Pub Date : 2026-03-01Epub Date: 2026-01-06DOI: 10.1016/j.chemer.2026.126386
Lin Jia , Guolin Guo , Yan Zhao , Zhaobin Yan , Jianhua Wu , Wenya Yan , Tingting Zou
<div><div>Magmatic degassing is a key process during the ascent and evolution of basaltic magmas, providing critical insights into deep crust environments and geodynamics. Clinopyroxene, a ubiquitous ferromagnesian mineral in basaltic systems, exhibits compositional sensitivity to magmatic physicochemical conditions (e.g., temperature, pressure, H₂O content, oxygen fugacity) and thus serves as a valuable petrogenetic archive. This study investigates degassing events recorded by compositionally-zoned clinopyroxene phenocrysts in Late Cretaceous high-Mg basalts from the Ganzhou Basin, Jiangxi Province, China. Previous Sr-Nd-Pb-O isotope results indicated that these basalts were derived from an enriched mantle source without significant crustal contamination. Clinopyroxene grains predominantly exhibit distinct core-mantle-rim zoning. Equilibrium melt compositions, simulated based on clinopyroxene core, mantle, and rim compositions, yield high MgO contents (14.01–15.00 wt%), consistent with the high-Mg bulk-rock composition of Ganzhou basalts, despite minor discrepancies in some trace elements. Systematic major- and trace-element variations are observed across the zonal domains: Al₂O₃ contents progressively decrease from core to rim, while Fe, Ti, and trace elements increase significantly. Cores and mantles display characteristic negative Pb, Nd, and Zr anomalies. The decreasing Al₂O₃ trend reflects reduction tetrahedral Al<sup>3+</sup> occupancy in the clinopyroxene lattice with declining temperature and pressure during magmatic evolution, whereas the negative anomalies are attributed to early-stage magma evolution, geochemical imprints from the enriched mantle source, and ilmenite crystallization. Clinopyroxene thermobarometry reveals significant differences among zones: cores and mantles crystallized under relatively high temperatures, pressures, and melt water contents conditions, whereas rims and matrix clinopyroxenes formed under distinctly lower temperature, pressure, and melt water content. The sharp decrease in melt water content coupled with relatively stable Fe<sup>3+</sup>/ΣFe ratio from core to mantle, indicate a degassing/dehydration process in the middle-crust. The observed trends-sharp decrease in temperature, pressure, and Fe<sup>3+</sup>/ΣFe from mantle to rim, alongside a more gradual decline in melt water content, suggest magma eruption following degassing from a middle-crustal chamber. The contrasts between clinopyroxene phenocryst rims and matrix grains, characterized by further decreases in temperature and pressure but slight increases in H₂O content and Fe<sup>3+</sup>/ΣFe ratio, are interpreted as reflecting eruption into an oxidizing and hydrating atmospheric environment. Combine the regional tectonic setting, the formation of the Ganzhou Basin Late Cretaceous high-Mg basalts is related to an intra-continental extensional environment induced by westward subduction of the paleo-Pacific Plate beneath the Eurasian continent, wi
{"title":"Degassing in middle-crust magma chamber: Evidence from the texture and chemistry of the zonal clinopyroxene from the high magnesium basalt in Ganzhou Basin, Jiangxi, South China","authors":"Lin Jia , Guolin Guo , Yan Zhao , Zhaobin Yan , Jianhua Wu , Wenya Yan , Tingting Zou","doi":"10.1016/j.chemer.2026.126386","DOIUrl":"10.1016/j.chemer.2026.126386","url":null,"abstract":"<div><div>Magmatic degassing is a key process during the ascent and evolution of basaltic magmas, providing critical insights into deep crust environments and geodynamics. Clinopyroxene, a ubiquitous ferromagnesian mineral in basaltic systems, exhibits compositional sensitivity to magmatic physicochemical conditions (e.g., temperature, pressure, H₂O content, oxygen fugacity) and thus serves as a valuable petrogenetic archive. This study investigates degassing events recorded by compositionally-zoned clinopyroxene phenocrysts in Late Cretaceous high-Mg basalts from the Ganzhou Basin, Jiangxi Province, China. Previous Sr-Nd-Pb-O isotope results indicated that these basalts were derived from an enriched mantle source without significant crustal contamination. Clinopyroxene grains predominantly exhibit distinct core-mantle-rim zoning. Equilibrium melt compositions, simulated based on clinopyroxene core, mantle, and rim compositions, yield high MgO contents (14.01–15.00 wt%), consistent with the high-Mg bulk-rock composition of Ganzhou basalts, despite minor discrepancies in some trace elements. Systematic major- and trace-element variations are observed across the zonal domains: Al₂O₃ contents progressively decrease from core to rim, while Fe, Ti, and trace elements increase significantly. Cores and mantles display characteristic negative Pb, Nd, and Zr anomalies. The decreasing Al₂O₃ trend reflects reduction tetrahedral Al<sup>3+</sup> occupancy in the clinopyroxene lattice with declining temperature and pressure during magmatic evolution, whereas the negative anomalies are attributed to early-stage magma evolution, geochemical imprints from the enriched mantle source, and ilmenite crystallization. Clinopyroxene thermobarometry reveals significant differences among zones: cores and mantles crystallized under relatively high temperatures, pressures, and melt water contents conditions, whereas rims and matrix clinopyroxenes formed under distinctly lower temperature, pressure, and melt water content. The sharp decrease in melt water content coupled with relatively stable Fe<sup>3+</sup>/ΣFe ratio from core to mantle, indicate a degassing/dehydration process in the middle-crust. The observed trends-sharp decrease in temperature, pressure, and Fe<sup>3+</sup>/ΣFe from mantle to rim, alongside a more gradual decline in melt water content, suggest magma eruption following degassing from a middle-crustal chamber. The contrasts between clinopyroxene phenocryst rims and matrix grains, characterized by further decreases in temperature and pressure but slight increases in H₂O content and Fe<sup>3+</sup>/ΣFe ratio, are interpreted as reflecting eruption into an oxidizing and hydrating atmospheric environment. Combine the regional tectonic setting, the formation of the Ganzhou Basin Late Cretaceous high-Mg basalts is related to an intra-continental extensional environment induced by westward subduction of the paleo-Pacific Plate beneath the Eurasian continent, wi","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126386"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-09-30DOI: 10.1016/j.chemer.2025.126342
Ahmed Hasan Ahmed , Abdel-Kader M. Moghazi , Finlay M. Stuart , Shehta Abdallah , Moustafa Hashad , Kamal A. Ali
Mantle xenoliths from the Cenozoic volcanic fields of Harrat Hutaymah and Harrat Kishb, located in the western part of the Arabian Shield, consist of proto-granular lherzolite, harzburgite, and to a lesser extent dunite and wehrlite. The olivine displays variations in Mn, Ni, and Ca contents relative to the forsterite (Fo) content that is similar to that of residual mantle olivine, which crystallized after being exposed to low to intermediate degrees of melt derived from mantle peridotite. The elemental ratios of Ca-Fe-Ni-Mg-Mn in the olivine further indicate a contribution from peridotite. Pressure-temperature calculations and previous geochemical studies indicate that the peridotite xenoliths were entrained from below the crust-mantle boundary (~35 km in the mantle lithosphere) under the Arabian Shield. Olivine 3He/4He ratios range from 6.1 to 8.5 Ra, which overlap the range of <7 to 9 Ra recently reported for off-craton-derived subcontinental lithospheric mantle (SCLM) xenoliths and is consistent with mantle beneath the region. This tends to rule out the overprinting of the SCLM by fluids/melts derived from the deep upwelling mantle sampled by the Afar plume. However, the influence of deep mantle fluid may be cryptic and warrants further exploration because the He content of the Afar mantle plume is unknown.
{"title":"Chemistry and He isotope systematics of olivine as tracers of source in mantle xenoliths from Harrat Hutaymah and Harrat Kishb Cenozoic lava fields, Western Saudi Arabia","authors":"Ahmed Hasan Ahmed , Abdel-Kader M. Moghazi , Finlay M. Stuart , Shehta Abdallah , Moustafa Hashad , Kamal A. Ali","doi":"10.1016/j.chemer.2025.126342","DOIUrl":"10.1016/j.chemer.2025.126342","url":null,"abstract":"<div><div>Mantle xenoliths from the Cenozoic volcanic fields of Harrat Hutaymah and Harrat Kishb, located in the western part of the Arabian Shield, consist of proto-granular lherzolite, harzburgite, and to a lesser extent dunite and wehrlite. The olivine displays variations in Mn, Ni, and Ca contents relative to the forsterite (Fo) content that is similar to that of residual mantle olivine, which crystallized after being exposed to low to intermediate degrees of melt derived from mantle peridotite. The elemental ratios of Ca-Fe-Ni-Mg-Mn in the olivine further indicate a contribution from peridotite. Pressure-temperature calculations and previous geochemical studies indicate that the peridotite xenoliths were entrained from below the crust-mantle boundary (~35 km in the mantle lithosphere) under the Arabian Shield. Olivine <sup>3</sup>He/<sup>4</sup>He ratios range from 6.1 to 8.5 R<sub>a</sub>, which overlap the range of <7 to 9 R<sub>a</sub> recently reported for off-craton-derived subcontinental lithospheric mantle (SCLM) xenoliths and is consistent with mantle beneath the region. This tends to rule out the overprinting of the SCLM by fluids/melts derived from the deep upwelling mantle sampled by the Afar plume. However, the influence of deep mantle fluid may be cryptic and warrants further exploration because the He content of the Afar mantle plume is unknown.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126342"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Nanling WSn belt, a world-class metallogenic province, hosts multi-stages WSn mineralization, accurately constraining the evolutionary history of these polymetallic deposits is essential for understanding mineralization processes and building up their metallogenic models. The Xianghualing orefield, a significant Sn-polymetallic district within the Nanling WSn belt, displays notable multistage Sn mineralization. Cassiterite UPb geochronology on sulfide-type cassiterite ores from the Xinfeng mining area, skarn-type Sn ores from the Tangguanpu mining area, and F1 fault-controlled sulfide-type cassiterite ores in the Xianghualing orefield were involved in this study. The obtained cassiterite UPb ages are 147.8 ± 1.2 Ma, 145.2 ± 2.8 Ma, and 141 ± 23 Ma, respectively, while a vesuvianite dating result yields 154.7 ± 1.9 Ma. These ages are consistent with previously reported cassiterite UPb dates from the Tieshaping deposit within the orefield and the Xitian deposit in the northern part of the orefield, extending the temporal frame-work of the Xianghualing Sn mineralization and the southern Hunan Sn-polymetallic mineralization system into the Early Cretaceous. Combined with previous studies on magmatic-hydrothermal fluids associated with Sn mineralization in southern Hunan, we propose that highly evolved Cretaceous granites represent prime exploration targets for Sn deposits in this region.
{"title":"The multi-stages Sn mineralization process in the Xianghualing orefield: Constraints from cassiterite and vesuvianite UPb geochronology","authors":"Zhang Dexian , Zhou Jialing , Fang Ruize , Xiao Dian , Hu Ziqi","doi":"10.1016/j.chemer.2025.126360","DOIUrl":"10.1016/j.chemer.2025.126360","url":null,"abstract":"<div><div>The Nanling W<img>Sn belt, a world-class metallogenic province, hosts multi-stages W<img>Sn mineralization, accurately constraining the evolutionary history of these polymetallic deposits is essential for understanding mineralization processes and building up their metallogenic models. The Xianghualing orefield, a significant Sn-polymetallic district within the Nanling W<img>Sn belt, displays notable multistage Sn mineralization. Cassiterite U<img>Pb geochronology on sulfide-type cassiterite ores from the Xinfeng mining area, skarn-type Sn ores from the Tangguanpu mining area, and F1 fault-controlled sulfide-type cassiterite ores in the Xianghualing orefield were involved in this study. The obtained cassiterite U<img>Pb ages are 147.8 ± 1.2 Ma, 145.2 ± 2.8 Ma, and 141 ± 23 Ma, respectively, while a vesuvianite dating result yields 154.7 ± 1.9 Ma. These ages are consistent with previously reported cassiterite U<img>Pb dates from the Tieshaping deposit within the orefield and the Xitian deposit in the northern part of the orefield, extending the temporal frame-work of the Xianghualing Sn mineralization and the southern Hunan Sn-polymetallic mineralization system into the Early Cretaceous. Combined with previous studies on magmatic-hydrothermal fluids associated with Sn mineralization in southern Hunan, we propose that highly evolved Cretaceous granites represent prime exploration targets for Sn deposits in this region.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126360"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145571631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-07-12DOI: 10.1016/j.chemer.2025.126316
Justin Filiberto , Mikhail Yu. Zolotov , Erika Kohler , Piero D'Incecco , Dmitry A. Gorinov , Sriram S. Bhiravarasu , Matthew B. Weller , Jeremy F. Brossier , Iván López , Philippa J. Mason , Jemila A. Edmond , Nicola Mari , Goro Komatsu , Gaetano Di Achille , James B. Garvin
One of the biggest unknowns about Venus is how volcanically active it is today. Venus has a similar size and density to Earth, suggesting it may have a comparable composition, and therefore it is expected to be volcanically active; however, exploring Venus and confirming current volcanic activity is difficult because of the thick omnipresent optically opaque clouds that hamper traditional observations of the lower atmosphere and surface. Further, surface conditions make long-lived missions challenging. Despite the difficulty, there have been tantalizing hints of currently active or very recent volcanism. Here, we review what is known about active volcanism, point out gaps in knowledge to be addressed, and highlight techniques and approaches that need to be developed before the new decade of Venus exploration. It is crucial to constrain the activity and rate of volcanism today and through time to begin to understand the geodynamic state of the planet.
We find that the combination of all evidence strongly indicates that Venus is volcanically active today. The best evidence for active volcanism comes from combining data sets and approaches – specifically at Idunn Mons, Maat Mons, and Aramaiti Corona – in contrast to those from a single study or data set alone. Considering the evidence for activity, observations do not favor so-called “catastrophic” models of resurfacing, instead they are better represented by ongoing regional scale events. To reliably detect and characterize active or recent effusive basaltic volcanism new missions must collect high-resolution imaging, repeat observations, radar polarimetry, evidence of outgassing, and high-resolution topographical data that provide insights into surface changes over time. The ability to capture and interpret these data is vital for understanding Venus's geological activity, particularly in regions where volcanic processes are suspected to be ongoing.
{"title":"Assessing the evidence for active volcanism on Venus: current limitations and prospects for future investigations","authors":"Justin Filiberto , Mikhail Yu. Zolotov , Erika Kohler , Piero D'Incecco , Dmitry A. Gorinov , Sriram S. Bhiravarasu , Matthew B. Weller , Jeremy F. Brossier , Iván López , Philippa J. Mason , Jemila A. Edmond , Nicola Mari , Goro Komatsu , Gaetano Di Achille , James B. Garvin","doi":"10.1016/j.chemer.2025.126316","DOIUrl":"10.1016/j.chemer.2025.126316","url":null,"abstract":"<div><div>One of the biggest unknowns about Venus is how volcanically active it is today. Venus has a similar size and density to Earth, suggesting it may have a comparable composition, and therefore it is expected to be volcanically active; however, exploring Venus and confirming current volcanic activity is difficult because of the thick omnipresent optically opaque clouds that hamper traditional observations of the lower atmosphere and surface. Further, surface conditions make long-lived missions challenging. Despite the difficulty, there have been tantalizing hints of currently active or very recent volcanism. Here, we review what is known about active volcanism, point out gaps in knowledge to be addressed, and highlight techniques and approaches that need to be developed before the new decade of Venus exploration. It is crucial to constrain the activity and rate of volcanism today and through time to begin to understand the geodynamic state of the planet.</div><div>We find that the combination of all evidence strongly indicates that Venus is volcanically active today. The best evidence for active volcanism comes from combining data sets and approaches – specifically at Idunn Mons, Maat Mons, and Aramaiti Corona – in contrast to those from a single study or data set alone. Considering the evidence for activity, observations do not favor so-called “catastrophic” models of resurfacing, instead they are better represented by ongoing regional scale events. To reliably detect and characterize active or recent effusive basaltic volcanism new missions must collect high-resolution imaging, repeat observations, radar polarimetry, evidence of outgassing, and high-resolution topographical data that provide insights into surface changes over time. The ability to capture and interpret these data is vital for understanding Venus's geological activity, particularly in regions where volcanic processes are suspected to be ongoing.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126316"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-09-20DOI: 10.1016/j.chemer.2025.126340
Reza Ghezelbash , Abbas Maghsoudi , Mehrdad Daviran
In mineral exploration, detecting weak geochemical anomalies in covered areas remains a significant challenge due to overlapping backgrounds and anisotropic mineralization controls, particularly in tectonically complex regions like the Takhte-Soleyman district, northwest Iran, part of the Urumieh-Dokhtar magmatic arc (UDMA). This study addresses these issues by introducing a novel framework that enhances exploration targeting for gold (Au) and lead‑zinc (PbZn) deposits. The methodology integrates multifractal geochemical anomaly separation, including multifractal inverse distance weighting (MIDW), spectrum-area (S-A) and local singularity mapping (LSM) models, alongside distance-distribution analysis (DDA) and fuzzy c-means (FCM) clustering, to account for structural and geochemical complexities. Factor analysis identifies key elemental associations—Au with As and Sb, and PbZn with Ag and Cd—while DDA delineates northwest (NW) and northeast (NE) trending faults as critical controls, with approximately 85 % of Au and 77 % of PbZn deposits located within 1 km of these faults. The framework refines prospectivity models by optimizing FCM clustering with the VXB index, targeting high-potential zones. Results demonstrate FCM-based LSM's superior anomaly detection, achieving area under curve (AUC) values of 94.8 % for Au and 88.08 % for PbZn, with strong spatial correlations to known deposits, offering a practical tool for exploration in challenging environments. This approach advances mineral prospectivity mapping (MPM) by overcoming limitations of traditional methods, with potential applications to other metallogenic provinces.
{"title":"A new framework for exploration targeting: Integrating multifractal geochemical analysis, structural controls and fuzzy C-means unsupervised clustering","authors":"Reza Ghezelbash , Abbas Maghsoudi , Mehrdad Daviran","doi":"10.1016/j.chemer.2025.126340","DOIUrl":"10.1016/j.chemer.2025.126340","url":null,"abstract":"<div><div>In mineral exploration, detecting weak geochemical anomalies in covered areas remains a significant challenge due to overlapping backgrounds and anisotropic mineralization controls, particularly in tectonically complex regions like the Takhte-Soleyman district, northwest Iran, part of the Urumieh-Dokhtar magmatic arc (UDMA). This study addresses these issues by introducing a novel framework that enhances exploration targeting for gold (Au) and lead‑zinc (Pb<img>Zn) deposits. The methodology integrates multifractal geochemical anomaly separation, including multifractal inverse distance weighting (MIDW), spectrum-area (S-A) and local singularity mapping (LSM) models, alongside distance-distribution analysis (DDA) and fuzzy c-means (FCM) clustering, to account for structural and geochemical complexities. Factor analysis identifies key elemental associations—Au with As and Sb, and Pb<img>Zn with Ag and Cd—while DDA delineates northwest (NW) and northeast (NE) trending faults as critical controls, with approximately 85 % of Au and 77 % of Pb<img>Zn deposits located within 1 km of these faults. The framework refines prospectivity models by optimizing FCM clustering with the <em>V</em><sub><em>XB</em></sub> index, targeting high-potential zones. Results demonstrate FCM-based LSM's superior anomaly detection, achieving area under curve (AUC) values of 94.8 % for Au and 88.08 % for Pb<img>Zn, with strong spatial correlations to known deposits, offering a practical tool for exploration in challenging environments. This approach advances mineral prospectivity mapping (MPM) by overcoming limitations of traditional methods, with potential applications to other metallogenic provinces.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126340"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145160181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-11-19DOI: 10.1016/j.chemer.2025.126359
Linna LI , Jiangang JIAO , Yunfei MA
The Niancaowan mafic-ultramafic intrusion is located within the Bayan Obo Rift Zone of central Inner Mongolia. Systematic genetic investigations were conducted in this study to clarify the genetic relationship between the Niancaowan mafic-ultramafic intrusion and known CuNi deposits within the rift zone, as well as to assess the comparability of their mineralization potential. Through integrated petrographic observations, high-precision geochronological dating, whole-rock geochemical analyses, and zircon Hf isotope tracing, the research specifically focused on elucidating the magmatic source characteristics, rock-forming timing, and magmatic evolutionary processes of the intrusion. The Niancaowan mafic-ultramafic intrusion is predominantly composed of hornblende gabbro and gabbro-diabase. LA-ICP-MS zircon UPb dating reveals that the hornblende gabbro crystallized during the Early Permian (273.2 ± 3.5 Ma), which demonstrates temporal synchronicity with the emplacement ages of other mafic-ultramafic intrusions within the central-western Inner Mongolia rift system. Geochemical tracers further disclose significant zircon Hf isotopic heterogeneity, indicating that the parental magma was derived from partial melting of a lithospheric mantle source and underwent contamination by lower crustal materials during its ascent. Comparative analysis indicates that the zircon Hf isotopic compositions of the Niancaowan intrusion (εHf(t) = −17.0 to +1.4) are similar to those of typical regional intrusions such as the Wulantaolegai and Huanghuatan intrusions, revealing that crustal contamination was prevalent during the emplacement of mafic-ultramafic magmatic systems within the Bayan Obo Rift Zone. The incorporation of such crust-derived components may be controlled by the melting or assimilation processes of ancient basement rocks in the extensional setting of the rift zone. The petrological characteristics and quantitative modeling results indicate that the Niancaowan intrusion experienced relatively weak crustal contamination (4 %–8 %). If sulfide mineralization were to occur in this intrusion, it would primarily depend on deep-seated magmatic differentiation. Comparative studies between the Niancaowan intrusion and other intrusive bodies within the Bayan Obo Rift Zone reveal that the mineral exploration potential of mafic-ultramafic intrusions in the Bayan Obo Rift Zone should not be overlooked. Particular attention should be given to highly contaminated mafic-ultramafic intrusion clusters within the rift zone and multi-stage tectonic-magmatic convergence nodes.
{"title":"Petrogenesis of the Niancaowan mafic-ultramafic intrusion: Decoding magmatic evolution in the cuNi Metallogenic Province of the Bayan obo rift zone","authors":"Linna LI , Jiangang JIAO , Yunfei MA","doi":"10.1016/j.chemer.2025.126359","DOIUrl":"10.1016/j.chemer.2025.126359","url":null,"abstract":"<div><div>The Niancaowan mafic-ultramafic intrusion is located within the Bayan Obo Rift Zone of central Inner Mongolia. Systematic genetic investigations were conducted in this study to clarify the genetic relationship between the Niancaowan mafic-ultramafic intrusion and known Cu<img>Ni deposits within the rift zone, as well as to assess the comparability of their mineralization potential. Through integrated petrographic observations, high-precision geochronological dating, whole-rock geochemical analyses, and zircon Hf isotope tracing, the research specifically focused on elucidating the magmatic source characteristics, rock-forming timing, and magmatic evolutionary processes of the intrusion. The Niancaowan mafic-ultramafic intrusion is predominantly composed of hornblende gabbro and gabbro-diabase. LA-ICP-MS zircon U<img>Pb dating reveals that the hornblende gabbro crystallized during the Early Permian (273.2 ± 3.5 Ma), which demonstrates temporal synchronicity with the emplacement ages of other mafic-ultramafic intrusions within the central-western Inner Mongolia rift system. Geochemical tracers further disclose significant zircon Hf isotopic heterogeneity, indicating that the parental magma was derived from partial melting of a lithospheric mantle source and underwent contamination by lower crustal materials during its ascent. Comparative analysis indicates that the zircon Hf isotopic compositions of the Niancaowan intrusion (ε<sub>Hf</sub>(t) = −17.0 to +1.4) are similar to those of typical regional intrusions such as the Wulantaolegai and Huanghuatan intrusions, revealing that crustal contamination was prevalent during the emplacement of mafic-ultramafic magmatic systems within the Bayan Obo Rift Zone. The incorporation of such crust-derived components may be controlled by the melting or assimilation processes of ancient basement rocks in the extensional setting of the rift zone. The petrological characteristics and quantitative modeling results indicate that the Niancaowan intrusion experienced relatively weak crustal contamination (4 %–8 %). If sulfide mineralization were to occur in this intrusion, it would primarily depend on deep-seated magmatic differentiation. Comparative studies between the Niancaowan intrusion and other intrusive bodies within the Bayan Obo Rift Zone reveal that the mineral exploration potential of mafic-ultramafic intrusions in the Bayan Obo Rift Zone should not be overlooked. Particular attention should be given to highly contaminated mafic-ultramafic intrusion clusters within the rift zone and multi-stage tectonic-magmatic convergence nodes.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126359"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-09-30DOI: 10.1016/j.chemer.2025.126339
Emmanuel O. Kazimoto , Charles H. Kasanzu , Ernest Mulaya , Remigius Gama , Rachid Benaouda
This study presents new insights on the Litembo granite, a 30 km wide pluton located south of the Ubendian Belt in the southern Tanzania, East Africa. Whole-rock geochemistry, U-Pb zircon geochronology, and the Rb-Sr isotope system were used to determine its geochemical composition, age, and origin, contributing to regional geological and geodynamic context. The granite is metaluminous to peraluminous, ferroan, and calc-alkalic with high concentrations of Sr, Rb, Ba, High Field Strength Elements (HFSE; e.g., Zr, Y, Nb, and Ta), and high Ga/Al ratios. The total Rare Earth Element (REE) concentrations of the granite range from 335 to 693 ppm, showing fractionated REE patterns in the chondrite-normalized spider diagram ((La/Yb)CN = 9.40–15.41) and a negative Eu anomaly (Eu/Eu*; mean = 0.87). Primitive mantle-normalized spidegrams reveal negative patterns for Ti, Sr, P, Y, and Cs, along with enrichment in Large Ion Lithophile Elements (LILE; e.g. Rb and Ba). Geochemical features of the rock are akin to anorogenic (A-type) granites, implying formation of Litembo granite from a deep source melt, involving plagioclase, garnet, and amphibole and/or complex differentiation processes, under extensional tectonics. An initial 87Sr/86Sr ratio (∼0.7113) suggests evolved crustal origins, with a Rb–Sr imprecise age of about 658 ± 20 Ma. Laser ablation ICP-MS U-Pb zircon dating yields crystallisation ages of 737.1 ± 2.9 Ma and 730.1 ± 3.0 Ma, indicating emplacement between 730 and 740 Ma, followed thermal diffusion of Rb and Sr in the rock at about 660 Ma. These ages and compositional features align with the Tonian intraplate (alkaline and carbonatite magmatism) in southern Africa and support for a thermal event linked to Rodinia's breakup, preceding development of the Mozambique Belt.
{"title":"Geochemistry and U-Pb geochronology of the Neoproterozoic aluminous A-type granite in the south-western Tanzania: Implications to the Tonian geodynamic evolution of Southern Africa","authors":"Emmanuel O. Kazimoto , Charles H. Kasanzu , Ernest Mulaya , Remigius Gama , Rachid Benaouda","doi":"10.1016/j.chemer.2025.126339","DOIUrl":"10.1016/j.chemer.2025.126339","url":null,"abstract":"<div><div>This study presents new insights on the Litembo granite, a 30 km wide pluton located south of the Ubendian Belt in the southern Tanzania, East Africa. Whole-rock geochemistry, U-Pb zircon geochronology, and the Rb-Sr isotope system were used to determine its geochemical composition, age, and origin, contributing to regional geological and geodynamic context. The granite is metaluminous to peraluminous, ferroan, and calc-alkalic with high concentrations of Sr, Rb, Ba, High Field Strength Elements (HFSE; e.g., Zr, Y, Nb, and Ta), and high Ga/Al ratios. The total Rare Earth Element (REE) concentrations of the granite range from 335 to 693 ppm, showing fractionated REE patterns in the chondrite-normalized spider diagram ((La/Yb)<sub>CN</sub> = 9.40–15.41) and a negative Eu anomaly (Eu/Eu*; mean = 0.87). Primitive mantle-normalized spidegrams reveal negative patterns for Ti, Sr, P, Y, and Cs, along with enrichment in Large Ion Lithophile Elements (LILE; e.g. Rb and Ba). Geochemical features of the rock are akin to anorogenic (A-type) granites, implying formation of Litembo granite from a deep source melt, involving plagioclase, garnet, and amphibole and/or complex differentiation processes, under extensional tectonics. An initial <sup>87</sup>Sr/<sup>86</sup>Sr ratio (∼0.7113) suggests evolved crustal origins, with a Rb–Sr imprecise age of about 658 ± 20 Ma. Laser ablation ICP-MS U-Pb zircon dating yields crystallisation ages of 737.1 ± 2.9 Ma and 730.1 ± 3.0 Ma, indicating emplacement between 730 and 740 Ma, followed thermal diffusion of Rb and Sr in the rock at about 660 Ma. These ages and compositional features align with the Tonian intraplate (alkaline and carbonatite magmatism) in southern Africa and support for a thermal event linked to Rodinia's breakup, preceding development of the Mozambique Belt.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126339"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145269663","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-11-10DOI: 10.1016/j.chemer.2025.126345
Long Zhang , Dong Li , Juquan Zhang , Yongkui Wang , Ning Xu , Junfeng Li
On the western margin of the Jiaolai Basin (JLB), acidic volcanic rocks in the Shiqianzhuang Formation of the Qingshan Group are exposed to the eastern part of the Tan-lu fault zone. Bulk element analyses reveal that the rare earth element (REE) distribution pattern exhibits enrichment in light REEs, depletion in heavy REEs and are enriched in high field strength elements (HFSEs) and depleted in large ion lithophile elements (LILEs). The δEu values indicate negative Eu anomalies. The LA–ICP–MS zircon UPb ages are 109 ± 1.8 Ma, 115 ± 1.6 Ma and 126 ± 1 Ma, respectively, which are consistent with the range of gold mineralization in Jiaodong Peninsula (JEP). Comparison with the widespread mafic-intermediate-felsic dikes and the regional tectonic evolution of Tan-lu fault, it is concluded that the episodic developments of lithospheric thinning are in accordance with the extensive gold mineralization in the JEP during the Early Cretaceous. The acidic volcanic rocks documented that the JLB evolved from prototype into a volcanic basin, meanwhile, large-scale gold mineralization formed along the secondary branches of the Tan-lu fault in the Early Cretaceous, due to the combined effects of changes in the subduction angle of the Paleo-Pacific Plate, trench migration and changes in the subduction direction.
{"title":"Early Cretaceous volcanism and correlation with large-scale Au mineralization in the Jiaolai basin, Jiaodong Peninsula: Evidences of geochronology and geochemistry from the Qingshan Group","authors":"Long Zhang , Dong Li , Juquan Zhang , Yongkui Wang , Ning Xu , Junfeng Li","doi":"10.1016/j.chemer.2025.126345","DOIUrl":"10.1016/j.chemer.2025.126345","url":null,"abstract":"<div><div>On the western margin of the Jiaolai Basin (JLB), acidic volcanic rocks in the Shiqianzhuang Formation of the Qingshan Group are exposed to the eastern part of the Tan-lu fault zone. Bulk element analyses reveal that the rare earth element (REE) distribution pattern exhibits enrichment in light REEs, depletion in heavy REEs and are enriched in high field strength elements (HFSEs) and depleted in large ion lithophile elements (LILEs). The δEu values indicate negative Eu anomalies. The LA–ICP–MS zircon U<img>Pb ages are 109 ± 1.8 Ma, 115 ± 1.6 Ma and 126 ± 1 Ma, respectively, which are consistent with the range of gold mineralization in Jiaodong Peninsula (JEP). Comparison with the widespread mafic-intermediate-felsic dikes and the regional tectonic evolution of Tan-lu fault, it is concluded that the episodic developments of lithospheric thinning are in accordance with the extensive gold mineralization in the JEP during the Early Cretaceous. The acidic volcanic rocks documented that the JLB evolved from prototype into a volcanic basin, meanwhile, large-scale gold mineralization formed along the secondary branches of the Tan-lu fault in the Early Cretaceous, due to the combined effects of changes in the subduction angle of the Paleo-Pacific Plate, trench migration and changes in the subduction direction.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126345"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519727","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-11-07DOI: 10.1016/j.chemer.2025.126349
Zhihao Sun , Huan Li , Yuxuan Huang , Thomas J. Algeo , Wei Quan , Tao Xiao , Buqing Wang , Wenbo Sun , Weidong Ren
The Guangning area of the Yunkai Massif is rich in mineral resources and extensively intruded by granites that played a crucial role in the ore mineralization process. However, the high-precision geochronology and isotopic geochemistry of these granites remain understudied. This study presents the first detailed geochronological and geochemical characterization of Early Paleozoic granites from the Guangning area of the Yunkai Massif, South China Craton (SCC). Our results address a significant knowledge gap with regard to the magmatic history of this region and provide crucial geological evidence elucidating the Early Paleozoic tectonic evolution of the SCC. Via LA-ICP-MS UPb zircon geochronology, our study constrains the emplacement age of the Early Paleozoic Guangning granitic pluton to between 452.3 ± 1.3 Ma and 448.5 ± 1.6 Ma. Integrating these results with previous studies, we identify a prominent magmatic event in the Yunkai Massif during the Late Ordovician (~458–444 Ma). The Guangning granites display geochemical signatures typical of the high‑potassium calc-alkaline series and possess strong peraluminous affinities. These rocks are characterized by high SiO₂ (71.1–77.9 wt%) and Al₂O₃ (10.3–14.5 wt%) and low MgO (0.03–0.90 wt%), CaO (0–1.42 wt%), and total FeO contents (0.58–1.89 wt%). The samples show enrichment in high-field-strength elements and Pb, and depletion in Nb, Ce, P, and large-ion lithophile elements. The rare earth element (REE) patterns indicate significant fractionation, with enrichment in light REEs (LREEs) and negative Eu anomalies. The whole-rock εNd(t) values of the Guangning granites range from −9.8 to −8.7 with notable negative fSm/Nd anomalies (−0.4 to −0.3), and two-stage Nd model ages (TDM2) of ~1614–1528 Ma. The zircon εHf(t) values mostly range from −5.5 to −0.5, and the initial (176Hf/177Hf)i values are concentrated in the range of 0.28234 to 0.28248, with the two-stage depleted mantle model ages (TDM2) of ~1783–1468 Ma. These characteristics are typical of strongly peraluminous S-type granites, likely derived from mica dehydration melting at low temperatures of aluminous pelitic rocks in the Paleoproterozoic–Mesoproterozoic crust of the Cathaysia Block, and having undergone fractional crystallization episodes characterized by the involvement of plagioclase, K-feldspar, and biotite. Comprehensive analysis of the regional geological context indicates that the SCC experienced a dynamic shift from orogenic compression to post-orogenic extension at ~450–435 Ma, with the Guangning Early Paleozoic S-type granites forming during this transitional period.
{"title":"Geochemistry and petrogenesis of the Early Paleozoic Guangning granitic pluton in the Yunkai Massif, South China: Insights into magma evolution and tectonic setting","authors":"Zhihao Sun , Huan Li , Yuxuan Huang , Thomas J. Algeo , Wei Quan , Tao Xiao , Buqing Wang , Wenbo Sun , Weidong Ren","doi":"10.1016/j.chemer.2025.126349","DOIUrl":"10.1016/j.chemer.2025.126349","url":null,"abstract":"<div><div>The Guangning area of the Yunkai Massif is rich in mineral resources and extensively intruded by granites that played a crucial role in the ore mineralization process. However, the high-precision geochronology and isotopic geochemistry of these granites remain understudied. This study presents the first detailed geochronological and geochemical characterization of Early Paleozoic granites from the Guangning area of the Yunkai Massif, South China Craton (SCC). Our results address a significant knowledge gap with regard to the magmatic history of this region and provide crucial geological evidence elucidating the Early Paleozoic tectonic evolution of the SCC. Via LA-ICP-MS U<img>Pb zircon geochronology, our study constrains the emplacement age of the Early Paleozoic Guangning granitic pluton to between 452.3 ± 1.3 Ma and 448.5 ± 1.6 Ma. Integrating these results with previous studies, we identify a prominent magmatic event in the Yunkai Massif during the Late Ordovician (~458–444 Ma). The Guangning granites display geochemical signatures typical of the high‑potassium calc-alkaline series and possess strong peraluminous affinities. These rocks are characterized by high SiO₂ (71.1–77.9 wt%) and Al₂O₃ (10.3–14.5 wt%) and low MgO (0.03–0.90 wt%), CaO (0–1.42 wt%), and total FeO contents (0.58–1.89 wt%). The samples show enrichment in high-field-strength elements and Pb, and depletion in Nb, Ce, P, and large-ion lithophile elements. The rare earth element (REE) patterns indicate significant fractionation, with enrichment in light REEs (LREEs) and negative Eu anomalies. The whole-rock εNd(t) values of the Guangning granites range from −9.8 to −8.7 with notable negative f<sub>Sm/Nd</sub> anomalies (−0.4 to −0.3), and two-stage Nd model ages (T<sub>DM2</sub>) of ~1614–1528 Ma. The zircon εHf(t) values mostly range from −5.5 to −0.5, and the initial (<sup>176</sup>Hf/<sup>177</sup>Hf)<sub>i</sub> values are concentrated in the range of 0.28234 to 0.28248, with the two-stage depleted mantle model ages (T<sub>DM2</sub>) of ~1783–1468 Ma. These characteristics are typical of strongly peraluminous S-type granites, likely derived from mica dehydration melting at low temperatures of aluminous pelitic rocks in the Paleoproterozoic–Mesoproterozoic crust of the Cathaysia Block, and having undergone fractional crystallization episodes characterized by the involvement of plagioclase, K-feldspar, and biotite. Comprehensive analysis of the regional geological context indicates that the SCC experienced a dynamic shift from orogenic compression to post-orogenic extension at ~450–435 Ma, with the Guangning Early Paleozoic S-type granites forming during this transitional period.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126349"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145519725","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-12-01Epub Date: 2025-10-25DOI: 10.1016/j.chemer.2025.126344
Nils Reinhardt , Jens Gutzmer , Marcus Oelze , Joachim Krause , Mathias Burisch
Polymetallic W-(Sn), Sn-Zn±(In), and Zn-Pb±(Sn) skarns in the Schwarzenberg District of the western Erzgebirge are expressions of a polyphase mineral system that formed between >330 Ma and ~295 Ma. Due to the polyphase nature of the skarns, the physicochemical conditions of skarn formation and the actual timing of ore formation have remained poorly constrained. To better understand skarn-forming processes in the Erzgebirge, we obtained new mineral chemical data of prograde garnet from all major skarns across the Schwarzenberg District by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. Results illustrate that the oldest generation of skarns formed under relatively fluid-buffered conditions and high fluid/rock ratios. Associated garnet has a pronounced andradite component, contains low concentrations of HFSE, Mn, and Ga and is variably enriched in Sn, W, As, and Li. Elevated concentrations of HFSE, Mn, and Ga in garnet from skarns with skarnoid textures indicate that these formed under mainly rock-buffered conditions (low fluid/rock ratios). Associated garnet is dominantly grossular and invariably low in Sn and W concentrations. The mineral chemistry of garnet from the youngest skarn bodies indicates renewed ingress of magmatic-hydrothermal fluids marked by an intermediate grandite composition, low HFSE, Al, and Ga concentrations as well as a variable enrichment of Sn and W. Although these general patterns are well defined, our data also clearly reveal considerable variability of garnet compositions on the local scale. The same is true for Sn and W concentrations in garnet of all stages. These are found to be too variable as to constitute meaningful exploration vectors. However, they are well suited to place general constraints on the physicochemical conditions of polyphase skarn formation in the Schwarzenberg District.
二日格西施瓦施贝格地区多金属W-(Sn)、Sn- zn±（In）和Zn-Pb±（Sn）夕卡岩是形成于>；330 Ma ~ ~295 Ma之间的多相矿物体系的表现。由于矽卡岩的多相性质，矽卡岩形成的物理化学条件和成矿的实际时间仍然缺乏限制。为了更好地了解Erzgebirge矽卡岩的形成过程，我们利用电子探针和激光烧蚀-电感耦合等离子体质谱技术，从Schwarzenberg地区所有主要矽卡岩中获得了新的顺行石榴石矿物化学数据。结果表明，最老一代夕卡岩形成于相对流体缓冲条件和高液岩比条件下。伴生石榴石具有明显的赤铁矿成分，含有低浓度的HFSE、Mn和Ga，并以不同的方式富集Sn、W、As和Li。在具有类矽卡岩结构的矽卡岩中，石榴石中HFSE、Mn和Ga的浓度升高表明它们主要是在岩石缓冲条件下形成的（低流体/岩石比）。伴生石榴石以粗晶为主，且总是低锡、低钨浓度。来自最年轻矽卡岩体的石榴石的矿物化学表明岩浆热液流体的重新进入，其特征是中等花岗岩组成，低HFSE， Al和Ga浓度，以及Sn和w的可变富集。尽管这些一般模式被很好地定义，但我们的数据也清楚地揭示了石榴石组成在局部尺度上的相当大的变化。各阶段石榴石中锡、钨的浓度也是如此。人们发现这些变量太大，无法构成有意义的勘探向量。然而，它们很适合于对施瓦岑贝格地区多相矽卡岩形成的物理化学条件进行一般约束。
{"title":"Garnet mineral chemistry as proxy for skarn-forming processes in the Schwarzenberg District, Erzgebirge, Germany","authors":"Nils Reinhardt , Jens Gutzmer , Marcus Oelze , Joachim Krause , Mathias Burisch","doi":"10.1016/j.chemer.2025.126344","DOIUrl":"10.1016/j.chemer.2025.126344","url":null,"abstract":"<div><div>Polymetallic W-(Sn), Sn-Zn±(In), and Zn-Pb±(Sn) skarns in the Schwarzenberg District of the western Erzgebirge are expressions of a polyphase mineral system that formed between >330 Ma and ~295 Ma. Due to the polyphase nature of the skarns, the physicochemical conditions of skarn formation and the actual timing of ore formation have remained poorly constrained. To better understand skarn-forming processes in the Erzgebirge, we obtained new mineral chemical data of prograde garnet from all major skarns across the Schwarzenberg District by electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry. Results illustrate that the oldest generation of skarns formed under relatively fluid-buffered conditions and high fluid/rock ratios. Associated garnet has a pronounced andradite component, contains low concentrations of HFSE, Mn, and Ga and is variably enriched in Sn, W, As, and Li. Elevated concentrations of HFSE, Mn, and Ga in garnet from skarns with skarnoid textures indicate that these formed under mainly rock-buffered conditions (low fluid/rock ratios). Associated garnet is dominantly grossular and invariably low in Sn and W concentrations. The mineral chemistry of garnet from the youngest skarn bodies indicates renewed ingress of magmatic-hydrothermal fluids marked by an intermediate grandite composition, low HFSE, Al, and Ga concentrations as well as a variable enrichment of Sn and W. Although these general patterns are well defined, our data also clearly reveal considerable variability of garnet compositions on the local scale. The same is true for Sn and W concentrations in garnet of all stages. These are found to be too variable as to constitute meaningful exploration vectors. However, they are well suited to place general constraints on the physicochemical conditions of polyphase skarn formation in the Schwarzenberg District.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 4","pages":"Article 126344"},"PeriodicalIF":2.9,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145467011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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