Pub Date : 2026-02-10DOI: 10.1016/j.chemer.2026.126393
Nahid Naseri , Reza Zarei Sahamieh , Matthew I. Leybourne , Anderson Costa dos Santos , Ahmad Ahmadi Khalaji , Guilherme O. Gonçalves
The Pargeh plutonic complex in Central Alborz, Iran, was emplaced during the Early Eocene and consists mainly of olivine gabbros and monzodiorites with granular to ophitic textures. The olivine gabbros contain olivine, clinopyroxene, plagioclase, biotite, and accessory magnetite, ilmenite, and apatite, whereas the monzodiorites are composed of clinopyroxene, plagioclase, biotite, and > 10% alkali feldspar, together with accessory oxide phases and apatite. Apatite UPb dating yields emplacement ages of 57.1 ± 3.5 Ma (olivine gabbro) and 53.2 ± 2.7 Ma (monzodiorite), indicating Early Eocene magmatism. The rocks display high-K signatures, enrichment in large-ion lithophile elements (LILE), and depletion in high-field-strength elements (HFSE), along with negative NbTa anomalies and enrichment in Sr, Ba, U, and Pb—features typical of subduction-related geochemical influence. Whole-rock isotopic compositions (εNd(t) = +1.5 to +1.9; 87Sr/86Sr(i) = 0.7049–0.7053) indicate derivation from a metasomatized subcontinental lithospheric mantle (SCLM) influenced by subduction-related fluids. The parental mafic magmas—generated by low-degree partial melting of this hydrated mantle—underwent limited crustal assimilation and fractional crystallization within deep crustal zones, producing monzodioritic derivatives. These features collectively suggest that the Pargeh intrusion formed in an extensional, supra-subduction back-arc environment.
{"title":"Back - arc magmatism during Eocene subduction and closure of eastern Tethys: An insight from Alborz Magmatic Belt (NW Iran)","authors":"Nahid Naseri , Reza Zarei Sahamieh , Matthew I. Leybourne , Anderson Costa dos Santos , Ahmad Ahmadi Khalaji , Guilherme O. Gonçalves","doi":"10.1016/j.chemer.2026.126393","DOIUrl":"10.1016/j.chemer.2026.126393","url":null,"abstract":"<div><div>The Pargeh plutonic complex in Central Alborz, Iran, was emplaced during the Early Eocene and consists mainly of olivine gabbros and monzodiorites with granular to ophitic textures. The olivine gabbros contain olivine, clinopyroxene, plagioclase, biotite, and accessory magnetite, ilmenite, and apatite, whereas the monzodiorites are composed of clinopyroxene, plagioclase, biotite, and > 10% alkali feldspar, together with accessory oxide phases and apatite. Apatite U<img>Pb dating yields emplacement ages of 57.1 ± 3.5 Ma (olivine gabbro) and 53.2 ± 2.7 Ma (monzodiorite), indicating Early Eocene magmatism. The rocks display high-K signatures, enrichment in large-ion lithophile elements (LILE), and depletion in high-field-strength elements (HFSE), along with negative Nb<img>Ta anomalies and enrichment in Sr, Ba, U, and Pb—features typical of subduction-related geochemical influence. Whole-rock isotopic compositions (εNd(t) = +1.5 to +1.9; <sup>87</sup>Sr/<sup>86</sup>Sr(i) = 0.7049–0.7053) indicate derivation from a metasomatized subcontinental lithospheric mantle (SCLM) influenced by subduction-related fluids. The parental mafic magmas—generated by low-degree partial melting of this hydrated mantle—underwent limited crustal assimilation and fractional crystallization within deep crustal zones, producing monzodioritic derivatives. These features collectively suggest that the Pargeh intrusion formed in an extensional, supra-subduction back-arc environment.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126393"},"PeriodicalIF":2.9,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146173126","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 : 2026-02-09DOI: 10.1016/j.chemer.2026.126392
David A. Wood
Systematic and substantial temporal and local spatial variations in trace element and radiogenic isotope ratios are reviewed in basalts sequences from East Greenland, Iceland, Faeroe Islands, Rockall Trough, Hebridean Islands and the Mohns Ridge. These variations are indicative of local scale mantle heterogeneities relating to mantle plume influences in these zones of incipient rifting and slow-spreading extensional tectonics. The magnitude and range of key elemental and isotopic variations are reviewed and found to be similar in each region. To effectively characterize the compositional variations, two relevant reference compositions are employed: worldwide averages for mid-ocean ridge basalt (N-MORB) and intraplate basalt (WLD). Profiles of regional average trace element concentrations and Pb-isotopes normalized to the WLD reference also reveal characteristic patterns. Some basalt series from East Greenland, Faeroe Islands, Rockall Trough and the Hebridean Islands have been affected by crustal contamination. However, the trace element ratios and normalized profiles are still able to reveal mantle heterogeneities influencing those lava sequences. Based on the regional comparisons in spatial and temporal variations, dominated by fertile compositions in the earlier stages and more refractory compositions in the later stages, a conceptual petrogenetic model is developed and illustrated. This incorporates pulsed-plume diapirism and sequential, incremental upper mantle dynamic partial melting forming distinctive magma pulses, Asthenosphere outflow and magma mixing in an interconnected network of lower crustal, sill-like magma chambers are additional features of the model. This review reveals that in slow-spreading or incipient-rifting, extensional regions, where mantle plumes are laterally constrained for longer periods than at fast spreading ridges, a distinctive compositional evolution occurs in the basalt sequences generated.
{"title":"A review of the distinctive spatial and temporal compositions of basalt sequences associated with slow-spreading zones influenced by mantle plumes and their petrogenetic implications","authors":"David A. Wood","doi":"10.1016/j.chemer.2026.126392","DOIUrl":"10.1016/j.chemer.2026.126392","url":null,"abstract":"<div><div>Systematic and substantial temporal and local spatial variations in trace element and radiogenic isotope ratios are reviewed in basalts sequences from East Greenland, Iceland, Faeroe Islands, Rockall Trough, Hebridean Islands and the Mohns Ridge. These variations are indicative of local scale mantle heterogeneities relating to mantle plume influences in these zones of incipient rifting and slow-spreading extensional tectonics. The magnitude and range of key elemental and isotopic variations are reviewed and found to be similar in each region. To effectively characterize the compositional variations, two relevant reference compositions are employed: worldwide averages for mid-ocean ridge basalt (N-MORB) and intraplate basalt (WLD). Profiles of regional average trace element concentrations and Pb-isotopes normalized to the WLD reference also reveal characteristic patterns. Some basalt series from East Greenland, Faeroe Islands, Rockall Trough and the Hebridean Islands have been affected by crustal contamination. However, the trace element ratios and normalized profiles are still able to reveal mantle heterogeneities influencing those lava sequences. Based on the regional comparisons in spatial and temporal variations, dominated by fertile compositions in the earlier stages and more refractory compositions in the later stages, a conceptual petrogenetic model is developed and illustrated. This incorporates pulsed-plume diapirism and sequential, incremental upper mantle dynamic partial melting forming distinctive magma pulses, Asthenosphere outflow and magma mixing in an interconnected network of lower crustal, sill-like magma chambers are additional features of the model. This review reveals that in slow-spreading or incipient-rifting, extensional regions, where mantle plumes are laterally constrained for longer periods than at fast spreading ridges, a distinctive compositional evolution occurs in the basalt sequences generated.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126392"},"PeriodicalIF":2.9,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146173643","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 : 2026-01-26DOI: 10.1016/j.chemer.2026.126390
Xiao-Chun Li , Geng-Xin Deng , Xiao-Yun Nan , Xue-Yin Yuan , Hong-Rui Fan , Fang Huang
Most global rare earth element (REE) deposits are generated by liquids derived from carbonatitic-alkaline magmas. However, the nature of REE mineralizing liquids and how they were related to the carbonatite systems remain enigmatic. In this study, we present new Sr-Nd-Ba isotope data for a REE-rich, syenite‑carbonatite complex at Dong Pao, Vietnam to trace the generation process of the ore-forming liquid. The complex records early-stage K-feldspar crystallization to form syenite, followed by late-stage calcite crystallization forming carbonatite. The hydrothermal REE ores show identical initial Sr isotope ratios (0.7075 to 0.7083) and εNd(t) values (−4.6 to −7.5) with syenite and carbonatite (87Sr/86Sri: 0.7072–0.7079; εNd(t): −6.5 to −5.6), indicating a common source of these rocks. Importantly, the Dong Pao syenite, carbonatite, and REE ores show distinct variations in Ba isotope compositions, with the latter two rock domains having higher Ba isotope values (δ138/134Ba: 0.03‰ to 0.12‰) than syenite (δ138/134Ba: −0.03‰ to 0.03‰). This isotope signature is interpreted to result from extensive fractional crystallization of K-feldspar, which preferentially incorporates light Ba isotopes, thereby enriching the residual melts and fluids in heavy Ba isotopes. This provides strong evidence for the generation of ore-forming liquids through intensive magmatic evolution. The common occurrence of high-salinity melt-fluid inclusions in REE ores further support the involvement of chemically evolved, alkali- and volatile-rich liquids during mineralization. Because REE are incompatible in common rock-forming minerals, continuous and intensive melt-fluid evolution can significantly enhance the potential for REE ore formation. Collectively, these findings highlight the important role of chemically evolved, high-salinity liquids in REE mineralization, and demonstrates the utility of Ba isotopes as a novel tracer for ore-forming process in the carbonatite-alkaline systems.
{"title":"Large-scale REE mineralization linked to intensive evolution of carbonatitic-alkaline magmas to brine-melts: Insights from Sr-Nd-Ba isotopes","authors":"Xiao-Chun Li , Geng-Xin Deng , Xiao-Yun Nan , Xue-Yin Yuan , Hong-Rui Fan , Fang Huang","doi":"10.1016/j.chemer.2026.126390","DOIUrl":"10.1016/j.chemer.2026.126390","url":null,"abstract":"<div><div>Most global rare earth element (REE) deposits are generated by liquids derived from carbonatitic-alkaline magmas. However, the nature of REE mineralizing liquids and how they were related to the carbonatite systems remain enigmatic. In this study, we present new Sr-Nd-Ba isotope data for a REE-rich, syenite‑carbonatite complex at Dong Pao, Vietnam to trace the generation process of the ore-forming liquid. The complex records early-stage K-feldspar crystallization to form syenite<strong>,</strong> followed by late-stage calcite crystallization forming carbonatite. The hydrothermal REE ores show identical initial Sr isotope ratios (0.7075 to 0.7083) and εNd(t) values (−4.6 to −7.5) with syenite and carbonatite (<sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub>: 0.7072–0.7079; εNd(t): −6.5 to −5.6), indicating a common source of these rocks. Importantly, the Dong Pao syenite, carbonatite, and REE ores show distinct variations in Ba isotope compositions, with the latter two rock domains having higher Ba isotope values (δ<sup>138/134</sup>Ba: 0.03‰ to 0.12‰) than syenite (δ<sup>138/134</sup>Ba: −0.03‰ to 0.03‰). This isotope signature <strong>is</strong> interpreted to result from extensive fractional crystallization of K-feldspar, which preferentially incorporates light Ba isotopes<strong>,</strong> thereby enriching the residual melts and fluids in heavy Ba isotopes. This provides strong evidence for the generation of ore-forming liquids through intensive magmatic evolution. The common occurrence of high-salinity melt-fluid inclusions in REE ores further support the involvement of chemically evolved, alkali- and volatile-rich liquids during mineralization. Because REE are incompatible in common rock-forming minerals<strong>,</strong> continuous and intensive melt-fluid evolution can significantly enhance the potential for REE ore formation. Collectively, these findings highlight the important role of chemically evolved, high-salinity liquids in REE mineralization, and demonstrates the utility of Ba isotopes as a novel tracer for ore-forming process in th<strong>e</strong> carbonatite-alkaline systems.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126390"},"PeriodicalIF":2.9,"publicationDate":"2026-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146077410","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 : 2026-01-17DOI: 10.1016/j.chemer.2026.126388
Juan A. Moreno , Gilmara Santos da Cruz , Juan A. Dahlquist , Matías M. Morales Cámera , Priscila S. Zandomeni , Gabriela A. Gonzalez-Liedtke , Miguel A.S. Basei , Sanjeet K. Verma
The El Fierro pluton represents one of the late-stage plutons of the Choiyoi Magmatic Province in the Colangüil batholith (Frontal Cordillera, Argentina). New U‑Pb zircon dating yields a crystallisation age of 262 ± 2 Ma, with zircon antecrysts (∼273 Ma) indicating prolonged magmatic activity that overlaps with the early-stage Choiyoi I-type magmatism (ca. 270–290 Ma). This pluton is ferroan, alkali-calcic to calc-alkalic, and essentially weakly peraluminous (av. 1.05 ± 0.06), exhibiting high Ga/Al ratios, elevated HFSE concentrations (Ce + Zr + Nb + Y; av. 310 ± 147 ppm; range: 150–584 ppm), extreme F enrichment (6101–31,442 ppm) and relatively high zircon-saturation (775 ± 45 °C) and apatite-saturation temperatures (887 ± 78 °C), consistent with an A-type affinity. Isotope data (εHft = −7.0 to +1.25; εNdi ≈ −3), together with geochemical compositions, reflect a hybrid crustal source involving metasedimentary components likely metasomatized by mantle fluids. Accordingly, we interpret the El Fierro pluton as the product of crustal melting during lithospheric thinning and slab retreat, marking the onset of incipient rifting in southwestern Gondwana. This study highlights that A-type granites can be generated in extensional regimes within arc settings.
{"title":"Unravelling the origin of A-type granites in an extensional arc setting: Insights from the Permian El Fierro pluton, Colangüil batholith (Frontal Cordillera, Argentina)","authors":"Juan A. Moreno , Gilmara Santos da Cruz , Juan A. Dahlquist , Matías M. Morales Cámera , Priscila S. Zandomeni , Gabriela A. Gonzalez-Liedtke , Miguel A.S. Basei , Sanjeet K. Verma","doi":"10.1016/j.chemer.2026.126388","DOIUrl":"10.1016/j.chemer.2026.126388","url":null,"abstract":"<div><div>The El Fierro pluton represents one of the late-stage plutons of the Choiyoi Magmatic Province in the Colangüil batholith (Frontal Cordillera, Argentina). New U‑Pb zircon dating yields a crystallisation age of 262 ± 2 Ma, with zircon antecrysts (∼273 Ma) indicating prolonged magmatic activity that overlaps with the early-stage Choiyoi I-type magmatism (ca. 270–290 Ma). This pluton is ferroan, alkali-calcic to calc-alkalic, and essentially weakly peraluminous (av. 1.05 ± 0.06), exhibiting high Ga/Al ratios, elevated HFSE concentrations (Ce + Zr + Nb + Y; av. 310 ± 147 ppm; range: 150–584 ppm), extreme F enrichment (6101–31,442 ppm) and relatively high zircon-saturation (775 ± 45 °C) and apatite-saturation temperatures (887 ± 78 °C), consistent with an A-type affinity. Isotope data (εHf<sub>t</sub> = −7.0 to +1.25; εNd<sub>i</sub> ≈ −3), together with geochemical compositions, reflect a hybrid crustal source involving metasedimentary components likely metasomatized by mantle fluids. Accordingly, we interpret the El Fierro pluton as the product of crustal melting during lithospheric thinning and slab retreat, marking the onset of incipient rifting in southwestern Gondwana. This study highlights that A-type granites can be generated in extensional regimes within arc settings.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126388"},"PeriodicalIF":2.9,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022427","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 : 2026-01-14DOI: 10.1016/j.chemer.2026.126385
Bassam A. Abuamarah , Kirsten Drüppel , Mokhles K. Azer
The Jabal Qutn intrusion (JQI) is a Late Ediacaran post-collisional granitic intrusion in the northeastern part of the Arabian Shield, the western extension of the Neoproterozoic Arabian-Nubian Shield (ANS). The study area is dominated by Neoproterozoic rocks including sedimentary units of the Murdama group, granodiorites, and A-type granites. The latter form a ring complex that consists of an inner core of alkali feldspar granite and an incomplete outer zone of syenogranite with gradational contacts between them. The Qutn granites are mainly composed of feldspars, micas and quartz and contain a large variety of accessory phases including zircon, allanite, thorite, topaz, titanite, waimirite-(Y), bastnäsite, Nb-Ta oxides (columbite, qitianlingite and nioboaeschynite), wolframite, pyrochroite, apatite, and gold alloys (Au contents of 60–80 wt%). Rare mineral species such as qitianlingite and nioboaeschynite-(Y) are recorded for the first time in the whole ANS. In case of waimirite-(Y) the study area represents the third reported occurrence in the world. The granites are highly evolved (SiO2 = 72.69–76.65 wt%), and exhibit almost identical chondrite-normalized rare-earth elements patterns with slight enrichment in LREE compared to HREE [(La/Lu)n = 1.24–2.92] and prominent negative Eu anomalies (Eu/Eu* = 0.04–0.13). They show geochemical characteristics of anorogenic granites and continuous compositional trends for both major and trace elements, indicating a common source, i.e. partial melting of juvenile crust, followed by extensive fractional crystallization of feldspars, apatite, and Fe-Ti oxides associated with minor crustal contamination. The granites were emplaced at shallow depths (< 6 km) with their estimated crystallization temperatures ranging between ca. 780 and 850 °C. The late formation of F-rich minerals (topaz, fluorite, waimirite-(Y)) implies a F-rich composition of the parental magma with strong late-magmatic F- and REE-enrichment. Textural characteristics provide evidence for a strong metasomatic alteration in the late-magmatic stage that mainly occurred in the apical and marginal parts of the alkali feldspar granite, with the hydrothermal solutions being concentrated in the upper part of the magma chamber before complete crystallization of granitic magma
{"title":"Geochemistry and mineralogy of neoproterozoic exotic minerals-bearing post-collisional A-type granites of Jebel Qutn intrusion, Arabian shield, Saudi Arabia","authors":"Bassam A. Abuamarah , Kirsten Drüppel , Mokhles K. Azer","doi":"10.1016/j.chemer.2026.126385","DOIUrl":"10.1016/j.chemer.2026.126385","url":null,"abstract":"<div><div>The Jabal Qutn intrusion (JQI) is a Late Ediacaran post-collisional granitic intrusion in the northeastern part of the Arabian Shield, the western extension of the Neoproterozoic Arabian-Nubian Shield (ANS). The study area is dominated by Neoproterozoic rocks including sedimentary units of the Murdama group, granodiorites, and A-type granites. The latter form a ring complex that consists of an inner core of alkali feldspar granite and an incomplete outer zone of syenogranite with gradational contacts between them. The Qutn granites are mainly composed of feldspars, micas and quartz and contain a large variety of accessory phases including zircon, allanite, thorite, topaz, titanite, waimirite-(Y), bastnäsite, Nb-Ta oxides (columbite, qitianlingite and nioboaeschynite), wolframite, pyrochroite, apatite, and gold alloys (Au contents of 60–80 wt%). Rare mineral species such as qitianlingite and nioboaeschynite-(Y) are recorded for the first time in the whole ANS. In case of waimirite-(Y) the study area represents the third reported occurrence in the world. The granites are highly evolved (SiO<sub>2</sub> = 72.69–76.65 wt%), and exhibit almost identical chondrite-normalized rare-earth elements patterns with slight enrichment in LREE compared to HREE [(La/Lu)<sub><em>n</em></sub> = 1.24–2.92] and prominent negative Eu anomalies (Eu/Eu* = 0.04–0.13)<em>.</em> They show geochemical characteristics of anorogenic granites and continuous compositional trends for both major and trace elements, indicating a common source, i.e. partial melting of juvenile crust, followed by extensive fractional crystallization of feldspars, apatite, and Fe-Ti oxides associated with minor crustal contamination. The granites were emplaced at shallow depths (< 6 km) with their estimated crystallization temperatures ranging between ca. 780 and 850 °C. The late formation of F-rich minerals (topaz, fluorite, waimirite-(Y)) implies a F-rich composition of the parental magma with strong late-magmatic F- and REE-enrichment. Textural characteristics provide evidence for a strong metasomatic alteration in the late-magmatic stage that mainly occurred in the apical and marginal parts of the alkali feldspar granite, with the hydrothermal solutions being concentrated in the upper part of the magma chamber before complete crystallization of granitic magma</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126385"},"PeriodicalIF":2.9,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022428","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 : 2026-01-14DOI: 10.1016/j.chemer.2026.126389
Zhang Hanxiong , Wang Guiling , Zhang Wei , Wang Mengmeng
Geothermal resources are green renewable economic energy, and the efficient development and utilization of geothermal resources has become an important research direction of common concern for all countries in the world. Knowledge of the transport processes, circulation patterns, water-rock reactions, and geochemical change processes of geothermal water is an important prerequisite for the efficient development and utilization of geothermal resources. To elucidate the mechanisms of water-rock interaction and the circulation pathways of geothermal fluids, the Rongcheng geothermal field in Xiong'an New Area, China, was selected as the study area. An integrated approach combining hydrochemical analysis, stable isotope techniques, and hydrochemical inverse modeling was employed to systematically characterize the hydrogeochemical evolution of the groundwater systems. Hydrochemical analysis reveals that geothermal fluids are predominantly of the Na-Cl type, with total dissolved solids (TDS) exceeding 1000 mg/L, significantly higher than the Ca-HCO3 type shallow groundwater. Isotopic data (δ18O and δ2H) confirm origin for all water types is atmospheric precipitation, with geothermal fluids exhibiting a distinct “δ18O shift” and lower deuterium excess values, reflecting intensive water-rock interactions under high-temperature conditions. Results of water rock equilibrium state show that the water samples of the study area are partially equilibrated and immature. Saturation index (SI) calculations further demonstrate that chalcedony and quartz are closer to being saturated in the hydrologic reactions of the water compared with other minerals. Driven by distinct circulation pathways, carbonate geothermal water exhibit greater circulation depths and higher reservoir temperatures compared to those in sandstone reservoirs. Three circulation patterns (directions 1, 2, and 3) are proposed based on a combination of clustering analysis, water-rock interactions, inverse simulation of the water circulation paths, and a more refined conceptual model of the water circulation in typical profiles. It is concluded that direction 3 is a deep carbonate geothermal reservoir cycle and that the carbonate geothermal water exhibits more reduction and stronger water-rock reactions because the temperature and pressure of the environment are higher than those for directions 1 and 2. The results of geothermal water genesis patterns and circulation paths and scientific theoretical support for in-depth study of geothermal resources.
{"title":"Characterization of geothermal water-rock interaction processes and transport patterns using geochemical methods","authors":"Zhang Hanxiong , Wang Guiling , Zhang Wei , Wang Mengmeng","doi":"10.1016/j.chemer.2026.126389","DOIUrl":"10.1016/j.chemer.2026.126389","url":null,"abstract":"<div><div>Geothermal resources are green renewable economic energy, and the efficient development and utilization of geothermal resources has become an important research direction of common concern for all countries in the world. Knowledge of the transport processes, circulation patterns, water-rock reactions, and geochemical change processes of geothermal water is an important prerequisite for the efficient development and utilization of geothermal resources. To elucidate the mechanisms of water-rock interaction and the circulation pathways of geothermal fluids, the Rongcheng geothermal field in Xiong'an New Area, China, was selected as the study area. An integrated approach combining hydrochemical analysis, stable isotope techniques, and hydrochemical inverse modeling was employed to systematically characterize the hydrogeochemical evolution of the groundwater systems. Hydrochemical analysis reveals that geothermal fluids are predominantly of the Na-Cl type, with total dissolved solids (TDS) exceeding 1000 mg/L, significantly higher than the Ca-HCO<sub>3</sub> type shallow groundwater. Isotopic data (δ<sup>18</sup>O and δ<sup>2</sup>H) confirm origin for all water types is atmospheric precipitation, with geothermal fluids exhibiting a distinct “δ<sup>18</sup>O shift” and lower deuterium excess values, reflecting intensive water-rock interactions under high-temperature conditions. Results of water rock equilibrium state show that the water samples of the study area are partially equilibrated and immature. Saturation index (SI) calculations further demonstrate that chalcedony and quartz are closer to being saturated in the hydrologic reactions of the water compared with other minerals. Driven by distinct circulation pathways, carbonate geothermal water exhibit greater circulation depths and higher reservoir temperatures compared to those in sandstone reservoirs. Three circulation patterns (directions 1, 2, and 3) are proposed based on a combination of clustering analysis, water-rock interactions, inverse simulation of the water circulation paths, and a more refined conceptual model of the water circulation in typical profiles. It is concluded that direction 3 is a deep carbonate geothermal reservoir cycle and that the carbonate geothermal water exhibits more reduction and stronger water-rock reactions because the temperature and pressure of the environment are higher than those for directions 1 and 2. The results of geothermal water genesis patterns and circulation paths and scientific theoretical support for in-depth study of geothermal resources.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126389"},"PeriodicalIF":2.9,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146022429","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 : 2026-01-09DOI: 10.1016/j.chemer.2026.126387
Ashutosh Pandey , H.K. Sachan , Digvijay K. Dubey
The Precambrian geodynamic evolution of the proto-northern Indian continental margin remains elusive. Mafic magmatic rocks from the Lesser Himalayan Sequence, representing the northern extremity of the Indian Shield, provide key constraints on this evolution. This study presents new mineralogical and whole-rock geochemical data from mafic rocks in the Rudraprayag-Karnaprayag sector of the Garhwal Lesser Himalayan region, aiming to elucidate their genesis and geodynamic significance. The whole-rock geochemistry of the studied rocks exhibits enrichment in large-ion lithophile elements and depletion in high-field strength elements, with elevated Ba/Nb, Th/Yb, and La/Sm ratios, indicative of subduction-related metasomatism of the mantle source. The most primitive samples (with MgO > 7.5 wt%) exhibit major element systematics consistent with melts derived from a pyroxene-dominated mantle source, possibly produced by interaction between peridotite and siliceous melt. Estimated melting temperatures (1198–1385 °C) exclude the possibility of involvement of anomalously hot mantle plumes in the origin of these rocks and point towards a passive continental rifting setting. These observations suggest that the Paleoproterozoic mafic magmatic rocks of the Lesser Himalayan Sequence possibly originated in a continental back-arc extensional setting linked to an Andean-type active continental margin along the proto-northern Indian cratonic block. Our results support the evidence for an Andean-type active continental margin along the proto-northern Indian continental margin during the assembly of the Columbia supercontinent in the Paleoproterozoic.
{"title":"Petrogenesis of Paleoproterozoic mafic magmatic rocks from Garhwal Lesser Himalayan Sequence: Implications for Precambrian crustal recycling and geodynamic evolution of proto-northern Indian continental margin","authors":"Ashutosh Pandey , H.K. Sachan , Digvijay K. Dubey","doi":"10.1016/j.chemer.2026.126387","DOIUrl":"10.1016/j.chemer.2026.126387","url":null,"abstract":"<div><div>The Precambrian geodynamic evolution of the proto-northern Indian continental margin remains elusive. Mafic magmatic rocks from the Lesser Himalayan Sequence, representing the northern extremity of the Indian Shield, provide key constraints on this evolution. This study presents new mineralogical and whole-rock geochemical data from mafic rocks in the Rudraprayag-Karnaprayag sector of the Garhwal Lesser Himalayan region, aiming to elucidate their genesis and geodynamic significance. The whole-rock geochemistry of the studied rocks exhibits enrichment in large-ion lithophile elements and depletion in high-field strength elements, with elevated Ba/Nb, Th/Yb, and La/Sm ratios, indicative of subduction-related metasomatism of the mantle source. The most primitive samples (with MgO > 7.5 wt%) exhibit major element systematics consistent with melts derived from a pyroxene-dominated mantle source, possibly produced by interaction between peridotite and siliceous melt. Estimated melting temperatures (1198–1385 °C) exclude the possibility of involvement of anomalously hot mantle plumes in the origin of these rocks and point towards a passive continental rifting setting. These observations suggest that the Paleoproterozoic mafic magmatic rocks of the Lesser Himalayan Sequence possibly originated in a continental back-arc extensional setting linked to an Andean-type active continental margin along the proto-northern Indian cratonic block. Our results support the evidence for an Andean-type active continental margin along the proto-northern Indian continental margin during the assembly of the Columbia supercontinent in the Paleoproterozoic.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126387"},"PeriodicalIF":2.9,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145977864","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 : 2026-01-07DOI: 10.1016/j.chemer.2025.126384
Chandni Chaurasia , Satyajeet S. Thakur , Suresh C. Patel , Nainika Gour , Janisar M. Sheikh
X-ray elemental mapping and quantitative analysis of monazite grains contained in metapelites from the Greater Himalayan Sequence (crystalline core of the Himalaya) of the Dhauliganga Valley, Garhwal Himalaya were performed by electron probe micro-analyser to evaluate the zoning patterns. The rocks, from which monazites have been studied, include those with peak metamorphism (650–715 °C and 8.0–9.9 kbar) under subsolidus conditions and also those showing evidences of partial melting (<800 °C and 10.5 kbar). All the monazite analyses taken together show that Light Rare Earth Elements (LREEs) constitute 80–89 % of the total cation proportion (exclusive of P) and Heavy Rare Earth Elements (HREEs) 1–4 %, while other elements make 9–18 %. Zoning patterns vary from core–rim to patchy and irregular types. The rim is invariably Y-rich compared to the core. Compositional variability of monazites can be explained mostly by the brabantite substitution: 2REE3+ = (Th,U)4+ + Ca2+. Y shows negative correlation with LREE and positive correlation with HREE. The U-Th-Pb in situ analyses of one of the samples (HH52) suggests that the monazite grew at 26.28 ± 0.19 Ma. Likely metamorphic reactions for the growth of Y-poor monazite core and its resorption followed by overgrowth of Y-rich rim during progressive metamorphism have been explored. Phase equilibria considerations indicate that resorption and regrowth of monazite can occur in both subsolidus and suprasolidus regimes. The P–T path for the development of resorption–regrowth texture of monazite is inferred to be isothermal decompression in the case of subsolidus regime, and isobaric cooling to retrograde decompression in the case of suprasolidus conditions.
{"title":"Compositional zoning, crystal chemistry and metamorphic growth of monazite in the Greater Himalayan Sequence, Dhauliganga Valley, Garhwal Himalaya","authors":"Chandni Chaurasia , Satyajeet S. Thakur , Suresh C. Patel , Nainika Gour , Janisar M. Sheikh","doi":"10.1016/j.chemer.2025.126384","DOIUrl":"10.1016/j.chemer.2025.126384","url":null,"abstract":"<div><div>X-ray elemental mapping and quantitative analysis of monazite grains contained in metapelites from the Greater Himalayan Sequence (crystalline core of the Himalaya) of the Dhauliganga Valley, Garhwal Himalaya were performed by electron probe micro-analyser to evaluate the zoning patterns. The rocks, from which monazites have been studied, include those with peak metamorphism (650–715 °C and 8.0–9.9 kbar) under subsolidus conditions and also those showing evidences of partial melting (<800 °C and 10.5 kbar). All the monazite analyses taken together show that Light Rare Earth Elements (LREEs) constitute 80–89 % of the total cation proportion (exclusive of P) and Heavy Rare Earth Elements (HREEs) 1–4 %, while other elements make 9–18 %. Zoning patterns vary from core–rim to patchy and irregular types. The rim is invariably Y-rich compared to the core. Compositional variability of monazites can be explained mostly by the brabantite substitution: 2REE<sup>3+</sup> = (Th,U)<sup>4+</sup> + Ca<sup>2+</sup>. Y shows negative correlation with LREE and positive correlation with HREE. The U-Th-Pb in situ analyses of one of the samples (HH52) suggests that the monazite grew at 26.28 ± 0.19 Ma. Likely metamorphic reactions for the growth of Y-poor monazite core and its resorption followed by overgrowth of Y-rich rim during progressive metamorphism have been explored. Phase equilibria considerations indicate that resorption and regrowth of monazite can occur in both subsolidus and suprasolidus regimes. The P–T path for the development of resorption–regrowth texture of monazite is inferred to be isothermal decompression in the case of subsolidus regime, and isobaric cooling to retrograde decompression in the case of suprasolidus conditions.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126384"},"PeriodicalIF":2.9,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925916","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 : 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":"2026-01-06","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 : 2025-12-26DOI: 10.1016/j.chemer.2025.126383
Siobhan E.L. Kingham , Matthew Varnam , Lee M. Saper , Geoffrey D. Bromiley
High-temperature melting experiments in gas-mixing furnaces are used to simulate magmatic processes and provide insight into melt properties at controlled conditions. These experiments assume that rapid melting results in formation of homogeneous molten samples, especially when glassed starting materials are used. As part of an investigation of evaporative loss of moderately volatile elements (MVE) from lunar magma, we performed short-duration, superliquidus experiments using homogeneous glass starting materials. Powdered glass pellets and glass fragments were suspended on Pt wire loops, and rapidly inserted into the hotspot of a 1-atm vertical gas-mixing furnace at 1350 °C and log fO2 = IW to IW +2 (oxygen fugacity at, or 2 log units above, the Fe-FeO buffer). Samples were held within the furnace for 5–60 min before being drop-quenched into water. Scanning electron microscopy and electron probe microanalysis of sectioned run products evidence progressive MVE loss from samples, but with additional, unexpected, redistribution of refractory elements (SiO2, TiO2, MgO, FeO, Al2O3, CaO). Refractory element zonation reflects early heating processes, and is progressively eradicated during prolonged heating via diffusion. Zonation in shorter duration experiments also reveals variable, and sometimes chaotic, disruption of samples during quenching. We propose that refractive element zonation arises due to phase separation during heating, driven by partial devitrification of the interiors of glassy samples. Our results demonstrate that element redistribution during melting, and physical disruption of samples induced by quenching, can significantly affect chemical homogeneity. These effects should be considered when designing and interpreting data from short-duration high-temperature experiments.
{"title":"Major element zonation following rapid heating of homogeneous glass in superliquidus experiments","authors":"Siobhan E.L. Kingham , Matthew Varnam , Lee M. Saper , Geoffrey D. Bromiley","doi":"10.1016/j.chemer.2025.126383","DOIUrl":"10.1016/j.chemer.2025.126383","url":null,"abstract":"<div><div>High-temperature melting experiments in gas-mixing furnaces are used to simulate magmatic processes and provide insight into melt properties at controlled conditions. These experiments assume that rapid melting results in formation of homogeneous molten samples, especially when glassed starting materials are used. As part of an investigation of evaporative loss of moderately volatile elements (MVE) from lunar magma, we performed short-duration, superliquidus experiments using homogeneous glass starting materials. Powdered glass pellets and glass fragments were suspended on Pt wire loops, and rapidly inserted into the hotspot of a 1-atm vertical gas-mixing furnace at 1350 °C and log <em>f</em>O<sub>2</sub> = IW to IW +2 (oxygen fugacity at, or 2 log units above, the Fe-FeO buffer). Samples were held within the furnace for 5–60 min before being drop-quenched into water. Scanning electron microscopy and electron probe microanalysis of sectioned run products evidence progressive MVE loss from samples, but with additional, unexpected, redistribution of refractory elements (SiO<sub>2</sub>, TiO<sub>2</sub>, MgO, FeO, Al<sub>2</sub>O<sub>3</sub>, CaO). Refractory element zonation reflects early heating processes, and is progressively eradicated during prolonged heating via diffusion. Zonation in shorter duration experiments also reveals variable, and sometimes chaotic, disruption of samples during quenching. We propose that refractive element zonation arises due to phase separation during heating, driven by partial devitrification of the interiors of glassy samples. Our results demonstrate that element redistribution during melting, and physical disruption of samples induced by quenching, can significantly affect chemical homogeneity. These effects should be considered when designing and interpreting data from short-duration high-temperature experiments.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126383"},"PeriodicalIF":2.9,"publicationDate":"2025-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884250","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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