a 3.81 wt% grade. The screen analysis of the pulverized ore indicates that the 43–100 μm fraction is the dominant size, while the finer size fractions below 43 μm contain the bastnaesite and monazite, as well as huanghoite, parisite, aeschynite, and fergusonite. Microstructural characterization showed that the REMs were both coarse-grained and fine-grained, occurring as granular aggregates and fine disseminations within the gangue. Bastnaesite and monazite were the major REMs, with dominant amounts of cerium, lanthanum, praseodymium, and neodymium, while parasite was identified as an impurity. Huanghoite and parisite contained barium and calcium as impurities, respectively. Aeschynite and fergusonite were REMs that included niobium in their composition. Bastnaesite and monazite were found to contain a much higher rare earth content than huanghoite, parisite, aeschynite, and fergusonite. Potential methods for recovering rare earths from this ore, such as magnetic separation and froth flotation, have been identified and may be applicable to similar ferruginous rare earth-bearing ores.

Evidence of rare earth elements origin in acid mine drainage from the Iberian Pyrite Belt (SW Spain)

Acid mine drainage (AMD) is a worldwide pollution problem of watersheds. In addition to toxic metal(oid)s and acidity, many elements of economic interest are released into the environment, which make AMD a potential strategic secondary source of these elements such as rare earth elements (REE). Despite the importance of these metals, their origin in AMD is still uncertain. Recent hypotheses suggest preferential leaching of REE-enriched minerals as a possible source. Leaching tests with H2SO4 have been developed to simulate the interaction under AMD formation conditions with sulfide bodies and host rocks from two representative mining areas in the Iberian Pyrite Belt: the Perrrunal and Poderosa mines (SW of Spain). The REE patterns and Ce and Eu anomalies of the rock leachates have confirmed the geochemical relationship between the AMD and certain country rocks (felsic and mafic volcanics, and shales). A detailed chemical and mineralogical study has confirmed the existence of a diversity of minerals with high concentrations of REE. Thus, the minerals with the highest REE contents are also those with the fast dissolution kinetics under acid conditions: REE phosphates (monazite and xenotime type) and carbonates (parisite type). Finally, petrographic evidence of the selective leaching of these minerals clearly supports these minerals as the main source of REE in the AMD.

Dissolved rare earth element and neodymium isotope distributions in the South China Sea: Water mass source versus particle dissolution

Dissolved rare earth elements (REEs) and neodymium isotopes (ϵNd) have been jointly used to evaluate water mass mixing and lithogenic inputs in the ocean. As the largest marginal sea of the West Pacific, the South China Sea (SCS) is an ideal region for reconstructing past hydrological changes. However, its REE and ϵNd distributions and underlying controlling mechanisms remain poorly understood. On the basis of four seawater profiles spread across the SCS, this study presents dissolved REE concentrations and ϵNd data under summer condition to better understand the processes that potentially influence changes in these parameters and their marine cycling. The results show high concentrations of REEs and large variations in ϵNd (−6.7 to −2.8) in surface water, likely caused by the dissolution of riverine and marine particles. Comparison with published data from samples taken during the winter of different years in this and previous studies suggests a possible seasonal variability of middle REE enrichment. The SCS deep water shows a narrow ϵNd range from −4.3 to −3.4, confirming the dominant presence of the North Pacific Deep Water in the deep SCS. The intermediate water in the central SCS is characterized by a more negative ϵNd signal (–4.2 to –3.4) than that found in its counterpart in the West Pacific (–3.5 to –2.8), indicating alterations by deep water through three-dimensional overturning circulation from the northern to southern SCS below ~500 m. The contributions of external sources could be quantitatively estimated for the SCS in terms of Nd. The dissolution of particles from the SCS surrounding rivers (0.26–1.3 tons/yr in summer; 5.6–29 tons/yr in winter) and continental margins (2–12 tons/yr in summer; 23–44 tons/yr in winter) may play an important role in providing additional Nd to the SCS surface water.

Biosynthesis of bionanomaterials using Bacillus cereus for the recovery of rare earth elements from mine wastewater

The growing demand for rare earth elements (REEs) increasingly requires secondary resources such as mine wastewater containing high concentrations of REEs, to be used as a source of REEs. The current challenge is how to efficiently recover REEs from this feed source. In this paper, a functional bionanomaterial (FeNPs-EPS) was biosynthesized using Bacillus cereus as a possible means of recovering REEs. This composite was composed of both synthesized iron nanoparticles (FeNPs) and extracellular polymeric substances (EPS). Synthesis of the FeNPs-EPS composite via a one-step biosynthesis was confirmed by materials characterization. The peak in the material's UV–Vis spectra at 511 nm demonstrates the formation of FeNPs-EPS, where 3D-EEM showed that FeNPs-EPS was wrapped predominantly with tryptophan protein-like and humic acid-like substances. In addition, while FTIR indicated that the functional groups present in EPS where virtually identical to those observed in FeNPs-EPS, XPS demonstrated that Fe and O were the major elemental present as both FeO and Fe2O3. Zeta potential measurements indicated that FeNPs-EPS had good stability under different pH conditions, where BET analysis supported multilayer adsorption. Finally, on exposure to high concentrations of Eu(III) and Tb(III) in mine wastewater, the synthesized FeNPs-EPS demonstrated strong potential to remove two cations from the wastewater and hence a potentially practical way to efficiently recover REEs from such waste streams.

Excess of REE in plant foods as a cause of geophagy in animals in the Teletskoye Lake basin, Altai Republic, Russia

Geological and hydrobiogeochemical studies carried out in two areas in the Teletskoye Lake basin in the Altai Mountains suggest that geophagy among wild and domestic herbivores in the studied areas develops in mountain‑taiga with steppe landscapes on Proterozoic metamorphic rocks near the Paleozoic granitoids with high concentrations of magmatogenic minerals of rare earth elements (REE). This fact is the reason for high concentrations of REE in loose diluvial deposits and glacial deposits adjacent to granitoids, as well as in derivative soils and vegetation. REE concentrations in the vegetation of the studied territories were almost similar to the geophagy sites previously investigated in the Sikhote‑Alin. The geochemical specificity of landscapes revealed both in the Altai Mountains and in the Sikhote‑Alin may be the cause of REE imbalance in the hormonal system of the body. It forces animals to address the resulting problems with mineral sorbents of the quartz‑feldspar‑illite‑chlorite type which can remove the excess of REE from the body. When selecting these, the animals tend to find sodium‑enriched varieties if possible.

REE mineralization related to weathering of the late Permian Emeishan basalts

Paleo-weathering crust rare earth element (REE) sedimentary ores (PWREOs) (on-site weathering profiles (paleosols) and allogene deposits (claystones)) related to weathering of the Permian Emeishan basalts in western Guizhou Province, Southwest China, were selected to advance our understanding of the controls on mobilization and redistribution of the REEs during basalt weathering, which is crucial for efficient exploration for this type of deposits.REE concentrations in the paleosols ranged from 88.24 mg/kg to 1684.21 mg/kg (mean value 582.01 mg/kg). The entire paleosol profiles are enriched in light REEs (LREEs) relative to heavy REEs (HREEs). Intense weathering of the parent Emeishan basalts formed two enrichment zones hosted mainly within the BC horizon adjacent to the lower iron-pan horizon and near the BC-C horizon interface of the paleosol profiles. High‑titanium Emeishan basalts with a relatively high initial REE concentration (271.20 ± 94.29 mg/kg) is the basis for REE enrichment in paleosols. The kaolinite adsorption is crucial for REE immobilization in paleosol profiles. The paleosol profile developed in a flat landscape with good drainage conditions (e.g., ridgetop) (profile WNEM07 in this study) has a higher ∑REEs (reaching 1684.21 mg/kg), with mean values of LREEs/HREEs and (La/Yb)N up to 7.83 and 39.56. HREEs might preferentially migrate vertically and laterally in groundwater, resulting in the enrichment of those elements in the paleosol profile at footslope (profile WNEM06 in this study) and in the REE enrichment zone that near the BC-C horizon interface of the paleosol profiles. Kaolinite combined with REEs in the weathering products was continuously transported to the sediment basin by flowing water, thus causing further enrichment of REEs in claystones, ranging in concentrations from 89.06 mg/kg to 9964.95 mg/kg (mean 1151.39 mg/kg). The formation of PWREOs may include three stages, i.e., the formation of the Emeishan basalts with high initial REE contents during the magmatism of the Emeishan Large Igneous Province (ELIP), the primary enrichment of REEs in the weathering process of the Emeishan basalts, and the further enrichment of REEs in weathering product transportation and sedimentation.

Essential processes involving REE-enrichment in biogenic apatite in deep-sea sediment decoded via multivariate statistical analyses

Deep-sea sediments highly enriched in rare-earth elements (REE), termed “REE-rich mud,” have recently attracted attention as a potential mineral resource for industrially critical metals. Biogenic apatite or fish teeth and bone debris comprises the mineral phase which primarily hosts REE in deep-sea sediments; thus, biogenic apatite is a key material to decipher the formation process of REE-rich mud. We investigated the key process(es) controlling REE-enrichment in biogenic apatite through a novel data-driven approach. We analyzed the in situ chemical composition of biogenic apatite grains collected from REE-rich mud in the western North Pacific Ocean. Subsequently, the dataset of 685 analytical points × 35 elements was statistically analyzed via independent component analysis. Our new approach extracted four independent components (ICs) as geochemically meaningful and statistically independent signatures: substitution of elements into apatite lattice (IC1), the relatively rapid adsorption process that occurred at the sediment-water interface (IC2), elemental transfer from volcanic materials during early diagenesis (IC3), and metalliferous or detrital impurities physically adhering to or infiltrating apatite grains (IC4). Data distributions within the real and IC spaces provide insights into physicochemical processes involving elemental incorporation into biogenic apatite. We argue that after settlement on the seafloor, the fish bones and dentine in teeth adsorb REE from the overlying seawater and REE-enriched porewater at the sediment-water interface, resulting in the preferential enrichment of light rare-earth elements into apatite from these solutions. Further, that REE adsorbed on the apatite crystal surface was incorporated into the crystal lattice via substitution. The IC2 signal was intensified in the layers of “extremely REE-rich mud”, suggesting that the REE adsorption process was facilitated during the formation of layers with remarkably high bulk-sediment REE contents. This may reflect an increased supply of REE-carrier substances such as organic matter, which degraded on the seafloor and released REE at the sediment-water interface, which is associated with changes in paleoceanographic conditions including ocean surface bioproductivity.

Mineralogical, Geochronological, and Geochemical Characteristics of Early Cretaceous Granite in South China: Implications for Tectonic Evolution and REE Mineralization

One of the most important geological features of South China are the widespread Mesozoic igneous rocks that play a key role in revealing the tectonic evolution of South China. Due to the thick covering of vegetation and Quaternary sediments, the early Cretaceous magmatism in southwestern South China is still not well constrained. In this paper, we report newly identified early Cretaceous granites in Guangxi, South China. Zircon U–Pb dating results showed that representative fine-grained and coarse-grained granites in northeastern Guangxi indicate the early Cretaceous ages of 141 ± 3 Ma and 141 ± 4 Ma, respectively. Geochemically, both fine-grained and coarse-grained granites had high 10,000 × Ga/Al ratios and belonged to A-type granite. They had undergone high degrees of magma differentiation, as evidenced by extremely negative Sr, Ba, and Eu anomalies. They had high REE (rare earth elements) contents (&gt;451 ppm). The fine-grained granites were characterized by higher HREE (heavy rare earth elements) contents, lower LREE (light rare earth elements) contents, and lower LREE/HREE ratios than the coarse-grained granites. Integrated with regional geological data, the early Cretaceous granites were likely formed in a back-arc extensional environment in response to the increased subduction angle of the Paleo-Pacific plate. Different REE contents in the fine- and coarse-grained granites may be a result of fractional crystallization. Magma differentiation and hydrothermal alteration might have played an important role in REE mineralization of the early Cretaceous granites in Guangxi.

The role of nanofiltration modelling tools in the design of sustainable valorisation of metal-influenced acidic mine waters: The Aznalcóllar open-pit case

Acid Mine Waters (AMWs) are considered the most challenging environmental problem in the Iberian Pyrite Belt (South of Spain) so far, being characterised by an acidic pH (H2SO4-based), high content of heavy metals (e.g. Co, Pb, rare earth elements (REEs)) and non-metals (e.g. As). Nowadays, AMWs are being contemplated as a source of valuable metals (e.g. Zn, Cu, REEs), and different recovery routes have been studied (e.g. ion-exchange, membrane technologies). Among them, nanofiltration (NF) provides the possibility of water (or H2SO4) recovery and concentration of metals, which can be recovered in a subsequent stage. This work evaluates the performance of the Desal DK NF membrane to treat AMW from Aznalcóllar open-pit, which presents a low pH (2.6) and high contents of Zn (920 mg/L), Mg (2540 mg/L) and REEs (17 mg/L). The effect of solution pH on membrane performance was evaluated. Results showed that the equilibrium SO42-/HSO4- controlled the transport of species. Rejections of sulphate were around 84 % at pH 2.1 (prevalence of HSO4-) and increased to 92 % at pH 3.1 (prevalence of SO42-). Metal rejections remained higher than 74 % (except for monovalent species). Additionally, membrane permeances were determined using the Solution-Electro-Diffusion model coupled with reactive transport, and later used to assess the design of the process treatment of the AMW. Results demonstrated the possibility of concentrating metals and recovering H2SO4 as permeate, but also showed that gypsum and anhydrite precipitation can occur. Additionally, CAPEX and OPEX were estimated for a NF plant treating 2 Hm3/year.