Applied Geochemistry最新文献

{"title":"Provenance of oilfield brines and vertical connectivity of Middle to Upper Jurassic sequence in eastern Saudi Arabia","authors":"Peter Birkle ,&nbsp;Ahmed J. Zayer","doi":"10.1016/j.apgeochem.2025.106673","DOIUrl":"10.1016/j.apgeochem.2025.106673","url":null,"abstract":"<div><div>Knowledge of reservoir connectivity is crucial for optimizing oil recovery, accurately estimating reserves, planning well placement, and improving economics of an oil field. This study combines hydrochemical (major, minor, trace elements) and multi-isotopic techniques (δ²H, δ¹¹B, δ¹³C, ¹⁴C, δ¹⁸O_H2O, δ¹⁸O_SO4, δ³⁷Cl, δ⁸¹Br, δ³⁴S_SO4, ⁸⁷Sr/⁸⁶Sr) on oilfield brines to define reservoirs dynamics by tracing fluid provenance and migration. As case study, preserved bottom-hole water samples were recovered along a 1930’ vertical column of seven groundwater horizons from a Middle to Upper Jurassic carbonate-anhydrite sequence in an exploratory well in the eastern region of Saudi Arabia. Geochemical fluid homogeneities reveal hydraulic connectivity between the Lower Tithonian and Upper Kimmeridgian sequence, suggesting the presence of a single reservoir. Isotopic heterogeneities reveal sealing conditions between underlying Lower Kimmeridgian, Oxfordian (Hanifa), and Bathonian (Upper Dhruma) groundwater systems. Interlayered anhydrite strata resulted in possessing ambivalent hydrodynamic functionalities, either as conduits or seals. Studied formation waters are composed of Na–Cl to Na–Ca–Cl water type with a descending salinity from 210,500 mg/L (Tithonian) to 147,800 mg/L (Bathonian). Measured ¹⁴C concentrations from 2.01 pmC to 18.77 pmC point to recharge of the Jurassic sequence by infiltrating surface water during Late Pleistocene and Early Holocene, causing the mixing and partial replacement between 37 % and 55 % of fossil oilfield brine. A positive vertical trend of δ¹⁸O_SO4 - δ³⁴S_SO4 ratios, δ¹³C_PDB values between +8.4 ‰ and +16.2 ‰, and depleted δ¹¹B ratios reveal thermocatalytic sulfate reduction, methane production, and desorption of clay material, respectively, as major secondary water-rock interaction processes. As practical benefit, formation water analyses provide a low-cost and low-risk complementary tool to expensive and failure-prone production logging tools for evaluating reservoir conditions. The geochemical detection of hydraulic connectivity or compartmentalization between stratigraphic units represents a complimentary tool to trace the analogue migration of hydrocarbons within single or multiple pay zones.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106673"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"H–O–B–Li isotope systematics for assessing slab-derived fluids: Importance of postdehydration processes","authors":"Rofiqul Umam ,&nbsp;Ikuya Adachi ,&nbsp;Tsutomu Yamanaka","doi":"10.1016/j.apgeochem.2025.106667","DOIUrl":"10.1016/j.apgeochem.2025.106667","url":null,"abstract":"<div><div>In this study, the isotopic alteration of boron (B) and lithium (Li) in slab-derived fluids after they undergo dehydration processes is investigated using deep groundwater samples from the eastern Kii Peninsula of Japan. Isotopic and elemental analyses of hydrogen (H), oxygen (O), B, and Li reveal complex subsurface fluid mixing and geochemical interactions that exceed simple meteoric recharge. Three distinct groundwater groups were identified on the basis of δ²H–δ¹⁸O–Cl relationships: Group I has strong slab-derived water signatures, particularly along the Median Tectonic Line and near 34°50′N, with up to 60 % slab-derived contributions; Group II reflects mixing between meteoric water and ocean water; and Group III is predominantly meteoric. Spatial variations in δ¹¹B and δ⁷Li isotopes suggest that local geochemical processes such as clay adsorption, silicate weathering, and igneous rock contributions significantly alter the original slab-derived isotopic signals. Rayleigh-type fractionation models explain the increased isotopic values in some wells, whereas low δ¹¹B and δ⁷Li values elsewhere indicate localized sources. Notably, high Li values with low δ⁷Li values in the southwest indicate a Li supply from Miocene igneous intrusions beneath the Mesozoic accretionary complex. These findings highlight the need for an integrated multi-isotope approach to accurately trace fluid origins and reconstruct the geochemical pathways of slab-derived fluids in forearc groundwater systems.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106667"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modes of occurrence of critical elements in coals from the Guanbanwusu mine, Inner Mongolia, China: A novel stratigraphy-constrained sliding-window correlation approach","authors":"Wei Zhu ,&nbsp;Wei Liu ,&nbsp;Na Xu ,&nbsp;Robert B. Finkelman","doi":"10.1016/j.apgeochem.2025.106638","DOIUrl":"10.1016/j.apgeochem.2025.106638","url":null,"abstract":"<div><div>Critical metals such as rare earth elements and yttrium (REY), lithium, gallium, and germanium are essential to modern technologies, but face increasing supply uncertainties. Numerous studies have shown that coal is a promising alternative source for these critical metals. Understanding modes of occurrence of these elements is critical for efficient recovery from coal and its by-products. Traditional statistical analyses, performed on bulk mine datasets, overlook stratigraphic variability, limiting insight into elemental associations. To address this limitation, a sliding-window correlation analysis combined with stratigraphically-constrained Synthetic Minority Over-Sampling Technique was applied to investigate the modes of occurrence of critical elements in coal from the Guanbanwusu mine, Inner Mongolia, China, with specific consideration of vertical stratigraphy. The results reveal significant vertical heterogeneity in modes of occurrence of elements. Lithium exhibits strong correlations with kaolinite and chlorite across most coal benches but shows localized associations with inertinite in the lower part (benches G18-G12 and G8-G1). Gallium and germanium are primarily hosted in goyazite, with variable associations with boehmite, chlorite, and kaolinite. Rare earth elements and yttrium predominantly occur in goyazite, with affinity varying vertically: in upper benches, goyazite shows a stronger affinity for light REY, whereas in lower benches, it is enriched in both light REY and middle REY. In contrast, inertinite exhibits an opposite REY affinity compared to goyazite and chlorite. These trends demonstrate that the modes of occurrence of critical elements are not uniform throughout coal benches but are influenced by localized geochemical conditions and mineralogical variations.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106638"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145616824","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unique migration-distribution processes and pollution risks of typical elements from geothermal spring discharge: A systematic assessment on Gudui geothermal field (southern Tibet)","authors":"Xiuying Yang ,&nbsp;Hongbing Tan ,&nbsp;Zhiwei Shi ,&nbsp;Hongkai Zhu ,&nbsp;Kang Qiang ,&nbsp;Hao Long","doi":"10.1016/j.apgeochem.2025.106656","DOIUrl":"10.1016/j.apgeochem.2025.106656","url":null,"abstract":"<div><div>The Gudui geothermal field in southern Tibet, China's second-largest non-volcanic high-temperature geothermal system, exhibits vigorous hydrothermal activity, with widespread geothermal springs discharging harmful elements that threaten around environment. However, the enrichment and migration mechanisms of hazardous elements during geothermal spring discharge remain unclear, in particular, the unusual enriched and highly hazardous elements like Tl has not been drawn attention by previous researches. This study focuses on a high-temperature geothermal spring discharge area in Karugou watershed in Gudui and systematically track the distribution and partition law of As, Tl, and B in geothermal deposits, river water, sediments, and around farmland soils. Results indicate that concentrations of As, Tl, and B progressively increase along the river, with corresponding trends observed in sediments. Concentration of these elements exceed basic permission limits by 302.22, 1326.61 and 15.16 times, respectively. In farmland soils irrigated with river water, As and Tl levels at 40 cm depth exceed natural soil by 1.2 times, while surface B concentrations are over 4.2 times. Harmful elements from geothermal discharge exhibit systematic migration-distribution-partition patterns in geothermal deposits, river sediments, and soils, where elements first accumulate in geothermal deposits, with partial partitioning into travertine or sinter. With respect to As and B that enrich more in general travertine, Tl prefers to be enriched in sinter. Irrigation has distinctly introduced these elements into downstream farmland soils (0–40 cm). Such high enrichment poses significant potential environmental risks. Future geological events like tectonic activities, floods, or large-scale development could trigger massive release of these harmful elements from geothermal fluids or remobilization from river sediments, potentially endangering downstream populated areas. This study firstly highlights the uncommon natural hazardous elements like Tl enriched in geothermal spring and provides a reference for environmental impact assessments of geothermal exploitation in Tibet as well as worldwide.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106656"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reactive pathways of synthetic forsterite and Mg/Ni-serpentine: Insights into incipient dissolution and carbonation","authors":"Mattia Corti ,&nbsp;Daniela D'Alessio ,&nbsp;Mara Murri ,&nbsp;Giancarlo Capitani ,&nbsp;Marcello Campione ,&nbsp;Nadia Malaspina","doi":"10.1016/j.apgeochem.2025.106650","DOIUrl":"10.1016/j.apgeochem.2025.106650","url":null,"abstract":"<div><div>Carbon capture, utilisation and storage is among the key strategies to mitigate the increasing concentration of atmospheric carbon dioxide. Mineral carbonation stands out as a promising solution for long-term carbon sequestration by exploiting Ca–Mg-bearing oxides, hydroxides, and silicate minerals such as olivine and serpentine. Although the reaction occurs spontaneously in nature, it is strongly hindered by mineralogical and structural factors.</div><div>In this study, nanocrystalline pure forsterite and Mg- and Ni-endmember serpentines were synthesised as model phases to disentangle the role of composition, crystal structure, and morphology in incipient dissolution and carbonation and to maximise reactivity through increased surface-to-volume ratios. The choice of Ni-serpentine endmember aims to investigate the fate of Ni after dissolution and carbonation, considering that in nature serpentine can incorporate up to 0.5 wt% of nickel oxide. A systematic experimental strategy was designed to investigate their early-stage dissolution and carbonation behaviour under mild hydrothermal conditions (100 °C, <em>p</em>CO₂ ≤ 6 bar), using microwave-assisted treatments in a controlled environment. The products were thoroughly characterised, both as solid precipitates and aqueous components, through X-ray Powder Diffraction, Scanning Electron Microscopy, Transmission Electron Microscopy, micro-Raman and Inductively Coupled Plasma – Optical Emission Spectroscopy. This direct, parallel comparison reveals distinct behaviours among the tested materials, with forsterite and Mg-serpentine releasing Mg into solution and promoting the formation of hydrated Mg-carbonates, whereas Ni-serpentine nanocrystals remain largely inert, immobilising Ni within their structure. These findings have potential implications not only for carbon dioxide sequestration but also for critical metal recovery processes.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106650"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of electrode geometry on electrokinetic removal of heavy metals and salt ions from co-contaminated soils","authors":"Öznur Karaca ,&nbsp;Sonam Taneja ,&nbsp;Çetin Kantar ,&nbsp;Anil Kumar Haritash","doi":"10.1016/j.apgeochem.2025.106655","DOIUrl":"10.1016/j.apgeochem.2025.106655","url":null,"abstract":"<div><div>This study evaluated the performance of electrokinetic remediation on multi-metal-contaminated soil based on three electrode configurations: linear (1 anode–2 cathodes), trigonal (1 anode–2 cathodes), and square (1 anode–4 cathodes). The effects of co-contaminants and inter-ionic interferences on metal migration and removal were critically assessed. The findings revealed that the square configuration exhibited better removal efficiencies due to its improved electric field distribution and higher cathode coverage. With the same number of electrodes, the linear arrangement exhibited slightly better removal than the trigonal design, suggesting that spatial arrangement is a key factor in EK performance. The maximum removal was achieved for hexavalent chromium (Cr (VI)), followed by cadmium and lead, mainly because of the high complexation affinity of Cr (VI) for EDTA. Speciation analysis by Visual MINTEQ showed evidence of stable Cr–EDTA complexes being formed, allowing their mobilization. Introduction of EDTA not only enhanced the transport and solubility of target metals but also favoured the migration of natural cations (Na⁺, K⁺, Mg²⁺, Ca²⁺). In addition, harmful anions, SO₄²⁻ and Cl⁻ were reduced by 90 % and 80 %, respectively. The economic analysis confirmed the square configuration as the most cost-effective, with specific energy consumption (50 kWh/m³/g) and specific cost (701.5 US$/g). The study highlights the critical role of electrode arrangement in optimizing EKR processes and the mobilization and removal of heavy metals from polluted soils.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106655"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789480","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tracing chemical and biological O2 consumption in the subsurface by 18O isotope enrichment factors","authors":"Zhenchen Wan ,&nbsp;Yuxuan Tan ,&nbsp;Yunsong Zheng ,&nbsp;Xiuli Li ,&nbsp;Songhu Yuan","doi":"10.1016/j.apgeochem.2025.106647","DOIUrl":"10.1016/j.apgeochem.2025.106647","url":null,"abstract":"<div><div>Dissolved O₂ (DO) levels in the shallow subsurface, controlled by both chemical and biological processes, play an important role in contaminant transformation and attenuation. However, methods for tracing chemical and biological DO consumption are not available. Here we show that oxygen isotope enrichment factors (<em>ε</em>) can be used to trace the mechanisms of chemical and biological O₂ consumption in the shallow subsurface. In batch solution experiments, the <em>ε</em> values for O₂ consumption by dissolved Fe(II), dissolved organic carbon (DOC), and their mixtures at different C/Fe ratios (0.5∼20) were measured to range from -1.74 ‰ to -3.32 ‰. In the oxygenation of reduced clayed sediment suspension, the <em>ε</em> values were relatively small (-6.46 ‰) in the initial 15 h and increased to a large level (-18.14 ‰) afterward; while for the sand sediment suspension, the <em>ε</em> values were always small (ranging from -4.56 ‰ to -4.65 ‰) throughout the duration time of 24 h. Chemical probe and sterilized control experiments proved that the initial stage characterized with small <em>ε</em> values (&lt;-10 ‰) was dominated by chemical O₂ consumption and the subsequent stage with large <em>ε</em> values (&gt;-10 ‰) was dominated by biological O₂ consumption. As an effective indicator for distinguishing subsurface chemical and biological oxygen consumption pathways, <em>ε</em> will provide a new parameter for exploring carbon and nitrogen cycling and pollution transformation.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106647"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145681777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Regional geochemical prospecting for Li–Be rare earth deposits: A case study in Southern Xinjiang, China","authors":"Jingjing Gong ,&nbsp;Lujun Lin ,&nbsp;Jianweng Gao ,&nbsp;Yingjie Gao ,&nbsp;Hui Wu ,&nbsp;Yong Li ,&nbsp;Jianzhou Yang ,&nbsp;Zhuang Duan ,&nbsp;Zuohuai Yang ,&nbsp;Shixin Tang","doi":"10.1016/j.apgeochem.2025.106651","DOIUrl":"10.1016/j.apgeochem.2025.106651","url":null,"abstract":"<div><div>The exploration of critical minerals, such as lithium (Li) and beryllium (Be), plays a vital role in supporting various high-tech industries. The southern margin of Xinjiang, China, which extends from the Western Kunlun to the Altun Mountains, has revealed promising Li–Be rare metal deposits—including the Dahongliutan and Washixianan occurrences—suggesting considerable potential for further discoveries. Regional-scale geochemical surveys (ranging from 1:200,000 to 1:500,000) have provided extensive coverage of this area, yielding abundant geochemical data. While these datasets were originally collected decades ago, their full potential for identifying rare metal deposits via modern compositional data analysis (CoDA) methods has not been fully realized. In this study, we reuse these existing regional geochemical data and apply the isometric log-ratio robust principal component analysis (ilr-RPCA) method to develop a novel composite indicator for effectively delineating pegmatite-type Li–Be deposits. The results indicated that although conventional geochemical anomalies of Li and Be correlate well with known deposits, the intensity and spatial distribution of mineralization-related anomalies vary significantly, potentially leading to the omission of certain mineralized anomalies. Through ilr-RPCA, two distinct element associations were identified: (1) Li, Be, and B, which are closely linked to pegmatite-type Li–Be mineralization, and (2) La, Y, Zr, and Nb, representative of the geochemical background associated with acidic rock formations. Anomaly maps derived from the ratio between these two groups accurately pinpoint the locations of pegmatite-type Li–Be deposits, demonstrating the effectiveness of the CoDA approach in geochemical prospectivity mapping. Based on this approach, four prospective areas for rare metal mineralization have been delineated. This methodology offers practical guidance for mineral exploration companies and government agencies in their decision-making processes.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"197 ","pages":"Article 106651"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145736286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THEREDA: Thermodynamic reference database for geochemical modelling of nuclear waste disposal under saline conditions – Application, overview, and new developments","authors":"Helge C. Moog ,&nbsp;Marcus Altmaier ,&nbsp;Frank Bok ,&nbsp;Vinzenz Brendler ,&nbsp;Daniela Freyer ,&nbsp;Xavier Gaona ,&nbsp;Sven Hagemann ,&nbsp;Claudia Joseph ,&nbsp;George-Dan Miron ,&nbsp;Melanie Pannach ,&nbsp;Julia Sohr ,&nbsp;Wolfgang Voigt ,&nbsp;Marie Voss ,&nbsp;Laurin Wissmeier","doi":"10.1016/j.apgeochem.2025.106646","DOIUrl":"10.1016/j.apgeochem.2025.106646","url":null,"abstract":"<div><div>The Thermodynamic Reference Database (THEREDA) is designed for geochemical calculations in the context of repositories for radioactive waste under high-saline conditions. For this purpose, it adopts the Pitzer ion-interaction approach. THEREDA is currently the only database worldwide that allows comprehensive polythermal calculations (up to at least 100 °C) of the hexary system of the oceanic salts Na-K-Mg-Ca-Cl-SO₄-H₂O, including acids, bases, and CO₂/carbonates. Its validity is documented primarily, yet not exclusively, by application to solubility data. THEREDA's potential to predict the development of the geochemical environment, e.g. in the event of an intrusion of solution, constitutes a prerequisite for the engineering design of a nuclear waste repository with regard to the selection and placement of plug and sealing system components.</div><div>The focus of THEREDA lies on the calculation of solubilities of radionuclides (actinides, fission and activation products), chemotoxic and matrix elements e.g., canister materials, and compounds having an impact on the overall geochemical milieu in the near field of a repository under high-saline conditions.</div><div>Special features of THEREDA besides its focus on high-saline solutions are procedures for testing prior to any release combined with intercode-comparison, extensive and publicly available validation against published experimental data, and systematic application of a scheme to mark data with regard to quality, reliability, and origin. Traceability of data and validated experimental results to published sources is also emphasised. This documentation is in part realised in ready-to-use parameter files for users, and in part on the website (<span><span>www.thereda.de</span><svg><path></path></svg></span>). Another feature is the possibility for operation of THEREDA by several institutions in a net-worked manner.</div><div>To highlight THEREDA's potential, examples for applications of the database are given. Additionally, ongoing efforts for the further development of THEREDA are described in the outlook at the end of this article.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106646"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrogeochemical mechanisms of ore-bearing layer clogging during acid ISL of uranium","authors":"Xuefeng Liu ,&nbsp;Jinhui Liu ,&nbsp;Yongguo Xing ,&nbsp;Yihan Yang ,&nbsp;Ruyi Wang","doi":"10.1016/j.apgeochem.2025.106594","DOIUrl":"10.1016/j.apgeochem.2025.106594","url":null,"abstract":"<div><div>This study examined the hydrogeochemical mechanisms of permeability reduction during acid in situ leaching (ISL) in the C12 mining area of the Bayan Ula uranium deposit. It analyzed the spatiotemporal evolution of leaching solution chemistry and conducted hydrogeochemical modeling. The key processes influencing permeability were identified. SO₄²⁻ concentration decreased significantly over time. Ca²⁺ concentration initially increased and then declined. This change resulted from the enhanced dissolution of calcium-bearing minerals and subsequent gypsum precipitation. Spatially, Ca²⁺ showed an increasing and then decreasing trend along the flow path. This pattern corresponded to intensified mineral reactions. SO₄²⁻ progressively decreased along the pathway, with the main acid consumption zone located downstream. PHREEQC simulations indicated that Ca²⁺ mainly existed as free Ca²⁺ and CaSO₄ complexes. Gypsum formation occurred when Ca²⁺ exceeded the precipitation threshold (Ca²⁺_{b, CaSO4}). The saturation index (SI_CaSO4) and reaction condition index (RCI_Ca²⁺) showed that the tendency for gypsum precipitation weakened over time but increased downstream. This change was driven by pH-induced variations in SO₄²⁻ activity. These findings aligned with observed leaching solution chemistry. They confirmed that gypsum precipitation, especially in downstream regions, played a critical role in reducing ISL permeability.</div></div>","PeriodicalId":8064,"journal":{"name":"Applied Geochemistry","volume":"196 ","pages":"Article 106594"},"PeriodicalIF":3.4,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145733230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}