Journal of Geochemical Exploration最新文献

{"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}

{"title":"Handheld LIBS contribution to quantify critical elements during mining operations: The Beauvoir granite case study","authors":"Naila Mezoued,&nbsp;Cécile Fabre,&nbsp;Jean Cauzid,&nbsp;Zia Steven Kahou,&nbsp;Océane Rocher","doi":"10.1016/j.gexplo.2025.107689","DOIUrl":"10.1016/j.gexplo.2025.107689","url":null,"abstract":"<div><div>Developing innovative methodologies has become essential for mining companies to optimize resource management and achieve economic sustainability. The spectroscopic techniques such as laser-induced breakdown spectroscopy (LIBS), used for on-site analyses, have great potential to provide reliable qualitative and quantitative geochemical data to support rapid decision-making. In this context, handheld LIBS was used to predict the concentrations of the main targeted elements lithium (Li), and rubidium (Rb), on unprepared core samples from the Beauvoir granite, a rare-metal granite currently studied to achieve lithium exploitation by 2028. The models were built using different spectral parameters and statistical approaches. A comprehensive comparative analysis was conducted to determine the optimal protocol for each element. Signal variation over successive measurements, as well as the minimum number of analyses required to maintain a representative LIBS signal of the whole rock composition, were investigated. The predicted concentrations are consistent with the reference geochemical analyses confirming the ability of handheld LIBS to provide relevant analytical results, in a short period, directly at the exploitation site.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107689"},"PeriodicalIF":3.4,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143181098","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":"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}

{"title":"Growth history of garnet from the Dulong Sn-Zn-In polymetallic deposit: Geochemical and UPb age constraints and their metallogenic significance","authors":"Shiyu Liu ,&nbsp;Lin Ye ,&nbsp;Yuping Liu ,&nbsp;Hansheng Long ,&nbsp;Chen Wei ,&nbsp;Zhenzhong Xiang","doi":"10.1016/j.gexplo.2025.107699","DOIUrl":"10.1016/j.gexplo.2025.107699","url":null,"abstract":"<div><div>The Dulong skarn-type tin‑zinc‑indium (Sn-Zn-In) polymetallic deposit contains 5.5 million tonnes (Mt) Zn, 0.4 Mt. Sn, and 7 kt In. It is the third-largest cassiterite-sulfide deposit in China, and is located in the Laojunshan W<img>Sn polymetallic orefield on the southern margin of the Youjiang basin. While it is widely accepted that the Sn<img>Zn polymetallic mineralization is closely linked to the Yanshanian granites, the precise timing of skarn formation and its relationship to the granite magmatism has remained unclear due to a lack of reliable geochronological data. This has also hindered a comprehensive understanding of the ore-forming processes at Dulong. Garnet is a widely distributed major skarn mineral at Dulong. Field and laboratory studies have revealed two distinct garnet types (Grt I and II): Grt I is located near the main ore-controlling fault (F_M), while Grt II is found near a shallow granite porphyry in eastern Dulong. Both types of garnet exhibit a core-mantle-rim structure, indicating that they were formed by multistage fluid metasomatism. In this study, in situ LA-ICP-MS U<img>Pb dating was carried out on both types of garnet. Additionally, major and trace element analyses of the garnet and its coexisting pyroxene were conducted to examine the formation and evolution of the skarn. The results show that Grt I has generally higher ΣREE, Y, HFSE, and U concentrations, suggesting that it was formed under low W/R ratios in a relatively reducing environment. The garnet contains a grossular core (Grt Ia), andradite mantle (Grt Ib), and a grossular-andradite solid solution rim (Grt Ic), reflecting an initial increase and then decrease in the W/R ratio of the magmatic-hydrothermal system. During this process, the fluid pH was neutral-acidic, and the oxygen fugacity (<em>f</em>O₂) first decreased and then increased. In contrast, Grt II has lower ΣREE, Y, HFSE, and U concentrations, indicating its formation under higher W/R ratios in a more oxidizing environment. This garnet has also a grossular core (Grt IIa), andradite mantle (Grt IIb), and a grossular-andradite solid solution rim (Grt IIc). This reflects a system where the W/R ratio first increased and then decreased. The fluid pH shifted from neutral-acidic to acidic, and the <em>f</em>O₂ increased gradually. LA-ICP-MS U<img>Pb dating yielded 93 ± 2.4 Ma to 90.9 ± 0.7 Ma for Grt I and 80.4 ± 6.6 Ma for Grt II. Comparing these results with published data on the Cretaceous regional magmatism and Sn-polymetallic mineralization, we conclude that the magmatic-hydrothermal activity that formed Grt I and Grt II was associated with the concealed phase-II and phase-III Laojunshan granite, respectively. This study highlights the opportunities offered by garnet U<img>Pb dating for elucidating the formation age and ore genesis of Sn<img>Zn skarn systems.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107699"},"PeriodicalIF":3.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143224580","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":"Multistage hydrothermal fluids evolution and precipitation mechanism of the Hongshi Cu deposit in Eastern Tianshan, NW China: Insights from cathodoluminescence, fluid inclusions, trace elements of quartz and in situ S isotopes of sulfides","authors":"Wen-Xin Gu,&nbsp;Yin-Hong Wang,&nbsp;Jian-Ping Wang,&nbsp;Kang Wang,&nbsp;Wei Zhang,&nbsp;Hui Zhang","doi":"10.1016/j.gexplo.2025.107700","DOIUrl":"10.1016/j.gexplo.2025.107700","url":null,"abstract":"<div><div>The Hongshi Cu deposit is located in the southeastern Kalatag district in Eastern Tianshan, northwest China. The Cu mineralization is mainly hosted by volcaniclastic rocks of the Daliugou Formation and structurally controlled by fracture zones. Comprehensive analyses of fluid inclusions, in situ sulfur isotopes, and trace elements in quartz were employed to unravel the evolution of ore fluids, identify the sources of ore-forming components, and refine the understanding of ore genesis. The ore formation at Hongshi could be divided into three hydrothermal stages, consisting of quartz-pyrite (stage I), quartz-sulfide (stage II), and quartz-calcite (stage III). Five hydrothermal quartz generations have been identified through cathodoluminescence (CL) imaging, including Q1–1 and Q1–2 from stage I, Q2–1 and Q2–2 from stage II, and Q3 from stage III. Aqueous fluid inclusions from stage I exhibit relatively high temperatures (208–313 °C) and moderate salinities (3.1–9.3 wt% NaCl equiv.). Microthermobarometry results confine the quartz−sulfide veins to temperatures ranging from 151 to 243 °C and salinities of 1.9–7.2 wt% NaCl equiv. Quartz−calcite veins formed from low−temperature and low−salinity fluids, with homogenization temperatures and salinities of 123–168 °C and 0.53–3.23 wt% NaCl equiv., respectively. Based on in situ trace element analysis of the five quartz generations, the Ti concentrations for the ore fluids are 33.20–129.00 ppm (mea<em>n</em> = 79.88 ppm), 5.12–27.30 ppm (mean = 16.54 ppm), 1.01–17.20 ppm (mea<em>n</em> = 6.96 ppm), 1.48–9.98 ppm (mea<em>n</em> = 5.15 ppm), and 14.70–52.70 ppm (mean = 24.19 ppm). The Al concentrations for the ore fluids are 2058–4889 ppm (mean = 3562 ppm), 150–1916 ppm (mea<em>n</em> = 1109 ppm), 133–2470 ppm (mean = 926 ppm), 32–174 ppm (mean = 82 ppm), and 686–2296 ppm (mean = 1555 ppm). The trace element data and trends across the five generations of quartz are optimally interpreted as indicative of magmatically derived ore fluids that were subsequently diluted by meteoric water, resulting in mineralization. Fluid mixing is regarded as the primary mechanism responsible for Cu precipitation at Hongshi. Sulfides of pyrite, chalcopyrite, and sphalerite yield δ³⁴S_V-CDT values from −0.21 to +6.21 ‰, with no discernible systematic variations among the various paragenetic stages. The data presented herein support a magmatic origin for the Hongshi deposit. This study clarifies the role of fluid dilution in initiating Cu deposition and offers insights into the genesis of Cu-polymetallic epithermal deposits within the Eastern Tianshan region.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107700"},"PeriodicalIF":3.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182831","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 and mineralogical characterization of weathered granite hosting secondary uranium mineralization: A case study from the eastern part of the Reguibat shield, Northern Mauritania","authors":"Brahim Salem-Vall ,&nbsp;Akinade Shadrach Olatunji ,&nbsp;Ahmed Hamoud","doi":"10.1016/j.gexplo.2025.107698","DOIUrl":"10.1016/j.gexplo.2025.107698","url":null,"abstract":"<div><div>The eastern part of the Reguibat shield hosts significant uranium deposits in Northern Mauritania. Weathered granite identified as the uranium host rock. The study area located at the extreme eastern part of the Requibat shield hosts uraniferous granites form part of neobirimian ensemble belonging to yetti complex. The present investigation concerns the petrographic, geochemical and mineralogical characterization and secondary uranium mineralization genesis. Analyses were conducted using EPMA-EDS and ICP-MS. The study area is made up of two uraniferous granites, coarse-grained porphyritic pink with a mylonitic texture and medium-grained grey granite. Paragenesis consists mainly of Qtz + K-F + Pl + Bt + Ap + Sph + Zr + Amp + Cal + Cls ± granet ± Barite ± Ilmenite. Both granites represent monzogranite weakly peraluminous and shoshonitic. REE signature illustrates a negative anomaly of Eu (Eu/Eu* = 0.1 and 0.18 average), and slight fractionation of LREE from HREE remarkable particularly for grey granite ((La/Yb)_<em>N</em> = 5.37–10.27). Multielement spectra show significant enrichments in U, Ta, and Pb, depletions in Ba, Nd, and Eu of pink granite. However, grey granite highlights significant enrichments in U, and Pb, while showing depletions in Nb, Eu, Zr, and Ba.</div><div>Geochemistry of the rocks highlights the emergence of the processes of fractional crystallization. Petrogenetic indicator K/Rb ratio suggests rock moderately evolved derived from fractionated magma with potential involvement of crustal material. Rock generated in deep sources of the lower crust or the upper mantle by partial melting. Grey granite similar to A-type however pink granite is S-I-type fractionated to nofractionated granite. Tectonic diagrams placed confirm <em>syn</em>-collisional pink granite and grey granite as within plate granite setting.</div><div>Both granites exhibit low CIA and PIA indicting low to moderate weathered rocks. Uranium bearing minerals (Carnotite and Tyuyamunite) occur as small grains size (∼ 10 μm) associated with weathering products filling voids and fractures of the granitoids. The presence of calcite, Celestine, fluorite are the indictors of uranium mineralization formation within evaporitic context in dry and low-temperature conditions.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107698"},"PeriodicalIF":3.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182835","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":"OreGenes: An optimized neural network tool for ore deposits classification based on gold grain geochemistry","authors":"Angel A. Verbel ,&nbsp;Maria Emilia Schutesky ,&nbsp;Daniel D. Gregory ,&nbsp;Arturo Verbel","doi":"10.1016/j.gexplo.2025.107701","DOIUrl":"10.1016/j.gexplo.2025.107701","url":null,"abstract":"<div><div>Assessment of gold grains and their characterization in abundance and morphology can be used as a discriminatory tool for mineral deposits. However, the processes that lead to the formation of an ore deposit are multiscale and nonlinear. As a result, the elemental compositions recorded in gold grains during mineralization seem mostly irregular and unpredictable. Here, we took advantage of the capabilities of neural networks, computational models composed of layers of interconnected nodes. After training, it processed data through nonlinear transformations that approximate a complex natural function. It enabled the recognition of complex patterns and relationships in chemical variability observed in gold and relating it to the mineral system that formed the mineral, allowing for predictive modeling. This was achieved by using published trace element data in gold of four types of gold deposits (i.e., Orogenic, VMS, porphyry, and epithermal) from 47 different localities, obtained by laser ablation-inductively coupled plasma-mass spectrometry (LA- ICP-MS). The model was optimized by training five different architectures on the most influential elements, determined by principal component analysis (PCA). As a result, two hidden layers with ten neurons (series of nodes that process and transmit information) each were found to be the best architecture for using trace elements as predictors of the type of deposit that formed a natural gold grain. In order to encourage the use of the findings made in this paper, we introduce OreGenes, an app developed in Matlab2023b based on the best-obtained model. It allows any user who possesses compatible data the ability to import and process it to obtain a prediction with an average accuracy level of 88.9 % confidence to assess the mineral deposit type that an unknown gold grain came from, which grants the user the ability to have a powerful tool for exploration or research.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"271 ","pages":"Article 107701"},"PeriodicalIF":3.4,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143182306","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}