Journal of Geochemical Exploration最新文献

{"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":"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":"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}

{"title":"Hydrothermal alterations, geochemical vectoring, and their implications for the world-class Sossego IOCG deposit exploitation, Carajás Mineral Province, northern Brazil","authors":"Antonio Fabricio Franco dos Santos,&nbsp;Carlos Marcello Dias Fernandes","doi":"10.1016/j.gexplo.2025.107692","DOIUrl":"10.1016/j.gexplo.2025.107692","url":null,"abstract":"<div><div>The IOCG-type world-class Sossego deposit is a complex within the Carajás Mineral Province, Amazonian Craton (northern Brazil), with high Cu<img>Au contents (Cu &gt; 0.9 wt%) usually related to intensively hydrothermalized rocks. This deposit has the Pista, Sequeirinho/Baiano, and Sossego/Curral exploratory sectors. Their prevalent host lithologies are deformed or metamorphosed granitoids, felsic and mafic metavolcanics, and ultramafic rocks. Multivariate statistical analyzes of a broad whole-rock geochemical dataset (7834 samples) allow the characterization of the signatures of IOCG-style mineralization and constrain the conspicuous lithogeochemical units observed at the complex. Data treatment encompasses various diagrams based on the mineralogical association of these sectors and major and trace chemical elements that define parameters and limits for the characterization. The Pista sector reveals five lithogeochemical units, highlighting those with high silica and sodium and low iron values in areas closer to the ore zone. At the Sequeirinho/Baiano, nine units appear, where the distal portions to the ore zone reveal high sodium values; gradually changing to median values of sodium and calcium at the intermediate portion; and reaching high values of iron, calcium, and manganese closer to the mineralization. The Sossego/Curral sector has seven lithogeochemical units, where the more distal units to the mineralization zone have high sodium values, whereas those closer to the ore reveal enrichment in potassium, manganese, iron, and calcium. Implicit software-based 3D modeling and the AIOCG 1 and AIOCG 2 geochemical indices materialize these lithogeochemical units within vectors and visually show an enhanced geological overview of hydrothermal flows, their probable mineralogical paragenesis, and correlations with the mineralized zones. Hence, these results contribute to the Sossego Complex exploration, providing data for geometallurgical studies, mine operations improvement and predictability, safety increases, and better ore processing routines with expenditure reductions.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107692"},"PeriodicalIF":3.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182832","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":"Whole rock and zircon geochemistry of the Tieshan pluton in Daye region, Eastern China: Implication for petrogenesis and Fe-Cu-Au-(Co) mineralization","authors":"Bao Zhou ,&nbsp;Guang Wen ,&nbsp;Run-Jie Zhou ,&nbsp;Yue Sun ,&nbsp;Chang-Xiong Wu ,&nbsp;Jin Zhu ,&nbsp;Zhi-Jun Qin ,&nbsp;Xiao-Yang Liu ,&nbsp;Xiao-Zeng Cheng","doi":"10.1016/j.gexplo.2025.107687","DOIUrl":"10.1016/j.gexplo.2025.107687","url":null,"abstract":"<div><div>The Tieshan pluton is situated in the Daye region of the Middle-Lower Yangtze River Valley metallogenic belts. It consists mainly of quartz diorite and host abundant mafic microgranular enclaves (MMEs) and is associated with the renowned Daye Fe-Cu-Au-(Co) skarn deposit. The presence of disequilibrium textures in MMEs, including quenched margins, acicular apatite and elongated amphibole, provides evidence that the pluton underwent magma mixing involving mafic and felsic magma. In comparison with the Fe (4.20 wt% on average), Cu (28 ppm on average) and Co (10 ppm on average) concentrations in the quartz diorite, the Fe (7.26 wt% on average) and Cu (57 ppm on average) concentrations are doubled and Co (29 ppm on average) are tripled in MMEs. The recharge of mafic magma, therefore, likely adding significant amount of Fe, Cu and Co metals into the felsic magma, therefore enhancing the fertility of the Tieshan pluton.</div><div>Zircons from quartz diorite of the Tieshan pluton exhibit U-Pb ages of 138.2 ± 1.6 Ma and 136.9 ± 1.6 Ma, respectively. The zircon ε_Hf(<em>t</em>) values of the Tieshan quartz diorite (ranging from −17.6 to −16.1) closely match to those of the Cu-Fe-Au fertile granitoids in the Daye region. Zircons from the Tieshan quartz diorite display Eu/Eu* and Yb/Dy values ranging from 0.4 to 0.6 and 3.6 to 4.2, respectively. These ratios suggest substantial amphibole fractionation with minimal plagioclase fractionation and indicate high magmatic water contents. This is corroborated by the zircon oxybarometer-hygrometer analysis, which estimates the melt H₂O content to be between 8.3 and 10.3 wt%. The zircons from the Tieshan quartz diorite exhibit Ce⁴⁺/Ce³⁺ ratios of 67 to 201 and oxygen fugacity (log<em>f</em>O₂ values of ΔFMQ) from ΔFMQ+2.1 to ΔFMQ+2.8. The calculated zircon Ce⁴⁺/Ce³⁺ ratios and oxygen fugacity (log<em>f</em>O₂) for the quartz diorite from Tieshan pluton are comparable to the values of Tonglushan Cu-Fe-Au related fertile quartz diorite, indicating the similar oxygen fugacity of the Cu-Fe-Au ore-related magmas in Daye region. Our research demonstrates that the geochemistry of whole-rock and zircon is a powerful tool for identifying granitoids with potential for skarn Fe-Cu-Au-(Co) mineralization.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107687"},"PeriodicalIF":3.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182833","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":"Depositional age and source material of banded iron formations in the Western Shandong Province, North China Craton: Constraints from geochemistry, zircon UPb geochronology and SmNd isotope composition","authors":"Yan Zhang,&nbsp;Wei Xie,&nbsp;Dapeng Li,&nbsp;Qiang Liu,&nbsp;Yuqin Sun,&nbsp;Chenxi Zhang,&nbsp;Ke Geng,&nbsp;Pengfei Wei,&nbsp;Chao Zhang,&nbsp;Na Cai","doi":"10.1016/j.gexplo.2025.107691","DOIUrl":"10.1016/j.gexplo.2025.107691","url":null,"abstract":"<div><div>As an important iron ore concentration area in the North China Craton (NCC), the Western Shandong Province (WSP) is an ideal area to study the formation and evolution of banded iron formation (BIF). This paper performs a comparative study on the BIF deposits of Dong'e Shanzhuang (SZ), Yiyuan Hanwang (HW), Yishui Yangzhuang (YZ), Linyi Lanling (LL), and Jining Yandian (YD), from different BIF-hosted units and depths. Zircon U<img>Pb dating revealed that the depositional age of the WSP BIFs here was constrained to the Late Neoarchean (2.56–2.50 Ga), consistent with most of the BIF depositional age (2.55–2.52 Ga) in the NCC. The majority of BIFs have undergone greenschist- to amphibolite-facies metamorphism and associated magmatism that began at ∼2.49 Ga. The BIFs are characterized by depleted light rare earth elements (LREEs) and positive Y and negative Ce anomalies, indicating that BIFs precipitated from a variable mixing of seawater and minor high-T hydrothermal fluids. The other additional rare earth and yttrium (REY) sources such as fluvial inputs and (or) oceanic crust-derived fluxes are probably involved during the formation of BIFs. However, most supracrustal rocks and metagranitoids show a right-tilting trend in REY pattern, which is similar to that of the ocean island basalts (OIB) pattern, while the REY pattern of amphibolite is flat, similar to that of normal mid-ocean ridge basalts (N-MORB) pattern. The protoliths of supracrustal rocks in the Late Neoarchean reflect an evolution process from komatiite-tholeiite to calc-alkaline basalt-andesite-dacite, and BIFs were possibly formed in a volcanic-arc setting. The YZ BIF is the purest chemical sediment closest to seawater in the WSP, which can be used as a favourable archive for tracing ancient seawater. The variable initial <em>ε</em>_Nd(t) values of the BIFs and associated rocks were determined as +0.85 − +6.96, mostly between the depleted mantle and the chondritic uniform reservoir, indicating the seawater was largely affected by the depleted mantle material, but cannot excluded the contributions from continental crust. The Nd model age of different rocks of WSP BIFs was 2.80–2.58 Ga, corresponding to a large-scale continental crustal growth age of the NCC. The apparent isochron age fitted to the Sm<img>Nd isotope pseudo-isochron of 2685 ± 89 Ma represents a “paleo-isochron”, possibly corresponding to the age of the older ∼2.70 Ga continental crust growth event.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107691"},"PeriodicalIF":3.4,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143181708","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":"Neutral Mine Drainage prediction for different waste rock lithologies – Case study of Canadian Malartic","authors":"Vincent Marmier ,&nbsp;Benoît Plante ,&nbsp;Isabelle Demers ,&nbsp;Mostafa Benzaazoua","doi":"10.1016/j.gexplo.2025.107685","DOIUrl":"10.1016/j.gexplo.2025.107685","url":null,"abstract":"<div><div>Neutral Mine Drainage (NMD) can become a problem if not properly addressed when low sulfide waste rocks are disposed of at mine sites. However, NMD, as opposed to acid mine drainage (AMD), is difficult to predict using classical kinetic tests due to the contaminant immobilization processes that occur, namely sorption and precipitation. A method using modified ethylenediaminetetraacetic acid leaching procedure and sorption tests on a positive control was proposed, which allowed the method to be validated. However, this method needed to be applied to different lithologies to consider the geological variation within orebodies. The risk assessment method was therefore applied to four different lithologies from Canadian Malartic mine. Two lithologies from the Canadian Malartic pit (carbonated porphyry: CPO and carbonated greywacke: CGR) were shown to have sufficient zinc sorption capacity to accommodate the total potential contaminant load. The other two lithologies from the Barnat pit (altered ultramafic: AUM and talc and chlorite schist: TCH) had sorption capacities and potential contaminant contents that were relatively close for Ni, which occurs within talc minerals. The modified kinetic experiments showed that Ni was leached at concentrations &lt;1 mg/L. When Zn is the only metal considered for risk assessment of AUM and TCH, the risk of NMD generation is low. However, if all ions that could potentially occupy the same sorption sites as Zn (Ni, Co, Cu, Mn) are considered, the leaching risk increases. This study indicates that mineralogy should be considered in risk assessment and that further work is needed to include a release factor in the risk assessment of NMD.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107685"},"PeriodicalIF":3.4,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182834","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}