Extraction and mobilization of rare earth elements (REEs) from carbonatite-hosted deposits remains a major challenge due to the limitations of conventional acid-leaching processes. This study presents a potentially more environmentally compatible extraction approach for REE mobilization and capture from the Amba Dongar carbonatite complex, Gujarat, India, by integrating alkali roasting, water leaching, and clay-based adsorption–desorption. Inductively coupled plasma mass spectrometry (ICP-MS) analyses of carbonatite and carbonatite–fluorite samples revealed high total REE concentrations dominated by Ce and La. Alkali roasting with NaOH followed by water leaching effectively mobilized REEs under mild, acid-free conditions. Four natural clays—montmorillonite, bentonite, attapulgite, and kaolinite—were evaluated as low-cost adsorbents. Mineralogical and structural analyses using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Raman spectroscopy confirmed active surface and lattice sites responsible for REE uptake. Smectite clays (montmorillonite and bentonite) exhibited superior adsorption efficiency due to interlayer cation exchange, while attapulgite displayed moderate uptake but enhanced desorption associated with its channel-type morphology. Kaolinite exhibited the weakest performance due to its low cation exchange capacity. Ultraviolet–visible (UV–Vis) and fluorescence spectroscopy validated REE–clay interactions, displaying characteristic absorption (294, 343 nm) and emission features (200–390 nm). Overall, the observed adsorption hierarchy (montmorillonite ≈ bentonite > attapulgite > kaolinite) highlights the potential of this integrated approach as a preliminary and environmentally compatible framework for REE mobilization and selective capture from carbonatite-derived leachates.
The unique geochemical fingerprints of trace-element distribution patterns in sphalerite are particularly useful for discriminating Pb–Zn deposit types. In this study, we developed a high-performance sphalerite classification model for deposit types based on a dataset of sphalerite analyses, using tree-structured Parzen estimator (TPE) optimization with a support vector machine (SVM) algorithm. The dataset comprises 3117 analyses of sphalerite sourced from peer-reviewed publications covering 102 representative Pb–Zn deposits worldwide spanning five major genetic types, including sedimentary exhalative (SEDEX), volcanic massive sulfide (VMS), Mississippi Valley type (MVT), skarn, and epithermal deposits. Each analysis covers 12 critical trace elements (Mn, Fe, Co, Cu, Ga, Ge, Ag, Cd, In, Sn, Sb, and Pb). The optimized model demonstrated exceptional discriminative capability. It achieved a test-set accuracy of 0.9749 and delivered consistent performance across the precision, recall, and F1-score metrics. SHAP (SHapley Additive exPlanations) interpretability analysis revealed that key indicator elements (Mn, Ge, and Co) are critical for genetic classification, although there are distinct patterns of trace elements across deposit types. Dimensionality-reduction analyses (UMAP and t-SNE) reveal distinct clustering of magmatic-hydrothermal deposits (skarn, VMS, epithermal) and sedimentary-related systems (MVT, SEDEX), reflecting systematic differences in sphalerite trace-element signatures. This methodology was validated by conducting blind, machine-learning-based classification tests on the Fule and Haobugao Pb–Zn deposits. The results suggest that the TPE-optimized SVM model can identify interpretable geochemical patterns in sphalerite, making it an effective tool for distinguishing between different types of Pb–Zn deposits.
The Tuguanzhai–Maliping ion-adsorption rare earth element (iREE) deposit, located in the high-altitude Tengchong Block of southwestern China, challenges the conventional view that highly complex terrains are unfavorable for iREE mineralization. This study presents a detailed investigation of weathering profile 3239 within this deposit, which exhibits significant fractionation between light rare earth elements (LREE) and heavy rare earth elements plus yttrium (HREY), characterized by LREE enrichment in the upper section and HREY enrichment in the lower section. Through systematic analyses, including ore microscopy, mineralogy, whole-rock geochemistry, sequential extraction of REE phases, and mass balance calculations using Zr as an immobile reference element, the fractionation and enrichment behaviors of REE during weathering are constrained. The mass balance coefficient τHREY in profile 3239 reaches a maximum value of 6.31, indicating intense supergene enrichment of HREY that contrasts with the LREE-enriched signature of the parent rock. Vertical migration of REE within the profile reveals that the differentiation between LREE and HREY is not gradual but rather marked by an abrupt enrichment of HREY in the lower section, accompanied by a sharp decline in the REE/HREY ratio. Correlation analysis shows that τHREY is positively correlated with τTFe2O3 and τMnO, and exhibits a significantly stronger correlation with the colloidal fraction of REE than with other fractions, suggesting that Fe–Mn oxides/hydroxides exert control over HREY enrichment. In addition, τHREY shows strong correlations with τAl2O3, τK2O, and τNa2O, reflecting the link between alkaline feldspar leaching and HREY migration–adsorption processes. The notably strong correlation between τHREY and τLOI further implies that soil solutions or groundwater-rich horizons play a critical role in the formation of HREY-enriched layers. In contrast, τHREY displays weak correlations with weathering indices such as the chemical index of alteration (CIA), plagioclase index of alteration (PIA), Na-feldspar index of alteration (NIA), and K-feldspar index of alteration (KIA), indicating that HREY migration and enrichment are largely insensitive to the overall degree of weathering. This detailed profile-based study suggests that, under specific high-altitude geochemical and supergene conditions, significant HREY enrichment can occur within granitic weathering crusts, leading to the formation of HREY-enriched ore bodies characterized by a distinctive “reverse” fractionation pattern. These findings expand the genetic model of iREE deposits and provide a theoretical basis for REE exploration in nontraditional, topographically complex regions, although this understanding requires further validation through additional profile studies.
The present study discusses the geochemical, mineral composition, sulphur isotope and fluid inclusion studies of the Masayapeta copper prospect, Nellore Schist Belt, Southern India. The detailed integrated study reveals that surface samples have 0.13%–0.52% Cu, whereas subsurface drill core samples have 0.95%–1% Cu in quartz-chlorite-sericite schist, making it an interesting area for further investigation to understand the nature and genesis of the ore-forming processes. Ore petrographic study reveals that chalcopyrite and pyrite occur as dominant phases, followed by bornite and magnetite in different textural associations. These phases show strong late fluid alteration, i.e., conversion into chalcopyrite → covellite → digenite, indicating a replacement fluid path.
Masayapeta pyrite is characterized by elevated Co/Ni ratios (> 10), high core Co contents (0.06–2.1 wt%), low initial As concentrations (~ 0.25 wt%) and minimal incompatible element enrichment in cores, reflecting precipitation from high-temperature, reduced magmatic fluids exsolved directly from magmatic source. In contrast, it exhibits progressive As rimward enrichment (up to 0.99 wt%), oscillatory zoning with rising incompatible metals (Au to 0.13 wt%, Pb to 0.16 wt%, Ag to 0.23 wt%) and low Co/Ni ratios (1–10), indicative of evolved, cooler hydrothermal fluids influenced by boiling, mixing and meteoric dilution, which enhance metal mobility and copper fertility. The compositions of chalcopyrite (CuFeS2) and oxidized magnetite (high FeOᵀ, low TiO2, variable Al2O3) confirm high-T magmatic fluids under stable fS2–fO2, with bimodal Fe–Ti oxides indicating mafic-intermediate igneous precursors overprinted by felsic-hydrothermal alteration. This indicated the role of regional granitic magmatism for the evolution of an ore system, akin to the granite-greenstone belt, elsewhere. Fluid inclusions (Th 160–330 °C, salinity 0.66–9.32 wt% NaCl equiv., CO2-rich, densities 0.63–0.93 g/cm3) document hypersaline magmatic brines mixed with meteoric influx, driving copper sulphide precipitation. Furthermore, the δ34S values at Masayapeta (− 0.2‰ to − 12.3‰) reveal a hybrid sulphur budget blending magmatic-hydrothermal fluids with reduced sedimentary/biogenic sources. This is further amplified by isotopic fractionation via boiling, fluid mixing or disequilibrium sulphide precipitation in magmatic-hydrothermal systems. The above comparative study using various proxies indicates mixed signatures, i.e., a dominant magmatic fluid source, locally modified by meteoric input during late-stage hydrothermal evolution, signifies a magmatic-hydrothermal type of copper mineralization.
The accretion of terrestrial planets involved violent collisions among planetesimals, but the mechanisms of volatile element loss during these impacts remain debated. Chondrites, the building blocks of planets, preserve a direct record of these processes. To investigate the behavior of volatiles during impacts, we conducted a paired study of sulfur (S) and copper (Cu) elemental abundances and isotope compositions in shock-melted and unmelted portions of three ordinary chondrites (Chelyabinsk LL5, Viñales L4, Tassédet 004 H5). Our results reveal that sulfur is highly mobile during shock metamorphism. Its migration mechanism transitions from sulfide melt injection at lower shock levels to sulfide decomposition and S2 vapor transport at higher intensities. The latter process leads to substantial S loss and pronounced heavy isotope enrichment in shock melt pockets (SMPs). In contrast, copper exhibits limited volatility, resulting in negligible Cu isotope fractionation under most shock conditions. Measurable Cu loss and heavy isotope enrichment were observed only in the most intensely shocked sample. Mass balance modeling indicates that these processes occurred under extreme shock conditions, and the observed isotope fractionation is best explained by vaporization in a diffusion-limited regime. Our findings demonstrate that impact-induced vapor loss is an effective mechanism for planetary sulfur depletion, whereas the Cu inventory of planetary bodies was likely governed by sulfide segregation during magmatic differentiation rather than evaporation during accretionary collisions.
This study investigates the basement migmatitic Grey Granitoid Gneisses (GGG) along the southern margin of the Chhotanagpur Gneissic Complex (CGC) in the Eastern Indian Shield through detailed petrography, mineral chemistry, whole-rock geochemistry, LA–ICP–MS U–Pb zircon geochronology, Hf isotopic analysis, and petrogenetic–tectonic interpretation. The GGG consists of medium-grained, granoblastic mesosomes with compositions spanning tonalite, trondhjemite, granodiorite, and granite. These rocks exhibit calc-alkaline, I-type affinities are metaluminous to weakly peraluminous, and range from magnesian to ferroan. Zircon grains are stocky to moderately elongate, mostly subrounded to rounded, and display oscillatory zoning, consistent with magmatic crystallization. Both whole-rock and zircon REE patterns show moderate fractionation with negative Eu anomalies. Primitive mantle–normalized spider diagrams reveal enrichment in Rb, K, Ba, Th, and U, and pronounced depletion in Nb, Ta, Sr, P, and Ti—signatures characteristic of arc-related granitoids. Low Nb/U (4.07–7.3) and Ce/Pb (0.52–4.1) ratios, together with high Th/U ratios (9.48–11.14), further indicate a predominantly crustal source. U–Pb zircon dating constrains GGG magmatism to 1397 ± 18 Ma (MSWD = 1.9). Zircon Lu–Hf isotopic compositions [εHf(t) = + 2.52 to − 6.86; TDM2 = 1.7–2.4 Ga] suggest derivation from juvenile amphibolitic lower crust variably hybridized with older crustal components. The presence of inherited 1616 Ma zircons, along with enclaves of amphibolite and migmatite, attests to direct remelting of older crust. Petrogenetic modeling indicates that the GGG mesosomes formed through ~ 20% partial melting of high-K metabasalts (amphibolites). Collectively, these results suggest that the 1616 Ma amphibolitic crust in the study area originated within a regional Paleoproterozoic continental arc–back-arc system along the Satpura Orogenic Belt, and subsequently served as a fertile source for Mesoproterozoic hybrid magmatism.
Ferruginous cherts and associated siliciclastic rocks of the Neoproterozoic Buem Structural Unit (Eastern Ghana) provide a unique archive for reconstructing fluid sources, hydrothermal processes, and basin evolution along the margin of the West African Craton. This study presents new whole-rock major and trace element geochemical data from cherts, shales, and sandstones to constrain the origin of the ferruginous facies and evaluate the influence of hydrothermal activity and depositional redox conditions. The ferruginous cherts display enrichments in Fe2O3, Ba, Sr, and transition metals (Cu, Ni, Zn), together with elevated ΣREE and moderately fractionated chondrite-normalized patterns. Positive Eu anomalies (Eu/Eu* = 1.05–1.30), variable Ce anomalies, and high Y/Ho ratios (20–28) indicate mixing between seawater-derived silica and high-temperature hydrothermal fluids, likely sourced from mafic volcanic substrates. PAAS-normalized patterns of both cherts and siliciclastics suggest limited terrigenous dilution in the ferruginous cherts but significant detrital inputs in the shales and sandstones, dominated by felsic to intermediate crustal material. Trace element ratios including Th/U, V/Cr, Ni/Co, and U concentrations collectively indicate predominantly oxic to sub-oxic depositional conditions with localized reducing microenvironments associated with Fe–Mn-rich fluids. Provenance-sensitive indicators (e.g., La/Sc, Th/Sc, Zr/Hf) in the shales and sandstones, although deposited on a passive margin, point to a continental margin affinity consistent with the erosion of the Birimian Supergroup and Pan-African granitoid sources. These geochemical signatures reveal that the Buem basin evolved under the combined influence of hydrothermal venting, silica-iron precipitation, and sustained detrital influx from adjacent continental sources. The ferruginous cherts represent the main hydrothermal imprint in the sequence, whereas the siliciclastics record broader basin-scale provenance and redox signatures. These results refine the understanding of Neoproterozoic basin dynamics in southeastern Ghana and highlight the role of hydrothermal activity in shaping chemical sedimentation within the Pan-African orogenic framework.
Among the numerous scientific questions concerning the evolution of the Tethys on the Qinghai–Xizang Plateau, the initial breakup of the Lhasa terrane from northern Gondwana remains disputed. This controversy stems primarily from the scarcity of intraplate magmatic records associated with this event and insufficient systematic research into its genetic mechanisms. However, the discovery of a Mid-Permian Luerma within-plate basalt in the Western part of the Lhasa Terrane provides new evidence for the exploration of this issue. Building on U–Pb dating of zircon via laser ablation–inductively coupled plasma–mass spectrometry (LA‒ICP‒MS), the estimated age of the basalt is approximately CA. 261 ± 1 Ma. Geochemically, the rock belongs to the shoshonite–latite series and contains high levels of iron (Fe2O3, 4.67–5.57 wt%; FeO, 3.51–5.59 wt%), magnesium (MgO, 3.86–6.58 wt%), total alkalis (K2O + Na2O, 4.43–8.07 wt%), and titanium (TiO2, 2.00–3.78 wt%). Additionally, the basalt is enriched in large-ion lithophile elements and light and heavy rare-earth elements (LREEs/HREEs) whose ratios of the samples range from 9.92 to 16.92), with no apparent Eu or Ce anomalies (δEu, 0.88–1.07 and δCe, 0.81–1.22). Isotopically, the rock exhibits high εNd(t) (0.77–2.76) and εHf(t) (6.60–9.00) and low (87Sr/86Sr)i (0.703248–0.705597) values. These findings indicate that the basaltic magma originated from the partial melting of the upper mantle within a plate. This study revealed that the Lhasa terrane separated from northern Gondwana by at least the Mid-Permian.
The Qingshan Pb–Zn deposit is characterized by high-grade ores (averaging 7.72% Pb and 32.6% Zn) and significant structurally controlled mineralization, both of which are of substantial economic and genetic importance. Although previous studies have elucidated the sources of ore-forming materials and their structural controls, tectono-geochemical research has been predominantly confined to shallow subsurface workings, with analyses limited to two-dimensional anomalies at the individual level. Consequently, both the three-dimensional (3D) distribution and vertical zoning of these anomalies remain poorly understood, and a comprehensive spatial correlation framework is yet to be established. This gap impedes in-depth exploration planning. To address this issue, systematic tectono-geochemical sampling and analysis were conducted at three representative levels (1678, 1650, and 1608 m) within the mining area. The R-mode cluster and factor analyses identified three elemental associations: F1 (Ge, Hg, Pb, Zn, Cd, As, Sb, Cu, Ga, In, and W), representing a medium- to low-temperature ore-forming assemblage; F2 (Ni, V, Co, and Mo), corresponding to high-temperature elements; and F3 (Ba and Bi), reflecting a wall-rock alteration assemblage. The 3D anomaly superposition analysis indicates that: (1) the concealed orebody strikes NW and dips steeply SW, with a pronounced SE plunge; (2) ore-transporting structures (F1, F2) and ore-hosting structures (interlayer fault zones) collectively control mineralization; (3) the ore-controlling structures exhibit a step-like distribution; (4) the ore-forming fluids migrate vertically from deep to shallow levels and horizontally from SE to NW. Vertical zoning, determined by the concentration index method, shows a top-to-bottom sequence of Cu-As-Ba-Bi-W → Cd-Ge-Hg-Pb–Zn-Sb → In-Ga-Mo-Ni-V-Co, indicating a typical “inverted zoning” pattern. This inverted zoning pattern indicates multi-stage superposition of mineralization and suggests a significant downward extension of the orebodies and/or the presence of concealed orebodies at depth. Based on these findings, three prospective target areas are proposed, providing a scientific basis for deep exploration in Qingshan and guidance for similar deposits.
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