Pub Date : 2025-12-20DOI: 10.1016/j.epsl.2025.119717
Martin F. Miller
Refractory Ca-Al-rich inclusions (CAIs) in chondritic meteorites, the oldest known solids in the Solar System, are characterised by ‘mass-independently fractionated’ (MIF) oxygen isotopic compositions, with δ17O variations approximately equal to those of δ18O. The apparent absence of this characteristic from nearly all other oxygen-bearing constituents of early-formed asteroids, together with the brief formation interval for CAIs, indicates that the process responsible was localised and of short duration in the context of Solar System evolution. From reassessing a recent study of main group pallasite meteorites, it is argued that the oxygen isotopic compositions of their coexisting olivine and chromite potentially provide evidence that a minor component of solids containing MIF oxygen was accreted during formation of the parent planetesimal, or its precursors, shortly after CAI formation. Modelling indicates that a contribution of ∼1.6 ± 0.3 % conforming to δ17O ∼ δ18O – γ, for γ assigned as –1.21 or –3.45 (from literature data) is consistent with the reported measurements. If true, and the pallasite olivine and chromite derived from the mantle of an impacted planetesimal and the IIIAB parent body respectively, as proposed elsewhere, then a ‘residual’ MIF oxygen component must have been present in solids accreted by those early planetesimals, probably in the same feeder zone. A testable prediction is that such residual MIF oxygen may similarly have been accreted in more early-formed planetesimals than recognised hitherto. If so, its presence should be detectable from comparable measurements of coexisting oxygen-bearing minerals in the associated meteorites, subject to the δ18O range being of sufficient magnitude.
{"title":"Residual mass-independently fractionated oxygen present in solids accreted during planetesimal formation in the early Solar System: potential evidence from main group pallasites","authors":"Martin F. Miller","doi":"10.1016/j.epsl.2025.119717","DOIUrl":"10.1016/j.epsl.2025.119717","url":null,"abstract":"<div><div>Refractory Ca-Al-rich inclusions (CAIs) in chondritic meteorites, the oldest known solids in the Solar System, are characterised by ‘mass-independently fractionated’ (MIF) oxygen isotopic compositions, with δ<sup>17</sup>O variations approximately equal to those of δ<sup>18</sup>O. The apparent absence of this characteristic from nearly all other oxygen-bearing constituents of early-formed asteroids, together with the brief formation interval for CAIs, indicates that the process responsible was localised and of short duration in the context of Solar System evolution. From reassessing a recent study of main group pallasite meteorites, it is argued that the oxygen isotopic compositions of their coexisting olivine and chromite potentially provide evidence that a minor component of solids containing MIF oxygen was accreted during formation of the parent planetesimal, or its precursors, shortly after CAI formation. Modelling indicates that a contribution of ∼1.6 ± 0.3 % conforming to δ<sup>17</sup>O ∼ δ<sup>18</sup>O – γ, for γ assigned as –1.21 or –3.45 (from literature data) is consistent with the reported measurements. If true, and the pallasite olivine and chromite derived from the mantle of an impacted planetesimal and the IIIAB parent body respectively, as proposed elsewhere, then a ‘residual’ MIF oxygen component must have been present in solids accreted by those early planetesimals, probably in the same feeder zone. A testable prediction is that such residual MIF oxygen may similarly have been accreted in more early-formed planetesimals than recognised hitherto. If so, its presence should be detectable from comparable measurements of coexisting oxygen-bearing minerals in the associated meteorites, subject to the δ<sup>18</sup>O range being of sufficient magnitude.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"676 ","pages":"Article 119717"},"PeriodicalIF":4.8,"publicationDate":"2025-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789865","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 : 2025-12-18DOI: 10.1016/j.epsl.2025.119792
Yiran Wang , Aron J. Meltzner , Michael E. Oskin , Jennifer Quye-Sawyer , Lin Thu Aung , Noelynna Ramos
The accurate dating of Quaternary coral terraces has long been challenging due to recrystallization of aragonite corals. Here, we present an approach to infer terrace age based on (1) the linkage between sea-level drop and river knickpoint formation and (2) the history of sea-level rise and fall recorded by the elevation–age relationship of knickpoints. Our study in northwestern Luzon, Philippines, combines field surveys, sedimentological analysis, and topographic and river-profile analysis, through which we map the coral reef terrace extent and correlate terrace outer edges to the initiation location of major knickpoints in adjacent river profiles. Through χ transformation, the knickpoint retreat distance is equivalent to knickpoint/terrace age, and therefore the elevation–retreat distance relationship of the knickpoints can be used to determine the age of the correlated terrace. Using this method, we deduce that the lower coral reef terrace sequences (T1-T4) correspond to Marine Isotope Stages (MIS) 5a, 5c, 5e, and 7a, respectively. Furthermore, we suggest the coastal area is gently tilting seaward with an average uplift rate of ∼1 m/kyr, and the highest terrace surface (420–440 m) may be more than 400 kyr old. We propose that this technique offers a promising solution for dating coral reef terraces in uplifting coastal regions where absolute age-dating techniques fail due to diagenetic alteration, and for terraces associated with bedrock rivers that developed before the penultimate glacial period.
{"title":"Coral reef terrace age deduced from retreating knickpoints","authors":"Yiran Wang , Aron J. Meltzner , Michael E. Oskin , Jennifer Quye-Sawyer , Lin Thu Aung , Noelynna Ramos","doi":"10.1016/j.epsl.2025.119792","DOIUrl":"10.1016/j.epsl.2025.119792","url":null,"abstract":"<div><div>The accurate dating of Quaternary coral terraces has long been challenging due to recrystallization of aragonite corals. Here, we present an approach to infer terrace age based on (1) the linkage between sea-level drop and river knickpoint formation and (2) the history of sea-level rise and fall recorded by the elevation–age relationship of knickpoints. Our study in northwestern Luzon, Philippines, combines field surveys, sedimentological analysis, and topographic and river-profile analysis, through which we map the coral reef terrace extent and correlate terrace outer edges to the initiation location of major knickpoints in adjacent river profiles. Through χ transformation, the knickpoint retreat distance is equivalent to knickpoint/terrace age, and therefore the elevation–retreat distance relationship of the knickpoints can be used to determine the age of the correlated terrace. Using this method, we deduce that the lower coral reef terrace sequences (T1-T4) correspond to Marine Isotope Stages (MIS) 5a, 5c, 5e, and 7a, respectively. Furthermore, we suggest the coastal area is gently tilting seaward with an average uplift rate of ∼1 m/kyr, and the highest terrace surface (420–440 m) may be more than 400 kyr old. We propose that this technique offers a promising solution for dating coral reef terraces in uplifting coastal regions where absolute age-dating techniques fail due to diagenetic alteration, and for terraces associated with bedrock rivers that developed before the penultimate glacial period.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"676 ","pages":"Article 119792"},"PeriodicalIF":4.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145766090","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 : 2025-12-18DOI: 10.1016/j.epsl.2025.119787
Mariana A. Yilales , Nick MW Roberts , Collen-Issia Uahengo , Nathan Rochelle-Bates , Fred Bowyer , Rachel Wood
The middle-late Ediacaran (∼580 to >533 Ma) saw the emergence and early diversification of animals (metazoans), but the tempo of this event is obscured by a paucity of datable ash beds and uncertainties in global stratigraphic correlation through specific intervals. The Nama Group, Namibia, is of fundamental importance as this succession preserves a diverse terminal Ediacaran fossil assemblage that includes the first appearance of metazoan biomineralization, a key evolutionary innovation. The precise age of the lowermost Nama Group is unknown, however, with best estimates based on global chemostratigraphic correlation and inferred depositional rates suggesting that the onset of deposition was between ca. 555 and 551 Ma. Here we use uranium-lead (U-Pb) radioisotopic dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), to date early marine pseudomorphed calcite cements from the lower Nama Group. The analyses yield an absolute age of 549.3 ± 9.8 Ma and constitute the first independent time constraint for the lowermost Nama Group. The result is consistent with current chemostratigraphic age models and validates the use of in-situ U-Pb dating of early marine carbonate cements to constrain depositional ages.
{"title":"In-situ U-Pb dating of early marine carbonate cements constrains the age of the late Ediacaran lower Nama Group, Namibia","authors":"Mariana A. Yilales , Nick MW Roberts , Collen-Issia Uahengo , Nathan Rochelle-Bates , Fred Bowyer , Rachel Wood","doi":"10.1016/j.epsl.2025.119787","DOIUrl":"10.1016/j.epsl.2025.119787","url":null,"abstract":"<div><div>The middle-late Ediacaran (∼580 to >533 Ma) saw the emergence and early diversification of animals (metazoans), but the tempo of this event is obscured by a paucity of datable ash beds and uncertainties in global stratigraphic correlation through specific intervals. The Nama Group, Namibia, is of fundamental importance as this succession preserves a diverse terminal Ediacaran fossil assemblage that includes the first appearance of metazoan biomineralization, a key evolutionary innovation. The precise age of the lowermost Nama Group is unknown, however, with best estimates based on global chemostratigraphic correlation and inferred depositional rates suggesting that the onset of deposition was between ca. 555 and 551 Ma. Here we use uranium-lead (U-Pb) radioisotopic dating by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), to date early marine pseudomorphed calcite cements from the lower Nama Group. The analyses yield an absolute age of 549.3 ± 9.8 Ma and constitute the first independent time constraint for the lowermost Nama Group. The result is consistent with current chemostratigraphic age models and validates the use of <em>in-situ</em> U-Pb dating of early marine carbonate cements to constrain depositional ages.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"676 ","pages":"Article 119787"},"PeriodicalIF":4.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789356","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 : 2025-12-18DOI: 10.1016/j.epsl.2025.119788
Sara Campderrós , Leopoldo D. Pena , Ester Garcia-Solsona , Eduardo Paredes-Paredes , Albert Català , Jaime Frigola , Negar Haghipour , Isabel Cacho
The Atlantic Iberian margin is a dynamic region where oceanographic processes interact with continental sediment, influencing transport and deposition. To identify sediment sources and dominant transport dynamics we combine 87Sr/86Sr and ƐNd measurements on terrigenous sediments and 14C dating of planktonic foraminifera from core-tops along the margin. We present a new dataset of Sr-Nd isotope data from the Iberian Peninsula to characterize the isotopic composition of main river basins, considered potential sediment sources alongside African dust. By solving a ternary isotope mixing system, combined with a new statistical method to account for endmember isotopic distributions, we quantify the relative contribution of source areas to our samples. Our results reveal: 1) the margin is characterized by three isotopically distinct regions, 2) African dust is an important component of the terrigenous sediment (∼60 %), 3) regional differences in isotopic values reflect the influence of major river discharges: Guadalquivir in the south, Tagus in the centre, and Douro in the north, and 4) sediment transport follows a net northward direction along-slope. This sediment transport is attributed to the northward-flowing Mediterranean Outflow Water (MOW), which entrains and redistributes sediments along-slope. This is further supported by foraminifera 14C results, showing older radiocarbon ages along the MOW path, indicating sediment erosion. In contrast, younger radiocarbon ages are consistently found below MOW depths. The combined 87Sr/86Sr, ƐNd and 14C data suggest that MOW flow reduces sediment deposition along its path, transporting sediments northward, where it predominantly settles below the interface between MOW and the underlying North East Atlantic Deep Water.
{"title":"Sediment provenance and transport pathways along the Atlantic Iberian Margin","authors":"Sara Campderrós , Leopoldo D. Pena , Ester Garcia-Solsona , Eduardo Paredes-Paredes , Albert Català , Jaime Frigola , Negar Haghipour , Isabel Cacho","doi":"10.1016/j.epsl.2025.119788","DOIUrl":"10.1016/j.epsl.2025.119788","url":null,"abstract":"<div><div>The Atlantic Iberian margin is a dynamic region where oceanographic processes interact with continental sediment, influencing transport and deposition. To identify sediment sources and dominant transport dynamics we combine <sup>87</sup>Sr/<sup>86</sup>Sr and Ɛ<sub>Nd</sub> measurements on terrigenous sediments and <sup>14</sup>C dating of planktonic foraminifera from core-tops along the margin. We present a new dataset of Sr-Nd isotope data from the Iberian Peninsula to characterize the isotopic composition of main river basins, considered potential sediment sources alongside African dust. By solving a ternary isotope mixing system, combined with a new statistical method to account for endmember isotopic distributions, we quantify the relative contribution of source areas to our samples. Our results reveal: 1) the margin is characterized by three isotopically distinct regions, 2) African dust is an important component of the terrigenous sediment (∼60 %), 3) regional differences in isotopic values reflect the influence of major river discharges: Guadalquivir in the south, Tagus in the centre, and Douro in the north, and 4) sediment transport follows a net northward direction along-slope. This sediment transport is attributed to the northward-flowing Mediterranean Outflow Water (MOW), which entrains and redistributes sediments along-slope. This is further supported by foraminifera <sup>14</sup>C results, showing older radiocarbon ages along the MOW path, indicating sediment erosion. In contrast, younger radiocarbon ages are consistently found below MOW depths. The combined <sup>87</sup>Sr/<sup>86</sup>Sr, Ɛ<sub>Nd</sub> and <sup>14</sup>C data suggest that MOW flow reduces sediment deposition along its path, transporting sediments northward, where it predominantly settles below the interface between MOW and the underlying North East Atlantic Deep Water.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"676 ","pages":"Article 119788"},"PeriodicalIF":4.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789866","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 : 2025-12-18DOI: 10.1016/j.epsl.2025.119784
Neil C. Sturchio , Hao Yan , Alian Wang , W. Andrew Jackson , Huiming Bao , Chuck Y.C. Yan , Linnea J. Heraty , Yu Wei , Quincy H.K. Qu , Kevin S. Olsen
Some oxidized compounds in Martian soils may form through heterogeneous electrochemistry (HEC) stimulated by electrostatic discharge (ESD) during dust storms and dust devils. To test this hypothesis, we conducted medium-strength ESD experiments in a Mars simulation chamber and analyzed the Cl, O, and C isotopic compositions of the resulting chloride, (per)chlorate, and carbonate products. These ESD products exhibit substantial mass-dependent depletions in heavy isotopes relative to the reactants: ε37Cl from -11.3 ‰ to +2.0 ‰, ε18O from -34.5 ‰ to -12.9 ‰, and ε13C around -11.4 ‰. These results, when compared with isotopic measurements from recent Mars missions (ESA’s ExoMars Trace Gas Orbiter and the Sample Analysis at Mars (SAM) instrument package aboard NASA’s Curiosity rover) and Martian meteorites, indicate that HEC induced by Martian dust activities can account for a substantial portion of the (per)chlorates and carbonates identified at the surface of Mars and the HCl in its atmosphere.
{"title":"Isotope effects (Cl, O, C) of heterogeneous electrochemistry induced by Martian dust activities","authors":"Neil C. Sturchio , Hao Yan , Alian Wang , W. Andrew Jackson , Huiming Bao , Chuck Y.C. Yan , Linnea J. Heraty , Yu Wei , Quincy H.K. Qu , Kevin S. Olsen","doi":"10.1016/j.epsl.2025.119784","DOIUrl":"10.1016/j.epsl.2025.119784","url":null,"abstract":"<div><div>Some oxidized compounds in Martian soils may form through heterogeneous electrochemistry (HEC) stimulated by electrostatic discharge (ESD) during dust storms and dust devils. To test this hypothesis, we conducted medium-strength ESD experiments in a Mars simulation chamber and analyzed the Cl, O, and C isotopic compositions of the resulting chloride, (per)chlorate, and carbonate products. These ESD products exhibit substantial mass-dependent depletions in heavy isotopes relative to the reactants: ε<sup>37</sup>Cl from -11.3 ‰ to +2.0 ‰, ε<sup>18</sup>O from -34.5 ‰ to -12.9 ‰, and ε<sup>13</sup>C around -11.4 ‰. These results, when compared with isotopic measurements from recent Mars missions (ESA’s ExoMars Trace Gas Orbiter and the Sample Analysis at Mars (SAM) instrument package aboard NASA’s Curiosity rover) and Martian meteorites, indicate that HEC induced by Martian dust activities can account for a substantial portion of the (per)chlorates and carbonates identified at the surface of Mars and the HCl in its atmosphere.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"676 ","pages":"Article 119784"},"PeriodicalIF":4.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145766091","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 : 2025-12-18DOI: 10.1016/j.epsl.2025.119782
Abate A. Melaku , Gemechu B. Teferi , Takele Mihretie , Snorri Gudbrandsson , Yared Sinetebeb , Peter H. Barry , Tobias P. Fischer , Finlay M. Stuart , Ugur Balci , Sæmundur A. Halldórsson , Chris J. Ballentine , Darren J. Hillegonds , Emma L. Chambers , Derek Keir , Richard Bates , William Hutchison
Rift volcanoes are sites of intense volatile emissions. However, major uncertainties remain about the magnitude of rift volatile fluxes, particularly for greenhouse gases (e.g. CO2) and whether along-rift variations in degassing relate to changing mantle sources and/or rifting processes (i.e. melt production and lithospheric thinning). Here, we investigate CO2 flux and gas isotopes in Ethiopia; a mature, plume-influenced continental rift. We focus on one of the largest caldera volcanoes, Bora-Baricha-Tulu Moye (BBTM), which is situated in a region of high mantle melt production in the Central Main Ethiopian rift (∼500 km south-west the putative plume head). BBTM gases are characterized by plume-like 3He/4He values up to 17 Ra (the highest ever observed in Ethiopian Rift fumaroles) and we calculate total magmatic CO2 flux of 757–901 t d-1 (making BBTM the largest volcanic CO2 emitter in the Ethiopian Rift). Using our CO2 flux measurements, we estimate total CO2 emissions from Ethiopia’s volcanic systems to be 2500–9200 kt yr-1 and reveal important along-rift variation in CO2 flux. High CO2 flux sectors are found in Central Afar, as well as the Northern and Central Main Ethiopian Rift. These sectors are all regions of high partial melt content (evidenced by low seismic velocity in the underlying mantle) and also show the greatest 3He/4He values (>14 Ra). Cooccurrence of high mantle melt production, elevated CO2 emissions and high 3He/4He demonstrates that in mature continental rifts carbon emissions and plume volatile contributions are particularly elevated in regions of greatest lithospheric thinning and mantle melting.
裂谷火山是释放大量挥发性物质的地方。然而，裂谷挥发性通量的大小，特别是温室气体（如二氧化碳）的大小，以及沿裂谷脱气的变化是否与变化的地幔源和/或裂谷过程（即熔体产生和岩石圈变薄）有关，仍然存在重大的不确定性。在这里，我们研究了埃塞俄比亚的二氧化碳通量和气体同位素；一个成熟的、受羽状物影响的大陆裂谷。我们的重点是最大的火山口火山之一，Bora-Baricha-Tulu Moye (BBTM)，它位于埃塞俄比亚中部裂谷的高地幔熔体生产区域（假定的羽头西南约500公里）。BBTM气体以羽状的3He/4He值为特征，高达17 Ra（埃塞俄比亚裂谷喷气孔中观测到的最高值），我们计算出总岩浆CO2通量为757-901 t d-1（使BBTM成为埃塞俄比亚裂谷中最大的火山CO2排放者）。利用我们的二氧化碳通量测量，我们估计埃塞俄比亚火山系统的二氧化碳总排放量为2500 - 9200kt年-1，并揭示了二氧化碳通量沿裂谷的重要变化。高二氧化碳通量区位于阿法尔中部以及埃塞俄比亚北部和中部裂谷。这些扇区都是部分熔体含量高的区域（下伏地幔地震速度低），也显示出最大的3He/4He值（>14 Ra）。高地幔熔体产量、高CO2排放和高3He/4He的同时发生表明，在成熟大陆裂谷中，岩石圈减薄和地幔融化最严重的地区，碳排放和地幔柱挥发贡献特别高。
{"title":"Changing volatile emissions and sources along the Ethiopian Rift","authors":"Abate A. Melaku , Gemechu B. Teferi , Takele Mihretie , Snorri Gudbrandsson , Yared Sinetebeb , Peter H. Barry , Tobias P. Fischer , Finlay M. Stuart , Ugur Balci , Sæmundur A. Halldórsson , Chris J. Ballentine , Darren J. Hillegonds , Emma L. Chambers , Derek Keir , Richard Bates , William Hutchison","doi":"10.1016/j.epsl.2025.119782","DOIUrl":"10.1016/j.epsl.2025.119782","url":null,"abstract":"<div><div>Rift volcanoes are sites of intense volatile emissions. However, major uncertainties remain about the magnitude of rift volatile fluxes, particularly for greenhouse gases (e.g. CO<sub>2</sub>) and whether along-rift variations in degassing relate to changing mantle sources and/or rifting processes (i.e. melt production and lithospheric thinning). Here, we investigate CO<sub>2</sub> flux and gas isotopes in Ethiopia; a mature, plume-influenced continental rift. We focus on one of the largest caldera volcanoes, Bora-Baricha-Tulu Moye (BBTM), which is situated in a region of high mantle melt production in the Central Main Ethiopian rift (∼500 km south-west the putative plume head). BBTM gases are characterized by plume-like <sup>3</sup>He/<sup>4</sup>He values up to 17 R<sub>a</sub> (the highest ever observed in Ethiopian Rift fumaroles) and we calculate total magmatic CO<sub>2</sub> flux of 757–901 t d<sup>-1</sup> (making BBTM the largest volcanic CO<sub>2</sub> emitter in the Ethiopian Rift). Using our CO<sub>2</sub> flux measurements, we estimate total CO<sub>2</sub> emissions from Ethiopia’s volcanic systems to be 2500–9200 kt yr<sup>-1</sup> and reveal important along-rift variation in CO<sub>2</sub> flux. High CO<sub>2</sub> flux sectors are found in Central Afar, as well as the Northern and Central Main Ethiopian Rift. These sectors are all regions of high partial melt content (evidenced by low seismic velocity in the underlying mantle) and also show the greatest <sup>3</sup>He/<sup>4</sup>He values (>14 R<sub>a</sub>). Cooccurrence of high mantle melt production, elevated CO<sub>2</sub> emissions and high <sup>3</sup>He/<sup>4</sup>He demonstrates that in mature continental rifts carbon emissions and plume volatile contributions are particularly elevated in regions of greatest lithospheric thinning and mantle melting.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"676 ","pages":"Article 119782"},"PeriodicalIF":4.8,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789867","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 : 2025-12-11DOI: 10.1016/j.epsl.2025.119767
Alexis Gauthier , Nadaya Cubas , Laetitia Le Pourhiet
Seamounts on oceanic plates are thought to affect the dynamics of accretionary prism at subduction zones, particularly the slip behavior. Geophysical studies show that pore fluid overpressure is associated with the nucleation of shallow slow slip events (SSEs). We use numerical simulations in which the subducting plate bends in response to tectonic, gravitational collapse and surface processes to capture structural complexities arising from the subduction of buried seamounts and compute the resulting stress state. We show that tectonic slices of undeformed sediments develop on both sides of the seamount and that a basin forms atop the seaward slice. These structures, recognizable in seismic data, represent the long-term tectonic signature of seamount subduction.
Gravitational collapse only occurs when a critical lengthscale, we quantified, of perturbed accretionary prism is reached. Seamounts that are small enough, instead get decapitated and do not perturb the prism over a sufficient lengthscale to trigger gravitational collapse.
Stress analysis reveals that the seaward side of the seamount is under an extensional regime, whereas its landward side is in a compressive state. We thus propose that sustained pore fluid overpressure can only develop on the landward side. This mechanism supports observations along Hikurangi, where a highly reflective zone, interpreted as a zone of pore fluid overpressure, has been imaged downdip of the Papaku seamount. Since this zone coincides with the largest slip magnitudes of shallow SSEs, we propose that the landward slice of undeformed sediments presents favorable conditions for SSEs nucleation.
{"title":"Tectonic structures and stress state associated with seamount subduction in accretionary prism. Implications for slip behavior","authors":"Alexis Gauthier , Nadaya Cubas , Laetitia Le Pourhiet","doi":"10.1016/j.epsl.2025.119767","DOIUrl":"10.1016/j.epsl.2025.119767","url":null,"abstract":"<div><div>Seamounts on oceanic plates are thought to affect the dynamics of accretionary prism at subduction zones, particularly the slip behavior. Geophysical studies show that pore fluid overpressure is associated with the nucleation of shallow slow slip events (SSEs). We use numerical simulations in which the subducting plate bends in response to tectonic, gravitational collapse and surface processes to capture structural complexities arising from the subduction of buried seamounts and compute the resulting stress state. We show that tectonic slices of undeformed sediments develop on both sides of the seamount and that a basin forms atop the seaward slice. These structures, recognizable in seismic data, represent the long-term tectonic signature of seamount subduction.</div><div>Gravitational collapse only occurs when a critical lengthscale, we quantified, of perturbed accretionary prism is reached. Seamounts that are small enough, instead get decapitated and do not perturb the prism over a sufficient lengthscale to trigger gravitational collapse.</div><div>Stress analysis reveals that the seaward side of the seamount is under an extensional regime, whereas its landward side is in a compressive state. We thus propose that sustained pore fluid overpressure can only develop on the landward side. This mechanism supports observations along Hikurangi, where a highly reflective zone, interpreted as a zone of pore fluid overpressure, has been imaged downdip of the Papaku seamount. Since this zone coincides with the largest slip magnitudes of shallow SSEs, we propose that the landward slice of undeformed sediments presents favorable conditions for SSEs nucleation.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"675 ","pages":"Article 119767"},"PeriodicalIF":4.8,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734591","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 : 2025-12-11DOI: 10.1016/j.epsl.2025.119779
Eirini M. Poulaki , Cailey B. Condit , Margaret L. Odlum , Jason N. Ott , Megan E. Ferrell
The subduction plate interface accommodates deformation between the downgoing and overriding plates and features a range of mechanical and chemical processes that influence the strength and slip behavior of this zone. Apatite, a calcium phosphate accessory mineral, records these subduction processes including metamorphism, metasomatism, and deformation. It can deform, recrystallize, and archive chemical processes through its trace elements across the pressure and temperatures conditions that span the depths at the bottom of the subduction seismogenic zone. We leverage these apatite characteristics in a metabasite within an exhumed subduction complex on Andros Island, Greece to demonstrate that apatite grains show multiple deformation mechanisms and inform on fluid’s composition and role in deformation processes. Apatite deformation mechanisms are dependent on the surrounding mineral phases, with grains within the chlorite matrix exhibiting evidence of dissolution-precipitation while grains in contact with strong mineral phases (e.g., clinozoisite, albite) deform by dislocation-accommodated deformation. Dislocations formed by prism 〈c〉 slip in apatite act as pathways for fluid mobile elements during deformation while dislocations formed by basal 〈a〉 slip did not facilitate trace element diffusivity, likely due to a crystallographic control. We also show that apatite is a powerful geochemical archive recording infiltration of aqueous sedimentary fluids with small amounts of CO2 during metasomatism. We highlight the utility of in-situ apatite geochemistry in polymetamorphic and polydeformed rocks. We show that even at the grain scale, lattice impurities will control the geochemical signatures.
俯冲板块界面容纳了下行板块和上覆板块之间的变形，并具有一系列影响该带强度和滑移行为的机械和化学过程。磷灰石是一种磷酸钙辅助矿物，记录了这些俯冲过程，包括变质作用、交代作用和变形作用。它可以变形、再结晶，并通过其微量元素在压力和温度条件下记录化学过程，这些条件跨越了俯冲发震带底部的深度。我们利用这些磷灰石特征在希腊安德罗斯岛的一个潜没杂岩中发现的变质岩中，证明磷灰石颗粒具有多种变形机制，并为流体成分和变形过程中的作用提供了信息。磷灰石的变形机制取决于周围的矿物相，绿泥石基质中的颗粒表现出溶解沉淀的证据，而与强矿物相（如斜沸石、钠长石）接触的颗粒则通过位错调节变形而变形。磷灰石中棱柱状< c >滑移形成的位错是变形过程中流体流动元素的通道，而基底< a >滑移形成的位错可能受晶体学控制，不能促进微量元素的扩散。我们还表明，磷灰石是一个强大的地球化学档案，记录了在交代过程中含有少量CO2的含水沉积流体的渗透。我们强调了原位磷灰石地球化学在多变质和多变形岩石中的应用。我们发现，即使在晶粒尺度上，晶格杂质也会控制地球化学特征。
{"title":"Apatite records mechanical and chemical processes over the lifetime of a subduction interface, Andros Island, Greece","authors":"Eirini M. Poulaki , Cailey B. Condit , Margaret L. Odlum , Jason N. Ott , Megan E. Ferrell","doi":"10.1016/j.epsl.2025.119779","DOIUrl":"10.1016/j.epsl.2025.119779","url":null,"abstract":"<div><div>The subduction plate interface accommodates deformation between the downgoing and overriding plates and features a range of mechanical and chemical processes that influence the strength and slip behavior of this zone. Apatite, a calcium phosphate accessory mineral, records these subduction processes including metamorphism, metasomatism, and deformation. It can deform, recrystallize, and archive chemical processes through its trace elements across the pressure and temperatures conditions that span the depths at the bottom of the subduction seismogenic zone. We leverage these apatite characteristics in a metabasite within an exhumed subduction complex on Andros Island, Greece to demonstrate that apatite grains show multiple deformation mechanisms and inform on fluid’s composition and role in deformation processes. Apatite deformation mechanisms are dependent on the surrounding mineral phases, with grains within the chlorite matrix exhibiting evidence of dissolution-precipitation while grains in contact with strong mineral phases (e.g., clinozoisite, albite) deform by dislocation-accommodated deformation. Dislocations formed by prism 〈c〉 slip in apatite act as pathways for fluid mobile elements during deformation while dislocations formed by basal 〈a〉 slip did not facilitate trace element diffusivity, likely due to a crystallographic control. We also show that apatite is a powerful geochemical archive recording infiltration of aqueous sedimentary fluids with small amounts of CO<sub>2</sub> during metasomatism. We highlight the utility of in-situ apatite geochemistry in polymetamorphic and polydeformed rocks. We show that even at the grain scale, lattice impurities will control the geochemical signatures.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"675 ","pages":"Article 119779"},"PeriodicalIF":4.8,"publicationDate":"2025-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734590","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}
Marius Hills, located in the central Oceanus Procellarum on the nearside of the Moon, is a significant volcanic complex, characterized by hundreds of domes and cones. Understanding its subsurface density structure is essential for enhancing our knowledge of lunar volcanic activity and its evolutionary history, yet it remains controversial. To investigate the density structure underneath Marius Hills, we developed a gravity inversion method based on the L1 norm and total variation regularization in spherical coordinates. We validated the method through a synthetic model test. We then applied it to the inversion of gravity data derived from the GRAIL mission in Marius Hills. Our results reveal two distinct high-density anomalies in the northern and southern segments of Marius Hills. The northern anomaly is located at 14–29 km depth directly beneath the shield volcano of Marius Hills, with a density contrast of ∼620 kg/m³ and a volume of about 60 × 60 × 15 km³. The southern anomaly exhibits a density contrast of ∼440 kg/m³ and a size of 75 × 75 × 15 km³ at depths of 18–33 km. These two dense anomalies are likely solidified basaltic magma chambers situated near the crust-mantle boundary, that served as magma sources for the volcanic activities in Marius Hills.
{"title":"Three-dimensional density structure underneath the Marius Hills volcanic complex on the Moon","authors":"Shiyu Zhang , Bo Chen , Qian Huang , Changyi Xu , Xiaolong Wei","doi":"10.1016/j.epsl.2025.119770","DOIUrl":"10.1016/j.epsl.2025.119770","url":null,"abstract":"<div><div>Marius Hills, located in the central Oceanus Procellarum on the nearside of the Moon, is a significant volcanic complex, characterized by hundreds of domes and cones. Understanding its subsurface density structure is essential for enhancing our knowledge of lunar volcanic activity and its evolutionary history, yet it remains controversial. To investigate the density structure underneath Marius Hills, we developed a gravity inversion method based on the L1 norm and total variation regularization in spherical coordinates. We validated the method through a synthetic model test. We then applied it to the inversion of gravity data derived from the GRAIL mission in Marius Hills. Our results reveal two distinct high-density anomalies in the northern and southern segments of Marius Hills. The northern anomaly is located at 14–29 km depth directly beneath the shield volcano of Marius Hills, with a density contrast of ∼620 kg/m³ and a volume of about 60 × 60 × 15 km³. The southern anomaly exhibits a density contrast of ∼440 kg/m³ and a size of 75 × 75 × 15 km³ at depths of 18–33 km. These two dense anomalies are likely solidified basaltic magma chambers situated near the crust-mantle boundary, that served as magma sources for the volcanic activities in Marius Hills.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"675 ","pages":"Article 119770"},"PeriodicalIF":4.8,"publicationDate":"2025-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734592","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 : 2025-12-08DOI: 10.1016/j.epsl.2025.119771
Fabio Arzilli , Giuseppe La Spina , Emily C. Bamber , Daniele Morgavi , Lorenzo Fedele , Lucia Mancini , Marko Prašek , Ileana Santangelo , Giulia Chiominto , Annamaria Perrotta , Thomas Lemaire , Hélène Balcone-Boissard , Daniele Giordano , Claudio Scarpati
Intermediate to evolved alkaline magmas (phono-tephritic, tephri-phonolitic and phonolitic) exhibit a wide range in eruptive style and have produced some of the most catastrophic eruptions in human history, such as the 79 AD Plinian eruption of Vesuvius (Italy). However, eruptive dynamics are driven by complex, non-linear conduit processes during magma ascent, requiring a holistic approach to investigate their influence on explosivity. This study integrates synchrotron radiation X-ray computed microtomography (SRµCT) with a 1D steady-state conduit model, to investigate how crystal-bubble interactions, pre-eruptive conditions, outgassing, and magma composition affect eruptive style at alkaline volcanic systems, using Vesuvius as a case study.
We analyse pyroclasts from the 79 AD Plinian and 1944 lava-fountaining eruptions using SRμCT. Our SRµCT results reveal that heterogeneous bubble nucleation can be promoted further by leucite crystals, contributing to the high bubble number densities (>10⁴ mm⁻³) observed in Plinian products. Despite high bubble connectivity, low throat-pore size ratios (the ratio between the radii of the throat and connected vesicles) and elevated tortuosity restrict gas–melt separation during fast magma ascent, promoting fragmentation. Numerical simulations reveal tephri-phonolitic and phonolitic magmas are prone to fragmentation across diverse conditions, producing highly explosive eruptions. Only relatively high temperatures (>1050 °C) and low bubble number densities (102 to 103 mm-3) can promote lava flow and fountaining activity. Instead, phono-tephritic magmas exhibit highly explosive eruptions at considerably lower temperatures (<950 °C). Temperature controls magma viscosity, influencing the ascent rate and the outgassing efficiency, which, in turn, affects conduit dynamics and the eruptive behaviour.
Our findings highlight that for alkaline systems, the parameter space which is conducive to highly explosive eruptions expands as the magma composition evolves and its viscosity increases. These insights enhance our understanding of eruption mechanisms, providing critical insights for assessing volcanic hazard and emergency planning at alkaline volcanic systems.
{"title":"The role of crystal-bubble interactions, outgassing and magma composition in the ascent dynamics of alkaline magmas: Implications for eruptions at Vesuvius","authors":"Fabio Arzilli , Giuseppe La Spina , Emily C. Bamber , Daniele Morgavi , Lorenzo Fedele , Lucia Mancini , Marko Prašek , Ileana Santangelo , Giulia Chiominto , Annamaria Perrotta , Thomas Lemaire , Hélène Balcone-Boissard , Daniele Giordano , Claudio Scarpati","doi":"10.1016/j.epsl.2025.119771","DOIUrl":"10.1016/j.epsl.2025.119771","url":null,"abstract":"<div><div>Intermediate to evolved alkaline magmas (phono-tephritic, tephri-phonolitic and phonolitic) exhibit a wide range in eruptive style and have produced some of the most catastrophic eruptions in human history, such as the 79 AD Plinian eruption of Vesuvius (Italy). However, eruptive dynamics are driven by complex, non-linear conduit processes during magma ascent, requiring a holistic approach to investigate their influence on explosivity. This study integrates synchrotron radiation X-ray computed microtomography (SRµCT) with a 1D steady-state conduit model, to investigate how crystal-bubble interactions, pre-eruptive conditions, outgassing, and magma composition affect eruptive style at alkaline volcanic systems, using Vesuvius as a case study.</div><div>We analyse pyroclasts from the 79 AD Plinian and 1944 lava-fountaining eruptions using SRμCT. Our SRµCT results reveal that heterogeneous bubble nucleation can be promoted further by leucite crystals, contributing to the high bubble number densities (>10⁴ mm⁻³) observed in Plinian products. Despite high bubble connectivity, low throat-pore size ratios (the ratio between the radii of the throat and connected vesicles) and elevated tortuosity restrict gas–melt separation during fast magma ascent, promoting fragmentation. Numerical simulations reveal tephri-phonolitic and phonolitic magmas are prone to fragmentation across diverse conditions, producing highly explosive eruptions. Only relatively high temperatures (>1050 °C) and low bubble number densities (10<sup>2</sup> to 10<sup>3</sup> mm<sup>-3</sup>) can promote lava flow and fountaining activity. Instead, phono-tephritic magmas exhibit highly explosive eruptions at considerably lower temperatures (<950 °C). Temperature controls magma viscosity, influencing the ascent rate and the outgassing efficiency, which, in turn, affects conduit dynamics and the eruptive behaviour.</div><div>Our findings highlight that for alkaline systems, the parameter space which is conducive to highly explosive eruptions expands as the magma composition evolves and its viscosity increases. These insights enhance our understanding of eruption mechanisms, providing critical insights for assessing volcanic hazard and emergency planning at alkaline volcanic systems.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"675 ","pages":"Article 119771"},"PeriodicalIF":4.8,"publicationDate":"2025-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145734589","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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