Pub Date : 2026-01-29DOI: 10.1016/j.epsl.2026.119865
Anthony J. Fuentes , Liam Courtney-Davies , Rebecca Flowers , Yiming Zhang , Nicholas Swanson-Hysell
{"title":"Reply to the comment of Rasmussen et al., on: Evolution of iron formation to ore during Ediacaran to early Paleozoic tectonic stability","authors":"Anthony J. Fuentes , Liam Courtney-Davies , Rebecca Flowers , Yiming Zhang , Nicholas Swanson-Hysell","doi":"10.1016/j.epsl.2026.119865","DOIUrl":"10.1016/j.epsl.2026.119865","url":null,"abstract":"","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119865"},"PeriodicalIF":4.8,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090146","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 : 2026-01-29DOI: 10.1016/j.epsl.2026.119886
Jiangyang Zhang , Robert J. Stern , Fan Zhang , Jian Lin , Hongfeng Yang
The Challenger Deep in the southernmost Mariana Trench is the deepest area on Earth, yet the physical cause of its exceptional depth remains debated. Here, we quantify the mechanical factors that produce this extreme trench relief and explain why it occurs there. Bathymetric analysis shows that this segment exhibits a steeper outer-trench slope and tighter plate curvature than both the northern Mariana and other global trenches. Applying a buoyancy-loaded elastic plate bending model constrained by bathymetry and deep slab geometry, we isolate two key controls on trench depth through forward and inversion tests: a reduced near-trench elastic thickness and a moderate slab–mantle density contrast. Additional two-dimensional flexure experiments demonstrate that narrower slab segments experience greater deflection under the same load, implying that limited along-strike width mechanically enhances local bending. This effect is realized in nature by a slab tear near 144°30′ E, which isolates a narrow, weakly anchored slab tip and thereby concentrates curvature at the Challenger Deep. Our results suggest that the extreme depth of the Challenger Deep arises from the combined effects of slab negative buoyancy, lithospheric weakening, and slab segmentation, which together localize flexure to produce the deepest trench on Earth.
{"title":"Unusually tight bending of subducting pacific plate causes the extreme depth of challenger deep","authors":"Jiangyang Zhang , Robert J. Stern , Fan Zhang , Jian Lin , Hongfeng Yang","doi":"10.1016/j.epsl.2026.119886","DOIUrl":"10.1016/j.epsl.2026.119886","url":null,"abstract":"<div><div>The Challenger Deep in the southernmost Mariana Trench is the deepest area on Earth, yet the physical cause of its exceptional depth remains debated. Here, we quantify the mechanical factors that produce this extreme trench relief and explain why it occurs there. Bathymetric analysis shows that this segment exhibits a steeper outer-trench slope and tighter plate curvature than both the northern Mariana and other global trenches. Applying a buoyancy-loaded elastic plate bending model constrained by bathymetry and deep slab geometry, we isolate two key controls on trench depth through forward and inversion tests: a reduced near-trench elastic thickness and a moderate slab–mantle density contrast. Additional two-dimensional flexure experiments demonstrate that narrower slab segments experience greater deflection under the same load, implying that limited along-strike width mechanically enhances local bending. This effect is realized in nature by a slab tear near 144°30′ E, which isolates a narrow, weakly anchored slab tip and thereby concentrates curvature at the Challenger Deep. Our results suggest that the extreme depth of the Challenger Deep arises from the combined effects of slab negative buoyancy, lithospheric weakening, and slab segmentation, which together localize flexure to produce the deepest trench on Earth.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119886"},"PeriodicalIF":4.8,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090731","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 : 2026-01-28DOI: 10.1016/j.epsl.2026.119887
Jie Dong , Chunjing Wei , Shuguang Song , Guochun Zhao , Guibin Zhang
Ultrahigh-temperature metamorphism (UHTM) is significant for constraining the thermal-mechanical evolution of continental crust, which can periodically occur within one orogenic cycle involving subduction, collision and subsequent extension stages. However, multi-episode UHTM within one orogenic cycle has been rarely reported. Here, we performed a comprehensive investigation of petrography, phase equilibria modelling, and zircon U-Pb dating for felsic and Mg-Fe-Al granulites from the Kunlun-Qaidam Massif in north Qingzang Plateau. Three episodes of metamorphism were inferred, involving two episodes of low pressure (LP)-UHTM intervened by an episode of medium-pressure and high-temperature (MP-HT) metamorphism. The first episode LP-UHTM (I) exhibits peak P–T conditions of 0.5–0.8 GPa/930–1050 °C, occurring at >460 Ma. The second episode MP-HT metamorphism (II) was achieved by compressional cooling from the LP-UHT conditions to MP-HT conditions of >0.9–1.2 GPa/<820–900 °C. This was followed by decompressional heating to another episode of LP-UHTM (III) with conditions of 0.55–0.75 GPa/900–1070 °C at >410 Ma. Combining our metamorphic studies and other geological data, a three-stage tectonic model is proposed: (a) oceanic slab rollback inducing an arc-backarc extension and the LP-UHTM (I) during the late-stage subduction of the Proto-Tethys Ocean; (b) continental subduction-collision leading to the thickening of hot arc-backarc crust and the MP-HT metamorphism (II) after the closure of the Proto-Tethys Ocean, and (c) post-collisional crustal thinning and mantle upwelling related to lithosphere delamination resulting in the LP-UHTM (III). It is for the first time that we recognize two episodes of LP-UHTM occurring within < 50 Myr in one orogenic cycle.
{"title":"Two episodes of ultrahigh-temperature metamorphism within one orogenic cycle","authors":"Jie Dong , Chunjing Wei , Shuguang Song , Guochun Zhao , Guibin Zhang","doi":"10.1016/j.epsl.2026.119887","DOIUrl":"10.1016/j.epsl.2026.119887","url":null,"abstract":"<div><div>Ultrahigh-temperature metamorphism (UHTM) is significant for constraining the thermal-mechanical evolution of continental crust, which can periodically occur within one orogenic cycle involving subduction, collision and subsequent extension stages. However, multi-episode UHTM within one orogenic cycle has been rarely reported. Here, we performed a comprehensive investigation of petrography, phase equilibria modelling, and zircon U-Pb dating for felsic and Mg-Fe-Al granulites from the Kunlun-Qaidam Massif in north Qingzang Plateau. Three episodes of metamorphism were inferred, involving two episodes of low pressure (LP)-UHTM intervened by an episode of medium-pressure and high-temperature (MP-HT) metamorphism. The first episode LP-UHTM (I) exhibits peak <em>P–T</em> conditions of 0.5–0.8 GPa/930–1050 °C, occurring at >460 Ma. The second episode MP-HT metamorphism (II) was achieved by compressional cooling from the LP-UHT conditions to MP-HT conditions of >0.9–1.2 GPa/<820–900 °C. This was followed by decompressional heating to another episode of LP-UHTM (III) with conditions of 0.55–0.75 GPa/900–1070 °C at >410 Ma. Combining our metamorphic studies and other geological data, a three-stage tectonic model is proposed: (a) oceanic slab rollback inducing an arc-backarc extension and the LP-UHTM (I) during the late-stage subduction of the Proto-Tethys Ocean; (b) continental subduction-collision leading to the thickening of hot arc-backarc crust and the MP-HT metamorphism (II) after the closure of the Proto-Tethys Ocean, and (c) post-collisional crustal thinning and mantle upwelling related to lithosphere delamination resulting in the LP-UHTM (III). It is for the first time that we recognize two episodes of LP-UHTM occurring within < 50 Myr in one orogenic cycle.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119887"},"PeriodicalIF":4.8,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090728","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 : 2026-01-28DOI: 10.1016/j.epsl.2026.119882
U. Balci , L. Di Nicola , J.G. Fitton , R.N. Taylor , F.M. Stuart
The upwelling mantle plume beneath Iceland flows southwest down the Reykjanes Ridge. Several prominent V-shaped ridges (VSRs) and troughs (VSTs) extend obliquely from the ridge that are believed to result from pulses of hotter plume mantle. The intimate connection between heat and primordial He in the deep mantle means that the mantle beneath the Reykjanes Ridge should have elevated 3He/4He. A new high resolution He isotope study of basaltic glasses from southernmost Iceland (63°N) to 55°N along the Reykjanes Ridge demonstrates a broad peak of 3He/4He (16.0 Ra) centred around 60°N that coincides with the first topographic high (VSR-1). The magnitude of the He isotope anomaly broadly scales with the excess temperature inferred from crustal thickness. This supports the hypothesis that thickened oceanic crust is a consequence of a pulse of hotter mantle within the upwelling plume that flows down the Reykjanes Ridge. The along-ridge 3He/4He peak at 59-62°N is significantly longer (320 km) than the thickened oceanic crust of VSR-1 (60-70 km). This can most simply be explained if the hot mantle blob is surrounded by a high 3He/4He mantle carapace that has a temperature similar to the surrounding mantle. As helium diffusion is orders of magnitude slower than heat, this relationship can be most simply explained if the outer region of the hot, He-rich blob has lost heat to the surrounding mantle during transit from the core-mantle boundary, yet retained the deep mantle He isotope fingerprint.
{"title":"Tracking deep mantle heat and volatiles in the Iceland plume from a high-density survey of helium isotopes along the Reykjanes Ridge","authors":"U. Balci , L. Di Nicola , J.G. Fitton , R.N. Taylor , F.M. Stuart","doi":"10.1016/j.epsl.2026.119882","DOIUrl":"10.1016/j.epsl.2026.119882","url":null,"abstract":"<div><div>The upwelling mantle plume beneath Iceland flows southwest down the Reykjanes Ridge. Several prominent V-shaped ridges (VSRs) and troughs (VSTs) extend obliquely from the ridge that are believed to result from pulses of hotter plume mantle. The intimate connection between heat and primordial He in the deep mantle means that the mantle beneath the Reykjanes Ridge should have elevated <sup>3</sup>He/<sup>4</sup>He. A new high resolution He isotope study of basaltic glasses from southernmost Iceland (63°N) to 55°N along the Reykjanes Ridge demonstrates a broad peak of <sup>3</sup>He/<sup>4</sup>He (16.0 R<sub>a</sub>) centred around 60°N that coincides with the first topographic high (VSR-1). The magnitude of the He isotope anomaly broadly scales with the excess temperature inferred from crustal thickness. This supports the hypothesis that thickened oceanic crust is a consequence of a pulse of hotter mantle within the upwelling plume that flows down the Reykjanes Ridge. The along-ridge <sup>3</sup>He/<sup>4</sup>He peak at 59-62°N is significantly longer (320 km) than the thickened oceanic crust of VSR-1 (60-70 km). This can most simply be explained if the hot mantle blob is surrounded by a high <sup>3</sup>He/<sup>4</sup>He mantle carapace that has a temperature similar to the surrounding mantle. As helium diffusion is orders of magnitude slower than heat, this relationship can be most simply explained if the outer region of the hot, He-rich blob has lost heat to the surrounding mantle during transit from the core-mantle boundary, yet retained the deep mantle He isotope fingerprint.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119882"},"PeriodicalIF":4.8,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090736","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 : 2026-01-27DOI: 10.1016/j.epsl.2026.119861
Maximilian Schulze, Gerd Steinle-Neumann
Davemaoite (CaSiO3), a major rock-forming mineral in the Earth’s lower mantle, adopts a perovskite structure, which is known for the rapid diffusion of extrinsic oxygen vacancies (OV). Here, we use molecular dynamics simulations in conjunction with a machine learning potential to systematically investigate extrinsic OV diffusion in davemaoite at lower mantle conditions. We determine diffusion coefficients (Dv) for a series of temperatures along isobars of 25, 50, 75, 100 and 125 GPa and find that computed diffusivities closely follow an Arrhenian behavior. The pre-exponential factor is pressure independent with -6.53 ± 0.06 and the activation enthalpy increases nonlinearly with pressure from 0.87 eV to 1.66 eV. On the basis of the Arrhenian model, we predict that Dv decreases throughout the lower mantle by at least one order of magnitude along geotherms representative of the ambient mantle and subducted lithosphere. We argue that despite the high OV diffusivities, the davemaoite component of subducted oceanic crust does not achieve complete redox equilibration with the surrounding mantle on its way to the core-mantle boundary, and that significant redox exchange is limited to the upper parts of the lower mantle. Finally, we provide arguments that the electrical conductivity of most parts of the lower mantle cannot be explained by ionic conductivity and that its electrical conductivity must therefore be determined by iron-induced polaron hopping.
{"title":"Oxygen vacancy diffusion in davemaoite (CaSiO3 perovskite): Implications for the redox equilibrium and the electrical conductivity of Earth’s lower mantle","authors":"Maximilian Schulze, Gerd Steinle-Neumann","doi":"10.1016/j.epsl.2026.119861","DOIUrl":"10.1016/j.epsl.2026.119861","url":null,"abstract":"<div><div>Davemaoite (CaSiO<sub>3</sub>), a major rock-forming mineral in the Earth’s lower mantle, adopts a perovskite structure, which is known for the rapid diffusion of extrinsic oxygen vacancies (OV). Here, we use molecular dynamics simulations in conjunction with a machine learning potential to systematically investigate extrinsic OV diffusion in davemaoite at lower mantle conditions. We determine diffusion coefficients (<em>D</em><sub>v</sub>) for a series of temperatures along isobars of 25, 50, 75, 100 and 125 GPa and find that computed diffusivities closely follow an Arrhenian behavior. The pre-exponential factor is pressure independent with <span><math><mrow><mi>log</mi><msubsup><mi>D</mi><mi>v</mi><mo>∘</mo></msubsup><mspace></mspace><mo>=</mo><mspace></mspace></mrow></math></span>-6.53 ± 0.06 and the activation enthalpy increases nonlinearly with pressure from 0.87 eV to 1.66 eV. On the basis of the Arrhenian model, we predict that <em>D</em><sub>v</sub> decreases throughout the lower mantle by at least one order of magnitude along geotherms representative of the ambient mantle and subducted lithosphere. We argue that despite the high OV diffusivities, the davemaoite component of subducted oceanic crust does not achieve complete redox equilibration with the surrounding mantle on its way to the core-mantle boundary, and that significant redox exchange is limited to the upper parts of the lower mantle. Finally, we provide arguments that the electrical conductivity of most parts of the lower mantle cannot be explained by ionic conductivity and that its electrical conductivity must therefore be determined by iron-induced polaron hopping.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119861"},"PeriodicalIF":4.8,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090726","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 : 2026-01-27DOI: 10.1016/j.epsl.2026.119826
Connor A. Diaz , Rebecca M. Flowers , Carolyn A. Crow , James R. Metcalf , Rita Economos
Understanding the shock conditions of shergottites during their ejection from the Martian surface is important for deconvolving the pre-ejection thermal and geological history from the ejection overprint in Martian meteorite samples. Here, we investigate Martian meteorite Northwest Africa (NWA) 12241 to better quantify absolute temperatures and local variability in shock-induced thermal events and implications for deciphering the Martian meteorite record. NWA 12241 is classified petrologically as low-shock based on its limited shock features. However, new Raman identification of tuite, a high-pressure phosphate polymorph, demonstrates that minimum temperatures of 1100 °C were achieved in some regions of the sample during ejection. (U-Th)/He dating of merrillite yields a wide range of dates from 2.0 ± 0.3 Ma to 191.7 ± 2.7 Ma, interpreted as the ejection and crystallization ages of NWA 12241, respectively. Thermal history modeling suggests that heterogeneous shock heating is required to explain the merrillite data distribution, with local shock temperatures of ≤570 °C necessary to account for preservation of the older dates. Together, the tuite occurrence and (U-Th)/He data support at least 530 °C (and up to 1730 °C) of variability in the peak shock temperature across this small (7.21 g, ∼4 cm) sample. These findings highlight intense thermal heterogeneity and localized high-temperature microenvironments in an otherwise low-shock meteorite, illustrating the value of (U-Th)/He thermochronology for refining interpretations of localized shock effects in Martian meteorites.
{"title":"Heterogeneous ejection temperatures recorded in a “low-shock” Martian meteorite by (U-Th)/He thermochronology and a high-pressure phosphate polymorph","authors":"Connor A. Diaz , Rebecca M. Flowers , Carolyn A. Crow , James R. Metcalf , Rita Economos","doi":"10.1016/j.epsl.2026.119826","DOIUrl":"10.1016/j.epsl.2026.119826","url":null,"abstract":"<div><div>Understanding the shock conditions of shergottites during their ejection from the Martian surface is important for deconvolving the pre-ejection thermal and geological history from the ejection overprint in Martian meteorite samples. Here, we investigate Martian meteorite Northwest Africa (NWA) 12241 to better quantify absolute temperatures and local variability in shock-induced thermal events and implications for deciphering the Martian meteorite record. NWA 12241 is classified petrologically as low-shock based on its limited shock features. However, new Raman identification of tuite, a high-pressure phosphate polymorph, demonstrates that minimum temperatures of 1100 °C were achieved in some regions of the sample during ejection. (U-Th)/He dating of merrillite yields a wide range of dates from 2.0 ± 0.3 Ma to 191.7 ± 2.7 Ma, interpreted as the ejection and crystallization ages of NWA 12241, respectively. Thermal history modeling suggests that heterogeneous shock heating is required to explain the merrillite data distribution, with local shock temperatures of ≤570 °C necessary to account for preservation of the older dates. Together, the tuite occurrence and (U-Th)/He data support at least 530 °C (and up to 1730 °C) of variability in the peak shock temperature across this small (7.21 g, ∼4 cm) sample. These findings highlight intense thermal heterogeneity and localized high-temperature microenvironments in an otherwise low-shock meteorite, illustrating the value of (U-Th)/He thermochronology for refining interpretations of localized shock effects in Martian meteorites.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119826"},"PeriodicalIF":4.8,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090732","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 : 2026-01-24DOI: 10.1016/j.epsl.2026.119857
Megan Elysia Flansburg , Daniel Fritz Stockli , Eirini Maria Poulaki , Konstantinos Soukis , Lisa Danielle Stockli
Oligo-Miocene large-magnitude extension and the formation of metamorphic core complexes accommodated exhumation of High Pressure/Low Temperature (HP/LT) rocks in the eastern Mediterranean. Previous studies on Ios Island in the southern Cyclades have associated mylonitic fabrics exposed within the crystalline Cycladic Basement and along its contact with the overlying Cycladic Blueschist Unit, termed the South Cycladic Shear Zone, with Oligo-Miocene extension in the backarc of the retreating Hellenic subduction zone. We utilized apatite U-Pb geo-thermochronology, combined with Ti-in-Quartz and quartz c-axis opening-angle thermometry and microstructural characterization of mylonitic fabrics, to constrain the timing of mylonitization preserved in the footwall of the South Cycladic Shear Zone. Apatite U-Pb ages of the high-temperature (> ca. 500°C) mylonites in the Basement Core are Permo-Carboniferous (ca. 302—270 Ma), with two samples yielding apparent Mesozoic apatite U-Pb ages and whose U-Pb and REE systematics may have been perturbed by Cenozoic tectonics. Despite lower-temperature (300—400°C) mylonitization within the South Cycladic Shear Zone, rocks there preserve exclusively Permo-Carboniferous (ca. 307–297 Ma) apatite U-Pb ages, corresponding to either relict high-temperature quartz domains (ca. >500°C) or a detrital age signature sourced from the Cycladic Basement, but not to Cenozoic movement along the interface. The dominance of Permian cooling ages suggests that significant exhumation of the Cycladic Basement occurred prior to and concurrent with deposition of the earliest Cycladic Blueschist Unit in the late Permian to early Triassic, and that Cycladic core complexes preserve high-temperature fabrics related to pre-Miocene extension. Importantly, this work advises caution when assuming the age of mylonitic fabrics in the footwalls of metamorphic core complexes across the globe without integrating deformation conditions within thermochronometric and geochemical context.
{"title":"Permian mylonites in the footwall of a Miocene Cycladic core complex (Ios, Greece): Insights from (micro)structurally integrated apatite U-Pb petrochronology","authors":"Megan Elysia Flansburg , Daniel Fritz Stockli , Eirini Maria Poulaki , Konstantinos Soukis , Lisa Danielle Stockli","doi":"10.1016/j.epsl.2026.119857","DOIUrl":"10.1016/j.epsl.2026.119857","url":null,"abstract":"<div><div>Oligo-Miocene large-magnitude extension and the formation of metamorphic core complexes accommodated exhumation of High Pressure/Low Temperature (HP/LT) rocks in the eastern Mediterranean. Previous studies on Ios Island in the southern Cyclades have associated mylonitic fabrics exposed within the crystalline Cycladic Basement and along its contact with the overlying Cycladic Blueschist Unit, termed the South Cycladic Shear Zone, with Oligo-Miocene extension in the backarc of the retreating Hellenic subduction zone. We utilized apatite U-Pb geo-thermochronology, combined with Ti-in-Quartz and quartz c-axis opening-angle thermometry and microstructural characterization of mylonitic fabrics, to constrain the timing of mylonitization preserved in the footwall of the South Cycladic Shear Zone. Apatite U-Pb ages of the high-temperature (> ca. 500°C) mylonites in the Basement Core are Permo-Carboniferous (ca. 302—270 Ma), with two samples yielding apparent Mesozoic apatite U-Pb ages and whose U-Pb and REE systematics may have been perturbed by Cenozoic tectonics. Despite lower-temperature (300—400°C) mylonitization within the South Cycladic Shear Zone, rocks there preserve exclusively Permo-Carboniferous (ca. 307–297 Ma) apatite U-Pb ages, corresponding to either relict high-temperature quartz domains (ca. >500°C) or a detrital age signature sourced from the Cycladic Basement, but not to Cenozoic movement along the interface. The dominance of Permian cooling ages suggests that significant exhumation of the Cycladic Basement occurred prior to and concurrent with deposition of the earliest Cycladic Blueschist Unit in the late Permian to early Triassic, and that Cycladic core complexes preserve high-temperature fabrics related to pre-Miocene extension. Importantly, this work advises caution when assuming the age of mylonitic fabrics in the footwalls of metamorphic core complexes across the globe without integrating deformation conditions within thermochronometric and geochemical context.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119857"},"PeriodicalIF":4.8,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036668","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 : 2026-01-24DOI: 10.1016/j.epsl.2026.119863
Alexander J. Clark , Xiaoqing Liu , Madalina Jaggi , Stefano M. Bernasconi , Victoria E. Taylor , A. Nele Meckler , Heather M. Stoll
The Early Eocene Climatic Optimum (EECO) is a time interval of great interest to the paleoclimate community due to the overall hot temperatures and polar amplification reconstructed by multiple temperature proxies. However, these conditions have been hard to reproduce in climate models and temperature estimates from different proxy carriers for the same regions can differ by 10 °C. Coccolith clumped isotopes—with a robust calibration recently established from laboratory cultures and sediment traps—represent an as-yet untested temperature proxy for this interval. Coccoliths are produced by coccolithophores with well-constrained depth and ecological preferences and therefore provide a clear depth and seasonal target for a proxy-model comparison for the late EECO (∼51.0–50.3 Ma).
We measured coccolith clumped isotopes in 15 globally distributed sites and find a 10 °C upper ocean meridional temperature gradient, similar to previous studies using different proxy systems and carriers such as Mg/Ca and δ18O in foraminifera. We compare our coccolith clumped isotope-derived temperatures to the DeepMIP model compilation, using the known modern ecological constraints of coccolithophores, and divide the model simulations into groups sorted by the difference in global mean surface temperature relative to preindustrial levels (ΔGMST). The best fitting model simulations have ΔGMST between 9.0–13.0 °C. Proxy-model temperature differences up to ±6 °C reveal a hemispheric asymmetry, with warmer proxy/colder model temperatures in the Southern Ocean and cooler proxy/warmer model temperatures in the northern mid-latitudes, highlighting the need for improved model constraints to more accurately simulate ocean circulation and heat transport phenomena.
{"title":"Seasonal upper ocean temperatures from coccolith clumped isotopes and a proxy-model comparison for the late Early Eocene Climatic Optimum","authors":"Alexander J. Clark , Xiaoqing Liu , Madalina Jaggi , Stefano M. Bernasconi , Victoria E. Taylor , A. Nele Meckler , Heather M. Stoll","doi":"10.1016/j.epsl.2026.119863","DOIUrl":"10.1016/j.epsl.2026.119863","url":null,"abstract":"<div><div>The Early Eocene Climatic Optimum (EECO) is a time interval of great interest to the paleoclimate community due to the overall hot temperatures and polar amplification reconstructed by multiple temperature proxies. However, these conditions have been hard to reproduce in climate models and temperature estimates from different proxy carriers for the same regions can differ by 10 °C. Coccolith clumped isotopes—with a robust calibration recently established from laboratory cultures and sediment traps—represent an as-yet untested temperature proxy for this interval. Coccoliths are produced by coccolithophores with well-constrained depth and ecological preferences and therefore provide a clear depth and seasonal target for a proxy-model comparison for the late EECO (∼51.0–50.3 Ma).</div><div>We measured coccolith clumped isotopes in 15 globally distributed sites and find a 10 °C upper ocean meridional temperature gradient, similar to previous studies using different proxy systems and carriers such as Mg/Ca and δ<sup>18</sup>O in foraminifera. We compare our coccolith clumped isotope-derived temperatures to the DeepMIP model compilation, using the known modern ecological constraints of coccolithophores, and divide the model simulations into groups sorted by the difference in global mean surface temperature relative to preindustrial levels (ΔGMST). The best fitting model simulations have ΔGMST between 9.0–13.0 °C. Proxy-model temperature differences up to ±6 °C reveal a hemispheric asymmetry, with warmer proxy/colder model temperatures in the Southern Ocean and cooler proxy/warmer model temperatures in the northern mid-latitudes, highlighting the need for improved model constraints to more accurately simulate ocean circulation and heat transport phenomena.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119863"},"PeriodicalIF":4.8,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036669","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 : 2026-01-24DOI: 10.1016/j.epsl.2026.119866
Joseph A. Stewart , Laura F. Robinson , James W.B. Rae , Naomi Pratt , Tianyu Chen , Maria Luiza de Carvalho Ferreira , Andrea Burke , Tao Li , Tina van de Flierdt
Atmospheric CO2 and the temperature of the interior Atlantic Ocean both increased in 2-steps during the last deglaciation, particularly during Heinrich Stadial 1 (HS1; ∼16 ka) and the Younger Dryas (YD; ∼12 ka). However, what drove these punctuated rises remains a long-standing question. The role of deep-ocean carbon storage, release, and redistribution continues to be debated. To establish the role of ocean circulation in deglacial carbon and nutrient cycling, we present new multi-proxy data in sub-fossil corals from mid-depths in the Equatorial Atlantic, including boron isotopes (δ11B; seawater pH), Ba/Ca (seawater [Ba] and refractory nutrients), and neodymium isotopes (εNd; provenance of seawater signal). Corals are dated to a precise radiometric age scale and combined with previously published radiocarbon and temperature proxy measurements on the same samples. Our data reveal abrupt intervals (∼500 years) of notably low pH, Ba-rich, and radiocarbon-depleted (old) waters at 15.4 and 12.0 ka during HS1 and the YD at depths of ∼1700 m. However, very low εNd (unradiogenic) values suggest that these corals were bathed in northern-sourced Atlantic waters throughout the deglaciation. These results imply that these (old) carbon- and nutrient-rich intermediate waters were not sourced from the carbon- and nutrient-rich Southern Ocean via Antarctic Intermediate Water (AAIW). Instead, carbon and nutrient accumulation at mid-depths in the tropical Atlantic was likely the result of remineralisation of organic matter at times of Atlantic Meridional Overturning Circulation (AMOC) slowdown. The Atlantic Ocean interior was therefore accumulating heat and carbon during these times when deepwater flushing was minimal, thus acting to partially dampen atmospheric CO2 rise and warming caused by ventilation of the Southern and Pacific Oceans.
{"title":"Accumulation of remineralised carbon and nutrients in the mid-depth Atlantic during Heinrich Stadial 1 and the Younger Dryas","authors":"Joseph A. Stewart , Laura F. Robinson , James W.B. Rae , Naomi Pratt , Tianyu Chen , Maria Luiza de Carvalho Ferreira , Andrea Burke , Tao Li , Tina van de Flierdt","doi":"10.1016/j.epsl.2026.119866","DOIUrl":"10.1016/j.epsl.2026.119866","url":null,"abstract":"<div><div>Atmospheric CO<sub>2</sub> and the temperature of the interior Atlantic Ocean both increased in 2-steps during the last deglaciation, particularly during Heinrich Stadial 1 (HS1; ∼16 ka) and the Younger Dryas (YD; ∼12 ka). However, what drove these punctuated rises remains a long-standing question. The role of deep-ocean carbon storage, release, and redistribution continues to be debated. To establish the role of ocean circulation in deglacial carbon and nutrient cycling, we present new multi-proxy data in sub-fossil corals from mid-depths in the Equatorial Atlantic, including boron isotopes (δ<sup>11</sup>B; seawater pH), Ba/Ca (seawater [Ba] and refractory nutrients), and neodymium isotopes (ε<sub>Nd</sub>; provenance of seawater signal). Corals are dated to a precise radiometric age scale and combined with previously published radiocarbon and temperature proxy measurements on the same samples. Our data reveal abrupt intervals (∼500 years) of notably low pH, Ba-rich, and radiocarbon-depleted (old) waters at 15.4 and 12.0 ka during HS1 and the YD at depths of ∼1700 m. However, very low ε<sub>Nd</sub> (unradiogenic) values suggest that these corals were bathed in northern-sourced Atlantic waters throughout the deglaciation. These results imply that these (old) carbon- and nutrient-rich intermediate waters were not sourced from the carbon- and nutrient-rich Southern Ocean via Antarctic Intermediate Water (AAIW). Instead, carbon and nutrient accumulation at mid-depths in the tropical Atlantic was likely the result of remineralisation of organic matter at times of Atlantic Meridional Overturning Circulation (AMOC) slowdown. The Atlantic Ocean interior was therefore accumulating heat and carbon during these times when deepwater flushing was minimal, thus acting to partially dampen atmospheric CO<sub>2</sub> rise and warming caused by ventilation of the Southern and Pacific Oceans.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119866"},"PeriodicalIF":4.8,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090729","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}
The potential for strong induced earthquakes in industrial production fields is largely controlled by the spatial arrangement of pre-existing faults shaped by regional tectonics. The 2021 Ms 6.0 Luxian earthquake in the southern Sichuan basin is an unusual case in which the seismogenic fault geometry deviates from the prevailing regional stress field and geological framework. To date, the seismogenic environment and the tectonic processes responsible for this destructive event remain poorly understood. In this study, we present a sedimentary shear-wave velocity model and eleven moment tensor solutions across the Luxian shale gas field, derived using data collected by our newly deployed seismic network. Our results reveal previously unrecognized, nearly reversed lateral variations in the amplitudes of synclinal low-velocity anomalies between terrestrial and marine strata, in addition to a first-order velocity contrast that correlates with the regional anticline–syncline architecture. The central Yujiasi syncline exhibits weaker low-velocity anomalies in the shallow terrestrial strata than areas to the north and south, reflecting lower strain intensity likely influenced by shallower décollement layers. Detected seismicity and anomalous reverse-faulting events with fold-parallel P-axes (including the Ms 6.0 earthquake) cluster mainly within two strain transition zones of the Yujiasi syncline, where stress is expected to concentrate and form fold-normal fault planes. These observations provide direct evidence that heterogeneous folding regulates the spatial distribution of induced seismicity in the southern Sichuan basin. They also help identify areas susceptible to induced seismic hazards and provide guidance for planning hydraulic fracturing operations in the region.
{"title":"Induced seismicity in the southern Sichuan basin regulated by heterogeneous folding","authors":"Bingfeng Zhang , Xuewei Bao , Mengfan Jiang , Kecheng Zhou","doi":"10.1016/j.epsl.2026.119860","DOIUrl":"10.1016/j.epsl.2026.119860","url":null,"abstract":"<div><div>The potential for strong induced earthquakes in industrial production fields is largely controlled by the spatial arrangement of pre-existing faults shaped by regional tectonics. The 2021 Ms 6.0 Luxian earthquake in the southern Sichuan basin is an unusual case in which the seismogenic fault geometry deviates from the prevailing regional stress field and geological framework. To date, the seismogenic environment and the tectonic processes responsible for this destructive event remain poorly understood. In this study, we present a sedimentary shear-wave velocity model and eleven moment tensor solutions across the Luxian shale gas field, derived using data collected by our newly deployed seismic network. Our results reveal previously unrecognized, nearly reversed lateral variations in the amplitudes of synclinal low-velocity anomalies between terrestrial and marine strata, in addition to a first-order velocity contrast that correlates with the regional anticline–syncline architecture. The central Yujiasi syncline exhibits weaker low-velocity anomalies in the shallow terrestrial strata than areas to the north and south, reflecting lower strain intensity likely influenced by shallower décollement layers. Detected seismicity and anomalous reverse-faulting events with fold-parallel P-axes (including the Ms 6.0 earthquake) cluster mainly within two strain transition zones of the Yujiasi syncline, where stress is expected to concentrate and form fold-normal fault planes. These observations provide direct evidence that heterogeneous folding regulates the spatial distribution of induced seismicity in the southern Sichuan basin. They also help identify areas susceptible to induced seismic hazards and provide guidance for planning hydraulic fracturing operations in the region.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"679 ","pages":"Article 119860"},"PeriodicalIF":4.8,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146036670","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号