Heavy Rare Earth Research Articles

Trace elements in coralline algae as a new proxy for seawater chemistry and metal pollution

The abundances of some macronutrients, and trace elements (K, Al, P, V, Mn, Co, Ni, Cu, Zn, Rb, Sr, Mo, Cs, Ba, Pb, Th, U, Y and REE) were determined in a series of coralline algae (Lithothamnion corallioides) samples (n = 101) collected alive in the Bay of Brest and the Iroise Sea (Western Brittany, NW France), in order to assess the potential of these algae as archives of seawater chemistry and potential metal pollution. REE and Y (REY) patterns are similar in shape to those of local seawater, exhibiting similar La, Ce and Y anomalies, but with abundances ranging between 4 and 5 orders of magnitude higher than seawater values. Variations in La anomalies (La/La* = 1.29–2.08), Y anomalies (Y/Ho = 38.6–55.8), and heavy rare earth enrichments (Prsn/Ersn = 0.22–0.52) are consistent with mixing of seawater with rivers flowing into the Bay of Brest. The behavior of other trace elements, such as Al and Cs, also reflects this mixing. Other parameters and processes can control the abundances of the other elements measured. For example, the presence of organic matter in studied samples controls the abundances of K and Rb. The abundances of base metals (e.g., Co, Ni, Cu) are highly sensitive to the various pollutants present in the Bay of Brest. In particular, the Pb content of coralline algae clearly reflects the pollution caused by mining of a nearby Pb deposit from the 18th to the early 20th century. Our results demonstrate the potential of coralline algae not only for tracing water masses, but also for studying metal pollution.

Continental subduction in Paleoproterozoic: Insights from ∼ 1.9 Ga nepheline syenite in the North China craton

Subduction of continent is known as a feature of modern plate tectonics, and it is still unclear whether such a process also occurred in the early Precambrian. Despite of ultra-high pressure metamorphism of terrestrial rocks as a proxy of continental subduction, magmatism produced during continental subduction is also a potential alternative. The North China craton is well-known for the occurrence of 1.9 Ga retrograde eclogite, which was likely originated from the subducting oceanic crust along the Trans-North China Orogen (TNCO). Here a nepheline syenite (the Aohu pluton), the first of the kind from the TNCO, is discovered in Yunzhong Mts. It comprises nepheline (∼20 vol%), albite (50–55 vol%), K-feldspar (5–10 vol%), biotite (∼10 vol%), and calcite (∼5 vol%), with minor accessory minerals. No associated mafic or silicic rocks are outcropped in the pluton. SHRIMP zircon U-Pb analyses yield a crystallization age of 1893 ± 13 Ma and a metamorphic overprinting of 1871 ± 17 Ma. The rocks have medium SiO2 contents (51.9–58.9 wt%), low MgO (0.6–1.6 wt%) and Mg# (24–34), but high Al2O3 (20.0–22.9 wt%) and extremely high K2O + Na2O contents (10.0–13.6 wt%; Na2O/K2O = 1.3–2.6). They are enriched in light rare earth elements (REEs) and large ion lithophile elements, but relatively depleted in heavy REEs and high field strengthen elements. They have extremely low compatible elements (e.g., Ni and Cr). They show high (87Sr/86Sr)i ratios (0.706–0.707) but low εNd(t) values (−5.3 to −6.0; Nd T2DM = ca. 2.7 Ga). Their zircon in-situ εHf(t) values have a wide range (0 to −5.7; Hf T2DM = 2.5–2.85 Ga). The absence of mafic component and the extremely low-Mg feature, as well as their trace element patterns and initial Sr-Nd isotopes being compatible with melts derived from the Archean mafic crustal enclaves in the region, support a continental crust origin for the Aohu nepheline syenite. Based on comparison and modeling, we suggest that its generation was most likely under ultra-high pressure condition. It is thus proposed that continental subduction (into the mantle) might have occurred in the TNCO during the Paleoproterozoic.

Features of rare earth elements geochemistry in coals of Central Kazakhstan

AbstractThis research presents the results of a comprehensive study of mineralogical and geochemical features of REE distribution in coals of Central Kazakhstan deposits—Karaganda coal basin and Shubarkol deposit, which have large hard coal reserves and are industrially important for the coal industry of Kazakhstan; the research is based on 205 samples of clayey interlayers and coal seams. It shows basic patterns of distribution and features of concentration for impurity elements, gives an estimate of the impurity elements concentration, including REE, defines conditions and factors of their accumulation, and studies features of their forms in coal and coal-bearing rocks, which allows estimating the mechanisms of their migration and conditions of accumulation. According to the results of geochemical indicators, the article establishes the factors of REE dislocation, reveals the composition of margin rocks that have influenced REE concentration in coal seams, and the presented latest data on mineralogy allowed to establish the ways of their transportation to the paleobasin during the syn- and epigenetic periods of formation of the coal deposits of Central Kazakhstan being researched. It was found that the coals are insignificantly enriched with heavy lanthanides from Ho to Lu. The distribution curves of UCC normalized REE values in the coals are similar and coincide, but they are less than the average value for world coal, and amount to only one-third of the UCC. It was found that the highest concentrations of all REE are characteristic of clayey interlayers and oxidized coals. The La/Yb ratio in this case increases upwards along the section, indicating mainly clastogenic mechanism of REE delivery to the coals. In coal and clay samples, the predominant mineral form of REE is light lanthanide phosphates. Identified particles of REE from minerals and their composition peculiarities suppose autigene nature of their formation. The formation of the bulk of autigene minerals occurred during the maturation of brown coals and their transformation into hard ones.

The enrichment and separation of lanthanides ions from wastewater using solvent sublation coupled with high speed countercurrent chromatography

Rare earth elements are non-renewable resources. During their processing, a lot of wastewater are produced, which poses a danger to human beings and the environment. Herein, the enrichment method of solvent sublation for La (III), Ce (III), Gd (III) and Er (III) was designed and established. Enrichment parameters pH, flotation time, extractant concentration and air flow rate were optimized. The result showed that the highest recovery of La (III) reached up to 92.33 % under the optimized conditions of pH 8, 10 min of flotation time, 0.15 mol L-1 of the extractant 2-ethylhexyl phosphate acid-2-ethylhexyl ester and 30 mL min−1 of air flow rate. The light rare earth element Ce (III) and heavy rare earth elements Gd (III) and Er (III) were also examined and obtained with maximum recovery. The stability of the extractant complexation with rare earth ions and the mechanism of competitive extraction were studied by density functional theory calculations. The extraction ability was following sequence of La (III) < Ce (III) < Gd (III) < Er (III). The enrichment of rare earth elements from real water samples was investigated and obtained result was consistent with the experiment result of synthetic solutions. The established high speed countercurrent chromatography method was used to successfully separate La (III), Ce (III), Gd (III) and Er (III) from the solution of rare earth ions enriched by solvent sublation.

Efficient separation for yttrium and heavy rare earth elements using functionalized quaternary ammonium ionic liquids

Given the similar ionic radii of heavy rare earth elements (HREEs), sixteen functionalized ionic liquids (FILs) with potential extraction and separation properties were designed and prepared, also their feasibilities for yttrium (Y) separation from HREEs were evaluated. The results show that [N16MOP][HDA] is the optimal extractant for Y separation from other HREEs, achieving a Ho/Y separation factor of 2.82. The extraction reaction is based on an ion pair mechanism, where a HoCl3 molecule is extracted by two [N16MOP][HDA] molecules. Complete stripping of the loaded rare earth elements (REEs) can be achieved using 0.1 mol/L hydrochloric acid. Deionized water is used as a scrubbing agent, the average separation coefficient between Y and other HREEs during the scrubbing process is 2.5. After six cycles of continuous operation for 15 h, the organic phase maintains stable extraction and separation capabilities, demonstrating good recyclability and periodic stability. This study introduces a sustainable method for separating Y from HREEs using novel FILs, which is more efficient and consumes fewer chemical reagents. The results of this study indicate that the introduction of functionalized cation in FIL enhances the affinity and selectivity of HREEs. This provides valuable insights into the design of FIL-based extractents and their potential applications in sustainable rare earth separation.

Linkage between Granite Weathering and Gully Erosion in Subtropical Region

Granites, widely distributed in the Earth’s crust, undergo pedogenic processes, shaping diverse soil-mantled landscapes influenced by climatic factors in different regions. Investigating the geochemical signatures in granite weathering profiles across varying climatic conditions provides valuable insights into the intricate interplay between weathering and landscape evolution. In this study, the geochemical features, particularly major and rare earth elements, and the weathering degree of granites across temperate to subtropical regions in China were examined. The results indicated significant variations in the geochemical characteristics of granite weathering profiles, both at a pedon and regional scale (p &lt; 0.01). With increasing hydrothermal conditions from north to south, soil pH shifted from neutral to acidic, accompanied by the leaching of major elements (K2O, Na2O, CaO, and MgO) and the enrichment of Al and Fe. The total rare earth elements (∑REEs) ranged from 75 to 352 ppm, and light rare earth elements (LREEs) from 71 to 317 ppm, exhibiting less significant variations across the study area, while heavy rare earth elements (HREEs) showed higher concentrations in the subtropical region (3 to 35 ppm). Plagioclases dominated the weathering process in temperate regions, with K-feldspar progressively increasing and, eventually, dominating from temperate to subtropic regions, resulting in a shift in clay minerals from 2:1-type in the temperate to 1:1-type in the subtropic. The chemical index of alteration (CIA) and comprehensive weathering index (W) increased from fresh rock to residual soils along the weathering profiles and from north to south across the study area, ranging from 50.72 to 97.44 and 35.11 to 70.62, respectively. The intensified granite weathering degree was significantly influenced by climatic conditions (p &lt; 0.05), especially the multi-year average precipitation (22.4%) and relative humidity (9.1%) (p &lt; 0.01). Gully erosion on the granite weathering mantle was concentrated in granites with a comprehensive weathering index exceeding 52.51, and the spatial variation of the granite weathering degree aligned with the spatial distribution of gully density across the study area.

Geochemical Signatures of Mafic Volcanic Rocks in Modern Oceanic Settings and Implications for Archean Mafic Magmatism

Abstract Greenstone belts are dominated by mafic volcanic rocks with geochemical characteristics that indicate a range of possible geodynamic influences. Many analogies with modern tectonic settings have been suggested. Increasing exploration of the modern oceans and comprehensive sampling of volcanic rocks from the sea floor are now providing unique opportunities to characterize different melt sources and petrogenesis that can be more closely compared to greenstone belts. In this study, we have compiled high-quality geochemical analyses of more than 2,850 unique samples of submarine mafic volcanic rocks (&amp;lt;60 wt % SiO2) from a wide range of settings, including mid-ocean ridges, ridge-hotspot intersections, intraoceanic arc and back-arc spreading centers, and ocean islands. The compiled data show significant geochemical variability spanning the full range of compositions of basalts found in greenstone belts. This diversity is interpreted to be due to variable crustal thickness, dry melting versus wet melting conditions, mantle mixing, and contamination. In particular, different melting conditions have been linked to mantle heterogeneity, complex mantle flow regimes, and short-lived tectonic domains, such as those associated with diffuse spreading, overlapping spreading centers, and triple junctions. These are well documented in the microplate mosaics of the Western Pacific. Systematic differences in mafic volcanic rock compositions in modern oceanic settings are revealed by a combination of principal components analysis and unsupervised hierarchical clustering of the compiled data. Mafic volcanic rocks from most arc-back arc systems have strongly depleted mantle signatures and well-known subduction-related chemistry such as large ion lithophile element (LILE) enrichment in combination with strong negative Nb-Ta anomalies and low heavy rare earth elements (HREEs). This contrasts with mafic volcanic rocks in Archean greenstone belts, which show no, or at least weaker, subduction-related chemistry, a less depleted mantle, less wet melting, and variable crustal contamination. The differences are interpreted to be the result of the lower mantle temperatures, thinner crust, and subduction-related processes of present-day settings. However, mafic rocks that are geochemically identical to those in Archean greenstone belts occur in many modern back-arc basins, including the Lau basin, East Scotia ridge, Bransfield Strait, and Manus basin, which are characterized by fertile mantle sources, high heat flow, and complex spreading regimes typical of small-scale microplate mosaics. These types of settings are recognized as favorable for volcanogenic massive sulfide (VMS) deposits in modern and ancient greenstone belts, and therefore the particular geochemical signatures of the mafic volcanic rocks are potentially important for area selection in base metal exploration.

Insights from Dikes for Multistage Granitic Magmatism in the Huayangchuan Uranium Polymetallic Deposit, Qinling Orogen

The Huayangchuan U-polymetallic deposit in the Qinling Orogen is a newly verified carbonatite-hosted deposit on the southern margin of the North China Craton (NCC) in Central China. Granitic magmatism is extensively developed in the Huayangchuan deposit area and is lacking analysis on the reasons for these situations; however, its ages, petrogenesis, and relationship with uranium mineralization are not well constrained. Zircon U–Pb ages for the hornblende-bearing granite porphyry and medium-fine-grained biotite granites in close proximity to carbonatite rocks are 229.8 ± 1.1 and 135.3 ± 0.6 Ma, respectively. High-K calc-alkaline series and weakly peraluminous Triassic hornblende-bearing granite porphyry are slightly enriched in light rare earth elements (LREE) with flat heavy rare earth element (HREE) patterns, enriched in Ba and Sr, and depleted in Nb, Ta, P, and Ti, i.e., geochemical characteristics similar to those of adakite-like rocks. The Early Cretaceous medium-fine-grained biotite granites are characterized by LREE enrichment and flat HREE patterns, which belong to high-K calc-alkaline series, and metaluminous belong to weakly peraluminous I-type granite, with U and large ion lithophile element (LILE) enrichment and high field strength element depletion. The high initial 87Sr/86Sr ratios and enriched Nd (εNd(t) = −10.7 to −9.5 and −19.9 to −18.9, respectively) and Hf (εHf(t) = −21.8 to −13.0 and −30.5 to −19.0, respectively) isotopes revealed that both granitic rocks from the Huayangchuan deposit mainly originated from lower crustal materials, generated by partial melting of the ancient basement materials of the Taihua Group. Triassic hornblende-bearing granite porphyry is significantly different from the mantle origin of the contemporaneous U-mineralization carbonatite. In combination with tectonic evolution, we argue that the Qinling Orogenic Belt was affected by the subduction of the North Mianlian Ocean during the Late Triassic. The ongoing northward subduction of the Yangtze Craton resulted in crustal thickening, forming large-scale Indosinian carbonatites, U-polymetallic mineralization, and contemporaneous intermediate-acid magmatism. Additionally, due to the tectonic system transformation caused by Paleo-Pacific Plate subduction, intracontinental lithosphere extension and lithospheric thinning occurred along the southern NCC margin in the Early Cretaceous. Intense magma underplating of the post-orogeny created a large number of magmatic rocks. The tremendous heat could have provided a thermal source and dynamic mechanism for the Yanshanian large-scale U-polymetallic mineralization events.

Rare Earth Elements in Sediments from the Laptev Sea Shelf: Insight into Sources and Distribution Factors

The study of rare earth elements (REEs) in marine sediments is a powerful geochemical tool for determining depositional processes and sediment provenance, as well as for understanding paleoenvironmental changes. In this context, we present REE, some major and trace elements, grain size, and mineralogy data on surface and core sediments, which were collected in different areas of the eastern Laptev Sea Shelf (LSS; Arctic Ocean). The primary objective of this paper was to assess the principal controlling factors influencing REE concentration and their vertical to lateral distribution. The total REE content (ΣREE) ranged from 139 ppm to 239 ppm within the studied sediment samples, predominantly consisting of silt. The normalized REE distribution patterns, based on North American Shale Composite (NASC) standard, exhibited an enrichment in light REE (LREE) when compared to heavy REE (HREE), which is similar to that in Lena River suspended particulate matter. The primary sources of REEs in the eastern LSS were both the suspended particulate matter from the Lena River and sediments originating from the coastal ice complex. The spatial distribution of REEs was primarily contingent upon the distance from sediment sources and prevailing hydrological conditions and was generally characterized by a decrease in REE concentration seaward. There was a moderate positive correlation between ΣREE and mean grain size in the studied surface sediment. However, this relationship was specific only for surface samples and was not found in the sediment cores, indicating that sediment grain size does not play a significant role in the REE vertical distribution. The strong positive correlation between ΣREE and Al, K, Ti, V, Cr, Zr, Hf, and Th suggests that REEs are hosted by not only heavy but also clay minerals. The vertical fluctuations of LREE/HREE, Eu/Eu*, (La/Lu)N can point at variable dominance of one or another REE source for during sediment accumulation.

Instrumental Neutron Activation Analysis (INAA) As-sessment of REE of Soil from Mining Site Umuahia, Abia State, South East, Nigeria

In this work, the main goal was to examine the REE concentration and distribution pattern in soil from Umuahia, Abia State, Southeast, Nigeria, in a clay mining site compared with a non-contaminated site approximately 3 km away. The REE were determined by Instrumental Neutron Activation Analysis (INAA) at IPEN, Brazil. The main mineralogy of the samples was determined by XRD. The following REE were determined: Ce, Eu, La, Lu, Nd, Sm, Tb and Yb. Soil samples from the mining area present quartz and kaolinite as their main constituents, with REE concentrations comparable with that of the Upper Continental Crust and the North American Shale Composite. The calculated Geoaccumulation index (IGeo) indicate that REE have natural origin and ∑LREEN/∑HREEN ratio show an enrichment of the light over heavy REE, in samples of the clay mining area.

Fabrication of Fe-CoS2@N-doped C electrode for highly efficient and durable electrosorption of Yb(III) from aqueous solutions

In this study, the novel Fe-doped CoS2@nitrogen-doped carbon (Fe-CoS2@NC) composites were manufactured and investigated as the capacitive deionization (CDI) electrode materials for electrosorption of Yb(III). The as-prepared materials were characterized with X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, N2 adsorption–desorption test with Brunauer-Emmett-Teller method, Raman spectroscopy, and X-ray photoelectron spectroscopy. The electrochemical tests, including cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy, revealed that Fe-CoS2@NC exhibited the better electrochemical performance with a specific capacitance of 58.41 F g−1 than Fe-CoS2@0.5NC and Fe-CoS2. The electrosorption results demonstrated that Fe-CoS2@NC possessed the Yb(III) uptake of 129.4 mg·g−1 within 60 min at a voltage of 1.2 V and a flow rate of 20 mL·min−1. After five successive sorption–desorption cycles, the electrosorption efficiency of Fe-CoS2@NC remained at 98 %, exhibiting the robust durability for future industrial application. Furthermore, Fe-CoS2@NC also showed the favorable electrosorption performance towards various rare earth ions, especially for heavy rare earth ions. The mechanism analysis indicated that the impressive electrosorption performance is attributed to the synergistic contribution by the electric double layers of carbonaceous matrix and the pseudo-capacitance that induced by the redox reactions of Fe atom.

Solvent extraction for high separation strategy of light and heavy rare earth elements from a sulfate-leached solution of low-grade monazite

A novel separation strategy for light REEs (Ce4+ and La3+) and heavy REEs (Y3+ and Eu3+) from a low-grade monazite ore leached solution in a sulfate medium was studied to achieve a higher selectivity of metal ions. A prior separation of higher valence Ce4+ was performed using 8.0 vol% Cyanex 923, 0.2 mol/L H2SO4 in the aqueous feed, an organic-to-aqueous (O/A) phase ratio of 1, and a temperature of 25 °C, yielding the separation factor β(Ce4+/REEs3+) = 9424. A reductive back-extraction of Ce2(SO4)3 was efficiently performed using a solution mixture of H2SO4 + H2O2 with concentrations ≥1.0 mol/L each. Further, Y3+ from Ce4+-depleted solution was selectively extracted using 2.0 vol% Cyanex 572 organic extractant and 0.2 mol/L H2SO4 in aqueous feed at an O/A ratio of 1, yielding a separation factor of 6438 at 25 °C. The subsequent extraction of Eu3+ over La3+ was carried out at 2.5 vol% D2EHPA, 0.05 mol/L H2SO4 in the aqueous feed, an O/A ratio of 1, and a temperature of 55 °C, yielding β(Eu3+/La3+) = 5787. Both Y3+ and Eu3+ from the individually loaded organics were stripped with an efficiency of ∼ 99.9% by contact with 2.0 mol/L (COOH)2 prepared in a 1.0 mol/L HCl solution. The remaining La3+ in the raffinate was directly precipitated by adding ≥0.01 mol/L (COOH)2 crystals at 90 °C. This article provides an efficient and highly selective recovery of REEs from a low-grade monazite leached solution with higher separation values β(Ce4+/REEs3+) = 9424 and β(Eu3+/La3+) = 5787.

Provenance, chemical weathering, and sedimentary environment of the aquifer sediments: Implication for arsenic enrichment in groundwater

High arsenic (As) groundwater has been widely observed in the world, but the provenance, chemical weathering, and sedimentary environment of aquifer sediments hosting high As groundwater remain poorly understood. The geochemical and isotopic characteristics of high-resolution aquifer sediments were investigated to unravel the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments. The average values of rare earth elements (REEs) showed the enrichment of light REEs and flat heavy REEs in the aquifer and the Yellow River sediments. The chemical index of alteration reflected incipient and moderate weathering (41 to 71). The δ13CSOM (−27.4‰ ± 4.3‰) and C/N values (8.1 ± 5.8) indicated aquatic environment of sedimentation. Shallow aquifer sediments mostly had relatively high ΣREEs contents and negative Eu anomalies, demonstrating that the aquifer sediments were mainly derived from the Yellow River (up to 94.3% ± 5%). Deep aquifer sediments had relatively low ΣREEs contents and positive Eu anomalies, which originated from the Yinshan Mountains (up to 72.2% ± 20.4%) principally with igneous and metamorphic rocks. Moreover, recycling of the Yellow River sediments from Northeastern Tibetan Plateau enhanced the silicate weathering and increased contents of Fe/Mn oxides and As. The δ13CSOM and C/N values evidenced that organisms of paleo-lake or paleo-Yellow River were responsible for abundant sedimentary organic matter. Concentrations of Fe, Mn, and As were high in shallow groundwater from the plain. The As enrichment in the shallow groundwater was jointly controlled by the provenance and chemical weathering of the aquifer sediments (14%), sedimentary environment (10%), reductive dissolution (35%) of Fe/Mn oxides, As desorption under elevated pH (20%), and competitive adsorption of HCO3- (21%). This study systematically reveals the roles of provenance, chemical weathering, and sedimentary environment of the aquifer sediments and highlights joint contributions of geochemical processes and geochemical conditions to As enrichment in groundwater.

Eocene crustal thickening in the Tethyan Himalaya: Insights from Barrovian metamorphism and granite geochemistry from the Ramba area

Magmatism, structures, and metamorphism in the Ramba dome of the Tethyan Himalaya were investigated to shed light on orogenic processes during the early stages of the India-Asia collision. Deformed granite dikes in the dome envelope yield zircon U-Pb ages of ca. 45 Ma. These Eocene granites have adakitic, Na-rich compositions (K2O/Na2O = 0.20−0.61), weak to no Eu anomaly, enrichment in Sr, depletion in heavy rare earth elements and Y, and low MgO and Mg# contents. These characteristics contrast with the Miocene potassic granites in the core of the dome and suggest that the Eocene adakites were derived from the high-pressure melting of crustal amphibolites in a thick crust. The mica schists of the dome envelope have an early foliation (S1) that is overprinted by upright folds (F2). Phase-equilibria modeling of garnet and staurolite mica schists suggests a Barrovian-type, prograde P-T evolution in association with S1, with peak conditions of 6.7−7.2 kbar/590−605 °C and 7.3−7.8 kbar/650−670 °C, respectively, which are typical of crustal thickening metamorphism. Monazites from S1-dominated staurolite mica schists yield metamorphic ages of ca. 51−49 Ma, while those from the late foliation (S2) that transposed S1 give younger ages of ca. 10 Ma. The integration of geochemical, structural, metamorphic, and geochronological data suggests that peak Barrovian D1 metamorphism and adakitic magmatism occurred in the Eocene in response to crustal thickening. The results provide critical constraints for addressing the crustal shortening deficit of the region.

Geology and Geochemical Characterization of Basement Rocks Around Burumburum Area North Central Basement Complex Nigeria

The geology and the geochemical characterization of rocks around Burumburum area north central basement complex of Nigeria was studied. Twelve (12) rocks samples were prepared for petrographic studies through a standard procedure while thirty (30) whole rocks samples were analyzed using X-ray Fluorescence (XRF) and Inductively Coupled Plasma Mass Spectrometry(ICP-MS). The result of the field investigation revealed that the study area is underlain by migmatites, gneisses, biotite microgranites, fine grained biotite granites, medium grained biotite granites, porphyritic biotite-hornblende granites, granodiorites, syenites, diorites, dolerites, quartzite, pegmatites and aplites. The geochemical characterizations of the granites, granodiorites, syenites based on Na&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O/K&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O versus SiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; showed acidic compositions while diorites and dolerites are intermediate to basic compositions. The granites, granodiorites, syenites, diorites and dolerites are generally peraluminous (ASI&amp;gt;1.1) to metaluminous (ASI≤1). The granitic rocks, diorites, dolerites and syenites plotted mainly in shoshonite series while the granodiorites occur in High-K calc-alkaline fields. The granitic rocks, syenites, diorite and dolerites based on A/CNK versus SiO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; are of I-type while granodiorites are of S-type. The multi-elements discrimination trends for granites, granodiorites, syenites, diorites and dolerites revealed relative enrichment in Large Ion Lithophile Elements (LILE: Ba, La, Rb, and Th and depletion in High Field Strength Elements (HFSE: Nb, P, Ti and Sr) which indicates crustal contamination of magma. The enrichment in the light rare earth element (LREE) relative to heavy rare earth element (HREE) for granodiorites, fine grained biotite granites, medium grained biotite granites (except medium grained biotite granites S12 and S14 with positive Eu), porphyritic biotite-hornblende granites and syenites with negative Eu anomaly suggest moderate to high degree of fractionation. The enrichment in light rare earth element (LREE) for diorites and dolerites relative to moderate to flat HREE with weak negative Eu anomaly indicates low degree of fractionation. The Y+Nb vs Rb, Y vs Nb, Ta + Yb vs Rb and Yb vs Ta tectonic discrimination diagram revealed that granites and syenites plotted mainly within volcanic arc granite, syn-collisional granite and in the within plate granites fields, the granodiorites clearly plotted in the within the plate granites field. The tectonic ternary molecular proportions MgO – FeOt – Al&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3 &amp;lt;/sub&amp;gt;revealed that dolerites and diorites plotted mainly in the spreading center island field.

Mineral Chemistry and Chronology Investigation of Uraninite in the Jinguanchong Uranium Deposit in Eastern Hunan Province and the Implications for Geological Significance.

Jinguanchong deposit, a part of the Mingyuefeng ore field in eastern Hunan Province, China, is a typical perigranitic uranium deposit (a subtype of granite-related deposit) discovered recently with considerable uranium mineralization. Herein, uraninite, the primary ore mineral in the deposit, was investigated via scanning electron microscopy and electron probe microanalysis. Additionally, laser ablation-inductively coupled plasma-mass spectrometry was used for the first time to determine the in situ U-Pb age and the rare-earth element characteristics of uraninite. Uraninite mainly comprises UO2, CaO, and PbO with a low ThO2 content. Uraninite exhibits a low total content of rare-earth elements with a distinct fractionation between light and heavy rare-earth elements while displaying a negative Eu anomaly. The presence of major elements and rare-earth elements in uraninite suggests its formation within a hydrothermal environment at moderate to low temperatures below 350 °C, thereby classifying the Jinguanchong deposit as a typical hydrothermal vein-type uranium deposit. The uranium metallogenic age is determined to be 93.8 ± 1.4 Ma, falling within the midlate Cretaceous period. This age corresponds to the Mesozoic lithospheric extension and thinning events (approximately 85-95 Ma) in South China, suggesting that the formation of the Jinguanchong uranium deposit might be associated with the tectonic dynamics of lithospheric extension and thinning.

Discussion of the W-Sn-REE Metallogenic Background in the Nanling Region of South China: Evidence from Satellite Gravity and Magnetic Data

The Nanling region is located at the intersection of the Yangtze Block and Cathaysia Block and is characterized by complex geological and tectonic processes, as well as distinct W-Sn-REE mineralization. Despite extensive research on the mineralization of W-Sn and REE deposits in the Nanling region, the factors impacting the distribution pattern of eastern tungsten and western tin deposits, as well as the mechanism of REE enrichment in the parent rocks, remain uncertain. Deep structural and tectonic variability plays a crucial role in the formation of mineral deposits in the upper crust. Information on deep structural and tectonic variability is contained in the Moho depth, Curie depth, effective elastic thickness, lithospheric density, and thermal structure derived from the processing and inversion of satellite gravity and magnetic data. In this paper, we comprehensively analyse satellite gravity and magnetic data from the Nanling region, integrating the processing and inversion results with the tectonic evolution of this region and relevant geological information. It is hypothesized that the Chenzhou–Linwu fault serves as a channel for mineral and thermal transfer in the Sn ore aggregation zone, facilitating the material transport from the deep mantle to the surface and ultimately leading to the formation of Sn-enriched granite. The collection area of tungsten ore is more weakly associated with the Chenzhou–Linwu fault, and through deep heat transfer, tungsten components are primarily concentrated in the Earth’s crust to produce W-enriched granite. The primary source of REE enrichment in the parent rocks associated with REE mineralization is predominantly derived from the felsic crust, and the rapid intrusion of deep magma resulting from the subduction and retraction of the Palaeo-Pacific Plate is a contributing factor to the contrasting enrichment of light and heavy rare-earth elements. Mineral crystalline differentiation is relatively high, leading to the formation of ore-forming parent rocks with high heavy rare-earth element contents.

Petrogenesis and tectonic implications of the Bloubergstrand basaltic andesites, Tygerberg Formation, Malmesbury Group, Pan-African Saldania Belt, southwestern Africa

Abstract The Bloubergstrand Member, consisting of mafic to intermediate tuffs and flows within the Tygerberg Formation of the Malmesbury Group, is a crucial but understudied component of the western Saldania Belt in southwestern Africa. With a U-Pb zircon age of 555 ± 5 Ma, these volcanic rocks provide valuable insights into the origins and, more broadly, the tectonic setting of the Saldania Belt during the final stages of Malmesbury Group sedimentation in the context of the construction of southwestern Gondwana at approximately 560 to 540 Ma. The Bloubergstrand Member amygdaloidal volcanic rocks vary from basaltic andesitic to andesitic and have experienced varying degrees of alteration. The volcanic rocks are enriched in the large ion lithophile elements (LILE) relative to the high field strength elements (HFSE). When normalised to primitive mantle values, they show enrichment in Cs, Rb, K and Pb and mild enrichment in Th, U, Zr and Hf, with the light rare earth elements (LREE) enriched relative to the heavy rare earth elements (HREE). They are depleted in Ba, Nb, Ta, Sr, Eu, P and Ti. εNd(t) values are mildly negative ranging from -3.60 to -2.39, and Nd TDM model ages range from 1.4 to 1.7 Ga. Initial 87Sr/86Sr ratios vary from 0.70478 to 0.70620, with one higher value of 0.72270, the latter likely due to extensive alteration. The Bloubergstrand Member volcanic rocks exhibit characteristics suggesting their origin from partial melting of lithospheric to transitional asthenospheric upper mantle, influenced by sediment-derived melts and variable degrees of crustal contamination. With continental arc basalt compositions and similarities to shoshonites, the samples reflect variable degrees of partial melting and source heterogeneities. Fractional crystallisation of pyroxenes, hornblende, and plagioclase contributes to compositional variability. Erupting in a continental arc margin, likely part of the Arachania block of the Kalahari craton, separated during the Tonian break-up of Rodinia, the volcanics were associated with the Marmora basin formed by eastward-directed subduction below the western Kaapvaal Craton margin. Extruded in a distal position relative to the Cuchilla Dionisio Arc in present-day southern Brazil and Uruguay, these volcanic rocks preceded the closure of the southern Marmora basin. The mantle melting, possibly a result of slab roll-back, break-off, ridge subduction, or a combination, served as a precursor to the lower crustal heating that generated the granitic magmas of the Cape Granite Suite.

Effect of Calcination Atmosphere on the Acid Leaching Recovery of Rare Earth Elements in Coal-Byproducts

ABSTRACT Thermal treatment of coal byproducts has been shown to improve leaching characteristics of rare earth elements (REEs) in bituminous coal sources due to its influence on the associated minerals. This study investigated the impact of the calcination atmosphere on REE leaching behavior in different density fractions of Baker and Fire Clay seam coarse refuse sources using a thermogravimetric analyzer to create an oxidizing or reducing atmosphere at a desired temperature for 2 h. The effect on leaching characteristics was evaluated using 1.2 M sulfuric acid at 75°C for 5 h at 1% w/v solid concentration. Rare earth element (REE) recovery for the 2.2 specific gravity (SG) sink fraction improved by approximately 15 absolute percentage points at 1000°C relative to the 600°C calcined sample in an inert atmosphere and equilibrated within 10 min from the start of the test. Contrarily, thermal treatment at 1000°C under oxidizing atmosphere significantly reduced the REE recovery due to sintering of the clays, which limited access to the RE minerals for leaching. In general, thermal treatment of heavier fractions in both atmospheres significantly improved the light REE (LREE) recovery while the increase in heavy REE (HREE) recovery was relatively less. As common clay minerals in the coal sources, kaolinite and illite samples were tested under the same conditions and using a digital scanning calorimeter. The findings confirmed that the improvement observed in REE leaching through thermal treatment at 600°C was due to decarbonization for the lighter density fractions and dehydroxylation of clays.

Utility and influence mechanism of densification modulation on grain boundary diffusion in NdFeB magnets

Grain boundary diffusion technology is pivotal in the preparation of high-performance NdFeB magnets. This study investigates the factors that affect the efficiency of grain boundary diffusion, starting from the properties of the diffusion matrix. Through the adjustment of the sintering process, we effectively prepared magnets with varied densities that serve as the matrix for grain boundary diffusion with TbHx diffusion. The mobility characteristics of the Nd-rich phase during the densification stage are leveraged to ensure a more extensive distribution of heavy rare earth elements within the magnets. According to the experimental results, the increase in coercivity of low-density magnets after diffusion is significantly greater than that of relatively high-density magnets. The coercivity values measured are 805.32 kA/m for low-density magnets and 470.3 kA/m for high-density magnets. Additionally, grain boundary diffusion notably enhances the density of initial low-density magnets, addressing the issue of low density during the sintering stage. Before the diffusion treatment, the Nd-rich phases primarily concentrate at the triangular grain boundaries, resulting in an increased number of cavity defects in the magnets. These cavity defects contain atoms in a higher energy state, making them more prone to transition. Consequently, the diffusion activation energy at the void defects is lower than the intracrystalline diffusion activation energy, accelerating atom diffusion. The presence of larger cavities also provides more space for atom migration, thereby promoting the diffusion process. After the diffusion treatment, the proportion of bulk Nd-rich phases significantly decreases, and they infiltrate between the grains to fill the cavity defects, forming continuous fine grain boundaries. Based on these observations, the study aims to explore how to utilize this information to develop an efficient technique for grain boundary diffusion.