Pub Date : 2025-12-18DOI: 10.1016/j.gexplo.2025.107962
Ko Kumada , Yoshiyasu Takefuji
This paper critically examines methodological limitations in hydrochemical contamination studies, focusing on Principal Component Analysis (PCA) applications to the Gafsa basin in Tunisia. While PCA, as employed by Boschetti et al. (2025), effectively identified primary contamination sources from phosphate mining and agriculture, its inherent linearity assumptions fundamentally constrain its ability to represent complex environmental processes. We demonstrate how complementary methodologies—Feature Agglomeration, Independent Component Analysis, and High Variance Gene Selection—create a more comprehensive analytical framework capable of capturing nonlinear relationships, hierarchical structures, and statistically independent variation sources that PCA might overlook. This integrated approach enhances result reliability through methodological triangulation, providing environmental managers with more accurate contamination profiles that reflect the true complexity of groundwater systems.
{"title":"Beyond principal component analysis: Nonparametric and nonlinear approaches for robust analysis of Gafsa basin groundwater","authors":"Ko Kumada , Yoshiyasu Takefuji","doi":"10.1016/j.gexplo.2025.107962","DOIUrl":"10.1016/j.gexplo.2025.107962","url":null,"abstract":"<div><div>This paper critically examines methodological limitations in hydrochemical contamination studies, focusing on Principal Component Analysis (PCA) applications to the Gafsa basin in Tunisia. While PCA, as employed by Boschetti et al. (2025), effectively identified primary contamination sources from phosphate mining and agriculture, its inherent linearity assumptions fundamentally constrain its ability to represent complex environmental processes. We demonstrate how complementary methodologies—Feature Agglomeration, Independent Component Analysis, and High Variance Gene Selection—create a more comprehensive analytical framework capable of capturing nonlinear relationships, hierarchical structures, and statistically independent variation sources that PCA might overlook. This integrated approach enhances result reliability through methodological triangulation, providing environmental managers with more accurate contamination profiles that reflect the true complexity of groundwater systems.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107962"},"PeriodicalIF":3.3,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837187","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 : 2025-12-18DOI: 10.1016/j.gexplo.2025.107960
Spartak Hovhannisyan , Nona Movsisyan , Mane Kostanyan , Kristina Sargsyan , Konstantin Pyuskyulyan , Olga Belyaeva
Cross-validation of different interpolation methods - Inverse Distance Weighting (IDW), Ordinary Kriging, and Empirical Bayesian Kriging - was performed to map the spatial distribution of radioactivity in agricultural soils of Kotayk region, Armenia. Variogram analysis was used to characterize the spatial pattern of naturally occurring radionuclides (226Ra, 232Th, 40K) and artificial radionuclide 137Cs, as well as gross beta activity in soil.
Variogram results indicated weak spatial correlation for 226Ra and 40K, reflecting regional-scale heterogeneity, while 232Th exhibited no discernible spatial structure, suggesting that its distribution is influenced primarily by highly localized processes. In contrast, the distribution of 137Cs appeared to be influenced by a regional factor, altitude, in combination with local altitude-dependent factors. Mechanical disturbance caused by plowing reduced 137Cs activity in arable lands, as the top 5 cm of soil, which is rich in 137Cs, mixes with deeper layers that are poor in 137Cs. These lands also showed the highest prediction errors compared to undisturbed land use types such as pastures and grasslands.
For gross beta activity, Ordinary Kriging with a Gaussian variogram model provided the most effective predictors, whereas an exponential variogram model performed best for 137Cs. Empirical Bayesian Kriging proved most effective for mapping naturally occurring radionuclides. Overall, this comparative assessment of interpolation methods provides important methodological insights for improving spatial predictions of radionuclides in heterogeneous agricultural environments.
{"title":"Comparing interpolation methods for GIS-based mapping of agricultural soil radioactivity","authors":"Spartak Hovhannisyan , Nona Movsisyan , Mane Kostanyan , Kristina Sargsyan , Konstantin Pyuskyulyan , Olga Belyaeva","doi":"10.1016/j.gexplo.2025.107960","DOIUrl":"10.1016/j.gexplo.2025.107960","url":null,"abstract":"<div><div>Cross-validation of different interpolation methods - Inverse Distance Weighting (IDW), Ordinary Kriging, and Empirical Bayesian Kriging - was performed to map the spatial distribution of radioactivity in agricultural soils of Kotayk region, Armenia. Variogram analysis was used to characterize the spatial pattern of naturally occurring radionuclides (<sup>226</sup>Ra, <sup>232</sup>Th, <sup>40</sup>K) and artificial radionuclide <sup>137</sup>Cs, as well as gross beta activity in soil.</div><div>Variogram results indicated weak spatial correlation for <sup>226</sup>Ra and <sup>40</sup>K, reflecting regional-scale heterogeneity, while <sup>232</sup>Th exhibited no discernible spatial structure, suggesting that its distribution is influenced primarily by highly localized processes. In contrast, the distribution of <sup>137</sup>Cs appeared to be influenced by a regional factor, altitude, in combination with local altitude-dependent factors. Mechanical disturbance caused by plowing reduced <sup>137</sup>Cs activity in arable lands, as the top 5 cm of soil, which is rich in <sup>137</sup>Cs, mixes with deeper layers that are poor in <sup>137</sup>Cs. These lands also showed the highest prediction errors compared to undisturbed land use types such as pastures and grasslands.</div><div>For gross beta activity, Ordinary Kriging with a Gaussian variogram model provided the most effective predictors, whereas an exponential variogram model performed best for <sup>137</sup>Cs. Empirical Bayesian Kriging proved most effective for mapping naturally occurring radionuclides. Overall, this comparative assessment of interpolation methods provides important methodological insights for improving spatial predictions of radionuclides in heterogeneous agricultural environments.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107960"},"PeriodicalIF":3.3,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837201","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 : 2025-12-15DOI: 10.1016/j.gexplo.2025.107959
Amirreza Bitaraf , Reza Ghezelbash
This study presents an advanced and reproducible geochemical targeting workflow that integrates multiple unsupervised machine learning algorithms with multifractal modeling to improve early-stage prospectivity analysis in greenfield terrains. We evaluate and systematically compare DBSCAN, Self-Organizing Maps (SOM), and K-series clustering (K-means, K-medians, and K-medoids) using 800 stream-sediment samples from the Hashtjin district located in the Urumieh–Dokhtar Magmatic Belt (UDMB), NW Iran—an important region for porphyry-epithermal copper systems. To address the inherent closed-nature problem in compositional geochemical data, Isometric Log-Ratio (ILR) transformation was applied to ensure valid multivariate analysis, and the BoxCox transformation was subsequently used for normalizing purposes. Multi-fractal CN modeling was then employed to derive anomaly thresholds and delineate anomalous sample catchment basins (SCBs). PCA detected a strong Cu–Au–Mo–As correlation reflecting porphyry-style mineralization, and these elements were used as inputs for clustering.
DBSCAN, optimized using the Silhouette index (ε = 0.110, MinPts = 2), demonstrated the best performance by accurately defining coherent spatial anomalies and effectively distinguishing noise, with the highest success-rate and AUC values among all tested algorithms. SOM captured element-zoning patterns associated with alteration halos, while K-series methods showed lower reliability due to sensitivity to outliers and skewed value distributions. A novel about the weighted-hybrid integration of DBSCAN and SOM and K-Series methods was developed to combine spatial robustness with multivariate pattern recognition. This hybrid approach significantly reduced the initial ~2500 km2 study area to ~1.85 % for very strong anomalies and ~ 12 % when including strong anomalies—representing an efficient regional screening scale for prioritizing follow-up surveys. Therefore, three high-priority target zones were identified: (1) a southeastern zone near the Gollujeh Cu ± Au occurrence with strong geochemical and structural–subvolcanic controls, (2) a central-northern CuMo prospective zone associated with intrusive contacts, and (3) scattered anomalies aligned with fault-controlled hydrothermal pathways. The spatial agreement of anomalies with magmatic units, major faults, and hydrothermal alteration strengthens the exploration significance of the results. This study highlights the effectiveness of a transparent and repeatable unsupervised learning workflow for geochemical exploration in data-limited regions, providing a valuable decision-support tool for future prospectivity modeling across similar metallogenic belts worldwide.
{"title":"Evaluation of SOM, DBSCAN, and K-series clustering algorithms for CuAu anomaly exploration in sample catchment basins: A case study from Hashtjin district, NW Iran","authors":"Amirreza Bitaraf , Reza Ghezelbash","doi":"10.1016/j.gexplo.2025.107959","DOIUrl":"10.1016/j.gexplo.2025.107959","url":null,"abstract":"<div><div>This study presents an advanced and reproducible geochemical targeting workflow that integrates multiple unsupervised machine learning algorithms with multifractal modeling to improve early-stage prospectivity analysis in greenfield terrains. We evaluate and systematically compare DBSCAN, Self-Organizing Maps (SOM), and K-series clustering (K-means, K-medians, and K-medoids) using 800 stream-sediment samples from the Hashtjin district located in the Urumieh–Dokhtar Magmatic Belt (UDMB), NW Iran—an important region for porphyry-epithermal copper systems. To address the inherent closed-nature problem in compositional geochemical data, Isometric Log-Ratio (ILR) transformation was applied to ensure valid multivariate analysis, and the BoxCox transformation was subsequently used for normalizing purposes. Multi-fractal C<img>N modeling was then employed to derive anomaly thresholds and delineate anomalous sample catchment basins (SCBs). PCA detected a strong Cu–Au–Mo–As correlation reflecting porphyry-style mineralization, and these elements were used as inputs for clustering.</div><div>DBSCAN, optimized using the Silhouette index (ε = 0.110, MinPts = 2), demonstrated the best performance by accurately defining coherent spatial anomalies and effectively distinguishing noise, with the highest success-rate and AUC values among all tested algorithms. SOM captured element-zoning patterns associated with alteration halos, while K-series methods showed lower reliability due to sensitivity to outliers and skewed value distributions. A novel about the weighted-hybrid integration of DBSCAN and SOM and K-Series methods was developed to combine spatial robustness with multivariate pattern recognition. This hybrid approach significantly reduced the initial ~2500 km<sup>2</sup> study area to ~1.85 % for very strong anomalies and ~ 12 % when including strong anomalies—representing an efficient regional screening scale for prioritizing follow-up surveys. Therefore, three high-priority target zones were identified: (1) a southeastern zone near the Gollujeh Cu ± Au occurrence with strong geochemical and structural–subvolcanic controls, (2) a central-northern Cu<img>Mo prospective zone associated with intrusive contacts, and (3) scattered anomalies aligned with fault-controlled hydrothermal pathways. The spatial agreement of anomalies with magmatic units, major faults, and hydrothermal alteration strengthens the exploration significance of the results. This study highlights the effectiveness of a transparent and repeatable unsupervised learning workflow for geochemical exploration in data-limited regions, providing a valuable decision-support tool for future prospectivity modeling across similar metallogenic belts worldwide.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107959"},"PeriodicalIF":3.3,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787712","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 : 2025-12-10DOI: 10.1016/j.gexplo.2025.107957
Zhiliang Wang , Xuebing Zhang , Yaochao Sun , Yanjie Geng , Guanghuan Huang , Miaomiao Zhang , Chenlong Li , Zeling Wang
The Wuzunbulake gold deposit, located in the eastern section of the South Tianshan Orogenic Belt, is an important orogenic gold deposit discovered in the southern part of the Kumishi region. Although previous studies have revealed the development of pyrite-sericite alteration proximal to ore bodies in orogenic gold deposits, research on short-wavelength infrared (SWIR) exploration indicators from alteration minerals and its controlling mechanisms remain limited. The Wuzunbulake gold deposit exhibits well-developed host rock alteration. Through microscopic observation and SWIR spectroscopy, 14 alteration minerals, including muscovite, phengite, illite, and chlorite, have been identified. Petrographic observations reveal that muscovite, occurring as coarse-grained scaly aggregates with bright interference colors, predominantly develops in host rocks proximal to the ore bodies. In contrast, phengite occurs as fine-grained aggregates with oriented arrangements in distal metamorphic sandstones. SWIR studies have revealed that muscovite with lower Al-OH (Pos2200) absorption peak values is predominantly developed in mineralized bodies, while phengite with higher Pos2200 is widely distributed across various lithologies. Additionally, the Pos2200 values of the white mica group show negative correlations with AlIV and AlVI, and positive correlations with Si and Fe + Mg. The gold ore bodies of Wuzunbulake gold deposit are spatially consistent with the transition zone from high to low IC values, indicating that gold mineralization occurred in an environment transitioning from high to low temperatures. This is consistent with the geological characteristics of orogenic gold deposits formed within ductile-brittle shear zones. For white mica group minerals, the Pos2200 values of hydrothermal muscovite is lower than the corresponding median values, and can serve as an approximate boundary distinguishing hydrothermal muscovite from metamorphic phengite. The white mica group minerals with Pos2200 ≤ 2216.5 nm (median values for Line 0 and 07 of Zone I) and Pos2200 ≤ 2216.3 nm (median values for Line 31 and 47 of Zone II), and IC values ranging from 7 to 12, can be used as new exploration indicators for the Wuzunbulake gold deposit.
{"title":"Application of white mica minerals to exploration of orogenic gold deposit: A case study of Wuzunbulake gold deposit, South Tianshan (NW China)","authors":"Zhiliang Wang , Xuebing Zhang , Yaochao Sun , Yanjie Geng , Guanghuan Huang , Miaomiao Zhang , Chenlong Li , Zeling Wang","doi":"10.1016/j.gexplo.2025.107957","DOIUrl":"10.1016/j.gexplo.2025.107957","url":null,"abstract":"<div><div>The Wuzunbulake gold deposit, located in the eastern section of the South Tianshan Orogenic Belt, is an important orogenic gold deposit discovered in the southern part of the Kumishi region. Although previous studies have revealed the development of pyrite-sericite alteration proximal to ore bodies in orogenic gold deposits, research on short-wavelength infrared (SWIR) exploration indicators from alteration minerals and its controlling mechanisms remain limited. The Wuzunbulake gold deposit exhibits well-developed host rock alteration. Through microscopic observation and SWIR spectroscopy, 14 alteration minerals, including muscovite, phengite, illite, and chlorite, have been identified. Petrographic observations reveal that muscovite, occurring as coarse-grained scaly aggregates with bright interference colors, predominantly develops in host rocks proximal to the ore bodies. In contrast, phengite occurs as fine-grained aggregates with oriented arrangements in distal metamorphic sandstones. SWIR studies have revealed that muscovite with lower Al-OH (Pos2200) absorption peak values is predominantly developed in mineralized bodies, while phengite with higher Pos2200 is widely distributed across various lithologies. Additionally, the Pos2200 values of the white mica group show negative correlations with Al<sup>IV</sup> and Al<sup>VI</sup>, and positive correlations with Si and Fe + Mg. The gold ore bodies of Wuzunbulake gold deposit are spatially consistent with the transition zone from high to low IC values, indicating that gold mineralization occurred in an environment transitioning from high to low temperatures. This is consistent with the geological characteristics of orogenic gold deposits formed within ductile-brittle shear zones. For white mica group minerals, the Pos2200 values of hydrothermal muscovite is lower than the corresponding median values, and can serve as an approximate boundary distinguishing hydrothermal muscovite from metamorphic phengite. The white mica group minerals with Pos2200 ≤ 2216.5 nm (median values for Line 0 and 07 of Zone I) and Pos2200 ≤ 2216.3 nm (median values for Line 31 and 47 of Zone II), and IC values ranging from 7 to 12, can be used as new exploration indicators for the Wuzunbulake gold deposit.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107957"},"PeriodicalIF":3.3,"publicationDate":"2025-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787713","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 : 2025-12-08DOI: 10.1016/j.gexplo.2025.107958
Haowei Gu , Xiheng He , Hayden Dalton , Yanshuang Wu , Xiaohua Deng
The Jingerquan rare-metal deposit is the only known pegmatite-type LiBe rare-metal deposit in the Eastern Tianshan. However, the age of Jingerquan deposit remains poorly constrained due to limited studies. In this study we use ArAr and RbSr dating for micas from different pegmatite zones to determine the mineralization age. The electron probe microanalysis (EPMA) results indicate that the chemical composition of muscovite shows a significant variation trend from the barren pegmatite zone to the Li-Be-rich pegmatite zone. Muscovite coexisting with spodumene in the mineralized zone has relatively high contents of Al₂O₃, MnO, Li₂O, and F, whereas muscovite in the barren zone has relatively high contents of FeO and MgO. Other elements such as SiO₂, TiO₂, K₂O, and Na₂O show minor differences in content. Both muscovite and biotite from the barren pegmatite zone are characterized by FeO enrichment. In-situ RbSr dating of muscovite from the barren pegmatite zone yielded an age of 234.2 ± 9.3 Ma (all ages reported to 2σ). The ArAr ages of muscovite in the barren zone are 242.5 ± 0.9 Ma, 242.8 ± 0.8 Ma, 240.9 ± 0.9 Ma and 239.5 ± 1.6 Ma, the ArAr ages of biotite are 239.8 ± 1.0 Ma, 238.6 ± 1.1 Ma, and the muscovite coexisting with spodumene yielded the ArAr ages of 236.3 ± 1.5 Ma and 237.2 ± 1.2 Ma. Through the geochronological study of mica, the metallogenic age of the Jingerquan rare-metal deposit is constrained to approximately 237–236 Ma, while the formation of the pegmatite occurred between 250 and 234 Ma. This study demonstrates that the Jingerquan LiBe rare-metal deposit formed during the Triassic period in a stable intraplate environment through prolonged slow cooling and crystallization.
{"title":"Mica ArAr and in-situ RbSr geochronology for the Jingerquan rare-metal pegmatite deposit, Eastern Tianshan","authors":"Haowei Gu , Xiheng He , Hayden Dalton , Yanshuang Wu , Xiaohua Deng","doi":"10.1016/j.gexplo.2025.107958","DOIUrl":"10.1016/j.gexplo.2025.107958","url":null,"abstract":"<div><div>The Jingerquan rare-metal deposit is the only known pegmatite-type Li<img>Be rare-metal deposit in the Eastern Tianshan. However, the age of Jingerquan deposit remains poorly constrained due to limited studies. In this study we use Ar<img>Ar and Rb<img>Sr dating for micas from different pegmatite zones to determine the mineralization age. The electron probe microanalysis (EPMA) results indicate that the chemical composition of muscovite shows a significant variation trend from the barren pegmatite zone to the Li-Be-rich pegmatite zone. Muscovite coexisting with spodumene in the mineralized zone has relatively high contents of Al₂O₃, MnO, Li₂O, and F, whereas muscovite in the barren zone has relatively high contents of FeO and MgO. Other elements such as SiO₂, TiO₂, K₂O, and Na₂O show minor differences in content. Both muscovite and biotite from the barren pegmatite zone are characterized by FeO enrichment. In-situ Rb<img>Sr dating of muscovite from the barren pegmatite zone yielded an age of 234.2 ± 9.3 Ma (all ages reported to 2σ). The Ar<img>Ar ages of muscovite in the barren zone are 242.5 ± 0.9 Ma, 242.8 ± 0.8 Ma, 240.9 ± 0.9 Ma and 239.5 ± 1.6 Ma, the Ar<img>Ar ages of biotite are 239.8 ± 1.0 Ma, 238.6 ± 1.1 Ma, and the muscovite coexisting with spodumene yielded the Ar<img>Ar ages of 236.3 ± 1.5 Ma and 237.2 ± 1.2 Ma. Through the geochronological study of mica, the metallogenic age of the Jingerquan rare-metal deposit is constrained to approximately 237–236 Ma, while the formation of the pegmatite occurred between 250 and 234 Ma. This study demonstrates that the Jingerquan Li<img>Be rare-metal deposit formed during the Triassic period in a stable intraplate environment through prolonged slow cooling and crystallization.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107958"},"PeriodicalIF":3.3,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734606","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}
The Kuh-e-Esfand porphyry copper prospect, situated 90 km southeast of Jiroft, is associated with Oligocene-Miocene Jebal-e-Barez-type intrusives in the Kerman Cenozoic Magmatic Assambladge (KCMA). In this area, quartz diorite, diorite, and granodiorite porphyry intrusions are emplaced within the Eocene Razak volcanic rocks. Hydrothermal alteration in the study area includes potassic, a deep potassic zone characterized by quartz, sericite, K-feldspar, chlorite ± anhydrite, phyllic, argillic, and propylitic zones. Mineralization, mainly as chalcopyrite and pyrite, occurs predominantly in the transition between potassic and phyllic zones, which extends mostly within the quartz diorite unit.
On the Al/(Ca + Na + K) vs. An (%) diagram, plagioclase data of quartz diorite units plot along the discriminating line of barren and fertile porphyry Cu intrusions with a more tendency to fertile field (average Al/(Ca + Na + K) = 1.3). Ca- amphiboles in the quartz diorite intrusion are classified as low-Al (AlT = 0.7–1.6) and high-Al (AlT = 1.9–2.12) groups. Low-Al amphiboles, characterized by lower water content and higher chlorine concentrations are crystallized at lower temperatures (720.9–0.8 °C), pressures (0.51–0.89 kbar), and under more oxidizing conditions (ΔNNO = 1.47–1.96), compared to high-Al amphiboles, which formed at higher temperatures (866.5–921.7 °C), pressures (1.94–4.02 kbar), and lower oxidation states (ΔNNO = 0.99–1.05). Low-Al amphiboles formed under conditions more favorable for mineralization. Furthermore, re-equilibrated biotites are of Mg-rich, showing high Mg/(Mg + Fe) ratios with low Mn and AlVI values, which is analogous to those of fertile porphyry Cu intrusions. Geochemical data indicate a hydrous/oxidized calc-alkaline I-type magma that drived from the interaction of mantle-derived magmas with crustal materials in a subduction-related geotectonic setting. The geological, magmatic and geochemical characteristics of the Kuh-e-Esfand prospect are consistent with porphyry Cu mineralization potential.
{"title":"Fertility assessment of the Kuh-e-Esfand porphyry Cu intrusion in SE Iran: Evidences from silicate chemistry","authors":"Alireza Zarasvandi , Afsaneh Soltani , Nader Taghipour , Mohsen Rezaei , Johann G. Raith , Adel Saki , Ghazal Zarasvandi","doi":"10.1016/j.gexplo.2025.107956","DOIUrl":"10.1016/j.gexplo.2025.107956","url":null,"abstract":"<div><div>The Kuh-e-Esfand porphyry copper prospect, situated 90 km southeast of Jiroft, is associated with Oligocene-Miocene Jebal-e-Barez-type intrusives in the Kerman Cenozoic Magmatic Assambladge (KCMA). In this area, quartz diorite, diorite, and granodiorite porphyry intrusions are emplaced within the Eocene Razak volcanic rocks. Hydrothermal alteration in the study area includes potassic, a deep potassic zone characterized by quartz, sericite, K-feldspar, chlorite ± anhydrite, phyllic, argillic, and propylitic zones. Mineralization, mainly as chalcopyrite and pyrite, occurs predominantly in the transition between potassic and phyllic zones, which extends mostly within the quartz diorite unit.</div><div>On the Al/(Ca + Na + K) vs. An (%) diagram, plagioclase data of quartz diorite units plot along the discriminating line of barren and fertile porphyry Cu intrusions with a more tendency to fertile field (average Al/(Ca + Na + K) = 1.3). Ca- amphiboles in the quartz diorite intrusion are classified as low-Al (Al<sub>T</sub> = 0.7–1.6) and high-Al (Al<sub>T</sub> = 1.9–2.12) groups. Low-Al amphiboles, characterized by lower water content and higher chlorine concentrations are crystallized at lower temperatures (720.9–0.8 °C), pressures (0.51–0.89 kbar), and under more oxidizing conditions (ΔNNO = 1.47–1.96), compared to high-Al amphiboles, which formed at higher temperatures (866.5–921.7 °C), pressures (1.94–4.02 kbar), and lower oxidation states (ΔNNO = 0.99–1.05). Low-Al amphiboles formed under conditions more favorable for mineralization. Furthermore, re-equilibrated biotites are of Mg-rich, showing high Mg/(Mg + Fe) ratios with low Mn and Al<sup>VI</sup> values, which is analogous to those of fertile porphyry Cu intrusions. Geochemical data indicate a hydrous/oxidized calc-alkaline I-type magma that drived from the interaction of mantle-derived magmas with crustal materials in a subduction-related geotectonic setting. The geological, magmatic and geochemical characteristics of the Kuh-e-Esfand prospect are consistent with porphyry Cu mineralization potential.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107956"},"PeriodicalIF":3.3,"publicationDate":"2025-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787711","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 : 2025-12-04DOI: 10.1016/j.gexplo.2025.107955
Thais Caroline Murer , Carlos Roberto de Souza Filho
The P-REE-Th Nolans Bore deposit is located in the Northern Territory of Australia and is one of the few known deposits where rare earth elements (REE) are hosted in monomineralic fluorapatite veins. The formation of these REE-fluorapatite veins occurred due to the interaction of carbonatite magma with granulite facies rocks during the peak of metamorphism. In this study, we utilized spectral data from the visible to shortwave infrared (VNIR-SWIR) region, collected at specific points along the drill core, to identify diagnostic parameters of REE host minerals. These data, combined with geochemical analysis, allowed us to estimate the total concentration of rare earth elements (TREE) in the deposit rocks. Our results demonstrated that absorption features indicative of REE could be detected at wavelengths of 580, 744, 804, and 872 nm. Reflectance spectroscopy confirmed the presence of REE in the fluorapatite veins and rocks rich in kaolinite and smectite. Machine learning models were tested to predict TREE concentrations from spectral data. Among the tested models, PLSR and LightGBM achieved comparable overall accuracy, though LightGBM provided more reliable interval predictions. The Multiple-instance learning (MIL) model exhibited higher dispersion, particularly at intermediate TREE values. These findings suggest that reflectance spectroscopy, in conjunction with geochemical data and machine learning algorithms, can be employed to develop models for quantifying REE based on a sample's spectral signature. The predictions made by this model can help determine the spatial distribution of ore content throughout drill cores, reducing reliance on large samples for geochemical testing and decreasing the time required for core analysis.
{"title":"VNIR-SWIR Spectroscopy and Machine Learning: A new approach for Rare Earth Element detection and quantification in fluorapatite veins (Nolans Bore Deposit, Australia)","authors":"Thais Caroline Murer , Carlos Roberto de Souza Filho","doi":"10.1016/j.gexplo.2025.107955","DOIUrl":"10.1016/j.gexplo.2025.107955","url":null,"abstract":"<div><div>The P-REE-Th Nolans Bore deposit is located in the Northern Territory of Australia and is one of the few known deposits where rare earth elements (REE) are hosted in monomineralic fluorapatite veins. The formation of these REE-fluorapatite veins occurred due to the interaction of carbonatite magma with granulite facies rocks during the peak of metamorphism. In this study, we utilized spectral data from the visible to shortwave infrared (VNIR-SWIR) region, collected at specific points along the drill core, to identify diagnostic parameters of REE host minerals. These data, combined with geochemical analysis, allowed us to estimate the total concentration of rare earth elements (TREE) in the deposit rocks. Our results demonstrated that absorption features indicative of REE could be detected at wavelengths of 580, 744, 804, and 872 nm. Reflectance spectroscopy confirmed the presence of REE in the fluorapatite veins and rocks rich in kaolinite and smectite. Machine learning models were tested to predict TREE concentrations from spectral data. Among the tested models, PLSR and LightGBM achieved comparable overall accuracy, though LightGBM provided more reliable interval predictions. The Multiple-instance learning (MIL) model exhibited higher dispersion, particularly at intermediate TREE values. These findings suggest that reflectance spectroscopy, in conjunction with geochemical data and machine learning algorithms, can be employed to develop models for quantifying REE based on a sample's spectral signature. The predictions made by this model can help determine the spatial distribution of ore content throughout drill cores, reducing reliance on large samples for geochemical testing and decreasing the time required for core analysis.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107955"},"PeriodicalIF":3.3,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734608","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}
Pyrite, a prevalent mineral in gold deposits, records valuable information about fluid evolution and physicochemical conditions through its textures and composition. The Xiaoyingpan Au deposit in the North China Craton, characterized by multistage mineralization and deformation, provides an ideal setting to investigate these processes. This study integrates electron back-scattered diffraction (EBSD), trace element analysis, and S isotopes to decipher the paragenesis of three pyrite generations (Py1, Py2, Py3) and their implications for fluid evolution and gold endowment at Xiaoyingpan. Petrographic and EBSD results reveal that euhedral Py1 underwent plastic deformation and was subsequently altered to porous and inclusion-rich Py2 via deformation-assisted coupled dissolution-reprecipitation (CDR) reactions. Foam-like Py3 aggregates formed by deformation-induced dynamic recrystallization of Py1. Trace element compositions demonstrate contrasting behaviors during CDR and deformation: lattice-bound elements (Co, Ni) remained immobile, while inclusion-hosted elements (Au, Ag, Te, Cu, Pb) were extensively remobilized and enriched in Py2b domains, highlighting the critical role of deformation microstructures in controlling element redistribution. Consistent S isotope values across all pyrite types suggest a homogeneous S source, with later fluids primarily remobilizing pre-existing metals. We propose a multi-fluid model wherein a metal-rich fluid precipitated Py1 with tellurides and native gold, establishing the primary mineralization. Subsequent reactive and metal-poor fluids drove the dissolution-reprecipitation (forming Py2) and recrystallization (forming Py3) of Py1, respectively, modifying textures and locally upgrading gold grades without introducing significant new metals. This study highlights the importance of EBSD and trace element analyses to decipher formation mechanisms of complex textures in pyrite, which can be used to reveal mineralization and overprinting events in Au deposits.
{"title":"Mobilization of trace elements associated with deformation of pyrite from the Xiaoyingpan Au deposit, North China: Implications for fluid evolution and gold mineralization","authors":"Dazhao Wang , Chaojian Qin , Shimin Zhen , Cheng-Biao Leng","doi":"10.1016/j.gexplo.2025.107954","DOIUrl":"10.1016/j.gexplo.2025.107954","url":null,"abstract":"<div><div>Pyrite, a prevalent mineral in gold deposits, records valuable information about fluid evolution and physicochemical conditions through its textures and composition. The Xiaoyingpan Au deposit in the North China Craton, characterized by multistage mineralization and deformation, provides an ideal setting to investigate these processes. This study integrates electron back-scattered diffraction (EBSD), trace element analysis, and S isotopes to decipher the paragenesis of three pyrite generations (Py1, Py2, Py3) and their implications for fluid evolution and gold endowment at Xiaoyingpan. Petrographic and EBSD results reveal that euhedral Py1 underwent plastic deformation and was subsequently altered to porous and inclusion-rich Py2 via deformation-assisted coupled dissolution-reprecipitation (CDR) reactions. Foam-like Py3 aggregates formed by deformation-induced dynamic recrystallization of Py1. Trace element compositions demonstrate contrasting behaviors during CDR and deformation: lattice-bound elements (Co, Ni) remained immobile, while inclusion-hosted elements (Au, Ag, Te, Cu, Pb) were extensively remobilized and enriched in Py2b domains, highlighting the critical role of deformation microstructures in controlling element redistribution. Consistent S isotope values across all pyrite types suggest a homogeneous S source, with later fluids primarily remobilizing pre-existing metals. We propose a multi-fluid model wherein a metal-rich fluid precipitated Py1 with tellurides and native gold, establishing the primary mineralization. Subsequent reactive and metal-poor fluids drove the dissolution-reprecipitation (forming Py2) and recrystallization (forming Py3) of Py1, respectively, modifying textures and locally upgrading gold grades without introducing significant new metals. This study highlights the importance of EBSD and trace element analyses to decipher formation mechanisms of complex textures in pyrite, which can be used to reveal mineralization and overprinting events in Au deposits.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107954"},"PeriodicalIF":3.3,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683204","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 : 2025-12-03DOI: 10.1016/j.gexplo.2025.107945
Ian Burron , Mostafa Fayek , Julie Brown , Alfredo Camacho
The Kiggavik Uranium (U) Project in Nunavut, Canada hosts U deposits for which both unconformity-related and metasomatic‑iron-alkali-calcic genetic models have been proposed. We propose a five-phase genetic model consisting of: (1) albitization; (2) hematization and illitization; (3) bleaching and primary (U1) mineralization; (4) ∼1450 Ma to 274 Ma overprinting events linked to distant tectonic and igneous events, and: (5) geologically recent (∼471 Ka to 36 Ka) overprinting linked to subglacial meteoric fluids.
M2 muscovite formed during albitization of granitic rocks and is Ar-Ar dated to ∼1820–1830 Ma, which is consistent with igneous and seismic activity and albitite-hosted U mineralization in the region. M2 muscovite has δ2H values as high as +129 ‰. This high value is unprecedented in terrestrial minerals. M2 is in equilibrium with isotopically heavy (δ18O and δ2H values of +10.4 ± 2.1 ‰ and + 130 ± 31 ‰, respectively) fluids proposed to have been produced through multiple cycles of seismically-induced fluid boiling, phase separation, and condensation.
Multiple generations of illite, formed through retrograde metamorphic (Il1) and subsequent hydrothermal (Il2-Il5) processes, are present. Il3 and Il5 are isotopically consistent with precipitation from basinal fluids and with subsequent overprinting by meteoric fluids, while Il4 is isotopically consistent with highly fractionated, boiled fluids. Il3-Il5 illites yield post U1 Ar-Ar dates, reflecting overprinting events.
Highly fractionated fluids are strongly linked to albitization and an early albitite-style U mineralization event. Both highly fractionated and basinal fluids may have been involved in U1 mineralization. Basinal and meteoric fluids are strongly linked to post-depositional alteration events.
加拿大Nunavut的Kiggavik铀(U)项目拥有铀矿床，其不整合成因模式和交代-铁-碱-钙成因模式已被提出。我们提出了一个五阶段的遗传模型，包括：(1)脂肪化；(2)溶血和消毒；(3)漂白和原生矿化（U1）；(4)与遥远的构造和火成岩事件有关的~ 1450 Ma ~ 274 Ma套印事件，以及(5)与冰下大气流体有关的地质近代（~ 471 Ka ~ 36 Ka）套印事件。M2白云母形成于花岗岩体钠长石化时期，Ar-Ar年代为~ 1820-1830 Ma，与该区火成岩和地震活动以及钠长石含铀成矿作用一致。M2白云母的δ2H值高达+129‰。如此高的价值在陆生矿物中是前所未有的。M2与同位素重流体（δ18O和δ2H值分别为+10.4±2.1‰和+ 130±31‰）处于平衡状态，这些流体可能是通过地震诱发的流体沸腾、相分离和冷凝的多次循环产生的。通过逆行变质（Il1）和随后的热液（Il2-Il5）过程形成的多代伊利石。Il3和Il5的同位素特征与盆地流体沉淀和随后的大气流体套印相一致，而Il4的同位素特征与高度分馏的沸腾流体相一致。Il3-Il5 illites在U1 Ar-Ar日期后产生，反映套印事件。高分馏流体与钠长石化和早期钠长石型铀成矿事件密切相关。高分馏流体和盆地流体可能都参与了U1矿化。盆地流体和大气流体与沉积后蚀变事件密切相关。
{"title":"Extreme H isotope fractionation of phyllosilicates from the Kiggavik Uranium deposits","authors":"Ian Burron , Mostafa Fayek , Julie Brown , Alfredo Camacho","doi":"10.1016/j.gexplo.2025.107945","DOIUrl":"10.1016/j.gexplo.2025.107945","url":null,"abstract":"<div><div>The Kiggavik Uranium (U) Project in Nunavut, Canada hosts U deposits for which both unconformity-related and metasomatic‑iron-alkali-calcic genetic models have been proposed. We propose a five-phase genetic model consisting of: (1) albitization; (2) hematization and illitization; (3) bleaching and primary (U1) mineralization; (4) ∼1450 Ma to 274 Ma overprinting events linked to distant tectonic and igneous events, and: (5) geologically recent (∼471 Ka to 36 Ka) overprinting linked to subglacial meteoric fluids.</div><div>M2 muscovite formed during albitization of granitic rocks and is Ar-Ar dated to ∼1820–1830 Ma, which is consistent with igneous and seismic activity and albitite-hosted U mineralization in the region. M2 muscovite has δ<sup>2</sup>H values as high as +129 ‰. This high value is unprecedented in terrestrial minerals. M2 is in equilibrium with isotopically heavy (δ<sup>18</sup>O and δ<sup>2</sup>H values of +10.4 ± 2.1 ‰ and + 130 ± 31 ‰, respectively) fluids proposed to have been produced through multiple cycles of seismically-induced fluid boiling, phase separation, and condensation.</div><div>Multiple generations of illite, formed through retrograde metamorphic (Il1) and subsequent hydrothermal (Il2-Il5) processes, are present. Il3 and Il5 are isotopically consistent with precipitation from basinal fluids and with subsequent overprinting by meteoric fluids, while Il4 is isotopically consistent with highly fractionated, boiled fluids. Il3-Il5 illites yield post U1 Ar-Ar dates, reflecting overprinting events.</div><div>Highly fractionated fluids are strongly linked to albitization and an early albitite-style U mineralization event. Both highly fractionated and basinal fluids may have been involved in U1 mineralization. Basinal and meteoric fluids are strongly linked to post-depositional alteration events.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107945"},"PeriodicalIF":3.3,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683203","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}
Intermediate-sulfidation epithermal deposits are known to be associated with porphyry Cu and high-sulfidation epithermal deposits but also have recently been reviewed to be related to low-sulfidation epithermal deposits in back arcs or post-collisional porphyry Mo deposits. In this study, the newfound low- to intermediate-sulfidation epithermal AgPbZn mineralization is shown to be linked with the nearby Wulanwuzhu'er porphyry Cu deposit in the post-collisional setting of the eastern Kunlun Orogen based on field relationships, alteration and mineralization, zircon and rutile LA-ICP-MS UPb dating, and in situ sulfide trace elements and sulfur isotopes. Late Triassic porphyries intruded into deformed Devonian monzogranites along the fault zones were involved in the Wulanwuzhu'er CuAg mineralization. The AgPbZn mineralization includes pyrite, chalcopyrite, pyrrhotite, sphalerite, galena, and argentite disseminated or in veins with kaolinization, sericitization, and chloritization. The Wulanwuzhu'er Cu deposit hosts veinlet-disseminated pyrite and chalcopyrite associated with potassic and sericitic alteration. Magmatic zircon in the Cu mineralized porphyry and magmatic hydrothermal rutile in Ag mineralized Devonian monzogranites yield similar LA-ICP-MS UPb ages of 213.2 ± 1.8 Ma and 211.7 ± 8.4 Ma, respectively. In situ trace elements and sulfur isotopes for pyrrhotite, six types of pyrite, and two types of chalcopyrite and sphalerite suggest that fluids for the Cu deposit ascended to shallow fault zones and underwent boiling to form the Ag mineralization. Therefore, other porphyry Cu, porphyry Mo, skarn Cu, and low- to intermediate-sulfidation epithermal Ag polymetallic deposits pertinent to Late Triassic post-collisional porphyries in the eastern Kunlun Orogen warrant further research and exploration for relevant styles of mineralization.
{"title":"Late Triassic post-collisional porphyry systems in the eastern Kunlun Orogen, Northern Tibet: Insights from the Wulanwuzhu'er CuAg mineralization","authors":"Zhongyuan Ma , Jinyang Zhang , Yong Zhang , Jianxun Yuan , Jiaxing Chai , Lanxin Zhang","doi":"10.1016/j.gexplo.2025.107943","DOIUrl":"10.1016/j.gexplo.2025.107943","url":null,"abstract":"<div><div>Intermediate-sulfidation epithermal deposits are known to be associated with porphyry Cu and high-sulfidation epithermal deposits but also have recently been reviewed to be related to low-sulfidation epithermal deposits in back arcs or post-collisional porphyry Mo deposits. In this study, the newfound low- to intermediate-sulfidation epithermal Ag<img>Pb<img>Zn mineralization is shown to be linked with the nearby Wulanwuzhu'er porphyry Cu deposit in the post-collisional setting of the eastern Kunlun Orogen based on field relationships, alteration and mineralization, zircon and rutile LA-ICP-MS U<img>Pb dating, and <em>in situ</em> sulfide trace elements and sulfur isotopes. Late Triassic porphyries intruded into deformed Devonian monzogranites along the fault zones were involved in the Wulanwuzhu'er Cu<img>Ag mineralization. The Ag<img>Pb<img>Zn mineralization includes pyrite, chalcopyrite, pyrrhotite, sphalerite, galena, and argentite disseminated or in veins with kaolinization, sericitization, and chloritization. The Wulanwuzhu'er Cu deposit hosts veinlet-disseminated pyrite and chalcopyrite associated with potassic and sericitic alteration. Magmatic zircon in the Cu mineralized porphyry and magmatic hydrothermal rutile in Ag mineralized Devonian monzogranites yield similar LA-ICP-MS U<img>Pb ages of 213.2 ± 1.8 Ma and 211.7 ± 8.4 Ma, respectively. <em>In situ</em> trace elements and sulfur isotopes for pyrrhotite, six types of pyrite, and two types of chalcopyrite and sphalerite suggest that fluids for the Cu deposit ascended to shallow fault zones and underwent boiling to form the Ag mineralization. Therefore, other porphyry Cu, porphyry Mo, skarn Cu, and low- to intermediate-sulfidation epithermal Ag polymetallic deposits pertinent to Late Triassic post-collisional porphyries in the eastern Kunlun Orogen warrant further research and exploration for relevant styles of mineralization.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107943"},"PeriodicalIF":3.3,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145645621","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}
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