Pub Date : 2026-03-01Epub 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":"2026-03-01","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 : 2026-03-01Epub 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":"2026-03-01","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}
This study presents the integrated investigation of the Prithvipur Greenstone Belt (PGB) in the Bundelkhand Craton, combining petrography, major and trace element geochemistry, and whole-rock SmNd isotope systematics to elucidate the origin and evolution of the high-Mg basalts and basalts. The high-Mg basalts exhibit elevated MgO (25–12.5 wt%), Al2O3 (13–3.7 wt%), Mg# (82–65), Ni (1248–190 ppm), and Cr (2954–846 ppm), indicating derivation from a refractory mantle source that underwent moderate partial melting (∼30%) at mantle liquidus temperatures (Tliq °C) of ∼1522–1352 °C. Their low TiO2 (0.8–0.3 wt%), negative NbTi anomalies, fractionated REE patterns, and flat to slightly depleted HREE trends (Gd/Yb = 1.46–0.64) suggest melting of a depleted, shallow mantle source with minimal garnet influence. In contrast, associated basalts display lower Mg# (61–45), Ni (201–68 ppm), and Cr (596–62 ppm), higher TiO2 (1.9–0.5 wt%), and moderate LREE enrichment (La/Sm = 3.8–1.1). Together, these traits indicate derivation from evolved melts via fractional crystallization or generation in a subduction setting involving residual garnet. Critically, SmNd isotopes reveal a fundamental mantle dichotomy. High-Mg basalts possess negative initial εNd(t) values (−6.42 to −1.70), signaling an enriched mantle source or significant crustal interaction. In contrast, coeval basalts exhibit strongly positive εNd(t) values (+4.37 to +6.82), requiring a highly depleted mantle source. This isotopic divergence, despite limited alteration, provides robust evidence for significant Neoarchean mantle heterogeneity beneath the craton. The geochemistry of its mafic–ultramafic volcanic suite, high-Mg basalts, and basalts, reveals a two-stage mantle melting history driven by a mantle plume. High-Mg basalts represent higher-degree, deeper (∼160 km) melts from the hot plume core, while basalts formed at shallower depths (∼22 km) from the cooler plume periphery. Fractional crystallization of clinopyroxene ± olivine primarily controlled magmatic evolution, with minor crustal assimilation recorded locally. We propose the PGB formed in a hybrid plume-subduction setting during a major ∼2.7 Ga mantle overturn event. This terrane, alongside the Babina and Mauranipur belts, records the craton's evolution from Paleoarchean TTG crust formation through Neoarchean plume magmatism and arc accretion, highlighting the dynamic interplay between deep-seated mantle plumes and shallow tectonic processes in the growth of Archean continental crust.
{"title":"Plume-lithospheric mantle interaction for the origin of Archean mafic–ultramafic volcanics of the Prithvipur Greenstone Belt, Bundelkhand Craton, India: Geochemical and SmNd isotopic constraints","authors":"Balaram Sahoo , Pradip Kumar Singh , Ajay Kumar , Debajyoti Paul , Sanjeet Kumar Verma , Elson P. Oliveira , Torres Sánchez Darío , Dakshita , P.M. Ranjith","doi":"10.1016/j.chemer.2026.126391","DOIUrl":"10.1016/j.chemer.2026.126391","url":null,"abstract":"<div><div>This study presents the integrated investigation of the Prithvipur Greenstone Belt (PGB) in the Bundelkhand Craton, combining petrography, major and trace element geochemistry, and whole-rock Sm<img>Nd isotope systematics to elucidate the origin and evolution of the high-Mg basalts and basalts. The high-Mg basalts exhibit elevated MgO (25–12.5 wt%), Al<sub>2</sub>O<sub>3</sub> (13–3.7 wt%), Mg# (82–65), Ni (1248–190 ppm), and Cr (2954–846 ppm), indicating derivation from a refractory mantle source that underwent moderate partial melting (∼30%) at mantle liquidus temperatures (Tliq °C) of ∼1522–1352 °C. Their low TiO<sub>2</sub> (0.8–0.3 wt%), negative Nb<img>Ti anomalies, fractionated REE patterns, and flat to slightly depleted HREE trends (Gd/Yb = 1.46–0.64) suggest melting of a depleted, shallow mantle source with minimal garnet influence. In contrast, associated basalts display lower Mg# (61–45), Ni (201–68 ppm), and Cr (596–62 ppm), higher TiO<sub>2</sub> (1.9–0.5 wt%), and moderate LREE enrichment (La/Sm = 3.8–1.1). Together, these traits indicate derivation from evolved melts via fractional crystallization or generation in a subduction setting involving residual garnet. Critically, Sm<img>Nd isotopes reveal a fundamental mantle dichotomy. High-Mg basalts possess negative initial εNd(t) values (−6.42 to −1.70), signaling an enriched mantle source or significant crustal interaction. In contrast, coeval basalts exhibit strongly positive εNd(t) values (+4.37 to +6.82), requiring a highly depleted mantle source. This isotopic divergence, despite limited alteration, provides robust evidence for significant Neoarchean mantle heterogeneity beneath the craton. The geochemistry of its mafic–ultramafic volcanic suite, high-Mg basalts, and basalts, reveals a two-stage mantle melting history driven by a mantle plume. High-Mg basalts represent higher-degree, deeper (∼160 km) melts from the hot plume core, while basalts formed at shallower depths (∼22 km) from the cooler plume periphery. Fractional crystallization of clinopyroxene ± olivine primarily controlled magmatic evolution, with minor crustal assimilation recorded locally. We propose the PGB formed in a hybrid plume-subduction setting during a major ∼2.7 Ga mantle overturn event. This terrane, alongside the Babina and Mauranipur belts, records the craton's evolution from Paleoarchean TTG crust formation through Neoarchean plume magmatism and arc accretion, highlighting the dynamic interplay between deep-seated mantle plumes and shallow tectonic processes in the growth of Archean continental crust.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126391"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147395773","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 : 2026-03-01Epub Date: 2025-12-08DOI: 10.1016/j.chemer.2025.126375
Lidong Zhang , Yue Liu , Kewei Zhang , Ziqiang Zha , Jianeng Wu , Wenjun Xuan , Huiyuan Zhang
The Nenjiang–Heihe district, on the eastern margin of the Central Asian Orogenic Belt, hosts porphyry CuMo and epithermal Au systems emplaced through multiple tectonomagmatic episodes. To extract process–diagnostic signals from regional geochemistry and convert them into practical exploration targets, we applied compositional balance analysis (CoBA) and the concentration–area (C–A) fractal model to stream–sediment geochemical data collected from the Nenjiang–Heihe region, China. Compositional hierarchical clustering and a suite of data– and knowledge–driven balances identify three complementary geochemical patterns: (i) Fe–oxide–rich intermediate–mafic domains that define broad NNE–NE corridors coincident with volcanic belts and major faults; (ii) porphyry/base–metal chalcophile behavior (e.g., b01, b02, b03, b08, b7, b26, and b31) that captures Cu anomalies along permeable structures; and (iii) felsic–HFSE/LILE fertility and volatile–rich epithermal overprints, highlighted by b05, b06, b07, b15, and b16, localized over or adjacent to intermediate–felsic intrusions. C–A breakpoints provide objective thresholds that delineate statistically significant targets. Highest–priority prospects occur where b01–b02 highs overlap at fault intersections and locally coincide with b06 anomalies. The results demonstrate that CoBA, coupled with C–A segmentation, offers a low–cost, and interpretable framework for prospectivity mapping in forest–swamp terrain, mitigating closure effects and enhancing weak but geologically meaningful signals for decision–making.
{"title":"Compositional balance analysis for geochemical prospectivity mapping in Nenjiang–Heihe region, China","authors":"Lidong Zhang , Yue Liu , Kewei Zhang , Ziqiang Zha , Jianeng Wu , Wenjun Xuan , Huiyuan Zhang","doi":"10.1016/j.chemer.2025.126375","DOIUrl":"10.1016/j.chemer.2025.126375","url":null,"abstract":"<div><div>The Nenjiang–Heihe district, on the eastern margin of the Central Asian Orogenic Belt, hosts porphyry Cu<img>Mo and epithermal Au systems emplaced through multiple tectonomagmatic episodes. To extract process–diagnostic signals from regional geochemistry and convert them into practical exploration targets, we applied compositional balance analysis (CoBA) and the concentration–area (C–A) fractal model to stream–sediment geochemical data collected from the Nenjiang–Heihe region, China. Compositional hierarchical clustering and a suite of data– and knowledge–driven balances identify three complementary geochemical patterns: (i) Fe–oxide–rich intermediate–mafic domains that define broad NNE–NE corridors coincident with volcanic belts and major faults; (ii) porphyry/base–metal chalcophile behavior (e.g., <em>b01</em>, <em>b02</em>, <em>b03</em>, <em>b08, b7</em>, <em>b26</em>, and <em>b31</em>) that captures Cu anomalies along permeable structures; and (iii) felsic–HFSE/LILE fertility and volatile–rich epithermal overprints, highlighted by <em>b05, b06</em>, <em>b07, b15</em>, and <em>b1</em>6, localized over or adjacent to intermediate–felsic intrusions. C–A breakpoints provide objective thresholds that delineate statistically significant targets. Highest–priority prospects occur where <em>b01–b02</em> highs overlap at fault intersections and locally coincide with <em>b06</em> anomalies. The results demonstrate that CoBA, coupled with C–A segmentation, offers a low–cost, and interpretable framework for prospectivity mapping in forest–swamp terrain, mitigating closure effects and enhancing weak but geologically meaningful signals for decision–making.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126375"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145791277","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 : 2026-03-01Epub Date: 2025-12-15DOI: 10.1016/j.chemer.2025.126376
Luís Portela, Maria Rosário Azevedo, Jorge Medina, Beatriz Valle Aguado
The Lusinde fine-grained biotite granite is a small pluton intruded into the metamorphic basement of the Central Iberian Zone during the waning stages of the Variscan Orogeny. LA-ICP-MS zircon UPb ages constrain pluton emplacement to ca. 297–295 Ma. Mineralogical and geochemical data reveals that the intrusion corresponds to a strongly ferroan, peraluminous, reduced A2-type granite (∆FMQ = −3.4 to −1.7, zircon oxybarometry), characterised by a narrow compositional range (SiO2 = 67.7–68.8 wt%), elevated FeOT/FeOT + MgO (0.90–0.92) and 10,000 × Ga/Al (3.1–3.4) ratios, high REE, LILE and HFSE contents and strong depletions in Ba, Sr, Nb, P, Eu and Ti. Decoupling between “mantle-like” Nd and zircon Hf (εNdi = −0.40 to +0.58; TDM2 = 0.81–0.95 Ga; zircon εHfi = −0.41 to +3.01; TDM2-Zrn = 1.08–1.30 Ga) and more “crust-like” Sr (87Sr/86Sri = 0.7097–0.7100) isotopic signatures suggests derivation from small degrees of partial melting of old juvenile mafic/intermediate rocks interlayered in the lower crust, with minor input from more evolved crustal sources. The only studied ferrodioritic enclave shares the A2-type affinity of the host granite and seems to have derived from a mixed source (enriched subcontinental lithospheric mantle and juvenile mafic crust), before injection into the silicic magma chamber. We propose that the generation of the Lusinde A-type granite magma and enclosed enclave occurred in a deep hot zone located at the mantle-lower crust interface, at about 7–10 kb and 850–950 °C, in an extensional post-collisional setting.
{"title":"Petrogenesis of an A2-type intrusion associated with the late-post-collisional calc-alkaline Variscan granites from central-northern Portugal (Central Iberian Zone)","authors":"Luís Portela, Maria Rosário Azevedo, Jorge Medina, Beatriz Valle Aguado","doi":"10.1016/j.chemer.2025.126376","DOIUrl":"10.1016/j.chemer.2025.126376","url":null,"abstract":"<div><div>The Lusinde fine-grained biotite granite is a small pluton intruded into the metamorphic basement of the Central Iberian Zone during the waning stages of the Variscan Orogeny. LA-ICP-MS zircon U<img>Pb ages constrain pluton emplacement to ca. 297–295 Ma. Mineralogical and geochemical data reveals that the intrusion corresponds to a strongly ferroan, peraluminous, reduced A<sub>2</sub>-type granite (∆FMQ = −3.4 to −1.7, zircon oxybarometry), characterised by a narrow compositional range (SiO<sub>2</sub> = 67.7–68.8 wt%), elevated FeO<sub>T</sub>/FeO<sub>T</sub> + MgO (0.90–0.92) and 10,000 × Ga/Al (3.1–3.4) ratios, high REE, LILE and HFSE contents and strong depletions in Ba, Sr, Nb, P, Eu and Ti. Decoupling between “mantle-like” Nd and zircon Hf (εNd<sub>i</sub> = −0.40 to +0.58; T<sub>DM2</sub> = 0.81–0.95 Ga; zircon εHf<sub>i</sub> = −0.41 to +3.01; T<sub>DM2-Zrn</sub> = 1.08–1.30 Ga) and more “crust-like” Sr (<sup>87</sup>Sr/<sup>86</sup>Sr<sub>i</sub> = 0.7097–0.7100) isotopic signatures suggests derivation from small degrees of partial melting of old juvenile mafic/intermediate rocks interlayered in the lower crust, with minor input from more evolved crustal sources. The only studied ferrodioritic enclave shares the A<sub>2</sub>-type affinity of the host granite and seems to have derived from a mixed source (enriched subcontinental lithospheric mantle and juvenile mafic crust), before injection into the silicic magma chamber. We propose that the generation of the Lusinde A-type granite magma and enclosed enclave occurred in a deep hot zone located at the mantle-lower crust interface, at about 7–10 kb and 850–950 °C, in an extensional post-collisional setting.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126376"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840874","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 : 2026-03-01Epub Date: 2025-12-23DOI: 10.1016/j.chemer.2025.126382
Guilherme Ferreira da Silva , Adalene Moreira Silva , Catarina Labouré Bemfica Toledo , Guilherme dos Santos Teles , Farid Chemale Junior , Evandro Luiz Klein , Artur Areal Braga
The gold-bearing metaconglomerates of the Jacobina Group exhibit complex mineralogical and geochemical features that are significant for gold exploration in the northern São Francisco Craton. A comprehensive analysis of pyrite chemistry patterns within the Jacobina Group was carried out using multivariate mineral chemistry techniques and geological constraints to elucidate their significance for gold exploration. Distinct pyrite types, distinguished by morphology, texture, and stratigraphic position, were identified through Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) analysis. The results reveal a clear positive correlation between trace elements within detrital and epigenetic pyrite populations, providing insights into their origin and evolution. Notably, the presence of accessory minerals such as sphalerite, chalcopyrite, and pyrrhotite serve as key indicators of late-stage hydrothermal alteration and potential gold mineralization. The dimensionality reduction techniques, including Uniform Manifold Approximation and Projection (UMAP), indicate a spatial distribution of pyrite populations across different stratigraphic units. Moreover, agglomerative clustering analysis indicates that both geological context and mineral chemistry are important for delineating exploration targets. Our findings demonstrate that integrating multivariate mineral chemistry analysis with geological constraints can enhance gold exploration strategies. This study provides valuable insights into the complex relationship between pyrite chemistry, geological processes, and gold mineralization within the Jacobina Group, advancing our understanding of auriferous metaconglomerate deposits.
{"title":"Pyrite chemistry patterns in gold-bearing metaconglomerates of the Jacobina Group, São Francisco Craton, Northeastern Brazil: Multivariate mineral chemistry insights and geological implications for gold exploration","authors":"Guilherme Ferreira da Silva , Adalene Moreira Silva , Catarina Labouré Bemfica Toledo , Guilherme dos Santos Teles , Farid Chemale Junior , Evandro Luiz Klein , Artur Areal Braga","doi":"10.1016/j.chemer.2025.126382","DOIUrl":"10.1016/j.chemer.2025.126382","url":null,"abstract":"<div><div>The gold-bearing metaconglomerates of the Jacobina Group exhibit complex mineralogical and geochemical features that are significant for gold exploration in the northern São Francisco Craton. A comprehensive analysis of pyrite chemistry patterns within the Jacobina Group was carried out using multivariate mineral chemistry techniques and geological constraints to elucidate their significance for gold exploration. Distinct pyrite types, distinguished by morphology, texture, and stratigraphic position, were identified through Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) analysis. The results reveal a clear positive correlation between trace elements within detrital and epigenetic pyrite populations, providing insights into their origin and evolution. Notably, the presence of accessory minerals such as sphalerite, chalcopyrite, and pyrrhotite serve as key indicators of late-stage hydrothermal alteration and potential gold mineralization. The dimensionality reduction techniques, including Uniform Manifold Approximation and Projection (UMAP), indicate a spatial distribution of pyrite populations across different stratigraphic units. Moreover, agglomerative clustering analysis indicates that both geological context and mineral chemistry are important for delineating exploration targets. Our findings demonstrate that integrating multivariate mineral chemistry analysis with geological constraints can enhance gold exploration strategies. This study provides valuable insights into the complex relationship between pyrite chemistry, geological processes, and gold mineralization within the Jacobina Group, advancing our understanding of auriferous metaconglomerate deposits.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126382"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145884252","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 : 2026-03-01Epub 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":"2026-03-01","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}
This paper presents first X-ray diffraction (XRD), scanning electron microscopy (SEM), bulk-rock geochemical analyses, isotopic (O-H-C) and differential thermal analysis-thermogravimetric (DTA-TG), physical and thermal tests of Sinandede kaolin deposit (SKD) formed by hydrothermal alteration of Lower Miocene dacitic-rhyodacitic tuffs. The mineralogical analyses revealed that the SKD comprises mainly kaolinite with dickite, illite, smectite-chlorite, Ca-montmorillonite, alunite, halloysite, feldspar, quartz, opal CT, hematite and anhydrite. Geochemically, Al2O3, H2O, Sr, S and Zr contents were markedly enriched, while Rb, Cs, U, Y and Ba were depleted compared with the parent rocks. The chondrite-normalized rare earth element (REE) patterns show identical trends characterized by light rare earth element (LREE) enrichment (La/Sm)CN = 1.96–10.96 and (La/Yb)CN = 20.51–37.08), heavy rare earth element (HREE) depletion (Gd/Yb)CN = 1.37–5.62), slightly Eu anomaly (Eu/Eu* <1), and positive Gd anomaly (Gd/Gd* = av.1.06). The δ18O values of the samples vary between +0.48 ‰ and, −4.96 ‰; δD values vary between −81.05 ‰ and − 89.97 ‰. On the other hand; δ13C (VPDB) values ranging between −25.70 ‰ and − 28.83 ‰ (VPDB) in kaolin samples are compatible with the δ13C (VPDB) values of hydrothermal waters mixed with meteoric water fed by C3 plants, indicating the contribution of meteoric water in SDK. Small positive Ce and Gd anomalies, which indicates the presence of a hypogene-supergene mix, further support the contribution of meteoric water. The SDK was formed as a result of post-magmatic hydrothermal activities at temperatures above 100 °C and influenced by both hypojene and supergene conditions. Technological tests suggest that the SDK can be used for wall and floor tiles in ceramic industry.
{"title":"Mineralogy, geochemistry and genesis of newly discovered Sinandede kaolin deposit (Balıkesir, NW Türkiye): Potential applications","authors":"Fazlı Çoban , Şenel Özdamar , Oral Sarıkaya , Gökhan Büyükkahraman , Zeynep Döner , Naşide Merve Sütçü","doi":"10.1016/j.chemer.2025.126364","DOIUrl":"10.1016/j.chemer.2025.126364","url":null,"abstract":"<div><div>This paper presents first X-ray diffraction (XRD), scanning electron microscopy (SEM), bulk-rock geochemical analyses, isotopic (O-H-C) and differential thermal analysis-thermogravimetric (DTA-TG), physical and thermal tests of Sinandede kaolin deposit (SKD) formed by hydrothermal alteration of Lower Miocene dacitic-rhyodacitic tuffs. The mineralogical analyses revealed that the SKD comprises mainly kaolinite with dickite, illite, smectite-chlorite, Ca-montmorillonite, alunite, halloysite, feldspar, quartz, opal CT, hematite and anhydrite. Geochemically, Al<sub>2</sub>O<sub>3</sub>, H<sub>2</sub>O, Sr, S and Zr contents were markedly enriched, while Rb, Cs, U, Y and Ba were depleted compared with the parent rocks. The chondrite-normalized rare earth element (REE) patterns show identical trends characterized by light rare earth element (LREE) enrichment (La/Sm)<sub>CN</sub> = 1.96–10.96 and (La/Yb)<sub>CN</sub> = 20.51–37.08), heavy rare earth element (HREE) depletion (Gd/Yb)<sub>CN</sub> = 1.37–5.62), slightly Eu anomaly (Eu/Eu* <1), and positive Gd anomaly (Gd/Gd* = av.1.06). The δ<sup>18</sup>O values of the samples vary between +0.48 ‰ and, −4.96 ‰; δD values vary between −81.05 ‰ and − 89.97 ‰. On the other hand; δ<sup>13</sup>C (VPDB) values ranging between −25.70 ‰ and − 28.83 ‰ (VPDB) in kaolin samples are compatible with the δ<sup>13</sup>C (VPDB) values of hydrothermal waters mixed with meteoric water fed by C3 plants, indicating the contribution of meteoric water in SDK. Small positive Ce and Gd anomalies, which indicates the presence of a hypogene-supergene mix, further support the contribution of meteoric water. The SDK was formed as a result of post-magmatic hydrothermal activities at temperatures above 100 °C and influenced by both hypojene and supergene conditions. Technological tests suggest that the SDK can be used for wall and floor tiles in ceramic industry.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126364"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658900","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 : 2026-03-01Epub Date: 2025-12-01DOI: 10.1016/j.chemer.2025.126365
Xuanchi Deng , Xiaofeng Li , Yiting Zhu , Heng Xu , Yong Yu
Li-Rb-Cs rare metal mineralization is closely linked to highly fractionated granites. However, the origin of Li-Rb-Cs rare metal mineralization during the shear-deformation remains unclear. The Gaoligong Shear Zone (GSZ) is situated along the eastern margin of Tibetan in southwestern China. It is a dextral strike-slip shear zone formed by the northward movement of the India Plate to relative to the Eurasia Plate during Oligocene-Miocene. Bulk mineral composition, together with EMPA and LA-ICP-MS data, reveal that Li-Rb-Cs-rich phlogopite occurs in Carboniferous metamorphic rocks of the GSZ. This phlogopite is enriched in F (4.29–5.06 wt%), Li (1281–1849 ppm), Rb (2550–3242 ppm), and Cs (386–1575 ppm), but depleted in Be (<1 ppm). In contrast, scapolite (marialite) intergrown with the Li-Rb-Cs-rich phlogopites is enriched in Be (31.31–91.34 ppm), and Ga (38.92–48.83 ppm), but poor in Li (1.86–18.71 ppm). Two phlogopite samples yield 40Ar39Ar plateau ages of 15.64 ± 0.36 Ma, and 14.44 ± 0.23 Ma, indicating Miocene formation. These ages coincide with major shearing and regional metamorphism in the Gaoligong area. This suggests the formation of Li-Rb-Cs-rich phlogopite may have been related to intense shearing and intracrustal melting. Magma-derived metasomatic hydrothermal fluids may have contributed to the formation of the Li-Rb-Cs-rich phlogopite and the Be-rich scapolite. The study suggests that the Li-Rb-Cs rare metal mineralization can form during the shear deformation and that F-rich phlogopite is a promising indicator for rare-metal exploration in the shear deformation zone.
{"title":"Shear-deformation related Li-Rb-Cs mineralization: The case study from mineral chemistry and 40Ar39Ar ages of phlogopite in the Gaoligong Shear Zone, eastern Tibetan","authors":"Xuanchi Deng , Xiaofeng Li , Yiting Zhu , Heng Xu , Yong Yu","doi":"10.1016/j.chemer.2025.126365","DOIUrl":"10.1016/j.chemer.2025.126365","url":null,"abstract":"<div><div>Li-Rb-Cs rare metal mineralization is closely linked to highly fractionated granites. However, the origin of Li-Rb-Cs rare metal mineralization during the shear-deformation remains unclear. The Gaoligong Shear Zone (GSZ) is situated along the eastern margin of Tibetan in southwestern China. It is a dextral strike-slip shear zone formed by the northward movement of the India Plate to relative to the Eurasia Plate during Oligocene-Miocene. Bulk mineral composition, together with EMPA and LA-ICP-MS data, reveal that Li-Rb-Cs-rich phlogopite occurs in Carboniferous metamorphic rocks of the GSZ. This phlogopite is enriched in F (4.29–5.06 wt%), Li (1281–1849 ppm), Rb (2550–3242 ppm), and Cs (386–1575 ppm), but depleted in Be (<1 ppm). In contrast, scapolite (marialite) intergrown with the Li-Rb-Cs-rich phlogopites is enriched in Be (31.31–91.34 ppm), and Ga (38.92–48.83 ppm), but poor in Li (1.86–18.71 ppm). Two phlogopite samples yield <sup>40</sup>Ar<img><sup>39</sup>Ar plateau ages of 15.64 ± 0.36 Ma, and 14.44 ± 0.23 Ma, indicating Miocene formation. These ages coincide with major shearing and regional metamorphism in the Gaoligong area. This suggests the formation of Li-Rb-Cs-rich phlogopite may have been related to intense shearing and intracrustal melting. Magma-derived metasomatic hydrothermal fluids may have contributed to the formation of the Li-Rb-Cs-rich phlogopite and the Be-rich scapolite. The study suggests that the Li-Rb-Cs rare metal mineralization can form during the shear deformation and that F-rich phlogopite is a promising indicator for rare-metal exploration in the shear deformation zone.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126365"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145658899","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 : 2026-03-01Epub Date: 2026-02-13DOI: 10.1016/j.chemer.2026.126394
Srinjoy Datta , Jiten Pattnaik , Amiya K. Samal , Rajesh K. Srivastava , Sayandeep Banerjee , Fanus Viljoen , Henriette Ueckermann
The lithospheric mantle beneath Archean cratons is compositionally heterogeneous, shaped by interactions between refractory peridotite and melts derived from subducted crustal materials, producing olivine-poor pyroxenitic domains. These heterogeneities can be effectively evaluated using olivine trace-element chemistry integrated with whole-rock geochemical constraints. We investigate olivine major- and trace-element compositions together with whole-rock geochemistry from the ca. 2.37–2.36 Ga, ca. 2.21 Ga, ca. 2.08 Ga, and ca. 1.89–1.88 Ga mafic dyke swarms from the Dharwar Craton. These swarms display negative NbTaTi anomalies, enrichment in large-ion lithophile elements, and LREE-enriched patterns, collectively indicating a metasomatized subcontinental lithospheric mantle (SCLM) source. Trace-element ratios suggest melt generation within a shallow, spinel-stability field. Although temporally distinct, the dyke swarms show overlapping mantle source characteristics. Olivine phenocrysts are moderately evolved (Fo 71–81) and display elevated Ni and lower Mn and Ca contents, with Mn/Zn (8.12–14.15), 100Mn/Fe (1.32–1.94), and 10,000Zn/Fe (10.77–18.44) ratios intermediate between peridotite- and pyroxenite-derived melts, indicating contributions from both lithologies. Together, olivine chemistry and whole-rock data support a hybrid mantle source comprising pyroxenitic domains within a peridotitic matrix. We interpret that subduction-related metasomatism prior to ca. 2.5 Ga introduced pyroxenitic components into the Dharwar lithospheric mantle, which were subsequently remobilized by Paleoproterozoic mantle plume activity, generating intermittent mafic magmatism over ∼550 Myr. This demonstrates that long-lived intraplate magmatism in Archean cratons can be sustained by selective melting of preserved fertile pyroxenitic domains within a stable lithosphere, without continuous mantle refertilization.
{"title":"Hybrid pyroxenitic–peridotitic lithospheric mantle beneath the Dharwar Craton recorded by ∼550 Myr of Paleoproterozoic mafic magmatism","authors":"Srinjoy Datta , Jiten Pattnaik , Amiya K. Samal , Rajesh K. Srivastava , Sayandeep Banerjee , Fanus Viljoen , Henriette Ueckermann","doi":"10.1016/j.chemer.2026.126394","DOIUrl":"10.1016/j.chemer.2026.126394","url":null,"abstract":"<div><div>The lithospheric mantle beneath Archean cratons is compositionally heterogeneous, shaped by interactions between refractory peridotite and melts derived from subducted crustal materials, producing olivine-poor pyroxenitic domains. These heterogeneities can be effectively evaluated using olivine trace-element chemistry integrated with whole-rock geochemical constraints. We investigate olivine major- and trace-element compositions together with whole-rock geochemistry from the ca. 2.37–2.36 Ga, ca. 2.21 Ga, ca. 2.08 Ga, and ca. 1.89–1.88 Ga mafic dyke swarms from the Dharwar Craton. These swarms display negative Nb<img>Ta<img>Ti anomalies, enrichment in large-ion lithophile elements, and LREE-enriched patterns, collectively indicating a metasomatized subcontinental lithospheric mantle (SCLM) source. Trace-element ratios suggest melt generation within a shallow, spinel-stability field. Although temporally distinct, the dyke swarms show overlapping mantle source characteristics. Olivine phenocrysts are moderately evolved (Fo 71–81) and display elevated Ni and lower Mn and Ca contents, with Mn/Zn (8.12–14.15), 100Mn/Fe (1.32–1.94), and 10,000Zn/Fe (10.77–18.44) ratios intermediate between peridotite- and pyroxenite-derived melts, indicating contributions from both lithologies. Together, olivine chemistry and whole-rock data support a hybrid mantle source comprising pyroxenitic domains within a peridotitic matrix. We interpret that subduction-related metasomatism prior to ca. 2.5 Ga introduced pyroxenitic components into the Dharwar lithospheric mantle, which were subsequently remobilized by Paleoproterozoic mantle plume activity, generating intermittent mafic magmatism over ∼550 Myr. This demonstrates that long-lived intraplate magmatism in Archean cratons can be sustained by selective melting of preserved fertile pyroxenitic domains within a stable lithosphere, without continuous mantle refertilization.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"86 1","pages":"Article 126394"},"PeriodicalIF":2.9,"publicationDate":"2026-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147395774","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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