Pub Date : 2025-02-10DOI: 10.1016/j.gexplo.2025.107706
Soran Qaderi , Abbas Maghsoudi , Mahyar Yousefi , Amin Beiranvand Pour
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) PbZn mineralization in the west of Semnan province, Iran.
{"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 , Abbas Maghsoudi , Mahyar Yousefi , 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}
Pub Date : 2025-02-03DOI: 10.1016/j.gexplo.2025.107695
Vladimir Puzyrev , Paul Duuring
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.
{"title":"Uncertainty quantification of geochemical data imputation using Monte Carlo dropout","authors":"Vladimir Puzyrev , 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}
Pub Date : 2025-01-30DOI: 10.1016/j.gexplo.2025.107688
Manju Sati , Rajagopal Krishnamurthi , Sakthi Saravanan Chinnasamy
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 > 51 wt%) and exhibits low ThO2 concentrations (<1.5 wt%) classified as anomalous values, in contrast to metamorphic monazite, contain lower LREEs (La2O3 + Ce2O3 < 45 wt%) and higher ThO2 (> 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 syn-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.
{"title":"Monazite chemistry and timing of mineralization at Paramanahalli, Chitradurga Greenstone Belt, Dharwar Craton, India: Implications for gold exploration","authors":"Manju Sati , Rajagopal Krishnamurthi , 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 ThO<sub>2</sub> 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 (La<sub>2</sub>O<sub>3</sub> + Ce<sub>2</sub>O<sub>3</sub> > 51 wt%) and exhibits low ThO<sub>2</sub> concentrations (<1.5 wt%) classified as anomalous values, in contrast to metamorphic monazite, contain lower LREEs (La<sub>2</sub>O<sub>3</sub> + Ce<sub>2</sub>O<sub>3</sub> < 45 wt%) and higher ThO<sub>2</sub> (> 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}
Pub Date : 2025-01-30DOI: 10.1016/j.gexplo.2025.107692
Antonio Fabricio Franco dos Santos, Carlos Marcello Dias Fernandes
The IOCG-type world-class Sossego deposit is a complex within the Carajás Mineral Province, Amazonian Craton (northern Brazil), with high CuAu contents (Cu > 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.
{"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, 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 > 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}
Pub Date : 2025-01-30DOI: 10.1016/j.gexplo.2025.107687
Bao Zhou , Guang Wen , Run-Jie Zhou , Yue Sun , Chang-Xiong Wu , Jin Zhu , Zhi-Jun Qin , Xiao-Yang Liu , Xiao-Zeng Cheng
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.
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 εHf(t) 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 (logfO2 values of ΔFMQ) from ΔFMQ+2.1 to ΔFMQ+2.8. The calculated zircon Ce4+/Ce3+ ratios and oxygen fugacity (logfO2) 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.
{"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 , Guang Wen , Run-Jie Zhou , Yue Sun , Chang-Xiong Wu , Jin Zhu , Zhi-Jun Qin , Xiao-Yang Liu , 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<sub>Hf</sub>(<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 H<sub>2</sub>O content to be between 8.3 and 10.3 wt%. The zircons from the Tieshan quartz diorite exhibit Ce<sup>4+</sup>/Ce<sup>3+</sup> ratios of 67 to 201 and oxygen fugacity (log<em>f</em>O<sub>2</sub> values of ΔFMQ) from ΔFMQ+2.1 to ΔFMQ+2.8. The calculated zircon Ce<sup>4+</sup>/Ce<sup>3+</sup> ratios and oxygen fugacity (log<em>f</em>O<sub>2</sub>) 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}
Pub Date : 2025-01-30DOI: 10.1016/j.gexplo.2025.107684
Wen-Sheng Li , Pei Ni , Xue-Fa Shi , Bing Li , Shao-Wen Liu , Stefano Albanese , Fei-Peng Fan , Guan-Hua Wang , An-Qi Hong
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.
{"title":"Mineralogy, geochemistry, and S isotope investigation of seafloor massive sulfides from the Yunzang hydrothermal field, South Atlantic Ridge","authors":"Wen-Sheng Li , Pei Ni , Xue-Fa Shi , Bing Li , Shao-Wen Liu , Stefano Albanese , Fei-Peng Fan , Guan-Hua Wang , 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 δ<sup>34</sup>SV-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}
Pub Date : 2025-01-30DOI: 10.1016/j.gexplo.2025.107690
Zhen Jia , Wenchang Li , Jianze Sha , Shiping Li , Fuchuan Chen , Mingguo Deng
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 UPb 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 HO 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.
{"title":"Genesis of the Yunlong Sn deposit in the Chongshan Shear Zone, Western Yunnan, SW China","authors":"Zhen Jia , Wenchang Li , Jianze Sha , Shiping Li , Fuchuan Chen , 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}
Pub Date : 2025-01-29DOI: 10.1016/j.gexplo.2025.107691
Yan Zhang, Wei Xie, Dapeng Li, Qiang Liu, Yuqin Sun, Chenxi Zhang, Ke Geng, Pengfei Wei, Chao Zhang, Na Cai
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 UPb 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 εNd(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 SmNd 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.
{"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, Wei Xie, Dapeng Li, Qiang Liu, Yuqin Sun, Chenxi Zhang, Ke Geng, Pengfei Wei, Chao Zhang, 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><sub>Nd</sub>(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}
Pub Date : 2025-01-29DOI: 10.1016/j.gexplo.2025.107689
Naila Mezoued, Cécile Fabre, Jean Cauzid, Zia Steven Kahou, Océane Rocher
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.
{"title":"Handheld LIBS contribution to quantify critical elements during mining operations: The Beauvoir granite case study","authors":"Naila Mezoued, Cécile Fabre, Jean Cauzid, Zia Steven Kahou, 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}
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 <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.
{"title":"Neutral Mine Drainage prediction for different waste rock lithologies – Case study of Canadian Malartic","authors":"Vincent Marmier , Benoît Plante , Isabelle Demers , 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 <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}
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