Geochemistry Geophysics Geosystems最新文献

{"title":"Growth and Chemical Evolution of the Kohistan Arc Crust, Northern Pakistan, Western Himalayas","authors":"Paul Sotiriou,&nbsp;Karsten M. Haase,&nbsp;Marcel Regelous","doi":"10.1029/2025GC012708","DOIUrl":"10.1029/2025GC012708","url":null,"abstract":"<p>Fossil arcs which expose the middle-lower crust have the potential to shed light on active arc processes because magmatic rocks from the entire history of the arc can be examined. We present new geochemical data from the middle crust of the Kohistan Arc and use existing geochemical and geochronological literature data from this arc to constrain the growth and chemical evolution of the arc crust by reconstructing the chemical evolution of intrusive and extrusive magmatism. The ultramafic-mafic lower crust of the Kohistan Arc is older than much of the intermediate-felsic middle-upper crust. The middle-upper crust of the Kohistan Arc has higher (Ce/Yb)_N and lower ¹⁴³Nd/¹⁴⁴Nd ratios than the older lower crust. The later intermediate to felsic plutons of this arc were formed by fractional crystallization of basaltic magmas. The Kohistan Arc formed in two main stages: (a) subduction initiation and early intra-oceanic arc (e.g., Izu-Bonin-Mariana) magmatism (155–100 Ma) that formed the lower crust; and (b) mature intra-oceanic arc (85–60 Ma) magmatism (e.g., Cascade Arc) followed by collisional (60–40 Ma) magmatism that generated the upper-middle crust. Stage 1 volcanic and plutonic rocks have low (Ce/Yb)_N ratios, whereas their Stage 2 equivalents have high (Ce/Yb)_N ratios. The (Ce/Yb)_N ratios and fractionation depths of the volcanic and plutonic rocks of the Kohistan Arc increased with decreasing age, reflecting the progressive maturation and crustal thickening of the arc. Lavas erupted at mature (∼100 Ma old) entirely intra-oceanic arcs are geochemically similar to those found at “continental” arcs (e.g., Cascade Arc).</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012708","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147579863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid Slab Rollback Drives Early Cretaceous Back-Arc Extension in NE China: Implication for Crustal Growth and Episodic Porphyry Mineralization","authors":"Honghui Wang,&nbsp;Xinghua Ma,&nbsp;Simon A. Wilde,&nbsp;Yong Lai,&nbsp;Zhenhua Zhou,&nbsp;Jinyu Yan","doi":"10.1029/2025GC012540","DOIUrl":"https://doi.org/10.1029/2025GC012540","url":null,"abstract":"<p>The subduction of the Paleo-Pacific Plate beneath the NE Asian continental margin induced extensive magmatism, providing an excellent opportunity to investigate the interplay between plate dynamics, arc magmatism, continental crust formation, and porphyry mineralization. Here, we integrate mineralogical, geochronological, geochemical, and isotopic analyses of diverse Early Cretaceous magmatic assemblages in the Yanbian Fold Belt (NE China), aiming to reconstruct the evolution of a transcrustal magmatic plumbing system and constrain the key factors controlling porphyry mineralization during slab rollback. Dioritic enclaves (∼123 Ma) represent rapidly ascending mantle-derived magmas that underwent magma mixing/mingling and quenching before solidification. Granitic intrusions (∼118 Ma) with low Sr/Y were attributed to a depleted crustal source with plagioclase and biotite fractionation. Mafic dikes (∼116 Ma) from a bimodal suite originated from a slab-fluid-metasomatized lithospheric mantle with increased input from the depleted mantle, whereas felsic dikes (∼115 Ma) with high Sr/Y resulted from melting of a juvenile lower crust under garnet amphibolite facies conditions. These rock assemblages record back-arc crustal growth, reworking, and maturation. Compared with earlier (peaking at ∼130 Ma) back-arc magmatism farther west in the Great Xing'an Range, our newly identified bimodal magmatism (initiated at ∼118 Ma) in the Yanbian area reveals a rapid rollback of ∼600 km within ∼12 Myr. Moreover, the late Early Cretaceous magmas exhibit significantly higher magmatic oxygen fugacity (ΔFMQ &gt; +1, where FMQ is the fayalite-magnetite-quartz oxygen fugacity buffer) than their Jurassic counterparts (with ΔFMQ values generally below +0.5), paralleling regional porphyry-related mineralization and revealing the critical role of slab rollback in modulating arc magmatic fertility. Our findings highlight how transient rollback episodes can generate diverse magmatic differentiation pathways and metallogenic triggers in supra-subduction zone settings.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012540","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147567639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-Scale Submarine Sediment Waves at Macauley Caldera Volcano: In Situ Evidence of High-Flux, Syn-Eruptive Submarine Transport","authors":"Shannon E. Frey,&nbsp;Martin Jutzeler,&nbsp;Matthieu Cartigny,&nbsp;Rebecca J. Carey","doi":"10.1029/2025GC012492","DOIUrl":"https://doi.org/10.1029/2025GC012492","url":null,"abstract":"<p>Two sediment cores were collected from a submarine sediment wave field on the flank of Macauley volcano. Combined with seismic reflection surveys and numerical modeling, we present an integrated model of the formation of large-scale, eruption-fed, submarine sediment waves. The sediment waves are large (&gt;100 m high, 1.5 km wide, tens of km long) and composed of juvenile ash and pumice lapilli of rhyolitic to dacitic composition. The sediment waves are interpreted to be related to the 6.3 ka caldera-forming eruption and Sandy Bay Tephra deposit on nearby Macauley Island. The sediment waves were deposited as cyclic steps and antidunes under supercritical, syn-eruptive density currents. Facies analysis indicates that the bedforms developed as amalgamated sets of m-sized bedforms. Numerical modeling and seismic reflection data show that early-stage density currents were rapid and erosive, whereas later currents persisted over days to weeks. Our data from Macauley volcano is compared to the submarine sediment waves from the 2022 eruption of Hunga volcano, and other known eruption-fed sediment waves. We discuss implications for the modeling of volcanic eruptions from their submarine deposits, as bedforms associated with supercritical density flows may be confused with volcanic turbidites that have critically different deposition and distribution patterns. Further, the self-erosive nature of supercritical density currents produces deposits composed of volcanic, syn-eruptive material that has been continuously mixed through deposition and may obscure any stratigraphic trends associated with eruption dynamics. We discuss the implications for tsunami prediction and modeling associated with the unpredictable nature of these events.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012492","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147567708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Large-Scale Submarine Sediment Waves at Macauley Caldera Volcano: In Situ Evidence of High-Flux, Syn-Eruptive Submarine Transport","authors":"Shannon E. Frey,&nbsp;Martin Jutzeler,&nbsp;Matthieu Cartigny,&nbsp;Rebecca J. Carey","doi":"10.1029/2025GC012492","DOIUrl":"https://doi.org/10.1029/2025GC012492","url":null,"abstract":"<p>Two sediment cores were collected from a submarine sediment wave field on the flank of Macauley volcano. Combined with seismic reflection surveys and numerical modeling, we present an integrated model of the formation of large-scale, eruption-fed, submarine sediment waves. The sediment waves are large (&gt;100 m high, 1.5 km wide, tens of km long) and composed of juvenile ash and pumice lapilli of rhyolitic to dacitic composition. The sediment waves are interpreted to be related to the 6.3 ka caldera-forming eruption and Sandy Bay Tephra deposit on nearby Macauley Island. The sediment waves were deposited as cyclic steps and antidunes under supercritical, syn-eruptive density currents. Facies analysis indicates that the bedforms developed as amalgamated sets of m-sized bedforms. Numerical modeling and seismic reflection data show that early-stage density currents were rapid and erosive, whereas later currents persisted over days to weeks. Our data from Macauley volcano is compared to the submarine sediment waves from the 2022 eruption of Hunga volcano, and other known eruption-fed sediment waves. We discuss implications for the modeling of volcanic eruptions from their submarine deposits, as bedforms associated with supercritical density flows may be confused with volcanic turbidites that have critically different deposition and distribution patterns. Further, the self-erosive nature of supercritical density currents produces deposits composed of volcanic, syn-eruptive material that has been continuously mixed through deposition and may obscure any stratigraphic trends associated with eruption dynamics. We discuss the implications for tsunami prediction and modeling associated with the unpredictable nature of these events.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012492","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147567638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rapid Slab Rollback Drives Early Cretaceous Back-Arc Extension in NE China: Implication for Crustal Growth and Episodic Porphyry Mineralization","authors":"Honghui Wang,&nbsp;Xinghua Ma,&nbsp;Simon A. Wilde,&nbsp;Yong Lai,&nbsp;Zhenhua Zhou,&nbsp;Jinyu Yan","doi":"10.1029/2025GC012540","DOIUrl":"https://doi.org/10.1029/2025GC012540","url":null,"abstract":"<p>The subduction of the Paleo-Pacific Plate beneath the NE Asian continental margin induced extensive magmatism, providing an excellent opportunity to investigate the interplay between plate dynamics, arc magmatism, continental crust formation, and porphyry mineralization. Here, we integrate mineralogical, geochronological, geochemical, and isotopic analyses of diverse Early Cretaceous magmatic assemblages in the Yanbian Fold Belt (NE China), aiming to reconstruct the evolution of a transcrustal magmatic plumbing system and constrain the key factors controlling porphyry mineralization during slab rollback. Dioritic enclaves (∼123 Ma) represent rapidly ascending mantle-derived magmas that underwent magma mixing/mingling and quenching before solidification. Granitic intrusions (∼118 Ma) with low Sr/Y were attributed to a depleted crustal source with plagioclase and biotite fractionation. Mafic dikes (∼116 Ma) from a bimodal suite originated from a slab-fluid-metasomatized lithospheric mantle with increased input from the depleted mantle, whereas felsic dikes (∼115 Ma) with high Sr/Y resulted from melting of a juvenile lower crust under garnet amphibolite facies conditions. These rock assemblages record back-arc crustal growth, reworking, and maturation. Compared with earlier (peaking at ∼130 Ma) back-arc magmatism farther west in the Great Xing'an Range, our newly identified bimodal magmatism (initiated at ∼118 Ma) in the Yanbian area reveals a rapid rollback of ∼600 km within ∼12 Myr. Moreover, the late Early Cretaceous magmas exhibit significantly higher magmatic oxygen fugacity (ΔFMQ &gt; +1, where FMQ is the fayalite-magnetite-quartz oxygen fugacity buffer) than their Jurassic counterparts (with ΔFMQ values generally below +0.5), paralleling regional porphyry-related mineralization and revealing the critical role of slab rollback in modulating arc magmatic fertility. Our findings highlight how transient rollback episodes can generate diverse magmatic differentiation pathways and metallogenic triggers in supra-subduction zone settings.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012540","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147567947","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magma Paths of the Karthala and La Grille Volcanoes (Grande Comore) Revisited: New Evidence From Geomorphology and Geochemistry","authors":"François J. P. Lötter,&nbsp;Nicolas Villeneuve,&nbsp;Andrea Di Muro,&nbsp;Nils Lenhardt,&nbsp;Laurent Michon,&nbsp;Pascale Besson,&nbsp;Hamid Soulé","doi":"10.1029/2025GC012529","DOIUrl":"https://doi.org/10.1029/2025GC012529","url":null,"abstract":"<p>Grande Comore, the westernmost island within the Madagascar Comoros Volcanic (MCV) chain, hosts two juxtaposed basaltic volcanoes, Karthala and La Grille, with contrasting lava geochemical signatures and eruption frequencies. Their formation and dynamics have been explained either by a mantle plume or, more recently, as part of a transtensional volcano-tectonic system. Understanding their individual development is key to resolving persistent geodynamic contradictions within the Comoros and improving volcanic hazard assessment. We integrate the morphology and spatial distribution of scoria cones with a new database of lava, and, for the first time, tephra compositions to constrain magma pathways. We classify cone-dense regions into four main clusters (SGC, KAR, CGC, and LAG) and four sub-clusters (KARa, KARb, KARc, and LAGa). Within Karthala, cone size weakly correlates with primitive mafic magma compositions, whereas no such relationship occurs at La Grille clusters. This indicates a developed, shallow plumbing system beneath Karthala and its absence beneath La Grille. Cone base orientation reveals that Karthala and La Grille volcanism is influenced by regional rifting, but only Karthala is influenced by edifice loading. Edifice-induced compositional filtering promotes lateral migration of primitive magmas and vertical ascent of evolved magmas, while regionally controlled rift zones channel evolved magmas to the center of the island. Recent eruption convergence/resurgence cycles suggest that future eruptions at Karthala will likely be constrained to the edifice of Karthala while La Grille's rare eruptions have only tectonic triggers. Active areas on Grande Comore are thus well constrained and more widespread than previously thought.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012529","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magma Paths of the Karthala and La Grille Volcanoes (Grande Comore) Revisited: New Evidence From Geomorphology and Geochemistry","authors":"François J. P. Lötter,&nbsp;Nicolas Villeneuve,&nbsp;Andrea Di Muro,&nbsp;Nils Lenhardt,&nbsp;Laurent Michon,&nbsp;Pascale Besson,&nbsp;Hamid Soulé","doi":"10.1029/2025GC012529","DOIUrl":"https://doi.org/10.1029/2025GC012529","url":null,"abstract":"<p>Grande Comore, the westernmost island within the Madagascar Comoros Volcanic (MCV) chain, hosts two juxtaposed basaltic volcanoes, Karthala and La Grille, with contrasting lava geochemical signatures and eruption frequencies. Their formation and dynamics have been explained either by a mantle plume or, more recently, as part of a transtensional volcano-tectonic system. Understanding their individual development is key to resolving persistent geodynamic contradictions within the Comoros and improving volcanic hazard assessment. We integrate the morphology and spatial distribution of scoria cones with a new database of lava, and, for the first time, tephra compositions to constrain magma pathways. We classify cone-dense regions into four main clusters (SGC, KAR, CGC, and LAG) and four sub-clusters (KARa, KARb, KARc, and LAGa). Within Karthala, cone size weakly correlates with primitive mafic magma compositions, whereas no such relationship occurs at La Grille clusters. This indicates a developed, shallow plumbing system beneath Karthala and its absence beneath La Grille. Cone base orientation reveals that Karthala and La Grille volcanism is influenced by regional rifting, but only Karthala is influenced by edifice loading. Edifice-induced compositional filtering promotes lateral migration of primitive magmas and vertical ascent of evolved magmas, while regionally controlled rift zones channel evolved magmas to the center of the island. Recent eruption convergence/resurgence cycles suggest that future eruptions at Karthala will likely be constrained to the edifice of Karthala while La Grille's rare eruptions have only tectonic triggers. Active areas on Grande Comore are thus well constrained and more widespread than previously thought.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012529","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparing Slab Viscous Dissipation Under Slab Distributed Weakening and Slab Segmentation Scenarios","authors":"Wenfa Zhou,&nbsp;Jiashun Hu,&nbsp;Keqing Li,&nbsp;Ting Yang","doi":"10.1029/2025GC012783","DOIUrl":"https://doi.org/10.1029/2025GC012783","url":null,"abstract":"<p>Subduction of cold, dense oceanic lithosphere is a key driver of plate tectonics and mantle convection. However, how much gravitational potential energy is internally dissipated by slab deformation during subduction remains debated and largely depends on the mechanisms of slab weakening. We develop two-dimensional geodynamic models to systematically investigate viscous dissipation within subducting slabs under two end-member scenarios: slab distributed weakening controlled by plastic yielding, and slab segmentation controlled by outer-rise faulting and grain size damage. In distributed weakening models, ∼20% of the gravitational potential energy is consumed by slab viscous dissipation, which is independent of the viscosity of the slab, consistent with previous laboratory and numerical studies. In segmentation models caused by grain size evolution and serpentinization, slab viscous dissipation increases significantly, with the dissipation ratio reaching up to <b>40%</b>. Slab segmentation alters the relationship between viscous dissipation and both effective viscosity and subduction velocity, breaking the conventional scaling laws based on fixed slab geometry. Moreover, by calculating viscous dissipation in global subduction zones, we infer that the average viscosity of subducting slabs does not exceed <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1.36</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mn>23</mn>\u0000 </msup>\u0000 <mspace></mspace>\u0000 <mtext>Pa</mtext>\u0000 <mo>·</mo>\u0000 <mi>s</mi>\u0000 </mrow>\u0000 <annotation> $1.36times {10}^{23},text{Pa}cdot mathrm{s}$</annotation>\u0000 </semantics></math> if slab segmentation is the dominant mode for global subduction zones. We estimate that 60%–80% of the gravitational potential energy is transferred to the surrounding mantle to drive mantle convection, regardless of the slab mode. These findings emphasize that accounting for more realistic rheological structures, including plastic yielding and slab segmentation in subduction models, is crucial for accurately quantifying energy partitioning within the Earth and understanding plate–mantle interactions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012783","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Comparing Slab Viscous Dissipation Under Slab Distributed Weakening and Slab Segmentation Scenarios","authors":"Wenfa Zhou,&nbsp;Jiashun Hu,&nbsp;Keqing Li,&nbsp;Ting Yang","doi":"10.1029/2025GC012783","DOIUrl":"https://doi.org/10.1029/2025GC012783","url":null,"abstract":"<p>Subduction of cold, dense oceanic lithosphere is a key driver of plate tectonics and mantle convection. However, how much gravitational potential energy is internally dissipated by slab deformation during subduction remains debated and largely depends on the mechanisms of slab weakening. We develop two-dimensional geodynamic models to systematically investigate viscous dissipation within subducting slabs under two end-member scenarios: slab distributed weakening controlled by plastic yielding, and slab segmentation controlled by outer-rise faulting and grain size damage. In distributed weakening models, ∼20% of the gravitational potential energy is consumed by slab viscous dissipation, which is independent of the viscosity of the slab, consistent with previous laboratory and numerical studies. In segmentation models caused by grain size evolution and serpentinization, slab viscous dissipation increases significantly, with the dissipation ratio reaching up to <b>40%</b>. Slab segmentation alters the relationship between viscous dissipation and both effective viscosity and subduction velocity, breaking the conventional scaling laws based on fixed slab geometry. Moreover, by calculating viscous dissipation in global subduction zones, we infer that the average viscosity of subducting slabs does not exceed <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mn>1.36</mn>\u0000 <mo>×</mo>\u0000 <msup>\u0000 <mn>10</mn>\u0000 <mn>23</mn>\u0000 </msup>\u0000 <mspace></mspace>\u0000 <mtext>Pa</mtext>\u0000 <mo>·</mo>\u0000 <mi>s</mi>\u0000 </mrow>\u0000 <annotation> $1.36times {10}^{23},text{Pa}cdot mathrm{s}$</annotation>\u0000 </semantics></math> if slab segmentation is the dominant mode for global subduction zones. We estimate that 60%–80% of the gravitational potential energy is transferred to the surrounding mantle to drive mantle convection, regardless of the slab mode. These findings emphasize that accounting for more realistic rheological structures, including plastic yielding and slab segmentation in subduction models, is crucial for accurately quantifying energy partitioning within the Earth and understanding plate–mantle interactions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012783","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Slab Gap-Related Intraplate Magmatism as a Proxy of Maximum Flat Slab Extent in Patagonia","authors":"C. R. Navarrete,&nbsp;G. M. Gianni,&nbsp;G. I. Massaferro,&nbsp;M. B. Lastra","doi":"10.1029/2025GC012895","DOIUrl":"10.1029/2025GC012895","url":null,"abstract":"<p>Establishing the frontal extent of ancient flat subduction events from the geologic record can be challenging. This difficulty arises because magmatic activity in the arc typically ceases during complete slab flattening, and other meaningful proxies are usually absent. To address this issue, we examine early Paleocene intraplate magmatic units in central Patagonia, specifically, the La Angostura and Pagasartundua basalts. These basalts erupted and were emplaced during the final phase of a significant flat subduction event, referred to as the Nalé flat slab. The small outcrops of these units are composed of metaluminous alkaline basalts, whose origin would be related to the decompression melting of the sub-slab asthenosphere. This melting likely occurred due to local slab gaps in the frontal section of a flattened slab, where the oceanic lithosphere resumed a steep angle. The resulting mantle primitive melts would have caused partial melting of minor portions of the upper slab (including eclogitized components). The interaction of these two end-member melts results in slight hybridization, as evidenced by positive anomalies in Cs, Pb, and Li, subtle Ta depletion, and local Th enrichment in the basalts. By recognizing these basalts and their geochemical characteristics in relation to the geodynamic context, we can establish the maximum frontal extent of a large-scale Late Cretaceous-Paleocene flat subduction event. Thus, this case represents the first ancient flat slab that is frontally constrained by slab gap-related intraplate magmatism, a pattern that could be replicated in other similar settings worldwide.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 3","pages":""},"PeriodicalIF":3.0,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012895","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147566553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}