Prolonged consumption of high-fluoride groundwater poses severe global public health risks, yet it remains unclear how fluoride enrichment drivers differ across geogenic zones of element excess (ZEE), where elevated elemental background concentrations readily trigger endemic fluorosis modulated by regional climatic conditions. This study presents the first cross-continental integrated hydrogeochemical and stable isotope comparison of fluoride enrichment mechanisms in two geologically distinct ZEEs: the volcanic Kenya Rift Valley and sedimentary Yuncheng Basin of northern China. Results demonstrate broader, more severe fluoride contamination across Yuncheng Basin (0.5‒14.1 mg/L, median 3.8 mg/L) than Kenya Rift Valley (0.01‒23.5 mg/L, median 0.9 mg/L). Groundwater from both sites is neutral to slightly alkaline, sodium-rich and calcium-poor, jointly shaped by rock weathering, evaporation, and cation exchange, yet fluoride enrichment mechanisms diverge distinctly: cation exchange exerts dominant control in Kenya, while evaporation, salt effects, competitive anion adsorption, and human activities exert stronger influences in Yuncheng, with coupled fluorite–calcium dissolution equilibrium acting as the universal core constraint on dissolved fluoride levels. This comparative evidence reveals divergent fluoride driving systems even within analogous element excess zones, indicating that caution should be exercised when evaluating groundwater fluoride hazards without site-specific geochemical discrimination.
The Late Permian to Early Triassic represents a critical period for understanding the tectonic evolution of the Paleo-Tethys Ocean, particularly regarding the transition from continental rifting to arc magmatism along the western margin of the Yangtze Plate. There is an exposed suite of gabbro in the carbonate and clastic rocks of the Upper Permian Shanglan Formation in the Madeng area, which is located in the eastern margin of the Lanping Basin. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U–Pb zircon dating yielded a weighted mean age of 236.3 ± 0.82 Ma, indicating that these gabbros were emplaced in the Late Triassic. The rocks belong to the calc-alkaline series and are characterized by high Na2O/K2O ratios (1.77–5.31), weak light rare earth element enrichment, significant large-ion lithophile element (e.g., Rb, U, and Sr) enrichment, and relative high-field-strength element (e.g., Nb) depletion. The δEu values range from 0.78 to 1.01, the zircon εHf(t) values range from −7.76 to 3.02, the whole-rock (87Sr/86Sr)i ratios range from 0.707501 to 0.708713, and the εNd(t) values are negative, ranging from −2.4 to −2.9. Based on the geological occurrence and petrogeochemical characteristics, the gabbro can be interpreted as having formed in an active continental margin setting (i.e., a continental margin arc). It constitutes part of the Jomda–Weixi–Yunxian arc magmatic belt, having developed along the western margin of the Yangtze Plate, and the magma was derived from enriched mantle that had been significantly modified by subduction-related fluids and sediments. This study provides new constraints on the eastward subduction dynamics along the Changning–Menglian suture zone.
The Geza arc belt in Yunnan Province, located in the southern segment of the Yidun arc, is one of the important newly discovered Cu–Mo–W polymetallic metallogenic belts in the Sanjiang Tethyan tectonic belt of southwestern China in recent years. During the Late Yanshanian, porphyry-skarn-type Mo(Cu) deposits and hydrothermal-type W(Mo) deposits formed in association with collisional magmatic intrusions. Among them, the Relin Cu–Mo–W polymetallic deposit is a typical representative of Late Yanshanian diagenesis and mineralization in this region. Based on systematic field work, this study conducted comprehensive research on the deposit geology, mineralogy, and geochemical compositions of scheelite from the Relin deposit, and examined its diagenetic and metallogenic ages combined with zircon U–Pb dating. Laser ablation–inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating results show that the ore-hosting monzogranite was formed in the Late Cretaceous, with weighted mean ages of 80.2 ± 0.6 Ma and 80.7 ± 0.6 Ma. The Sr isotopic compositions of scheelite (0.70774–0.7091) are in excellent agreement with those of the ore-hosting monzogranite (0.70746–0.70930), indicating a close temporal coupling between scheelite mineralization and Late Yanshanian magmatic activity. Geochemical characteristics reveal that scheelite has significantly higher total rare earth element (ΣREE) contents (723.48–6991.74 ppm) than the host monzogranite, with strong fractionation between light and heavy rare earth elements (LREE/HREE = 1.59–53.00, average = 16.87) and strongly negative Eu anomalies (average δEu = 0.37). This suggests that REEs, as incompatible elements, were preferentially enriched in the residual ore-forming fluid phase during magmatic evolution. The substitution of REE3+ in scheelite follows a mixed mechanism: it is dominated by the vacancy-coupled substitution (3Ca2+ = 2REE3+ + □Ca, □Ca denotes a Ca-site vacancy), with minor contributions from Na+ charge compensation (2Ca2+ = REE3+ + Na+) and Nb5+ charge compensation (Ca2+ + W6+ = REE3+ + Nb5+) substitutions. Scheelite in the mining area is significantly enriched in Mo (4060.12–30,441.51 ppm, average = 16,821.14 ppm), and the Mo enrichment is mainly derived from exsolution of the monzogranite. The oxidation state of Eu, combined with Mo contents and δEu values, indicates that the ore-forming fluids were predominantly oxidized. The Y/Ho ratios of scheelite range from 22.73 to 30.35, consistent with the Y/Ho ratios of regional monzogranites (27–30). Synergistic evidence from Sr–Nd isotopes suggests that the ore-forming fluids were derived from anatexis of ancient continental crust, with no large-scale fluid mixing or significant water–rock interaction. The Y/Ho geothermometer estimates that the mineralization temperature of scheelite was approximately 440 °C. In summary, this study proposes that scheelite in the Relin deposit formed during the late stage of magmatic evolution. When volatiles in the magmatic melt reached saturation, fluid exsolution occurred, and tungsten was preferentially released into the fluid phase, forming tungsten-rich ore-forming fluids. During the outward migration of exsolved ore-forming fluids, variations in physicochemical conditions promote the combination of WO42− in ore-bearing fluids with native Ca2+ from magma and minor Ca2+ released by plagioclase decomposition, generating scheelite (CaWO4). This process ultimately completes the mineralization of various types of scheelite hosted within the Late Yanshanian granites of the Relin Cu–Mo deposit.
Plutonic bodies commonly assemble incrementally, yet the significance of dispersed zircon U–Pb ages within individual plutonic samples remains debated. This study presents integrated geochemical, zircon U–Pb geochronological, and Lu–Hf isotopic data for the Emeishan granitoids from the western margin of the Yangtze Block. The relatively homogeneous εHf(t) values (+0.4 to +9.3 for granitoids; +3.0 to +7.6 for enclaves) indicate that they were generated by reworking of juvenile continental arc crust. Magmatic zircon U–Pb ages span ca. 900–800 Ma, with predominant age peaks at ca. 890, 860, and 810 Ma, suggesting multiple episodes of crustal reworking and incremental pluton assembly rather than discrete, independent magmatic phases. All granitoids exhibit A-type affinities, characterized by enrichment in large-ion lithophile elements and light rare earth elements, depletion in Nb, Ta, and Ti, negative Eu anomalies, and high zircon saturation temperatures (840–889 °C). Together with the youngest age population (ca. 810 Ma), these features indicate that the Emeishan granitoids were emplaced in an extensional setting and incorporated older antecrystic zircons. Consequently, single weighted-mean zircon ages may oversimplify the evolution of long-lived plutonic systems. Instead, the large zircon age spans of the Emeishan granitoids record episodic Neoproterozoic magmatism and protracted incremental pluton assembly along the western margin of the Yangtze Block.
Continental silicate weathering plays a fundamental role in shaping Earth's surface because of its influence on elemental redistribution and pedogenic processes within critical zones. In this study, we integrate geochemical and isotopic (δ44/40Ca and δ7Li) data from weathering profiles developed on the Cenozoic Penglai basalts, which are located along the northeastern coast of the Shandong Peninsula, North China, to investigate elemental and isotopic behavior during weathering. The fresh Penglai alkaline basalts are characterized by low δ44/40CaSRM915a values (0.56‰–0.73‰) and Ocean Island Basalt (OIB)-like trace element signatures. With progressive weathering, SiO2 decreases (from 45.19 wt.
Sequential hydrous pyrolysis was applied to an organic-rich source-rock sample from the Upper Devonian Domanik Formation of the Timan-Pechora Basin to investigate changes in hydrocarbon biomarkers during experimental maturation. The Domanik Formation is a major source-rock interval within the Domanik-Paleozoic petroleum system and is composed of organic-rich carbonate-siliceous deposits with predominantly type II kerogen and high petroleum-generative potential. The study compares the initial oil and source-rock extractable organic matter with generated liquid products and residual extracts obtained after three successive hydrous-pyrolysis stages at 300 °C for 72 h under closed-system conditions. The results show that repeated hydrous pyrolysis causes systematic changes in n-alkane, isoprenoid, sterane, and terpane parameters. Several commonly used correlation and maturity indices remain comparable between the initial oil and source-rock extract, but diverge markedly after successive pyrolysis stages. These observations indicate that sequential hydrous pyrolysis modifies biomarker signatures through continued generation, cracking, and redistribution of soluble organic products. Therefore, biomarker-based oil–oil and source rock–oil correlations should be interpreted cautiously when laboratory-generated products or strongly transformed fluids are compared directly. The observed increase in the C28/C29 sterane ratio during successive stages may reflect selective transformation of sterane precursors, but this interpretation remains a working hypothesis that requires further testing on additional samples. The study demonstrates the usefulness of sequential hydrous pyrolysis for tracing biomarker redistribution during maturation.
Non-destructive surface exposure (EDXRF) analyses for major and trace elements are widely used in archaeological investigations to characterize sources of artifacts and stone tools because these methods provide geochemical information on objects that usually cannot be destroyed. However, EDXRF methods are not used in most geological investigations where sample destruction is the norm. Thus, a variety of destructive whole rock chemical methods are relied upon for geoscientific research within geochemistry, volcanology, petrology, etc. In this paper, we examine the utility of benchtop EDXRF as a rapid and relatively inexpensive analytical method to correlate volcanic rocks in a variety of geological and archaeological situations and investigations. We compare EDXRF and WDXRF analytical results on four groups of Late Neogene through Quaternary volcanic rocks from the Jemez Mountains region: 1) Cerro del Medio obsidian, rhyolite, and pumice, 2) upper flow units of Tshirege Member, Bandelier Tuff, 3) porphyritic lavas from Rendija Canyon rhyodacite and pumiceous beds in the Puye Formation, and 4) vitreous and aphyric dacites and a basalt from various locations. Standard major element analyses by EDXRF and WDXRF methods are relatively comparable for glassy silicic rocks like rhyolite (e.g., ≤ 2 wt
Selenium hyperaccumulator species are a vital biomass resource for humans taking in Se, with its selenate transport intricately linked to leaf intracellular nutrient characteristics. However, prior research has not explored dynamic electrophysiological intracellular nutrient parameters and selenium tolerance of selenium hyperaccumulator species. This study investigated the selenium hyperaccumulator Cardamine violifolia (C. violifolia) by evaluating its growth, photosynthetic capacity, leaf selenium transport-accumulation coefficients, and electrophysiological traits, including intracellular nutrient parameters, cellular metabolic energy, and B-type dielectric properties. The results revealed the dynamics of intracellular electrophysiological parameters under varying selenate levels and identified the optimal (S1, 50 mg/L Se6+) and tolerable (S3, 150 mg/L Se6+) selenate concentrations for C. violifolia. Compared to the control (CK), the S1 treatment significantly enhanced key physiological parameters in C. violifolia. Specifically, we observed increases ranging from 11.76
The Hongshiyan large-scale Pb–Zn–Cu deposit is located in the Laojunshan Sn–W–Zn–In polymetallic ore concentration area in the southeastern South China Block. The deposit contains proven reserves of 0.43 Mt Pb + Zn and 18 kt Cu. The layered and stratiform orebodies are mainly hosted within phyllite and marble of the Cambrian Tianpeng Formation. Based on mineral assemblages and petrographic observations, the mineralization is subdivided into three successive stages: early (stage I), main (stage II), and late (stage III). The newly obtained in-situ Pb isotopic compositions of galena (206Pb/204Pb = 18.154–18.160, 207Pb/204Pb = 15.712–15.718, and 208Pb/204Pb = 38.464–38.512) indicate a homogeneous metal reservoir. These data also plot within the Pb isotopic field of the Late Cretaceous Laojunshan granite in the region. The wide range of sphalerite δ66Zn values (+ 0.29‰ to + 0.75‰) is predominantly controlled by Rayleigh fractionation during sphalerite precipitation. Rayleigh fractionation modeling yields an initial hydrothermal fluid δ66Zn value of + 0.3‰, which is highly consistent with that of the lower continental crust (0.28‰ ± 0.04‰). We therefore propose that the ore-forming materials of the Hongshiyan deposit originate from deep-seated Late Cretaceous granite.
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.
Phosphate minerals enriched in rare-earth elements (REEs) represent one of the typical mineral phases on the Moon. Nevertheless, their space weathering behavior remains insufficiently understood. In this study, two types of REE-enriched phosphate minerals—changesite-(Y) and monazite—were identified in the Chang’e-6 lunar soil sample, which was collected from the Apollo Basin on the lunar far side, a region characterized by low REE abundance. Their potential formation mechanisms are postulated as follows: (1) they originated as exogenous materials delivered as impact ejecta from thorium-enriched source regions within the South Pole-Aitken (SPA) basin; (2) they are products of crystallization during the late-stage solidification of the lunar magma ocean. Furthermore, the two phosphate phases exhibit contrasting records of solar wind radiation damage. Abundant radiation damage tracks are observed in changesite-(Y), whereas no such tracks are present in coexisting monazite or apatite, reflecting differential thermal histories at the microscale. These findings contribute to a better understanding of material transport and mixing processes within the SPA basin, reveal microscale heterogeneity in space weathering, and have implications for future in situ resource utilization on the Moon.
High-altitude river systems are increasingly vulnerable to climate warming, yet the nonlinear associations between climatic variability and nutrient mobilization remain poorly quantified. This study investigates river water-quality dynamics in the Tongtian River, a key headwater of the Yangtze River on the Qinghai-Tibetan Plateau, with particular attention to phosphorus responses to climatic forcing. Multi-season field observations and generalized additive models (GAMs) revealed seasonally differentiated and nonlinear associations between climatic conditions and total phosphorus (TP) concentrations. During the rainy season, TP showed a significant nonlinear association with 7-day mean air temperature, and first-derivative analysis suggested an apparent onset of accelerated TP increase at approximately 11.5 °C. However, the temperature–precipitation interaction was not statistically robust after accounting for lagged TP, indicating that rainy-season TP dynamics were more strongly associated with antecedent thermal conditions and temporal persistence than with a definitive compound temperature–precipitation effect. During the spring snowmelt period, TP dynamics showed strong temporal persistence, whereas the independent and interactive effects of temperature, precipitation, and snow depth were limited in the GAM framework. These results suggest that snowmelt-related phosphorus mobilization may contribute to spring TP variability, but the current dataset does not support a definitive temperature threshold or strong snow-related interaction. Overall, our findings indicate that phosphorus dynamics in high-altitude rivers are linked to seasonally shifting climatic and hydrological conditions, but threshold-like and compound responses should be interpreted as indicative rather than definitive mechanisms. These results provide a cautious quantitative basis for understanding climate–nutrient relationships in cold-region watersheds and highlight the need for higher-frequency hydrological and sediment observations in future assessments.
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
Fluid-mediated mineral transformations in subduction zones play a pivotal role in the deep-Earth water cycle. Using a diamond anvil cell combined with in situ Raman spectroscopy, we investigated the hydration reaction of talc that transforms into the 10 Å phase in both pure H2O and NaCl-H2O fluids under high-pressure, high-temperature conditions relevant to cold subduction zones. Our experimental results indicate that talc transforms into the 10 Å phase at significantly lower P–T conditions (3.5 GPa and 400 °C) than previously reported. The reaction kinetics exhibit a strong positive dependence on both temperature and pressure. Additionally, the presence of NaCl promotes the transformation rate. Under equivalent P–T conditions, the 10 Å phase formed within a shorter time frame in saline fluids than in pure water environments. Complementary thermodynamic calculations indicate that the 10 Å phase forms at lower pressures in NaCl-H2O fluids (at T < 550 °C) than in pure water environments. The thermodynamic conditions and kinetic processes of the talc-10 Å phase transition under saline conditions have profound implications for the deep-Earth water cycle in cold subducting slabs. This study provides essential experimental constraints for modeling fluid-mediated mineral transformations in natural subduction environments.
Access to clean drinking water is vital for protecting public health and achieving global sustainability goals; therefore, systematic hydrogeochemical monitoring is essential, particularly in ecologically sensitive and rapidly urbanizing hilly terrains. This study evaluates groundwater quality dynamics and dominant hydrochemical drivers in Himalayan foothill aquifer systems, using Dehradun (Uttarakhand, India) as the study area. Forty groundwater samples were systematically collected across citywide north-south and east-west transects during the summer season and analyzed for 13 physicochemical parameters. Drinking water suitability was assessed using the Water Quality Index (WQI), while spatial variability was examined by Inverse Distance Weighting (IDW)-based geospatial interpolation. The hydrochemical composition exhibited cationic dominance following the order Ca2+ > Mg2+ > Na+ > K+, while the anion dominance followed HCO3– > Cl⁻ > SO42-> NO3-. Boxplots and bivariate plots asserted the dominance of Ca-Mg-HCO3 chemistry and ion sources linked to mineral dissolution. Piper diagrams confirmed the prevalence of Ca-Mg-HCO3 hydrochemical facies, while Gibbs diagrams indicated rock-water interaction and carbonate weathering as the primary governing processes. To elucidate the processes that dominate groundwater chemistry, multivariate statistical techniques were employed. Pearson correlation revealed strong ionic associations, while principal component analysis (PCA) separated geogenic mineralization from anthropogenic influences. Hierarchical cluster analysis (HCA) further grouped the parameters into three consistent clusters, reinforcing the patterns revealed by PCA. WQI values ranged widely, classifying 7.5
Deep-sea rare earth elements and yttrium (REY)-rich mud has emerged as a promising alternative resource to meet the growing global demand for REY, yet the processes controlling REY enrichment in these deposits remain debated. In particular, the relative roles of apatite versus Fe–Mn (oxyhydr)oxides as REY sinks at the sediment–seawater interface are still poorly constrained by experimental data. In this study, batch experiments were conducted to evaluate REY sorption onto hydroxyapatite (Hap) and goethite (Goe). The two minerals exhibit sharply contrasting behaviors and mechanisms. Goe shows classical pH-dependent, reversible sorption, with preferential uptake of heavy REY under mildly acidic conditions, consistent with surface complexation. In contrast, Hap displays non-classical isotherms, pH-independent uptake, and minimal desorption over 10 days, suggesting a strong and potentially irreversible mechanism, most plausibly via structural incorporation. This interpretation is supported by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy coupled with energy-dispersive spectroscopy (TEM/EDS). Moreover, Hap reduces dissolved REY to concentrations approaching seawater level, whereas Goe does not. These results provide experimental constraints on REY enrichment mechanisms in deep-sea settings and suggest that while Fe (oxyhydr)oxides may contribute to initial scavenging, direct capture by Hap may dominate long-term REY retention. Our findings further highlight phosphate-rich zones as priority targets for future REY exploration.
Arsenic poisoning induced by high-arsenic (As) groundwater is a critical environmental and geological issue worldwide. Existing studies have confirmed the presence of geogenic high-As groundwater on the Xizang Plateau, yet its spatial distribution and enrichment mechanisms remain poorly understood. To address this, 83 water samples (75 groundwater, 5 rivers, 3 hot springs) were collected across Xizang in August 2023 and December 2024. All samples were analyzed for hydrochemical analysis of trace elements (As, Fe, etc.), major ions (Ca2+, HCO₃⁻, SO₄2-, etc.), and dissolved organic carbon (DOC). H-O-C-S isotopes were analyzed for selected samples. The results reveal that groundwater with As > 100 μg/L is predominantly located in the Ngari region. The groundwater is characterized as the Ca–HCO₃ type, primarily influenced by water-rock interactions. The pH values range from 7.18 to 9.24, indicating weakly alkaline conditions, with higher pH and redox potential observed in summer compared with winter. Seasonal variations show higher As concentrations but lower Fe levels in summer, where the weak As–Fe correlation suggests As release probably occurs via alkaline desorption, whereas the strong correlation in winter points to reductive dissolution likely being the dominant mechanism. The slope of the δD–δ18O relationship is < 8, indicating significant evaporation, which is more intense in summer. For samples with As > 50 μg/L, a negative correlation between As and δ13CDIC indicates that microbial degradation of organic carbon facilitates As mobilization, whereas a positive correlation between As and δ34SSO₄ suggests that sulfate reduction could also enhance As release. Overall, the release of As in groundwater is closely linked to the aforementioned biogeochemical processes.
