Journal of Geochemical Exploration最新文献

{"title":"The reduction process contributes to the generation of subduction-related Langmuri Cu-Ni sulfide deposits in the East Kunlun Orogen, Northern Tibetan Plateau","authors":"Xu Zhao ,&nbsp;Wanting Li ,&nbsp;Wenjun Li ,&nbsp;Chongwen Xu ,&nbsp;Hua Li ,&nbsp;Liang Li ,&nbsp;Yanning Wang ,&nbsp;Lebing Fu","doi":"10.1016/j.gexplo.2025.107843","DOIUrl":"10.1016/j.gexplo.2025.107843","url":null,"abstract":"<div><div>Ore-genesis of the subduction-related Cu-Ni sulfide deposits has not been well studied. This article focuses on the Langmuri Cu-Ni sulfide deposit in the East Kunlun Orogen (EKO) by studying the symbiotic ore-bearing olivine pyroxenite and ore-free gabbro. Twenty-seven Cu-Ni sulfide orebodies were defined in these ultramafic and mafic rocks in past years with Ni average grades up to 1.5 % and Cu average grades up to 0.18 %. The ore mineralization comprises sulfides (pyrite, chalcopyrite, pentlandite, and pyrrhotite) and oxides (chromite and magnetite). Zircon U-Pb dating shows that the Langmuri mafic-ultramafic rocks have similar emplacement ages (449.9 ± 3.9 Ma for the olivine pyroxenite, 450.8 ± 1.8 Ma for the gabbro), and they were generated during the northward subduction of the Proto-Tethys Ocean. These rocks were sourced from partial melting of a continuously enriched lithosphere mantle resulting from interaction with slab-derived fluids. The ore-bearing olivine pyroxenite had a basaltic parental magma. It underwent accumulation of olivine and minor chromite and crustal contamination during magmatic evolution, while the ore-free mafic rocks underwent fractional crystallization of olivine and chromite and the crustal contamination was insignificant. The oxidation state of the ore-bearing olivine pyroxenite at QFM-1 to QFM is lower than the values for normal arc magma and the ore-free gabbro, which should be associated with the crustal contamination. Based on these clues, we inferred that fractional crystallization of olivine and minor chromite occurred in a deep magmatic chamber, and these minerals accumulated locally to form olivine-rich ultramafic rocks. The magma that underwent fractional crystallization of these minerals is the parental magma for the ore-free gabbro, while the magma with accumulation of these minerals is heavier and transported more slowly, which makes it undergo significant crustal contamination during magmatic rising. The crustal contamination reduced the magma, resulting in the sulfur saturation in magma and the generation of Cu-Ni sulfide orebodies in the Late Ordovician subduction setting at EKO.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107843"},"PeriodicalIF":3.4,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144299038","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":"The fundamentals of rare earth element ion adsorption clay deposits: A mineral systems approach for exploration","authors":"Samantha C. Russo ,&nbsp;Ignacio González-Álvarez ,&nbsp;Helen A. Cocker ,&nbsp;Alex J. McCoy-West","doi":"10.1016/j.gexplo.2025.107845","DOIUrl":"10.1016/j.gexplo.2025.107845","url":null,"abstract":"<div><div>The exponential growth of demand for ‘green-technologies’ requires significantly increased production of critical elements, including rare earth elements (REE). Some of the most significant (and largest) REE deposits are associated with carbonatites. However, carbonatites are predominantly light-(L)REE-enriched, which has implications for meeting global heavy-(H)REE demand. As a result, REE ion adsorption clay deposits (IACD), which are examples of intense weathering, have sparked international interest as a HREE source (~80 % of global HREE are sourced from IACD). Therefore, this study presents a comprehensive review of REE IACD to understand their constraints, global distribution, and main features while applying a mineral systems approach.</div><div>The REE source for IACD, although typically granitic, is more diverse than traditionally thought, with the weathering of local igneous, metamorphic, and sedimentary rocks and external fluids (e.g., hydrothermal fluids and basinal brines) and lithologies (e.g., transport of weathering constituents rather than an in-situ source) supplying the REE required for IACD formation. Following the weathering of REE-rich source material, REE are liberated and mobilised in the weathering profile through pH-dependent complexation with ligands (e.g., F⁻, CO₃²⁻, SO₄²⁻, PO₄³⁻) or as hydrated REE species. The nature of the source (e.g., relative LREE- or HREE-enrichment) and fluids within the weathering profile (e.g., pH and ligand concentrations) control REE fractionation and relative LREE and HREE enrichment of a IACD. Once mobilised, REE are adsorbed out of solution and enriched onto clay minerals (e.g., kaolinite and halloysite), a process strongly controlled by pH and the physicochemical characteristics of the clays present, with REE adsorption most favourable under circumneutral conditions. To preserve REE enrichment (and IACD formation) through clay adsorption, a low erosional setting is required. Climates with excessive rainfall (e.g., tropical humid climates) may be problematic for REE IACD preservation through geological time, where excessive rainfall results in clay dissolution and saprolite collapse. The conceptual model provided in this study develops a framework that will be built upon in the coming years as our knowledge of these deposit types and global exploration continues.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107845"},"PeriodicalIF":3.4,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144471397","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":"Petrogenesis and factors controlling tungsten mineralization of Late Mesozoic granites from Xianxia intrusion and Zhuxiling tungsten deposit in Jiangnan tungsten belt, China","authors":"Likai Ge,&nbsp;Jun Yan,&nbsp;Qiaoqin Xie,&nbsp;Sujuan Zhou,&nbsp;Liu Yang,&nbsp;Quanzhong Li,&nbsp;Jiancheng Xie","doi":"10.1016/j.gexplo.2025.107844","DOIUrl":"10.1016/j.gexplo.2025.107844","url":null,"abstract":"<div><div>Globally, most tungsten deposits are closely and genetically related to granitic rocks, but only a small amount of granite can produce tungsten deposits. So far, there are still a topic of ongoing discussion about the controlling factors of ore-bearing granite formation. To investigate their controlling factors of the ore-forming granites, an inclusive research of zircon geochronology, apatite in-situ geochemistry, whole-rock major-trace elements and Sr-Nd-Pb isotopes was carried out for the Xianxia barren and Zhuxiling ore-forming intrusions in Jiangnan tungsten belt, China. Zircon U<img>Pb dating results show that Xianxia (133.8–140.1 Ma) and Zhuxiling (139.5–143.3 Ma) intrusions were emplaced in the Early Cretaceous. The Xianxia and Zhuxiling samples (SiO₂ = 62.04–70.40 wt%) predominantly are high-K calc-alkaline, weakly peraluminous monzogranite and syenogranite, exhibiting an affinity of weakly fractionated I-type granite, characterized by enrichment in LREEs, Rb, Th, and U, and negative anomalies in Eu (δEu = 0.68–0.90), Nb, P, and Ti. They also have relatively high Sr contents (247–549 ppm) and Sr/Y ratios (19.45–39.50), negative whole-rock εNd(t) values (−6.4 ∼ −5.0), high radiogenic Pb isotopic compositions, as well as high log<em>f</em>O₂ values (−22.03 to −11.35). The chemical and isotopic characteristics show that the Xianxia and Zhuxiling intrusions were likely derived from the mixing of Neoproterozoic crustal components with a little influx of mantle-derived magma. Compared with Xianxia samples (Kd ap-melt OH-F = 0.0047 (avg.) and Kdap-melt OH-Cl = 0.0912 (avg.) in apatite), Zhuxiling samples have higher halogen partitioning coefficient (Kd ap-melt OH-F = 0.0089 (avg.) and Kdap-melt OH-Cl = 0.1034 (avg.) in apatite), Sr and water contents (0.4762 wt% and 3.37 wt% of apatite and zircon), suggesting that it is more conducive to tungsten enrichment. A comprehensive discriminant analysis highlights that tungsten mineralization in weakly fractionated I-type granites is influenced by high-Sr content magma, increased alkalinity, elevated water and fluorine content, and active fluid dynamics. The results offer valuable insights into the conditions necessary for tungsten deposits in less evolved granitic systems, with broader implications for exploration strategies in similar geological settings.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107844"},"PeriodicalIF":3.4,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290837","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":"Redistribution of minor and trace elements in ore minerals in metamorphosed VMS deposits, Rävliden North, Skellefte district, Sweden","authors":"Jonathan Rincon ,&nbsp;Nils Jansson ,&nbsp;Helen Thomas ,&nbsp;Majka Christiane Kaiser ,&nbsp;Mac Fjellerad Persson ,&nbsp;Amir Morteza Azim Zadeh ,&nbsp;Yousef Ghorbani ,&nbsp;Christina Wanhainen","doi":"10.1016/j.gexplo.2025.107830","DOIUrl":"10.1016/j.gexplo.2025.107830","url":null,"abstract":"<div><div>The Rävliden North volcanogenic massive sulfide (VMS) deposit, in northern Sweden underwent polyphase deformation and greenschist to lower amphibolite facies metamorphism during the Svecokarelian orogeny. This caused remobilisation and recrystallisation of ore minerals, whose composition was analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and electron probe microanalysis (EPMA). Sphalerite, chalcopyrite, and pyrrhotite chemistry mirrors zonation of undeformed VMS deposits. Chalcopyrite-rich mineralisation contains higher Cu, Co, In, and lower Mn concentrations than sphalerite-rich mineralisation. Besides galena, Ag occurs in sulfosalts, tellurides, antimonides, and amalgams, which possibly formed through exsolutions from α-galena in <em>syn</em>- to post-tectonic structures. LA-ICP-MS imaging shows Ag-rich minerals in early syngenetic pyrite, in contrast to syn-metamorphic pyrite, indicating remobilisation during deformation. Despite sampling effects accounted for through linear mixed effects (LME) modelling, the results indicate that <em>syn</em>-metamorphic recrystallisation and remobilisation did not lead to substantial compositional changes in ore minerals. Instead, these processes partitioned Ga between sphalerite and chalcopyrite and enriched Ag, Cd, and Sb in minerals associated with younger parageneses. Zeolite-bearing veins in the hanging wall host sphalerite with the highest Ga, Ge, Cu, and Sb contents and galena with the lowest Bi, Te, and Tl contents. An origin potentially linked to far-field effects of the opening of the Iapetus Ocean or waning Timanian orogeny is discussed based on similarities to other vein- and breccia-hosted Zn<img>Pb deposits in Northern Sweden. This study provides the first multiple-mineral in-situ trace element dataset for a VMS deposit in the Skellefte district, enhances understanding of element redistribution during metamorphism, and identifies remobilised elements potentially vectoring mineralisation at depth. Moreover, this study enables tracing of penalty and by-product elements in downstream beneficiation processes.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107830"},"PeriodicalIF":3.4,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288961","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":"Geochemical characteristics and petrogenesis of uranium-bearing and barren granites in the Miao'ershan Batholith, South China: Implications for U mineralization","authors":"Cui Yang ,&nbsp;Xilian Chen ,&nbsp;Deru Xu ,&nbsp;Shaohao Zou ,&nbsp;Hengsong Zhang ,&nbsp;Zihang Fan ,&nbsp;Longfei Luo","doi":"10.1016/j.gexplo.2025.107829","DOIUrl":"10.1016/j.gexplo.2025.107829","url":null,"abstract":"<div><div>The Miao'ershan batholith in South China is an important domain for granite-hosted uranium mineralization, comprising both uranium-bearing (Douzhashan) and barren (Yangqiaoling and Xiangcaoping) granites. However, the processes governing uranium enrichment in granitic systems, as well as the factors responsible for the contrasting fertility of these granites remain poorly understood. This study integrates zircon U<img>Pb geochronology, zircon trace element geochemistry, and in situ chemical analysis of both discrete apatite grains and apatite inclusions within zircon to elucidate the petrogenetic processes and physicochemical conditions that distinguish uranium-bearing from barren granite. Zircon U<img>Pb dating constrains the crystallization ages of the Yangqiaoling, Xiangcaoping, and Douzhashan granites to 218.6 ± 1.8 Ma, 223.3 ± 1.9 Ma, and 213.5 ± 1.8 Ma to 212.2 ± 1.6 Ma, respectively. Variations in apatite Cl/F ratios, combined with published whole-rock geochemical data, indicate that the Douzhashan granite is a strongly peraluminous S-type granite derived from the partial melting of meta-sedimentary rocks, whereas the Yangqiaoling granite reflects a mixed magmatic source involving both meta-sedimentary and meta-igneous components, and the Xiangcaoping granite exhibits intermediate characteristics. Apatite trace element compositions reveal that the Douzhashan granite underwent a higher degree of magmatic differentiation than the barren granites, as evidenced by lower concentrations of Sr, Th, and light rare earth elements (LREE), reduced (La/Yb)_N and (Sm/Yb)_N ratios, and elevated contents Y and Mn. Geochemical proxies from both zircon and apatite, including (Eu/Eu*)_N, Ce/Nd, and Y/ΣREE ratios, suggest that all three granites crystallized under low oxygen fugacity conditions. Therefore, uranium enrichment in the Douzhashan granite was driven by a combination of distinct source characteristics, advanced magmatic differentiation and reduced magmatic conditions, which collectively enhanced uranium solubility and retention in the melt. These results provide new insights into the petrogenetic controls on granite-hosted uranium mineralization and establish a geochemical framework for guiding future uranium exploration in similar geological settings.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107829"},"PeriodicalIF":3.4,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144271001","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":"A new supervised learning framework for mineral prospectivity mapping: The three-class labeling (3CL) approach","authors":"Soran Qaderi,&nbsp;Abbas Maghsoudi","doi":"10.1016/j.gexplo.2025.107831","DOIUrl":"10.1016/j.gexplo.2025.107831","url":null,"abstract":"<div><div>Mineral exploration depends on the ability to accurately distinguish geological characteristics and predict mineralization zones. This study introduces a novel three-class labeling (3CL) strategy, which categorizes regions as mineralized, non-mineralized, and neutral. Compared to traditional two-class labeling (2CL), this approach reduces false positives and enhances prediction precision by capturing intermediate areas that do not fit clearly into mineralized or non-mineralized categories. To implement this approach, we employed the Random Forest method to model mineralization potential, training it with optimized hyperparameters using GridSearchCV. The optimized trained model evaluation metrics demonstrated that the 3CL model outperformed the 2CL one, with higher accuracy (98 % vs. 96 %), F1-score (0.98 vs. 0.96), and Kappa coefficient (0.97 vs. 0.92), confirming its superior capability in distinguishing prospective zones while reducing misclassification. The 3CL approach enhances the spatial precision of prediction maps and offers a more geologically realistic interpretation of mineralization potential. These findings highlight the practical advantages of 3CL in improving exploration efficiency and guiding decision-making for resource allocation in mineral prospectivity studies.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107831"},"PeriodicalIF":3.4,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144253616","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":"The Anthropigene: a new approach in environmental geochemistry to discriminate anomalies from natural background","authors":"Lucia Rita Pacifico ,&nbsp;Francesco Carotenuto ,&nbsp;Annalise Guarino ,&nbsp;Antonio Iannone ,&nbsp;Domenico Cicchella ,&nbsp;Stefano Albanese","doi":"10.1016/j.gexplo.2025.107832","DOIUrl":"10.1016/j.gexplo.2025.107832","url":null,"abstract":"<div><div>Assessing the geochemical background is critical for addressing soil contamination, particularly in regions with complex interactions between the natural geological context and anthropic activities. Traditional methods for distinguishing geochemical backgrounds from anthropogenic anomalies often struggle to account for overlapping signals in such areas, leading to limitations in accurately identifying contamination sources. This study introduces the “anthropigene” method, an adaptation of the “geochemical gene” method initially developed for mining applications in the environmental context. By classifying geochemical indicators (“genes”) associated with urban and agricultural contamination, the anthropigene provides a robust framework for distinguishing anthropogenic anomalies from natural geochemical signals. Applied to approximately 3000 topsoil samples from the Campania region in Italy, the method allowed the determination of multivariate geochemical patterns linked to urban and agricultural sources of contamination. Samples considered contaminated were eliminated from the original dataset, and the remaining data were used to assess geochemical backgrounds.</div><div>Results showed that the background values determined through the proposed approach significantly differed from those generated by applying Italian guidelines; they are also generally more conservative if used as a reference for a tier-one human health risk assessment and environmental restoration. Using the proposed method could have favorable practical implications for unveiling the presence of large-scale diffuse contamination processes that could be easily mistaken for natural enrichments due to their spatial extension.</div><div>The method certainly has wide margins for improvement, and future studies will focus on identifying specific indicators of anthropic processes not considered in this paper and improving the techniques for estimating background values at a regional scale.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"278 ","pages":"Article 107832"},"PeriodicalIF":3.4,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144253787","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":"Ore forming processes in the multi–stage polymetallic Baycheh-Bagh deposit, NW Iran: Insights from mineralogy, fluid inclusions and stable isotopes","authors":"Sayeh Rezazadeh ,&nbsp;Mohammad Reza Hosseinzadeh ,&nbsp;Johann G. Raith ,&nbsp;Mohsen Moayyed","doi":"10.1016/j.gexplo.2025.107818","DOIUrl":"10.1016/j.gexplo.2025.107818","url":null,"abstract":"<div><div>The Baycheh-Bagh polymetallic hydrothermal deposit, in the northwestern part of Urumieh Dokhtar magmatic arc of Iran, is hosted by volcanic and pyroclastic rocks. Multiple mineralization stages are recognized in polyphase veins: the first stage is mainly base-metal mineralization with tetrahedrite group minerals and native gold, the second stage mainly includes native Bi, Ni-Co-Fe arsenides and sulfoarsenides and the third one contains sulfosalts and minor sulfides. The host rocks are affected by hydrothermal alteration to variable degree. Quartz, white micas, adularia, chlorite, calcite and kaolinite are the main alteration minerals.</div><div>Fluid inclusion studies reveal that first stage formed mainly due to boiling of hotter high salinity (178.4 to 320.4 °C; avg. 17.5 eq. wt% NaCl) magmatic-hydrothermal fluids but minerals of stages II and III probably precipitated by mixing process of fluids with salinities of 9.7 to 17.5 eq. wt% NaCl eq. and temperatures of 107.4 to 215.1 °C.</div><div>Evidence suggesting that a reducing agent from a local source (hydrocarbons, pre-existing sulfides or Fe²⁺-bearing minerals in host rocks) could have played an important role in change of redox condition and precipitation of arsenides and sulfoarsenides during second stage.</div><div>Two sphalerite generations of first stage show FeS content variations (1.09 to 7.97 mol%). The large range of δ³⁴S values (−8.2 to 11.3 ‰) in sulfides from different stages and variation in isotope and chemical composition of different generations of hydrothermal carbonates in the study area indicate ore forming fluids are magmatic as well as partly non-magmatic in origin.</div><div>These results suggest that first stage mineralization of Baycheh-Bagh polymetallic veins occurs in intermediate sulfidation epithermal environment, while the second and third stages exhibit features of five-element style mineralization.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"277 ","pages":"Article 107818"},"PeriodicalIF":3.4,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204592","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":"Geochemical footprints of IOA and IOCG deposits in Northern Norrbotten, Sweden, and Cloncurry District, Australia","authors":"Olivier Blein ,&nbsp;Matthieu Harlaux ,&nbsp;Louise Corriveau ,&nbsp;Tero Niiranen ,&nbsp;Edward P. Lynch ,&nbsp;Vladimir Lisitsin ,&nbsp;Kathy Ehrig ,&nbsp;Jean-François Montreuil ,&nbsp;Blandine Gourcerol","doi":"10.1016/j.gexplo.2025.107820","DOIUrl":"10.1016/j.gexplo.2025.107820","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This paper addresses the complex hydrothermal evolution of Metasomatic Iron and Alkali-Calcic (MIAC) mineral systems based on a review of the lithogeochemical footprints of IOA and IOCG deposits in the northern Norrbotten province (Sweden) and the Cloncurry district (Australia). The use of Na-Ca-Fe-K-Mg molar barcodes on a lithogeochemical diagram tailored for these mineral systems allows to depict the evolution of MIAC systems along diagnostic metasomatic paths from high (HT) to low temperature (LT) alteration facies as follows: 1) HT or LT Na alteration (300–1000 °C); 2) HT Ca&lt;img&gt;Fe alteration (400–1000 °C); 3) HT K&lt;img&gt;Fe alteration (350–450 °C); 4) HT K and HT K-Ca-Mg alteration; 5) LT K&lt;img&gt;Fe, Na-Ca-Mg-Fe, and/or Na-Ca-Mg alteration (≤ ~350 °C); and 6) epithermal alteration (≤ 150 °C) and later stage hydrothermal veining. A distinct range of whole rock compositions and metal associations characterizes each alteration facies and can be captured by diagnostic molar barcodes and alteration indices. In northern Norrbotten, the IOA deposits are hosted in HT Ca&lt;img&gt;Fe alteration facies but regionally intensely albitized regions are overprinted by K&lt;img&gt;Fe alteration. The IOCG deposits are hosted in MIAC systems with zones of early Na (&lt;img&gt;Ca) alteration related to the regionally extensive albitite or scapolite alteration (Facies 1) and localized skarns. These are overprinted by HT Ca&lt;img&gt;Fe alteration (Facies 2) and HT to LT K&lt;img&gt;Fe alteration (Facies 3 and 5). The Cu&lt;img&gt;Au mineralization is not systematically associated with the iron oxide-rich breccias and the intense K-feldspar- or sericite-rich K&lt;img&gt;Fe alteration typical of many IOCG deposits worldwide. Instead, the lesser intensity of alteration and the abundance of mafic and ultramafic rocks in the environment lead to pattern enriched in Mg with relic of amphibole-rich alteration remaining in the assemblage as demonstrated for the Nautanen North IOCG deposit (Sweden). Consequently, the geochemical footprints of the Norrbotten Cu&lt;img&gt;Au deposits are distinct from magnetite-group (e.g., Great Bear magmatic zone, Canada) and hematite-group (e.g., Olympic Dam, Australia) IOCG deposits even if they have all the known alteration facies of MIAC systems. Conversely, IOCG deposits in northern Norrbotten show similarities to certain deposits in the Cloncurry district of Australia. In both regions, the IOCG deposits are associated with HT Ca&lt;img&gt;Fe and K&lt;img&gt;Fe alteration facies that commonly overprint early Na and/or Na&lt;img&gt;Ca alteration. In northern Norrbotten, IOA deposits are characterized by early Na alteration evolving towards Na&lt;img&gt;Ca alteration, then Fe-rich Ca&lt;img&gt;Fe alteration. These hydrothermal alteration types are subsequently superimposed by later K&lt;img&gt;Fe alteration. We conclude that the use of Na-Ca-Fe-K-Mg molar barcodes provides new insights to understand the evolution of MIAC systems and is a powerful approach for unraveling superimposed alteration trends, which can ","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"277 ","pages":"Article 107820"},"PeriodicalIF":3.4,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204597","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":"Fe, Cu and S isotopes as tracers of microbial reduction in the shale-hosted VMS deposits of the Iberian Pyrite Belt","authors":"S. García de Madinabeitia ,&nbsp;J. Velasco-Acebes ,&nbsp;J.I. Gil Ibarguchi ,&nbsp;G. Layne ,&nbsp;Y. Lahaye ,&nbsp;F. Molnár ,&nbsp;F. Tornos","doi":"10.1016/j.gexplo.2025.107819","DOIUrl":"10.1016/j.gexplo.2025.107819","url":null,"abstract":"<div><div>This study represents an exploration of the geochemistry of sulphide minerals from prominent shale-hosted volcanogenic massive sulphide deposits of the Iberian Pyrite Belt, including Sotiel-Migollas, Tharsis, Neves Corvo and Lousal using the non-traditional heavy stable isotopes of Fe and Cu along with the S light isotope. Sampling encompassed a diverse range of styles of mineralization, including the dominant fine-grained massive sulphides sometimes exhibiting sedimentary layering, carbonate-rich mounds dominated by sulphides-siderite and formed by the superposition of microbial mats in anoxic bottoms, underlying subseafloor feeder structures (stockworks) and disseminated pyrite within the altered host shales. The δ⁵⁶Fe_IRMM-014 values of pyrite exhibit a range from −2.62 to +2.58 ‰, while those of pyrrhotite range from −1.93 to −0.40 ‰. Chalcopyrite δ⁶⁵Cu_SRM-976 signature varies between −1.11 and + 0.95 ‰, while the measured δ³⁴S_V-CDT values fluctuate from −45.0 to +9.4 ‰ in pyrite, −6.8 to +2.1 ‰ in pyrrhotite, and − 10.1 to +6.2 ‰ in chalcopyrite. Notably, pyrite grains within massive sulphides consistently exhibit more negative and variable δ⁵⁶Fe and δ³⁴S values than those in the hydrothermally altered host shales (apart from Neves Corvo) and stockworks. These findings strongly imply that the exhalative mineralization incorporated substantial amounts of iron derived from the dissimilatory reduction of aqueous Fe⁺³, attributable to low-temperature (&lt;100–120 °C) microbial reduction and contemporaneous with biogenic sulphate reduction. Consequently, Fe in pyrite is likely inherited from both the reduced hydrothermal fluids venting on the seafloor and the microbial reduction of oxidized iron dissolved in ambient seawater. While the microbial influence on Cu isotope signatures is less evident, we infer its potential significance. Superimposed hydrothermal refining during the late percolation of hot hydrothermal fluids reveals a non-biogenic kinetic fractionation, with partial overprinting of the early mineralization and neoformation of sulphides depicting isotopically heavy δ⁵⁶Fe, δ⁶⁵Cu, and δ³⁴S signatures that are interpreted as of deep derivation.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"277 ","pages":"Article 107819"},"PeriodicalIF":3.4,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204593","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}