Pub Date : 2026-02-26DOI: 10.1016/j.gca.2026.02.034
Yishen Zhang, Rajdeep Dasgupta
{"title":"The effects of sulfur on near-liquidus phase relations of highly reduced basaltic melts with implications for magmatism in Mercury","authors":"Yishen Zhang, Rajdeep Dasgupta","doi":"10.1016/j.gca.2026.02.034","DOIUrl":"https://doi.org/10.1016/j.gca.2026.02.034","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"19 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147334711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-02-24DOI: 10.1016/j.gca.2026.02.032
Peng Wu, Fang Liu, Lei Li, Zhengjie Zhao, Jiaojiao Wu, Wenke Wang, Yajun An, Xin Li, Paul Savage, Mingxing Ling, Zhaofeng Zhang
Cerium (Ce) is an incompatible and redox-sensitive element, and stable Ce isotopes are emerging geochemical proxies for tracing Earth’s surface redox evolution that is complementary to traditional elemental ratios (e.g., Ce/Ce*). However, the robust application of this proxy requires a fundamental understanding of its behavior during high-temperature processes, which remains poorly constrained. To address this issue, we present Ce isotope compositions for a well-characterized suite of volcanic rocks from Hekla, Iceland, which spans a compositional range from basalt to rhyolite that were considered to have formed via fractional crystallization and/or mixing of cogenetic melts. Twenty-three samples yield a relatively uniform δ142Ce ranging from −0.007‰ to 0.070‰, with an average of 0.032 ± 0.045‰ (2 S.D.). The average δ142Ce of each lithology is 0.031 ± 0.032‰ for basalt, 0.019 ± 0.035‰ for basaltic andesite, 0.040 ± 0.045‰ for andesite, 0.064 ± 0.011‰ for dacite, and 0.009 ± 0.027‰ for rhyolite, respectively. Although a subtle δ142Ce variations in the evolved rocks is observed, the total Ce isotope fractionation (Δ142Ce = ∼0.07‰) is barely beyond the current analytical uncertainty, implying that the Ce isotope fractionation during magmatic differentiation at Hekla is limited. This is supported by the strongly incompatible behavior of Ce and near-constant oxygen fugacity throughout the Hekla differentiation sequence, indicating that the crystallizing phases remove only negligible amounts of Ce from the melt and therefore that significant fractionation of Ce isotopes is unlikely. Furthermore, mantle melting degree or melting depth have no effect on the Ce isotopes. Our findings demonstrate that high-temperature igneous processes are unlikely to significantly overprint primary Ce isotope signatures. Consequently, Ce isotopes may provide a robust tracer for investigating deep sediment recycling.
{"title":"Stable cerium isotope fractionation during basalt-rhyolite magmatic differentiation","authors":"Peng Wu, Fang Liu, Lei Li, Zhengjie Zhao, Jiaojiao Wu, Wenke Wang, Yajun An, Xin Li, Paul Savage, Mingxing Ling, Zhaofeng Zhang","doi":"10.1016/j.gca.2026.02.032","DOIUrl":"https://doi.org/10.1016/j.gca.2026.02.032","url":null,"abstract":"Cerium (Ce) is an incompatible and redox-sensitive element, and stable Ce isotopes are emerging geochemical proxies for tracing Earth’s surface redox evolution that is complementary to traditional elemental ratios (e.g., Ce/Ce*). However, the robust application of this proxy requires a fundamental understanding of its behavior during high-temperature processes, which remains poorly constrained. To address this issue, we present Ce isotope compositions for a well-characterized suite of volcanic rocks from Hekla, Iceland, which spans a compositional range from basalt to rhyolite that were considered to have formed via fractional crystallization and/or mixing of cogenetic melts. Twenty-three samples yield a relatively uniform δ<ce:sup loc=\"post\">142</ce:sup>Ce ranging from −0.007‰ to 0.070‰, with an average of 0.032 ± 0.045‰ (2 S.D.). The average δ<ce:sup loc=\"post\">142</ce:sup>Ce of each lithology is 0.031 ± 0.032‰ for basalt, 0.019 ± 0.035‰ for basaltic andesite, 0.040 ± 0.045‰ for andesite, 0.064 ± 0.011‰ for dacite, and 0.009 ± 0.027‰ for rhyolite, respectively. Although a subtle δ<ce:sup loc=\"post\">142</ce:sup>Ce variations in the evolved rocks is observed, the total Ce isotope fractionation (Δ<ce:sup loc=\"post\">142</ce:sup>Ce = ∼0.07‰) is barely beyond the current analytical uncertainty, implying that the Ce isotope fractionation during magmatic differentiation at Hekla is limited. This is supported by the strongly incompatible behavior of Ce and near-constant oxygen fugacity throughout the Hekla differentiation sequence, indicating that the crystallizing phases remove only negligible amounts of Ce from the melt and therefore that significant fractionation of Ce isotopes is unlikely. Furthermore, mantle melting degree or melting depth have no effect on the Ce isotopes. Our findings demonstrate that high-temperature igneous processes are unlikely to significantly overprint primary Ce isotope signatures. Consequently, Ce isotopes may provide a robust tracer for investigating deep sediment recycling.","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"97 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-02-24DOI: 10.1016/j.gca.2026.02.033
Arka P. Chatterjee, Julien Allaz, Christian Huberb, Luiz F.G. Morales, Amanda Ostwald, Olivier Bachmanna
Martian meteorites, the only available samples of Martian lithologies, provide unique insights into martian magmatism. Olivines in these meteorites contain complex phosphorus (P) zoning, which shed insights into the behaviour of mafic magmas in the martian crust. These olivines crystallized in multiple stages in ascending magmas, and preserved compositional zoning, particularly in P, due to its low diffusivity. Although previous studies have documented P zoning in martian olivines and attributed its formation to rapid crystallization events in magma storage zones within the crust, the processes responsible for the undercooling and fast olivine growth remain unresolved. This study addresses the challenge of interpreting P zoning in martian olivines to better understand the conditions which affected their crystallization histories. Using high-resolution P X-ray maps and microprobe traverses, we show that P zoning in olivine megacrysts from shergottites (martian basalts) and chassignites (martian dunites) consistently records rapid crystallization events at high undercooling due to magma ascent through the martian crust. These zoning patterns, observed in cores, mantles, and rims of olivines from hypabyssal and intrusive samples, highlight different crystallisation conditions during staging, ascent and emplacement of magmas at varying crustal depths. P zoning in olivine-phyric shergottites, viewed in the light of previous thermobarometry results, record initial olivine nucleation in the lower crust, ascent to the mid-crust and final rapid crystallization in the shallow subsurface. Similarly, we inferred multiple cycles of magma ascent and storage in the martian crust from the P zoning in poikilitic and non-poikilitic regions of a poikilitic shergottite. We also provide evidence from P zoning in olivines to differentiate between magma storage relatively deep in the crust and shallow, hypabyssal emplacement. The nature of P zoning during the final stages of olivine crystallization can serve as in-situ evidence of the eruptive behaviour of shallow magma bodies. Further analyses of available meteorites and olivines from future sample return missions will be fundamental to build a holistic model of martian magma plumbing systems and its evolution through time
{"title":"Phosphorus Zoning in Olivines: A critical tool for tracking magma ascent and storage in the martian crust","authors":"Arka P. Chatterjee, Julien Allaz, Christian Huberb, Luiz F.G. Morales, Amanda Ostwald, Olivier Bachmanna","doi":"10.1016/j.gca.2026.02.033","DOIUrl":"https://doi.org/10.1016/j.gca.2026.02.033","url":null,"abstract":"Martian meteorites, the only available samples of Martian lithologies, provide unique insights into martian magmatism. Olivines in these meteorites contain complex phosphorus (P) zoning, which shed insights into the behaviour of mafic magmas in the martian crust. These olivines crystallized in multiple stages in ascending magmas, and preserved compositional zoning, particularly in P, due to its low diffusivity. Although previous studies have documented P zoning in martian olivines and attributed its formation to rapid crystallization events in magma storage zones within the crust, the processes responsible for the undercooling and fast olivine growth remain unresolved. This study addresses the challenge of interpreting P zoning in martian olivines to better understand the conditions which affected their crystallization histories. Using high-resolution P X-ray maps and microprobe traverses, we show that P zoning in olivine megacrysts from shergottites (martian basalts) and chassignites (martian dunites) consistently records rapid crystallization events at high undercooling due to magma ascent through the martian crust. These zoning patterns, observed in cores, mantles, and rims of olivines from hypabyssal and intrusive samples, highlight different crystallisation conditions during staging, ascent and emplacement of magmas at varying crustal depths. P zoning in olivine-phyric shergottites, viewed in the light of previous thermobarometry results, record initial olivine nucleation in the lower crust, ascent to the mid-crust and final rapid crystallization in the shallow subsurface. Similarly, we inferred multiple cycles of magma ascent and storage in the martian crust from the P zoning in poikilitic and non-poikilitic regions of a poikilitic shergottite. We also provide evidence from P zoning in olivines to differentiate between magma storage relatively deep in the crust and shallow, hypabyssal emplacement. The nature of P zoning during the final stages of olivine crystallization can serve as in-situ evidence of the eruptive behaviour of shallow magma bodies. Further analyses of available meteorites and olivines from future sample return missions will be fundamental to build a holistic model of martian magma plumbing systems and its evolution through time","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"10 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147279987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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 : 2026-02-21DOI: 10.1016/j.gca.2026.02.022
Barbara J. Lyon, Michael C. Rowe, Andrew Langendam, Kathleen A. Campbell, Diego M. Guido, Ayrton R. Hamilton, Ema E. Nersezova, Amanda Galar, Dominique A. Stallard
{"title":"Impact of diagenesis and acidic alteration on microbial fabrics and trace element distributions in fossilised siliceous hot spring deposits","authors":"Barbara J. Lyon, Michael C. Rowe, Andrew Langendam, Kathleen A. Campbell, Diego M. Guido, Ayrton R. Hamilton, Ema E. Nersezova, Amanda Galar, Dominique A. Stallard","doi":"10.1016/j.gca.2026.02.022","DOIUrl":"https://doi.org/10.1016/j.gca.2026.02.022","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"12 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2026-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146778163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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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