Journal of Geochemical Exploration最新文献

{"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}

{"title":"Monazite chemistry and timing of mineralization at Paramanahalli, Chitradurga Greenstone Belt, Dharwar Craton, India: Implications for gold exploration","authors":"Manju Sati ,&nbsp;Rajagopal Krishnamurthi ,&nbsp;Sakthi Saravanan Chinnasamy","doi":"10.1016/j.gexplo.2025.107688","DOIUrl":"10.1016/j.gexplo.2025.107688","url":null,"abstract":"<div><div>Paramanahalli gold deposit, Chitradurga greenstone belt in the Western Dharwar Craton, is a shear zone-hosted/ structurally controlled, mineralization confined to carbonated metabasalt and Banded Iron Formation. Chlorite (Fe-rich) + quartz + ankerite + rutile + monazite ± pyrite ± gold is the mineral association found in the mineralized zone. Monazite from carbonated metabasalt (intensely altered rocks; proximal alteration zone) is interpreted as hydrothermal in origin, based on its mode of occurrence, texture, and chemical composition, particularly its low ThO₂ content, whereas monazite grains from schistose metabasalt (least altered rocks; distal alteration zone), found to be metamorphic. Hydrothermal monazite from the mineralized zone is enriched in light rare earth elements LREEs (La₂O₃ + Ce₂O₃ &gt; 51 wt%) and exhibits low ThO₂ concentrations (&lt;1.5 wt%) classified as anomalous values, in contrast to metamorphic monazite, contain lower LREEs (La₂O₃ + Ce₂O₃ &lt; 45 wt%) and higher ThO₂ (&gt; 1.5 wt%) identified as background values. The ratios such as Ce/Pr, La/Nd, La/Pr, along with REE trends, serve as diagnostic tools to target and exploration of orogenic gold deposits. This study highlights the utility of monazite as a geochemical tool to unravel mineralized zones, thereby enhancing exploration strategies for orogenic-type gold mineralization in the Dharwar Craton and similar terranes. Notably, we are the first to report the timing of a hydrothermal event related to gold mineralization at Paramanahalli by estimating the chemical ages (CHIME) of monazites through Electron Probe Micro Analysis. The study reveals two distinct ages: 2622 ± 08 Ma (older) and 2510 ± 12 Ma (younger), corresponding to metamorphism and <em>syn</em>-ore hydrothermal alteration/mineralization events, respectively. The Neoarchean mineralization event at Paramanahalli (2510 ± 12 Ma) aligns closely with ages estimated for gold mineralization in Ajjanahalli (2520 ± 9 Ma) and Gadag (2522 ± 6 Ma) within the Western Dharwar Craton. Our findings indicate that gold mineralization across the WDC is attributed to a regional tectono-thermal event around 2520 Ma, characterized by extensive fluid flux into the crust.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107688"},"PeriodicalIF":3.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143224581","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":"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":"Mineralogy, geochemistry, and S isotope investigation of seafloor massive sulfides from the Yunzang hydrothermal field, South Atlantic Ridge","authors":"Wen-Sheng Li ,&nbsp;Pei Ni ,&nbsp;Xue-Fa Shi ,&nbsp;Bing Li ,&nbsp;Shao-Wen Liu ,&nbsp;Stefano Albanese ,&nbsp;Fei-Peng Fan ,&nbsp;Guan-Hua Wang ,&nbsp;An-Qi Hong","doi":"10.1016/j.gexplo.2025.107684","DOIUrl":"10.1016/j.gexplo.2025.107684","url":null,"abstract":"<div><div>Research on the ore-forming model of modern seafloor hydrothermal sulfide deposits is of significant economic and scientific importance. The limited research on recently discovered seafloor sulfide deposits has resulted in a vague comprehension of water-rock interactions, metal origins, and the subsequent metal deposition process. The Yunzang hydrothermal field is located on the South Mid-Atlantic Ridge and represents a newly discovered seafloor hydrothermal sulfide deposit. However, the geological features, primary mineral assemblages of ores, and the source regions of metals in the hydrothermal field remain unclear. In this study, sulfides were analyzed using a TESCAN Integrated Mineral Analyser (TIMA) and in-situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to investigate trace element distributions and S isotope compositions. Analysis by TIMA shows that the Yunzang hydrothermal field is mainly composed of pyrite, chalcopyrite, and sphalerite. Two types of ore with distinct characteristics were identified, one rich in chalcopyrite and the other in sphalerite. Within these ores, two different types of pyrite were identified, namely colloform and euhedral pyrite. Colloform pyrite formed at low temperature in outer margins of the chimney is enriched in Mn, V, Ag, Tl and Cd. Euhedral pyrite formed at high temperature in inner zone of the chimney is enriched in Co, Se, Cu and Sn. The variation in trace elements within pyrite is primarily governed by the synergistic effects of fluid conditions (such as temperature and redox state) and the influx of ambient seawater that accompanies the chimney formation process. The higher concentrations of Mo and V in the pyrite found in the outer wall of the chimney indicate significant interactions between seawater and hydrothermal fluids. The lower Au/As ratio in pyrite proves that gold exists within the lattice of pyrite rather than in nano-particles. The lower concentrations of Sn and Bi in chalcopyrite suggest that ore-forming materials may primarily originate from leaching of the surrounding rocks, with a lack of magmatic volatile components. The Fe/Zn ratio in sphalerite indicates that the Yunzang hydrothermal field belongs to sediment-starved SMS, with the formation temperature of sphalerite ranging from 242 to 262 °C. The positive δ³⁴SV-CDT values of pyrite (1.0 ‰–3.7 ‰) suggest 83 %–96 % of S was derived from the leaching of basement basalts, 4 %–17 % from oxidation of seawater sulfate. Based on these analytical results, the growth history of chimney and the fluid source in the Yunzang hydrothermal field are proposed.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107684"},"PeriodicalIF":3.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143181100","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":"Genesis of the Yunlong Sn deposit in the Chongshan Shear Zone, Western Yunnan, SW China","authors":"Zhen Jia ,&nbsp;Wenchang Li ,&nbsp;Jianze Sha ,&nbsp;Shiping Li ,&nbsp;Fuchuan Chen ,&nbsp;Mingguo Deng","doi":"10.1016/j.gexplo.2025.107690","DOIUrl":"10.1016/j.gexplo.2025.107690","url":null,"abstract":"<div><div>The large-scale Yunlong Sn deposit is situated in the western Yunnan, SW China. The NNW- to NS-trending orebodies are hosted in the Cenozoic Chongshan shear zone, parallel with the regional foliation. To clarify the ore genesis at Yunlong, we analyzed the geochronology, trace elements, fluid inclusion and stable isotopes of the mineralized/altered rock samples from the mine. Tin mineralization at Yunlong is divided into three stages: (I) early-ore tourmaline–quartz–cassiterite, (II) main-ore cassiterite–sulfides–quartz, and (III) post-ore quartz-calcite stage. Cassiterite U<img>Pb dating reveals that stage I (28.6 ± 1.5 Ma) and II (27.8 ± 1.6 Ma) are coeval with the syn-kinematic leucogranite (35–29 Ma) in the shear zone, indicating a temporal link between the Sn mineralization and the Cenozoic tectono-magmatism. Trace element data (esp. Fe and W) suggest a magmatic origin for stage I and stage IIa mineralization, with those of IIb showing some wallrock input. Fluid inclusion study reveals that the stage I quartz contain a boiling fluid inclusion assemblage with similar homogenization temperature (339–515 °C) and varying salinity (4.3–52.8 wt% NaCl eqv), implying boiling as a vital cassiterite precipitating mechanism. Stage II and III fluid inclusions (mainly featuring V- and L-type) have lower homogenization temperatures (186–349 °C) and salinities (0.6–19.1 wt% NaCl eqv.). Analyses of the ore-related quartz H<img>O isotopes and sulfide S isotopes suggest a predominantly magmatic source for the ore fluid, respectively. In conclusion, we propose that the Yunlong Sn deposit is related to the Cenozoic magmatism and the tectonic shear at Chongshan, and that the Cenozoic Shear Zone in western Yunnan have potential for Sn mineralization.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107690"},"PeriodicalIF":3.4,"publicationDate":"2025-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372787","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}