Dunfeng Xiang, Qigui Mao, David Chew, Zhiyong Zhang, Lin Wu, Nan Wang, Chao Guo, Meng Zhang, Guoxiong Ma, He Yang, Wenjiao Xiao
The West Kunlun (WKL) orogen, a pivotal boundary on the western Tibetan Plateau, records the dynamic interplay between northward underthrusting Indian lithosphere and the Tarim craton. Despite its significance, the exhumation history and mechanisms of plateau growth in this region remain contentious. Here, apatite fission-track (AFT) and (U-Th)/He (AHe) thermochronology data from three bedrock elevation transects across the WKL were used to refine the Miocene exhumation processes in the region. Our results reveal a regionally consistent two-phase acceleration in late Miocene exhumation at ca. 11−10 and ca. 7−6 Ma. Integration with regional thermochronologic, magmatic, and seismic data shows a systematic younging of cooling ages and (ultra)potassic magmatism toward the WKL, alongside increasing exhumation rates. These trends reflect outward plateau expansion driven by progressive indentation of the Indian plate into Asia. This culminated at ca. 11−10 Ma, when the cratonic Indian slab directly impinged the Tarim craton, as evidenced by rapid surface uplift and the formation of ca. 10 Ma and younger (ultra)potassic magmas in the WKL orogen. Our findings highlight the coupling between deep lithospheric processes and surface deformation, providing critical constraints on the timing of the India-Tarim collision and the mechanisms driving plateau growth along the northwestern margin of the Tibetan Plateau.
{"title":"Late Miocene rapid exhumation in the West Kunlun range: Insights into Tibetan Plateau growth and India-Asia lithospheric collision","authors":"Dunfeng Xiang, Qigui Mao, David Chew, Zhiyong Zhang, Lin Wu, Nan Wang, Chao Guo, Meng Zhang, Guoxiong Ma, He Yang, Wenjiao Xiao","doi":"10.1130/g53642.1","DOIUrl":"https://doi.org/10.1130/g53642.1","url":null,"abstract":"The West Kunlun (WKL) orogen, a pivotal boundary on the western Tibetan Plateau, records the dynamic interplay between northward underthrusting Indian lithosphere and the Tarim craton. Despite its significance, the exhumation history and mechanisms of plateau growth in this region remain contentious. Here, apatite fission-track (AFT) and (U-Th)/He (AHe) thermochronology data from three bedrock elevation transects across the WKL were used to refine the Miocene exhumation processes in the region. Our results reveal a regionally consistent two-phase acceleration in late Miocene exhumation at ca. 11−10 and ca. 7−6 Ma. Integration with regional thermochronologic, magmatic, and seismic data shows a systematic younging of cooling ages and (ultra)potassic magmatism toward the WKL, alongside increasing exhumation rates. These trends reflect outward plateau expansion driven by progressive indentation of the Indian plate into Asia. This culminated at ca. 11−10 Ma, when the cratonic Indian slab directly impinged the Tarim craton, as evidenced by rapid surface uplift and the formation of ca. 10 Ma and younger (ultra)potassic magmas in the WKL orogen. Our findings highlight the coupling between deep lithospheric processes and surface deformation, providing critical constraints on the timing of the India-Tarim collision and the mechanisms driving plateau growth along the northwestern margin of the Tibetan Plateau.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"17 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145215822","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}
Anhydrite is considered a rare mineral phase in magmas, with only ∼33 documented occurrences worldwide. However, anhydrite readily decomposes in the near-surface environment, making it difficult to recognize its former presence in rocks collected at or near Earth’s surface. In such samples, only small anhydrite inclusions fully shielded within other minerals can have survived. During a recent field trip to the southwestern USA, we sampled 17 Laramide-age (ca. 40−80 Ma) magma systems, most of which are associated with porphyry copper deposits. A systematic search for anhydrite inclusions preserved within apatite, amphibole, plagioclase, and quartz phenocrysts in ∼100 rock samples by optical microscopy and Raman spectroscopy revealed that each of these 17 magma systems was at least temporarily anhydrite-saturated. Also, most previously identified magmatic anhydrite-bearing intrusions are associated with porphyry copper deposits, and both intrusive and volcanic rocks containing magmatic anhydrite show high Sr/Y ratios. These observations suggest that anhydrite saturation and porphyry copper formation are linked via magma fractionation at high pressure. Compared to average arc magmas, anhydrite-bearing magmas are unusually oxidized and sulfur-rich and seem to also be unusually water-rich. Hence, our preferred interpretation is that magma generation and/or fractionation at high pressure promotes the formation of superhydrous and oxidized magmas, which in turn promotes high sulfur contents and ultimately the precipitation of anhydrite. The high mineralization potential of these magmas does not need to result from their high sulfur content but could be caused by other properties of high-pressure magmas.
{"title":"Widespread anhydrite saturation in Laramide-age arc magmas of the southwestern USA","authors":"Andreas Audétat, Jia Chang, Sean P. Gaynor","doi":"10.1130/g53661.1","DOIUrl":"https://doi.org/10.1130/g53661.1","url":null,"abstract":"Anhydrite is considered a rare mineral phase in magmas, with only ∼33 documented occurrences worldwide. However, anhydrite readily decomposes in the near-surface environment, making it difficult to recognize its former presence in rocks collected at or near Earth’s surface. In such samples, only small anhydrite inclusions fully shielded within other minerals can have survived. During a recent field trip to the southwestern USA, we sampled 17 Laramide-age (ca. 40−80 Ma) magma systems, most of which are associated with porphyry copper deposits. A systematic search for anhydrite inclusions preserved within apatite, amphibole, plagioclase, and quartz phenocrysts in ∼100 rock samples by optical microscopy and Raman spectroscopy revealed that each of these 17 magma systems was at least temporarily anhydrite-saturated. Also, most previously identified magmatic anhydrite-bearing intrusions are associated with porphyry copper deposits, and both intrusive and volcanic rocks containing magmatic anhydrite show high Sr/Y ratios. These observations suggest that anhydrite saturation and porphyry copper formation are linked via magma fractionation at high pressure. Compared to average arc magmas, anhydrite-bearing magmas are unusually oxidized and sulfur-rich and seem to also be unusually water-rich. Hence, our preferred interpretation is that magma generation and/or fractionation at high pressure promotes the formation of superhydrous and oxidized magmas, which in turn promotes high sulfur contents and ultimately the precipitation of anhydrite. The high mineralization potential of these magmas does not need to result from their high sulfur content but could be caused by other properties of high-pressure magmas.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"1 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145215780","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}
Hongwei Ping, Xin Yang, Xiaofeng Liu, Xiaoqiang Li, Honghan Chen, Se Gong, Simon C. George
The Marinoan glaciation was one of the most severe known Snowball Earth climate events, terminating abruptly at ca. 635 Ma with the deposition of globally distributed cap carbonate sediments overlying glacial deposits. This extreme global warming event has been attributed to methane release from the destabilization of gas hydrates, as supported by the abnormally negative δ13C signatures (δ13C = −48‰ to −41‰) of calcite cements that occur in the cap dolostones. However, the hypothesis of gas hydrate destabilization is controversial as the timing of methane release and the methane origin are not clear. Here, we demonstrate that extremely 13C-depleted (δ13C = −51.9‰ to −50.9‰) calcite precipitation occurred much later (618 ± 5.8 Ma) than the termination of Marinoan glaciation in the cap dolostones in South China, and it was associated with thermogenic methane release, as supported by a fluid inclusion gas δ13C1 value (−38.7‰) and the C1/(C2 + C3) ratio measured in the most 13C-depleted calcites. Our findings prove that extremely negative δ13C signatures of calcite cements in cap dolostones are unrelated to clathrate destabilization, thus excluding this mechanism as a cause for the termination of the Marinoan Snowball Earth. This study not only refines our understanding of Ediacaran carbon cycling but also has implications for evaluating hydrocarbon generation in Precambrian sedimentary basins.
{"title":"Thermogenic methane release after Marinoan glaciation induced extremely 13C-depleted calcite precipitation in cap dolostones","authors":"Hongwei Ping, Xin Yang, Xiaofeng Liu, Xiaoqiang Li, Honghan Chen, Se Gong, Simon C. George","doi":"10.1130/g53668.1","DOIUrl":"https://doi.org/10.1130/g53668.1","url":null,"abstract":"The Marinoan glaciation was one of the most severe known Snowball Earth climate events, terminating abruptly at ca. 635 Ma with the deposition of globally distributed cap carbonate sediments overlying glacial deposits. This extreme global warming event has been attributed to methane release from the destabilization of gas hydrates, as supported by the abnormally negative δ13C signatures (δ13C = −48‰ to −41‰) of calcite cements that occur in the cap dolostones. However, the hypothesis of gas hydrate destabilization is controversial as the timing of methane release and the methane origin are not clear. Here, we demonstrate that extremely 13C-depleted (δ13C = −51.9‰ to −50.9‰) calcite precipitation occurred much later (618 ± 5.8 Ma) than the termination of Marinoan glaciation in the cap dolostones in South China, and it was associated with thermogenic methane release, as supported by a fluid inclusion gas δ13C1 value (−38.7‰) and the C1/(C2 + C3) ratio measured in the most 13C-depleted calcites. Our findings prove that extremely negative δ13C signatures of calcite cements in cap dolostones are unrelated to clathrate destabilization, thus excluding this mechanism as a cause for the termination of the Marinoan Snowball Earth. This study not only refines our understanding of Ediacaran carbon cycling but also has implications for evaluating hydrocarbon generation in Precambrian sedimentary basins.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"14 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209530","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}
Magmatic intrusions in nonvolcanic areas are believed to cause extensive CO2 degassing and seismicity. However, the size, geometry, and spatial relationships of these hypothesized intrusive bodies remain unclear due to a lack of high-resolution geophysical data, especially in Northeast China sedimentary basins. Here, we present a three-dimensional electrical resistivity model based on magnetotelluric data from the Songliao Basin in Northeast China. The model shows a low-resistivity anomaly at the Moho depth vertically connecting to two shallower, sill-like anomalies in the crust. These anomalies are interpreted as multilevel basaltic intrusions, with the mid-crust sills estimated to contain up to 150 km3 of melt. The layering of the crust, as well as the level of neutral buoyancy, plays a critical role in controlling the geometry and depth of the intrusions in the basins. Seismicity, high heat flow, and CO2 degassing indicate that this huge magmatic system, although located in a nonvolcanic area, is still active.
{"title":"Large, multilevel magmatic intrusions as an important carbon degassing source in a nonvolcanic setting","authors":"Yabin Li, Shiwen Li, Junhao Guo, Zikun Zhou, Shuai Qiao, Fengyan Wang, Guido Ventura, Wenliang Xu, Aihua Weng","doi":"10.1130/g53620.1","DOIUrl":"https://doi.org/10.1130/g53620.1","url":null,"abstract":"Magmatic intrusions in nonvolcanic areas are believed to cause extensive CO2 degassing and seismicity. However, the size, geometry, and spatial relationships of these hypothesized intrusive bodies remain unclear due to a lack of high-resolution geophysical data, especially in Northeast China sedimentary basins. Here, we present a three-dimensional electrical resistivity model based on magnetotelluric data from the Songliao Basin in Northeast China. The model shows a low-resistivity anomaly at the Moho depth vertically connecting to two shallower, sill-like anomalies in the crust. These anomalies are interpreted as multilevel basaltic intrusions, with the mid-crust sills estimated to contain up to 150 km3 of melt. The layering of the crust, as well as the level of neutral buoyancy, plays a critical role in controlling the geometry and depth of the intrusions in the basins. Seismicity, high heat flow, and CO2 degassing indicate that this huge magmatic system, although located in a nonvolcanic area, is still active.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"76 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145209529","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}
Chen Zhang, Dadong Liu, Min She, Jianhua He, Jim R. Underschultz, Andrew D. La Croix, Yixin Dong, Yuhan Huang
Fluid overpressure is a common phenomenon in sedimentary basins, and overpressure induced by hydrocarbon generation has attracted considerable attention. However, direct temporal constraints are lacking, and the evolutionary process remains poorly understood. Here, we provide absolute chronological constraints on the paleo−fluid pressure evolution in shales of the Sichuan Basin, China, by integrating in situ U-Pb dating with fluid inclusion analysis of bed-parallel calcite veins. Our results reveal that overpressure due to hydrocarbon generation during deep burial evolved in a two-stage, stepwise exponential manner with increasing thermal maturity. During the kerogen gas generation phase (236−156 Ma; Ro [vitrinite reflectance] = 1.3%−2.0%), fluid pressure increased slowly, and the pressure coefficient decreased gradually. Subsequently, during the advanced burial stage, both fluid pressure and the pressure coefficient increased abruptly by up to threefold, associated with oil-cracking gas generation (148−84 Ma; Ro >2.0%). Strong hydrocarbon generation, combined with low permeability, enables fluid overpressure to persist from deep burial through uplift to the present day. Our findings show that under tectonically quiescent conditions, fluid pressure in shale driven solely by hydrocarbon generation increases in a stepwise exponential manner rather than a continuous nonlinear trend and remains largely preserved even during uplift unless disrupted by faulting. This successful application highlights the broad potential of absolute geochronological constraints for refining models of fluid evolution in sedimentary basins.
{"title":"Direct constraints on shale fluid overpressure evolution from U-Pb dating of bed-parallel fracture-filling calcite","authors":"Chen Zhang, Dadong Liu, Min She, Jianhua He, Jim R. Underschultz, Andrew D. La Croix, Yixin Dong, Yuhan Huang","doi":"10.1130/g53931.1","DOIUrl":"https://doi.org/10.1130/g53931.1","url":null,"abstract":"Fluid overpressure is a common phenomenon in sedimentary basins, and overpressure induced by hydrocarbon generation has attracted considerable attention. However, direct temporal constraints are lacking, and the evolutionary process remains poorly understood. Here, we provide absolute chronological constraints on the paleo−fluid pressure evolution in shales of the Sichuan Basin, China, by integrating in situ U-Pb dating with fluid inclusion analysis of bed-parallel calcite veins. Our results reveal that overpressure due to hydrocarbon generation during deep burial evolved in a two-stage, stepwise exponential manner with increasing thermal maturity. During the kerogen gas generation phase (236−156 Ma; Ro [vitrinite reflectance] = 1.3%−2.0%), fluid pressure increased slowly, and the pressure coefficient decreased gradually. Subsequently, during the advanced burial stage, both fluid pressure and the pressure coefficient increased abruptly by up to threefold, associated with oil-cracking gas generation (148−84 Ma; Ro >2.0%). Strong hydrocarbon generation, combined with low permeability, enables fluid overpressure to persist from deep burial through uplift to the present day. Our findings show that under tectonically quiescent conditions, fluid pressure in shale driven solely by hydrocarbon generation increases in a stepwise exponential manner rather than a continuous nonlinear trend and remains largely preserved even during uplift unless disrupted by faulting. This successful application highlights the broad potential of absolute geochronological constraints for refining models of fluid evolution in sedimentary basins.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"6 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145195501","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}
Yuan Gao, Xing Tian, Yongyun Hu, Xiang Li, Wenju Cai, Jianming Qin, Jiaqi Guo, Xiaojing Du, Tyler Kukla, Daniel E. Ibarra, He Huang, Lixin Wu, Chengshan Wang
The El Niño−Southern Oscillation (ENSO) is the dominant mode of interannual climate fluctuation, generating teleconnections impacting global climate variability today. Its behavior in past greenhouse climates provides a useful perspective for understanding future ENSO under global warming. Despite annually resolved geologic evidence of active ENSO since the Late Cretaceous, ENSO operation at earlier greenhouse periods is poorly resolved. Here, we present evidence from annually resolved lacustrine sediments in northeast China showing signals of interannual precipitation variability 120 m.y. ago, with major frequency bands of 2−5 yr. A coupled climate simulation of the Early Cretaceous generates ENSO-like variability with similar 2−5 yr periodicities in tropical Pacific sea-surface temperatures and atmospheric teleconnection to northeast China precipitation. The Early Cretaceous ENSO-like variability shows higher frequency and stronger amplitude compared to modern ENSO, resembling predictions of future ENSO evolution.
El Niño−南方涛动（ENSO）是年际气候波动的主要模式，产生影响当今全球气候变率的遥相关。它在过去温室气候中的行为为理解全球变暖下未来ENSO提供了有用的视角。尽管自晚白垩纪以来每年都有ENSO活动的地质证据，但早期温室期的ENSO活动却很难得到解决。在这里，我们提供了来自中国东北湖泊沉积物的证据，显示了120亿年以前的年际降水变率信号，主要频带为2 - 5年。早白垩世的耦合气候模拟产生了类似enso的变率，热带太平洋海面温度和大气与东北降水的远相关具有相似的2 - 5年周期性。与现代ENSO相比，早白垩世ENSO样变率表现出更高的频率和更强的幅度，类似于对未来ENSO演变的预测。
{"title":"Active El Niño−Southern Oscillation−like interannual variability 120 million years ago","authors":"Yuan Gao, Xing Tian, Yongyun Hu, Xiang Li, Wenju Cai, Jianming Qin, Jiaqi Guo, Xiaojing Du, Tyler Kukla, Daniel E. Ibarra, He Huang, Lixin Wu, Chengshan Wang","doi":"10.1130/g53646.1","DOIUrl":"https://doi.org/10.1130/g53646.1","url":null,"abstract":"The El Niño−Southern Oscillation (ENSO) is the dominant mode of interannual climate fluctuation, generating teleconnections impacting global climate variability today. Its behavior in past greenhouse climates provides a useful perspective for understanding future ENSO under global warming. Despite annually resolved geologic evidence of active ENSO since the Late Cretaceous, ENSO operation at earlier greenhouse periods is poorly resolved. Here, we present evidence from annually resolved lacustrine sediments in northeast China showing signals of interannual precipitation variability 120 m.y. ago, with major frequency bands of 2−5 yr. A coupled climate simulation of the Early Cretaceous generates ENSO-like variability with similar 2−5 yr periodicities in tropical Pacific sea-surface temperatures and atmospheric teleconnection to northeast China precipitation. The Early Cretaceous ENSO-like variability shows higher frequency and stronger amplitude compared to modern ENSO, resembling predictions of future ENSO evolution.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"23 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145189431","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}
Eliel S.C. Anttila, John M. Cottle, Demian A. Nelson, Ryan P. Eden, Andrew R.C. Kylander-Clark
Intracontinental volcanism inboard of growing transform boundaries has often been associated with the opening of slab windows following the collision of an oceanic spreading ridge with the continental margin. Yet, the specific drivers of supra-slab-window volcanism remain unresolved, partly due to uncertainties surrounding the spatiotemporal evolution of volcanic activity inboard of the evolving transform boundary. We report the distribution, age, and geochemical evolution of volcanism above a slab window by integrating 33 new zircon U-Pb ages and paired zircon Hf isotope measurements from the Coast Range Volcanics of California (USA) into a paleogeographic reconstruction of western North America from 27 Ma to the present. A cluster of 18−15 Ma volcanic centers in central California are interpreted to have been driven by extension of the Transverse Ranges above a condensed geotherm, while a northwest-younging linear progression of volcanism, spanning ca. 27−3 Ma, is proposed to be associated with the vertical vorticity component of toroidal flow of the shallow mantle around the northwest-migrating trailing edge of the subducting Gorda slab. Furthermore, our model suggests that a 22−12 Ma gap in the northwest-younging volcanic trend was driven by occlusion of the Gorda slab edge by a thick crustal root in the southern Sierra Nevada. This occlusion likely also interrupted or redirected regional eastward shallow-mantle flow beneath the continental margin, putatively reducing asthenospheric traction on the base of the crust below western North America and driving increased rates of extension and volcanism in the Basin and Range province.
{"title":"Geodynamic controls on slab window volcanism: Insights from the spatiotemporal evolution of the Coast Range Volcanics, California, USA","authors":"Eliel S.C. Anttila, John M. Cottle, Demian A. Nelson, Ryan P. Eden, Andrew R.C. Kylander-Clark","doi":"10.1130/g53709.1","DOIUrl":"https://doi.org/10.1130/g53709.1","url":null,"abstract":"Intracontinental volcanism inboard of growing transform boundaries has often been associated with the opening of slab windows following the collision of an oceanic spreading ridge with the continental margin. Yet, the specific drivers of supra-slab-window volcanism remain unresolved, partly due to uncertainties surrounding the spatiotemporal evolution of volcanic activity inboard of the evolving transform boundary. We report the distribution, age, and geochemical evolution of volcanism above a slab window by integrating 33 new zircon U-Pb ages and paired zircon Hf isotope measurements from the Coast Range Volcanics of California (USA) into a paleogeographic reconstruction of western North America from 27 Ma to the present. A cluster of 18−15 Ma volcanic centers in central California are interpreted to have been driven by extension of the Transverse Ranges above a condensed geotherm, while a northwest-younging linear progression of volcanism, spanning ca. 27−3 Ma, is proposed to be associated with the vertical vorticity component of toroidal flow of the shallow mantle around the northwest-migrating trailing edge of the subducting Gorda slab. Furthermore, our model suggests that a 22−12 Ma gap in the northwest-younging volcanic trend was driven by occlusion of the Gorda slab edge by a thick crustal root in the southern Sierra Nevada. This occlusion likely also interrupted or redirected regional eastward shallow-mantle flow beneath the continental margin, putatively reducing asthenospheric traction on the base of the crust below western North America and driving increased rates of extension and volcanism in the Basin and Range province.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"42 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145154045","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}
Abdulwahab M. Bello, Abduljamiu O. Amao, Anas M. Salisu, Khalid Al-Ramadan
Dolomite formation remains a debated topic in sedimentary geology, particularly concerning the mechanisms driving its precipitation under natural conditions. While microbial processes have been well studied, the influence of abiotic factors, such as clay minerals, is less understood. This study uses hydrothermal reactor experiments at 80−250 °C to examine the role of clay minerals in post-compactional dolomitization. Results show that smectite and illite effectively promote dolomitization by providing nucleation sites and aiding Mg2+ dehydration through their highly negative surface charges. In contrast, kaolinite and dickite were less effective due to their charge neutrality. In calcite-kaolinite mixtures, dolomite formed at 200 °C when kaolinite partially converted to smectite but was inhibited at 250 °C due to dickite formation. Samples containing only calcite showed little to no dolomite formation, highlighting the role of reactive clays. Dolomitization occurred through two mechanisms: (1) complete calcite dissolution followed by dolomite nucleation, and (2) recrystallization with progressive Mg incorporation. These findings support clay-catalyzed dolomitization as a significant abiotic pathway in ancient muddy carbonates and mixed clastic-carbonate systems.
{"title":"Clay-driven dolomitization at moderate to high temperatures: Evidence from hydrothermal experiments","authors":"Abdulwahab M. Bello, Abduljamiu O. Amao, Anas M. Salisu, Khalid Al-Ramadan","doi":"10.1130/g53737.1","DOIUrl":"https://doi.org/10.1130/g53737.1","url":null,"abstract":"Dolomite formation remains a debated topic in sedimentary geology, particularly concerning the mechanisms driving its precipitation under natural conditions. While microbial processes have been well studied, the influence of abiotic factors, such as clay minerals, is less understood. This study uses hydrothermal reactor experiments at 80−250 °C to examine the role of clay minerals in post-compactional dolomitization. Results show that smectite and illite effectively promote dolomitization by providing nucleation sites and aiding Mg2+ dehydration through their highly negative surface charges. In contrast, kaolinite and dickite were less effective due to their charge neutrality. In calcite-kaolinite mixtures, dolomite formed at 200 °C when kaolinite partially converted to smectite but was inhibited at 250 °C due to dickite formation. Samples containing only calcite showed little to no dolomite formation, highlighting the role of reactive clays. Dolomitization occurred through two mechanisms: (1) complete calcite dissolution followed by dolomite nucleation, and (2) recrystallization with progressive Mg incorporation. These findings support clay-catalyzed dolomitization as a significant abiotic pathway in ancient muddy carbonates and mixed clastic-carbonate systems.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"2 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145133825","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}
Marta Marchegiano, Martin Ziegler, Or M. Bialik, David De Vleeschouwer
Reconstructing past climates in hot, arid regions is challenging due to scarce archives and proxies. Clumped isotopes (∆47) on sabkha calcite-aragonite minerals might alleviate this situation. We apply the ∆47 technique to modern and middle Miocene sabkha samples yielding temperatures of 25.2 ± 2.8 °C to 32.1 ± 3.0 °C. Results show that sabkha calcite-aragonite minerals mainly reflect summer half-year temperatures, when most precipitation occurs. Reconstructed δ18Owater (SMOW) (SMOW—standard mean ocean water) values (3.2 ± 1.0‰ and 5.2 ± 1.2‰) scale with the intensity of evaporation in these intertidal, supratidal, and lagoonal settings. Despite higher middle Miocene atmospheric CO2, reconstructed sabkha temperatures are similar to modern values, suggesting a low climate sensitivity. Thus, sabkha ∆47 is a valuable tool for paleotemperature reconstructions in low-latitudes continental settings.
由于缺乏档案和代理资料，重建炎热干旱地区过去的气候是具有挑战性的。sabkha方解石-文石矿物上的团块同位素（∆47）可能会缓解这种情况。我们将∆47技术应用于现代和中新世中期sabkha样品，得到的温度为25.2±2.8°C至32.1±3.0°C。结果表明，sabkha方解石文石矿物主要反映夏季半年温度，是降水最多的季节。重建的δ18Owater （SMOW - standard mean ocean water）值（3.2±1.0‰和5.2±1.2‰）与潮间带、潮上带和泻湖的蒸发强度呈正相关。尽管中新世中期大气CO2较高，但重建的sabkha温度与现代值相似，表明气候敏感性较低。因此，sabkha∆47对于低纬度大陆环境下的古温度重建是一个有价值的工具。
{"title":"Limited warming of middle Miocene arid low-latitude climates: Application of clumped isotopes in sabkha environments","authors":"Marta Marchegiano, Martin Ziegler, Or M. Bialik, David De Vleeschouwer","doi":"10.1130/g53550.1","DOIUrl":"https://doi.org/10.1130/g53550.1","url":null,"abstract":"Reconstructing past climates in hot, arid regions is challenging due to scarce archives and proxies. Clumped isotopes (∆47) on sabkha calcite-aragonite minerals might alleviate this situation. We apply the ∆47 technique to modern and middle Miocene sabkha samples yielding temperatures of 25.2 ± 2.8 °C to 32.1 ± 3.0 °C. Results show that sabkha calcite-aragonite minerals mainly reflect summer half-year temperatures, when most precipitation occurs. Reconstructed δ18Owater (SMOW) (SMOW—standard mean ocean water) values (3.2 ± 1.0‰ and 5.2 ± 1.2‰) scale with the intensity of evaporation in these intertidal, supratidal, and lagoonal settings. Despite higher middle Miocene atmospheric CO2, reconstructed sabkha temperatures are similar to modern values, suggesting a low climate sensitivity. Thus, sabkha ∆47 is a valuable tool for paleotemperature reconstructions in low-latitudes continental settings.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"115 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145127701","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}
Pilar Madrigal, Kaj Hoernle, Brian R. Jicha, Christian Timm, Dieter Garbe-Schönberg, William W. Sager, Folkmar Hauff, Maxim Portnyagin, Gene Yogodzinski
Our knowledge of the Cretaceous history of the northwestern Pacific plate relies on tectonic reconstructions that lack geochronologic and geochemical constraints due to the paucity of sampling in this area. We present new age and compositional data for samples from four Emperor seamounts: Meiji, Hanzei, Suizei, and Tenji. Tholeiites from Tenji (66 Ma) and Suizei (70 Ma) yield ages consistent with the expected age progression, whereas a trachytic sample from Hanzei (66 Ma, expected age of ca. 73 Ma) represents an alkalic post-shield event. The ridge-like morphology and depleted geochemistry of Meiji to Suizei seamounts and the age (78−75 Ma) and depleted composition of the volcanic elongated ridges (VERs) southeast of Detroit seamount (ca. 76 Ma) are consistent with plume-ridge interaction. The VERs account for the missing volume of volcanism expected from plume-ridge interaction for the oldest Emperor seamounts. A small seamount with mid-ocean ridge basalt−like geochemistry located east of northern Detroit seamount yielded an age of 100 Ma, representing a minimum age for the oceanic crustal sliver between the Emperor Trough and the Stalemate Fracture Zone. We propose ∼300 km of dextral offset along the Emperor Trough to explain the location of this older crustal sliver. Our new data provide important constraints on the poorly known early evolution of the Hawaiian-Emperor Seamount Chain and the Cretaceous Quiet Zone (Cretaceous Normal Superchron) geotectonic history of the northwestern Pacific plate.
{"title":"Early Emperor seamount evolution and geotectonics of the northwestern Pacific plate","authors":"Pilar Madrigal, Kaj Hoernle, Brian R. Jicha, Christian Timm, Dieter Garbe-Schönberg, William W. Sager, Folkmar Hauff, Maxim Portnyagin, Gene Yogodzinski","doi":"10.1130/g53477.1","DOIUrl":"https://doi.org/10.1130/g53477.1","url":null,"abstract":"Our knowledge of the Cretaceous history of the northwestern Pacific plate relies on tectonic reconstructions that lack geochronologic and geochemical constraints due to the paucity of sampling in this area. We present new age and compositional data for samples from four Emperor seamounts: Meiji, Hanzei, Suizei, and Tenji. Tholeiites from Tenji (66 Ma) and Suizei (70 Ma) yield ages consistent with the expected age progression, whereas a trachytic sample from Hanzei (66 Ma, expected age of ca. 73 Ma) represents an alkalic post-shield event. The ridge-like morphology and depleted geochemistry of Meiji to Suizei seamounts and the age (78−75 Ma) and depleted composition of the volcanic elongated ridges (VERs) southeast of Detroit seamount (ca. 76 Ma) are consistent with plume-ridge interaction. The VERs account for the missing volume of volcanism expected from plume-ridge interaction for the oldest Emperor seamounts. A small seamount with mid-ocean ridge basalt−like geochemistry located east of northern Detroit seamount yielded an age of 100 Ma, representing a minimum age for the oceanic crustal sliver between the Emperor Trough and the Stalemate Fracture Zone. We propose ∼300 km of dextral offset along the Emperor Trough to explain the location of this older crustal sliver. Our new data provide important constraints on the poorly known early evolution of the Hawaiian-Emperor Seamount Chain and the Cretaceous Quiet Zone (Cretaceous Normal Superchron) geotectonic history of the northwestern Pacific plate.","PeriodicalId":12642,"journal":{"name":"Geology","volume":"40 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2025-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145117007","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：