Pub Date : 2026-01-02DOI: 10.1016/j.gexplo.2025.107967
Go-Eun Kim , Woo-Jin Shin , Mukesh Kumar Gautam , Kwang-Sik Lee
South Korean ecosystems are increasingly exposed to elevated levels of potentially toxic elements (PTEs) originating from agricultural activities, fossil fuel combustion, and industrial emissions, which pose risks to soil health and ecosystem stability. This study investigated contamination levels and spatial distribution patterns of PTEs in South Korean topsoil. We analyzed 12 PTEs in 329 agricultural and 430 forest sites. Contamination exceedances were assessed using the geoaccumulation index (Igeo), degree of contamination (Cd), and pollution load index (PLI). The Igeo values for Al, Fe, Ti, and V were below one, indicating low accumulation, whereas Ni and As showed higher levels, with As reaching Class 5. Most samples fell within Igeo Classes 0–1, although significant accumulations of Cr, Zn, As, and Pb were observed in higher classes. Both Cd and PLI showed enrichment relative to the background levels, with forest soils showing greater enrichment, particularly for Cu, As, and Pb. Notably, forest soils had more samples in the highest contamination category (Cf ≥ 6). The spatial patterns of Igeo revealed localized contamination, and Al, Fe, and Ti exhibited consistent spatial trends across the different regions. The Cd and PLI maps showed regional variability. This study provides critical insights into the assessment of soil contamination and sustainable land management in South Korea.
{"title":"National-scale spatial variations in potentially toxic elements in agricultural and forest topsoil in South Korea","authors":"Go-Eun Kim , Woo-Jin Shin , Mukesh Kumar Gautam , Kwang-Sik Lee","doi":"10.1016/j.gexplo.2025.107967","DOIUrl":"10.1016/j.gexplo.2025.107967","url":null,"abstract":"<div><div>South Korean ecosystems are increasingly exposed to elevated levels of potentially toxic elements (PTEs) originating from agricultural activities, fossil fuel combustion, and industrial emissions, which pose risks to soil health and ecosystem stability. This study investigated contamination levels and spatial distribution patterns of PTEs in South Korean topsoil. We analyzed 12 PTEs in 329 agricultural and 430 forest sites. Contamination exceedances were assessed using the geoaccumulation index (I<sub><em>geo</em></sub>), degree of contamination (C<sub><em>d</em></sub>), and pollution load index (PLI). The I<sub><em>geo</em></sub> values for Al, Fe, Ti, and V were below one, indicating low accumulation, whereas Ni and As showed higher levels, with As reaching Class 5. Most samples fell within I<sub><em>geo</em></sub> Classes 0–1, although significant accumulations of Cr, Zn, As, and Pb were observed in higher classes. Both C<sub><em>d</em></sub> and PLI showed enrichment relative to the background levels, with forest soils showing greater enrichment, particularly for Cu, As, and Pb. Notably, forest soils had more samples in the highest contamination category (C<sub><em>f</em></sub> ≥ 6). The spatial patterns of I<sub><em>geo</em></sub> revealed localized contamination, and Al, Fe, and Ti exhibited consistent spatial trends across the different regions. The C<sub><em>d</em></sub> and PLI maps showed regional variability. This study provides critical insights into the assessment of soil contamination and sustainable land management in South Korea.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"283 ","pages":"Article 107967"},"PeriodicalIF":3.3,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145903898","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 : 2025-12-27DOI: 10.1016/j.gexplo.2025.107965
Xianyi Huang , Ke Xiao , Changhai Luo , Xiaosheng Cui , Jiale Wang , Xiang Sun
Understanding the mechanisms of gold micro-enrichment is critical for resolving ore-forming processes in orogenic gold systems. The Qinglonggou deposit, on the northern margin of the Qaidam Basin (NMQB), has long been debated with respect to its genesis and gold enrichment. We combine ore microscopy with in situ trace-element analyses of sulfides to address this problem. LA-ICP-MS data show that early pyrite (Py1) hosts the highest concentrations of Au, Sb, Ag, and Te, which decrease systematically from Py1 to Py3. Arsenopyrite contains 1–2 orders of magnitude higher concentrations of most ore-forming elements than coeval pyrite, reflecting abundant As lattice sites and structural defects that enhance incorporation of Au and chalcophile elements. All sulfide generations display a positive AuAs correlation, consistent with As-driven invisible‑gold solid solution, whereas arsenopyrite exhibits a negative AuSb correlation, implying that high Sb contents reduce its capacity to host Au. Trace-element systematics indicate derivation from a single evolving fluid that cooled progressively, underwent boiling during stage I and II, and became stable and depleted at stage III. Precipitation of visible gold during stage II was mainly associated with extensive Sb incorporation into arsenopyrite.
{"title":"Geological characteristics and gold enrichment mechanism of the Qinglonggou gold deposit in the northern margin of the Qaidam Basin","authors":"Xianyi Huang , Ke Xiao , Changhai Luo , Xiaosheng Cui , Jiale Wang , Xiang Sun","doi":"10.1016/j.gexplo.2025.107965","DOIUrl":"10.1016/j.gexplo.2025.107965","url":null,"abstract":"<div><div>Understanding the mechanisms of gold micro-enrichment is critical for resolving ore-forming processes in orogenic gold systems. The Qinglonggou deposit, on the northern margin of the Qaidam Basin (NMQB), has long been debated with respect to its genesis and gold enrichment. We combine ore microscopy with in situ trace-element analyses of sulfides to address this problem. LA-ICP-MS data show that early pyrite (Py1) hosts the highest concentrations of Au, Sb, Ag, and Te, which decrease systematically from Py1 to Py3. Arsenopyrite contains 1–2 orders of magnitude higher concentrations of most ore-forming elements than coeval pyrite, reflecting abundant As lattice sites and structural defects that enhance incorporation of Au and chalcophile elements. All sulfide generations display a positive Au<img>As correlation, consistent with As-driven invisible‑gold solid solution, whereas arsenopyrite exhibits a negative Au<img>Sb correlation, implying that high Sb contents reduce its capacity to host Au. Trace-element systematics indicate derivation from a single evolving fluid that cooled progressively, underwent boiling during stage I and II, and became stable and depleted at stage III. Precipitation of visible gold during stage II was mainly associated with extensive Sb incorporation into arsenopyrite.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107965"},"PeriodicalIF":3.3,"publicationDate":"2025-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145880759","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 : 2025-12-23DOI: 10.1016/j.gexplo.2025.107963
Maria Vaňková , Aleš Vaněk , Anastasiia Shalabai , Martin Mihaljevič , Vojtěch Ettler , Martin Racek , Petr Drahota , Petr Fleissig , Petra Vokurková , Tereza Zádorová , Vít Penížek , Tomáš Hrdlička , Ryan Mathur
This study presents silver (Ag) stable isotope ratios (expressed as δ109Ag) combined with mineralogy and speciation data in Ag-contaminated anthropogenic soils from a historic mining area at Kutná Hora, Czech Republic. Results showed large variability of soil Ag, both in concentrations (~0.5–100 mg/kg) and isotopic patterns (δ109Ag from −0.5 to +1.2 ‰, ±0.1 ‰ 2σ), resulting from differences in the source substrates, i.e. the composition of the original mining waste or slag. In other words, the data do not reflect the fractionation of Ag isotopes during pedogenesis and weathering processes, but rather the inherited 109Ag/107Ag signature of the hydrothermal ore and its genesis history. Examining our endmembers and their potential quantities, a tendency for soils to become isotopically lighter (depleted in the heavy 109Ag isotope) as the concentration of Ag increases was identified, and vice versa. This finding suggests that Ag-rich sulfides, primarily galena, generally favor the light 107Ag isotope over Ag-poor phases being enriched in the heavy isotope (109Ag). Given the negligible post-depositional isotopic effects and the overall high stability of Ag in the studied soils, it is theorized that Ag isotopes can serve as sensitive indicators for monitoring the origin and nature of Ag-containing sulfides and their weathering products. From a general contamination perspective, which is important on many levels, the Ag isotopic and concentration data demonstrate the following: (i) the low mass migration of Ag, and (ii) the well-preserved Ag isotopic patterns in ancient anthropogenic soils (≤17th century).
{"title":"Silver is immobile in Ag-rich mine waste: Isotopic evidence from anthropogenic soils","authors":"Maria Vaňková , Aleš Vaněk , Anastasiia Shalabai , Martin Mihaljevič , Vojtěch Ettler , Martin Racek , Petr Drahota , Petr Fleissig , Petra Vokurková , Tereza Zádorová , Vít Penížek , Tomáš Hrdlička , Ryan Mathur","doi":"10.1016/j.gexplo.2025.107963","DOIUrl":"10.1016/j.gexplo.2025.107963","url":null,"abstract":"<div><div>This study presents silver (Ag) stable isotope ratios (expressed as δ<sup>109</sup>Ag) combined with mineralogy and speciation data in Ag-contaminated anthropogenic soils from a historic mining area at Kutná Hora, Czech Republic. Results showed large variability of soil Ag, both in concentrations (~0.5–100 mg/kg) and isotopic patterns (δ<sup>109</sup>Ag from −0.5 to +1.2 ‰, ±0.1 ‰ 2σ), resulting from differences in the source substrates, i.e. the composition of the original mining waste or slag. In other words, the data do not reflect the fractionation of Ag isotopes during pedogenesis and weathering processes, but rather the inherited <sup>109</sup>Ag/<sup>107</sup>Ag signature of the hydrothermal ore and its genesis history. Examining our endmembers and their potential quantities, a tendency for soils to become isotopically lighter (depleted in the heavy <sup>109</sup>Ag isotope) as the concentration of Ag increases was identified, and <em>vice versa</em>. This finding suggests that Ag-rich sulfides, primarily galena, generally favor the light <sup>107</sup>Ag isotope over Ag-poor phases being enriched in the heavy isotope (<sup>109</sup>Ag). Given the negligible post-depositional isotopic effects and the overall high stability of Ag in the studied soils, it is theorized that Ag isotopes can serve as sensitive indicators for monitoring the origin and nature of Ag-containing sulfides and their weathering products. From a general contamination perspective, which is important on many levels, the Ag isotopic and concentration data demonstrate the following: (i) the low mass migration of Ag, and (ii) the well-preserved Ag isotopic patterns in ancient anthropogenic soils (≤17th century).</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107963"},"PeriodicalIF":3.3,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837186","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 : 2025-12-22DOI: 10.1016/j.gexplo.2025.107964
Yang Lan , Yan Li , Ke Liu , Long Chen , Haoran Huang , Xinyu Cheng , Zi Ye , Yujie Jiang , Meixian Wang
Heavy metal contamination in urban soils poses a significant threat to sustainable development and public health. Therefore, a systematic evaluation of the sources and risks of heavy metals in urban soils is essential. This study applies an improved Nemerow index, the matter-element extension model, and a Monte Carlo-based health risk model. In addition, it integrates lead isotope analysis, correlation analysis, Self-Organising Maps (SOM), Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR), and the MixSIAR isotopic mixing model. These methods are combined to enable accurate source apportionment and source-specific risk assessment. The results indicate that the high-value zones of all eight heavy metals are mainly distributed in the south-eastern part of the city. The overall ecological risk remains at a controllable level. Carcinogenic and non-carcinogenic risks for adults are negligible, whereas those for children reach 27.30 % and 3.14 %, respectively. Lead-isotope signatures indicate that coal combustion and traffic emissions are the principal sources of lead in soil. Source-health risk analysis suggests that coal combustion is likely an important contributor to overall pollution, with arsenic (As, a metalloid) and its coal-related inputs likely warranting greater attention in control strategies. Children appear to be a more vulnerable group requiring targeted protection. This study provides policy recommendations for preventing and controlling soil pollution in Lanzhou. It also bridges the gap in precise source identification and source-based risk assessment for urban soils.
{"title":"Isotopic tracing of lead for source-specific probabilistic health risk assessment of heavy metals in soils of Lanzhou, China","authors":"Yang Lan , Yan Li , Ke Liu , Long Chen , Haoran Huang , Xinyu Cheng , Zi Ye , Yujie Jiang , Meixian Wang","doi":"10.1016/j.gexplo.2025.107964","DOIUrl":"10.1016/j.gexplo.2025.107964","url":null,"abstract":"<div><div>Heavy metal contamination in urban soils poses a significant threat to sustainable development and public health. Therefore, a systematic evaluation of the sources and risks of heavy metals in urban soils is essential. This study applies an improved Nemerow index, the matter-element extension model, and a Monte Carlo-based health risk model. In addition, it integrates lead isotope analysis, correlation analysis, Self-Organising Maps (SOM), Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR), and the MixSIAR isotopic mixing model. These methods are combined to enable accurate source apportionment and source-specific risk assessment. The results indicate that the high-value zones of all eight heavy metals are mainly distributed in the south-eastern part of the city. The overall ecological risk remains at a controllable level. Carcinogenic and non-carcinogenic risks for adults are negligible, whereas those for children reach 27.30 % and 3.14 %, respectively. Lead-isotope signatures indicate that coal combustion and traffic emissions are the principal sources of lead in soil. Source-health risk analysis suggests that coal combustion is likely an important contributor to overall pollution, with arsenic (As, a metalloid) and its coal-related inputs likely warranting greater attention in control strategies. Children appear to be a more vulnerable group requiring targeted protection. This study provides policy recommendations for preventing and controlling soil pollution in Lanzhou. It also bridges the gap in precise source identification and source-based risk assessment for urban soils.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107964"},"PeriodicalIF":3.3,"publicationDate":"2025-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837202","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.2025.107961
Iker Martínez-del-Pozo , Mónica Celina Gómez-Pachón , Inmaculada Ferri-Moreno , Mari Luz García-Lorenzo , Saturnino Lorenzo , José Ignacio Barquero-Peralbo , Xabier Arroyo , Pablo Higueras , José María Esbrí
Regional soil geochemical surveys are essential for land-use planning and human health. However, projects involving large sample sets characterised using traditional laboratory techniques are costly, time-consuming and require a large number of reagents. Therefore, the use of portable X-ray fluorescence (pXRF) with an optimised measurement time and methodology, along with minimal sample preparation, allows for fast and effective measurements. In this study, using Soil-Fundamental Parameters (S-FP) method, a measurement time of 45 s and low sample preparation yielded acceptable results for K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb, Sr, Zr, and Pb, which were monitored with benchtop XRF equipment. The application of this methodology in Cuenca province, Spain, and the comparison with different European and national programmes provides consistency in the results, despite using different analytical techniques. It was observed that a systematic and regular sampling strategy avoids geochemical gaps, increasing the representativeness of the soil parent material in the samples. Distinct geochemical patterns have been identified, with a major group comprising Ti, Mn and Fe, and trace elements such as Cr, Ni, Cu, Zn, As, Rb, Sr, Zr and Pb, while K, Ca and Sr display individual distribution trends. Therefore, this study provides a rapid and economical way to characterise soil geochemistry in large areas and to establish background and reference levels over extensive regions.
{"title":"Portable X-ray fluorescence (pXRF) application to the determination of major and trace elements in large soil datasets for geochemical background assessment","authors":"Iker Martínez-del-Pozo , Mónica Celina Gómez-Pachón , Inmaculada Ferri-Moreno , Mari Luz García-Lorenzo , Saturnino Lorenzo , José Ignacio Barquero-Peralbo , Xabier Arroyo , Pablo Higueras , José María Esbrí","doi":"10.1016/j.gexplo.2025.107961","DOIUrl":"10.1016/j.gexplo.2025.107961","url":null,"abstract":"<div><div>Regional soil geochemical surveys are essential for land-use planning and human health. However, projects involving large sample sets characterised using traditional laboratory techniques are costly, time-consuming and require a large number of reagents. Therefore, the use of portable X-ray fluorescence (pXRF) with an optimised measurement time and methodology, along with minimal sample preparation, allows for fast and effective measurements. In this study, using Soil-Fundamental Parameters (S-FP) method, a measurement time of 45 s and low sample preparation yielded acceptable results for K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, As, Rb, Sr, Zr, and Pb, which were monitored with benchtop XRF equipment. The application of this methodology in Cuenca province, Spain, and the comparison with different European and national programmes provides consistency in the results, despite using different analytical techniques. It was observed that a systematic and regular sampling strategy avoids geochemical gaps, increasing the representativeness of the soil parent material in the samples. Distinct geochemical patterns have been identified, with a major group comprising Ti, Mn and Fe, and trace elements such as Cr, Ni, Cu, Zn, As, Rb, Sr, Zr and Pb, while K, Ca and Sr display individual distribution trends. Therefore, this study provides a rapid and economical way to characterise soil geochemistry in large areas and to establish background and reference levels over extensive regions.</div></div>","PeriodicalId":16336,"journal":{"name":"Journal of Geochemical Exploration","volume":"282 ","pages":"Article 107961"},"PeriodicalIF":3.3,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145837203","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.2025.107962
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}
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