Journal of Geochemical Exploration最新文献

{"title":"Apatite as a proxy for imaging the link between multistage hydrothermal alteration and anomalous gold enrichment in orogenic gold deposits: Evidence from the Jiaodong Peninsula, Eastern China","authors":"Dong Xie ,&nbsp;Liqiang Yang ,&nbsp;Xue Gao ,&nbsp;Gary O'Sullivan ,&nbsp;M. Santosh ,&nbsp;Wei Yang ,&nbsp;Zengsheng Li ,&nbsp;Tao Feng ,&nbsp;Jun Deng","doi":"10.1016/j.gexplo.2025.107716","DOIUrl":"10.1016/j.gexplo.2025.107716","url":null,"abstract":"<div><div>Orogenic gold deposits account for &gt;30 % of the global gold resources. To understand the abnormal enrichment process of gold and to improve their exploration efficiency, it is important to gain insights into the contribution of hydrothermal alteration to gold enrichment. The giant Jiaodong gold province is a world-class gold-mineralized region and is also the largest gold producer in China (with Au reserves of 5760 t). However, the relationship between multistage hydrothermal alteration and gold mineralization here remains equivocal. In this study, cathodoluminescence (CL) and elemental analysis of apatite from the Wang'ershan gold deposit are applied to different alteration assemblages to trace the multistage hydrothermal alteration and to evaluate its contribution to gold enrichment in orogenic gold deposits.</div><div>On the basis of petrographic features, four types of apatite are identified as: unaltered apatite (Ap1), apatite from K-feldspar alteration (Ap2), apatite from hematite-rutile alteration (Ap3), and apatite from pyrite-sericite-quartz alteration, which is directly associated with gold mineralization (Ap4). In general, the geochemical characteristics of apatite in K-feldspar alteration (Ap2) are similar to those of magmatic apatite (Ap1), and the fluids are rich in Ca, P, and REEs, which we correlate with magmatic differentiation in a reducing environment. The K-feldspar alteration is genetically related to Mesozoic magmatism but has no direct contribution to the enrichment of gold. In contrast, apatite from the hematite-rutile alteration (Ap3), which shows high oxygen fugacity, F enrichment, and depletion in REEs, is different from the chemistry of hydrothermal apatite in orogenic gold deposits. Combined with the behavior of Fe and Ti and the wide spatial distribution s of the hematite-rutile alteration process, we infer activation and enrichment of ore-forming materials before mineralization, which may also be a potential reason for the high gold endowment in Jiaodong. In the process of hematite-rutile alteration (Ap3) to pyrite-sericite-quartz alteration (Ap4), the fluid temperature, pressure, and oxygen fugacity decreased. The apatite from pyrite-sericite-quartz alteration (Ap4) have higher S, Cl, and Na contents than those from the former alteration, indicating that volatiles were involved in the mineralization process. The halo of hematite-rutile alteration in Ap3 apatite, formed prior to the mineralization. We propose that hematite-rutile alteration is a key indicator of mineralization in orogenic gold deposits.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107716"},"PeriodicalIF":3.4,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unconformity-related mineralization and fluid transfers in the northern Aquitaine Basin (France) revealed by fluid inclusions and S-Sr isotopes studies","authors":"Loïc Bouat ,&nbsp;Pierre Strzerzynski ,&nbsp;Véronique Gardien ,&nbsp;Guillaume Barré ,&nbsp;Yannick Branquet ,&nbsp;Jérémie Melleton ,&nbsp;Régis Mourgues","doi":"10.1016/j.gexplo.2025.107713","DOIUrl":"10.1016/j.gexplo.2025.107713","url":null,"abstract":"<div><div>In sedimentary basins, unconformity between basement and sediments is the ideal site where fluids from different sources can flow and mix, initiating the formation of ore deposits. In western Europe there are numerous F-Pb-Zn-Ba (±Ag, Ge) basin-hosted deposits located near the unconformity between Mesozoic Basins and the Variscan basement as for example the deposits of the Vendée Coast (France) containing fluorite, baryte, pyrite and quartz. Here, microthermometric data on the primary fluid inclusions of these minerals indicate salinity ranging from 1 to 20 wt% eq. NaCl and homogenization temperatures between 100 and 390 °C. We interpret these data as resulting of a fluids circulation in the ore deposit zone, with an early incursion of basin brines expelled by the leaching of Hettangian evaporites buried several tens of kilometers away, followed by an ascent of basement-derived fluids and, finally, a recharge of seawater. In other French deposits, the δ³⁴S isotopes of baryte are also consistent with a source of fluids from buried evaporites. The ⁸⁷Sr/⁸⁶Sr ratio of baryte demonstrates a crustal source of elements associated with brines-leached base metals and F<img>Ba. The process of buried-derived evaporites brines altering the basement along the unconformity is ubiquitous in all unconformity deposits in France.</div><div>With our results, we confirm that the basin deposits in the Southeastern Massif Central occur along structures formed during Tethys rifting at around 200 Ma, whereas in the Western part they form at ca. 145 Ma in link with the opening of the Bay of Biscay. This highlights that these basin-hosted deposits are preferentially formed during extensional activity in rifting settings, rather than in compressive settings.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107713"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of uranium-, vanadium- and chromium-bearing reduction spheroids in karst bauxite of the Unterlaussa mining district (Austria)","authors":"Ferdinand J. Hampl ,&nbsp;István Dunkl ,&nbsp;Burkhard C. Schmidt ,&nbsp;Viktor Bertrandsson Erlandsson ,&nbsp;Frank Melcher","doi":"10.1016/j.gexplo.2025.107709","DOIUrl":"10.1016/j.gexplo.2025.107709","url":null,"abstract":"<div><div>Abstract</div><div>Reduction spheroids are mm- to cm-scale spheroidal features that are formed by reduction processes and are mainly known from siliciclastic red beds. They consist of a bleached halo around a dark core that contains highly elevated contents of redox-sensitive elements such as U, V or Cr when compared to the host rock. Their formation mechanism is still poorly understood and reduction spheroids in rocks that are not associated with siliciclastic red beds are more than underexplored.</div><div>Here, we present geochemical and mineralogical results of U-bearing reduction spheroids hosted in karst bauxite of the Unterlaussa mining district (Austria). The goals of this paper are to (1) better understand the formation mechanism of reduction spheroids in non-siliciclastic host rocks that are not associated with typical red beds, and (2) to shed light on the mechanisms of U enrichment in karst bauxites. To this end, we used laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), scanning electron microscopy (SEM), micro-X-ray fluorescence (μ-XRF) and Raman spectroscopy.</div><div>Among several enriched elements such as ΣREE (La-Lu) up to 2.6 wt% or V up to 7.6 wt%, high contents of U and Cr are most characteristic for the dark cores of the reduction spheroids. Uranium-rich reduction spheroid cores with local contents of up to ∼47 wt% U were identified along with almost U-free cores, which can often be found next to each other. The U-bearing mineral was identified as carnotite and a paragenesis of newly described secondary spherical and acicular Cr-V-Al minerals was found responsible for the high Cr contents in the reduction spheroid cores. The reduction spheroids were formed shortly after the burial of the karst bauxite by an unsorted clay-rich sediment and two possible origins for mobilized U, V and Cr are discussed. In the most likely model, U-, V- and Cr-rich material together with organic matter were admixed during a redeposition of the uppermost zone of the karst bauxite. After the burial of the karst bauxite, the decomposition of the organic matter in this mixing zone locally mobilized elements by mineral dissolution, and organic-rich particles beneath the mixing zone generated locally reducing conditions that immobilized U, V and Cr in the developing reduction spheroid cores. This mechanism is suggested to be of significance for the formation of U-rich karst bauxites in general.</div><div>This paper establishes karst bauxite as a host rock of reduction spheroids and describes a possible process of U enrichment in karst bauxites. With this publication we provide evidence that reduction spheroids are not formed by a single mechanism which would allow a priori inferences from their occurrence in the geological record, and we present a model for the formation of U-rich karst bauxites.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107709"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143430244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Deciphering dissolved load geochemistry of the Upper Ganga Basin: Natural weathering vs human impact","authors":"Sugandha Panwar ,&nbsp;Shouye Yang ,&nbsp;Esha Ray ,&nbsp;Pallavi Singh ,&nbsp;Swati Uniyal ,&nbsp;Debajyoti Paul","doi":"10.1016/j.gexplo.2025.107702","DOIUrl":"10.1016/j.gexplo.2025.107702","url":null,"abstract":"<div><div>Traversing through one of Earth's most densely populated regions, the Ganga River carries the undeniable imprints of human activities. The present study aims to elucidate the relative contributions of natural weathering and anthropogenic processes in driving the dissolved load in the Upper Ganga Basin, investigating how these factors vary seasonally in mountainous regions while considering the diverse range of human influences. The study analyzed daily variations in major ions and trace elements in water samples collected from the Ganga River at Rishikesh during the year 2020, along with effluent, rainwater, faecal coliform, air quality, mobility data, and previously published data on Himalayan Rivers. A mass balance based forward model was applied to quantify contributions from atmospheric deposition, erosion, weathering, wastewater, and urban runoff. Co-occurrence network and principal component analysis were applied to decipher the interplay between natural weathering and human activities. Results indicate a seasonal shift in cation dominance, with anthropogenic activities peaking in the post-monsoon season. Carbonate weathering (73.6 % ± 7.9 %) followed by silicate weathering (15.2 % ± 5.1 %) dominated the cation load. Although urban runoff contributes to the dissolved load, geogenic sources (particularly carbonate rock weathering) are the primary contributors to heavy metals. Faecal bacteria levels of sewage samples were found to mirror chloride concentrations in the river. While natural weathering contributes significantly, residential pollution is a notable factor in altering the Upper Ganga River's dissolved load composition. To effectively restore the Ganga River, our findings emphasize understanding diverse pollution pathways and incorporating natural weathering processes into management plans.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107702"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Isolation and identification of anaerobic molybdenum(VI)-reducing bacteria in molybdenum mine sediments in Korea","authors":"Vo Anh Khoa Nguyen ,&nbsp;Hyeop-Jo Han ,&nbsp;Jong-Un Lee","doi":"10.1016/j.gexplo.2025.107711","DOIUrl":"10.1016/j.gexplo.2025.107711","url":null,"abstract":"<div><div>This study was conducted to isolate and identify anaerobic molybdenum(VI)-reducing bacteria from sediments and soils collected from molybdenum mine areas in Korea. Molybdenum, a trace element vital for biological systems, can pose environmental risks when present in high concentrations, particularly in mining areas. Soil and sediment samples were collected, and the physicochemical properties including pH and metal content were analyzed. Two bacterial strains, identified as <em>Klebsiella aerogenes</em> and <em>Klebsiella oxytoca</em>, were isolated and exhibited significant molybdenum(VI) reduction under anaerobic conditions, reducing over 90 % of the molybdenum within 72 h at an initial concentration of 15 mM. The study further explored the effects of alternative electron acceptors and donors, revealing that nitrate and sulfate did not inhibit Mo(VI) reduction, while acetate had little effect. The reduction likely occurred via fermentative processes rather than respiratory reduction, as evidenced by the absence of oxygen consumption, the preferential use of glucose as an electron donor, and the lack of competition from alternative electron acceptors such as nitrate and sulfate under anaerobic conditions. These findings suggest that microbial Mo(VI) reduction in mining environments could play a critical role in the geochemical cycling of molybdenum and provide a foundational basis for developing bioremediation strategies specifically tailored for mining-affected ecosystems.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107711"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Metallogeny and distribution of critical and strategic metals in the polymetallic vein mineralization at Kolchiko, Vertiskos Unit, northern Greece","authors":"Christos L. Stergiou ,&nbsp;Grigorios-Aarne Sakellaris ,&nbsp;Vasilios Melfos ,&nbsp;Panagiotis Voudouris ,&nbsp;Lambrini Papadopoulou ,&nbsp;Nikolaos Kantiranis ,&nbsp;Irena Peytcheva ,&nbsp;Alexandros Chatzipetros ,&nbsp;Dimitrina Dimitrova ,&nbsp;Elitsa Stefanova","doi":"10.1016/j.gexplo.2025.107708","DOIUrl":"10.1016/j.gexplo.2025.107708","url":null,"abstract":"<div><div>The Kolchiko polymetallic vein-hosted mineralization is part of a broad mineralization system in the Vertiskos crustal unit in northern Greece, which includes several gneiss- and mica-schist-hosted gold, copper and antimony bearing quartz veins. Mineralization includes gold-bearing arsenopyrite and pyrite, chalcopyrite, sphalerite occurring in massive to disseminated forms in quartz-veins, as well as quartz-pyrite veins. The mineralized veins are enveloped by hydrothermal halos related to sericitization of the mica-schist host rocks. Arsenopyrite and pyrite are the most abundant ore minerals, while enrichment in bismuth (&lt;992 ppm) and tellurium (&lt;3 ppm) are related to the variable occurrence of galenobismuthinite, hessite, tellurobismuthite and native bismuth. Particularly gold is enriched (&lt;9.2 ppm) in the massive veins. The ore parageneses, the mineral chemistry analysis and the fluid inclusions imply that the mineralization formation was characterized by two stages of magmatic-hydrothermal activity: 1) an early higher temperature (<em>T</em> = 300 to 444 °C) Fe-As-sulfide rich stage that produced the arsenopyrite- and pyrite-dominated polymetallic massive veins, and 2) a later lower temperature stage (<em>T</em> = 160 to 300 °C) characterized by the formation of Bi-sulfosalts and tellurides in the polymetallic quartz and quartz-pyrite veins. It is suggested that the gold-polymetallic mineralization at Kolchiko was developed under regional retrograde greenschist facies metamorphism and was structurally controlled by the onset of the late Oligocene to early Miocene dextral strike-slip fault zone, which is documented along the western edge of the Vertiskos Unit.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107708"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143379138","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemistry of the Oligocene-hosted manganese ores and the host sediments in the Thrace Basin, Türkiye: Implications for genesis and exploration of the Paratethyan Mn deposits","authors":"Hüseyin Öztürk ,&nbsp;Zeynep Cansu ,&nbsp;Feridun Hacılar ,&nbsp;Barrie Bolton","doi":"10.1016/j.gexplo.2025.107707","DOIUrl":"10.1016/j.gexplo.2025.107707","url":null,"abstract":"<div><div>The Early Oligocene Binkılıç Mn deposit occurs within the laminated clays and clayey carbonates of the Thrace Basin, NW Türkiye. Carbonatic and oxidic ores generally alternate with greenish to brownish grey laminated clays. The Mn-bearing laminated clays are unconformably overlain by deltaic Miocene sediments consisting of clay, sand and lignite.</div><div>Trace element and REE contents of the Mn oxides and the laminated host Oligocene clays of the Binkılıç Mn deposits are quite similar. Mn-bearing Oligocene clays and Mn oxides typically show enrichment in Ni, U, Tl, Mo, Co, W, As, Hg, Cu and V relative to PAAS. While Sr and Ba extremely enriched in Mn oxide ore relative to PASS, such enrichment is not observed in the Oligocene clay. A similar trace element enrichment of the Mn oxides and the host Oligocene clays indicates that both were formed under similar geochemical conditions. The fact that the oxidic manganese ore is rich in these trace elements, but the carbonate ore is poor, may indicate that a local reducing environment developed as a result of organic matter decomposition, and that Mn carbonates were formed secondarily in the post-burial stage.</div><div>Trace elements are highly enriched in Mn oxides and clays, are clearly organophylic elements and indicate that the bioproductivity of Paratethyan sea was high in the early Oligocene and that the Mn deposit was formed by anoxic processes as a result of the development, precipitation and decomposition of organic substances. Organic matter-rich sediments at the bottom of deep basins must have ensured the continuity of reducing conditions while transferring the high amount of organophylic trace elements to the seawater. Mn and other anoxia proxy elements were concentrated in the anoxic water column and then carried to shallow marine environments by upwelling deep currents, where they may have been precipitated as Mn oxides in the early Oligocene. In addition to Mn, we propose that a trace element association consisting of Ni, U, Tl, Mo, Co, W, As, Hg, Cu, V anomaly of the Oligocene clays can be used as a prospecting tool for Oligocene-hosted manganese deposits around the Paratethyan Basin.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107707"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143403169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assimilation of the chronology of mineral system components in prospectivity analysis procedure for mineral exploration targeting: Adaptation of recurrent neural networks","authors":"Soran Qaderi ,&nbsp;Abbas Maghsoudi ,&nbsp;Mahyar Yousefi ,&nbsp;Amin Beiranvand Pour","doi":"10.1016/j.gexplo.2025.107706","DOIUrl":"10.1016/j.gexplo.2025.107706","url":null,"abstract":"<div><div>Ore deposits are the end product of a series of complex geological processes that operate over time and scales. Given the importance of the time- and scale-dependent processes, this study aims to develop a mineral prospectivity modeling method through contribution of the chronology of ore deposition processes. To achieve this goal, three different architectures of recurrent neural networks (RNNs), i.e., simpleRNN (SRNN), long short-term memory (LSTM), and gated recurrent unit (GRU), were examined to integrate layers of mineral system-based exploration criteria for prospectivity mapping. To compare the time sequence-based prospectivity modeling method (TMPM), which was generated using RNNs, with existing MPM approaches that don't consider the sequence of the ore-forming geological events in the modeling procedure, we generated two prospectivity models using convolutional neural network (CNN) and a classical fuzzy gamma operator. The results obtained demonstrated excellent performance of the three RNN methods over the CNN and fuzzy approaches. To illustrate and demonstrate the method proposed we used a data set of Mississippi Valley-type (MVT) Pb<img>Zn mineralization in the west of Semnan province, Iran.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107706"},"PeriodicalIF":3.4,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143421457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cassiterite features and lifespan of Limu granite Ta-Nb-Sn-W ore-forming system in Guangxi, South China","authors":"Liuyun Ouyang ,&nbsp;Wenting Huang ,&nbsp;Jing Wu ,&nbsp;John Mavrogenes ,&nbsp;Juan Liao ,&nbsp;Jian Zhang ,&nbsp;Huaying Liang ,&nbsp;Shuang Yan ,&nbsp;Xiaoping Xia","doi":"10.1016/j.gexplo.2025.107696","DOIUrl":"10.1016/j.gexplo.2025.107696","url":null,"abstract":"<div><div>Rare metal deposits are clearly related to highly evolved granites. The Limu Li<img>F granite complex hosts early quartz vein-hosted W<img>Sn ore and late stage disseminated Ta-Nb-Sn ± W ore. To elucidate unique characteristics of cassiterite from Ta-Nb-Sn-W ore-forming system and the link between magmatic evolution and Nb<img>Ta mineralization, we analyzed textures and trace element compositions of cassiterites from both ore types, and conducted LA-ICP-MS U<img>Pb dating on cassiterites and columbite group minerals (CGMs). Both vein and disseminated cassiterites exhibit low Fe and high (Nb + Ta) contents with molar (Nb + Ta)/Fe ratios (&gt;7), significantly exceeding those of typical Sn-granite cassiterites (&lt;2). Late disseminated cassiterite displays high Nb and Ta oscillatory zoning eroded by low Nb<img>Ta domains, and intergrows with CGMs indicating a dissolution-reprecipitation process via hydrosilicate liquid during crystallization. Contrastingly, low and constant Zr/Hf (~4) suggest Zr and Hf remain stable in the hydrosilicate liquid. We proposed that high molar (Nb + Ta)/Fe ratios and eroded structures in cassiterites may indicate the potential Nb<img>Ta ore. Early quartz-vein cassiterites yielded ages of 215.5 ± 3.5 Ma, while late disseminated ores produced ages of 214.3 ± 2.4 Ma (cassiterite) and 212.7 ± 1.1 Ma (CGMs). Combined with previous zircon ages from early-stage granite (230–227 Ma), the Limu magmatic-hydrothermal system spans 15–16 Myrs. This long-lived magmatic-hydrothermal system depleted in Fe and enriched in (Nb + Ta), driven by continuous mantle-derived heat, likely underwent early fluid exsolution, triggering quartz vein W<img>Sn ores, followed by further melt evolution forming Nb-Ta-rich hydrosilicate liquid, which we consider a prerequisite for Nb<img>Ta enrichment and evolved to generate the late disseminated Ta-Nb-Sn ± W ore.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"273 ","pages":"Article 107696"},"PeriodicalIF":3.4,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479887","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Uncertainty quantification of geochemical data imputation using Monte Carlo dropout","authors":"Vladimir Puzyrev ,&nbsp;Paul Duuring","doi":"10.1016/j.gexplo.2025.107695","DOIUrl":"10.1016/j.gexplo.2025.107695","url":null,"abstract":"<div><div>Machine learning models have shown their promise in geochemical data imputation tasks. However, being black-box solvers, these models require more confidence in their predictions. Using uncertainty quantification methods for deep neural networks can increase the reliability of their predictions. In this paper, we use Monte Carlo Dropout to estimate uncertainty in geochemical data imputation. Multiple forward passes with different dropout configurations yield a predictive distribution for the unknown analytes. The mean of this distribution is used as the prediction, while the standard deviation expresses the uncertainty of the neural networks. Two different scenarios, namely the WACHEM and WAMEX databases containing multi-element geochemical data for rock samples, illustrate the predictive accuracy of the method and its capability to measure the associated uncertainty. Dropout values of 0.1–0.2 were identified as a good balance in prediction accuracy and model uncertainty.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"272 ","pages":"Article 107695"},"PeriodicalIF":3.4,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395634","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}