Geochemistry Geophysics Geosystems最新文献_第5页

Crustal Structure and Tectonic Origin of Late Cretaceous Oceanic Crust and Adjacent Caribbean Large Igneous Province in the Colombian Basin

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-21 DOI: 10.1029/2024GC011602

Juan Pablo Ramos, Paul Mann, Luis Carlos Carvajal-Arenas

{"title":"Crustal Structure and Tectonic Origin of Late Cretaceous Oceanic Crust and Adjacent Caribbean Large Igneous Province in the Colombian Basin","authors":"Juan Pablo Ramos, Paul Mann, Luis Carlos Carvajal-Arenas","doi":"10.1029/2024GC011602","DOIUrl":"https://doi.org/10.1029/2024GC011602","url":null,"abstract":"The tectonic origin of the Caribbean Large Igneous Province (CLIP) and its adjacent oceanic crust in the Colombian Basin are examined using 3D seismic reflection mapping, regional gravity and magnetic data mapping, and a compilation of CLIP radiometric ages. Using these data, we show how the CLIP and its adjacent oceanic crust formed by extensive and prolonged volcanism linked to a regional, east-west trending, extinct spreading ridge. Our 3D seismic mapping of the crustal structure in the Colombian Basin shows a northeast-striking transform fault separating two extinct ridge segments based on the abrupt shallowing (>10 km) of the Moho, and the changes in crustal thickness from 16 km to <4 km. Additional 3D mapping combined with mapping of regional gravity anomalies reveals other northeast-trending transform faults that offset the east-west-trending spreading ridge system. Integration of previously studied magnetic anomalies suggests that seafloor spreading in the Colombian and Venezuelan basins occurred during the primary period of CLIP formation from the Albian to Campanian (108–73 Ma). The presence of seaward dipping reflectors mapped using the 3D seismic reflection data further supports our hypothesis that the thickened crust of the CLIP accompanied seafloor spreading along the newly identified spreading ridge. The ages of CLIP basalts recovered from outcrops and offshore samples support our conclusions that the CLIP is largely the product of volcanic eruptions along a spreading ridge system over a period of 30 My and that the areas of normal oceanic crust adjacent to the spreading ridge records a gradual reduction in the magma supply to the spreading ridge.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011602","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143456142","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}

引用次数: 0

Consequences of a Global Slowdown in Seafloor Spreading for Sea Level and Mantle Heat Loss

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-21 DOI: 10.1029/2024GC011773

Colleen A. Dalton, Christian Huber, Timothy D. Herbert, Weimin Si

{"title":"Consequences of a Global Slowdown in Seafloor Spreading for Sea Level and Mantle Heat Loss","authors":"Colleen A. Dalton, Christian Huber, Timothy D. Herbert, Weimin Si","doi":"10.1029/2024GC011773","DOIUrl":"https://doi.org/10.1029/2024GC011773","url":null,"abstract":"Variations in global mean sea level over millions of years originate from changes in both the climate and solid Earth systems. Most previous studies of the solid Earth contribution to sea level focused on the past 100 Myr or longer with a temporal resolution of 10 Myr or coarser. Here, we consider how sea level was affected by a 35% global slowdown in ocean crust production that occurred during 15–6 Ma, as was recently identified from marine magnetic anomalies. We calculate how the seafloor area-age distribution evolves over time in response to the slowdown in crust production, exploring how assumptions about the initial condition and crust destruction rate affect the results. The slowdown decreases the proportion of young shallow seafloor relative to older deeper seafloor, which produces a sea-level fall of 24–30 m if the plate-cooling model is used to describe the age dependence of bathymetry and a slightly larger fall if the half-space cooling model is used. The slowdown also increases the prevalence of slow and ultraslow spreading centers, which, by inhibiting mantle melting, causes the ocean crust to thin by 0.5 km, with a concomitant additional 2-m sea-level fall. Although an easily interpretable record of sea-level variations from sequence stratigraphy does not exist for the past 15 Myr, data from coastal New Jersey and offshore Nova Scotia are broadly consistent with our predictions. If the slowdown affects volcanic degassing, atmospheric CO2, and the climate, thermosteric and ice effects can produce additional sea-level fall of >60 m.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011773","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143456143","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}

引用次数: 0

A Holocene Paleosecular Variation Record From the Northwestern Ross Sea, Antarctica

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-20 DOI: 10.1029/2024GC011912

Olivia J. Truax, Faye Nelson, Christina R. Riesselman, Christian Ohneiser, Jae Il Lee, Kyu-Cheul Yoo, Bob Dagg, Gary Wilson

{"title":"A Holocene Paleosecular Variation Record From the Northwestern Ross Sea, Antarctica","authors":"Olivia J. Truax, Faye Nelson, Christina R. Riesselman, Christian Ohneiser, Jae Il Lee, Kyu-Cheul Yoo, Bob Dagg, Gary Wilson","doi":"10.1029/2024GC011912","DOIUrl":"https://doi.org/10.1029/2024GC011912","url":null,"abstract":"We present a mid-to-late Holocene record of relative paleosecular variation from the Ross Sea region of Antarctica. The 6,700-year-long record of inclination, declination, and relative paleointensity from a marine sediment core collected near Cape Adare is independently dated using a combination of ramped pyrolysis oxidation and carbonate radiocarbon dates. Agreement between the large-scale features of the relative paleointensity record and the virtual axial geomagnetic dipole moment suggests that changes in the record are dominated by the dipole component of the Earth's geomagnetic field. Correspondence between the record and a non-independently dated reconstruction from the Antarctic Peninsula indicates regionally coherent changes in the geomagnetic field intensity in the southern high latitudes during the mid-to-late Holocene. The prominent features of the record serve as stratigraphic markers for hard-to-date Antarctic sedimentary records and a constraint on Holocene geomagnetic field behavior when incorporated into the next generation of geomagnetic field models.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011912","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143447009","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}

引用次数: 0

Mantle Dynamics of the Long-Lived Middle Yangtze Basaltic Field: Insight From a Combined Geochemical and Numerical Modeling Approach

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-19 DOI: 10.1029/2024GC012028

Hong-Kun Dai, Qing Xiong, Jian-Ping Zheng

{"title":"Mantle Dynamics of the Long-Lived Middle Yangtze Basaltic Field: Insight From a Combined Geochemical and Numerical Modeling Approach","authors":"Hong-Kun Dai, Qing Xiong, Jian-Ping Zheng","doi":"10.1029/2024GC012028","DOIUrl":"https://doi.org/10.1029/2024GC012028","url":null,"abstract":"Melting for the generation of intracontinental diffuse basaltic fields is generally ascribed to the effects from lithospheric dynamic processes, but how the asthenospheric dynamics influence the overlying lithosphere remains poorly known. Here, this is explored via a combined geochemical and numerical modeling study on the long-lived Middle Yangtze basaltic field adjacent to the Dabie orogenic belt, central China. This basaltic field with a southwestard younging trend consists of 110–40 Ma basaltic rocks that show alkaline to sub-alkaline major-oxide compositions, oceanic island basalt-like trace-element patterns and MORB-like Sr-Nd-Pb isotopic ratios. The elemental and isotopic signatures show that the basaltic episodes generally underwent fractionation in the crust-mantle transition zone from sub-alkaline parental melts, which were produced by decompression melting of asthenosphere under a thinned (<2 GPa) lithosphere. Thermodynamic-based Bayesian probabilistic inversions on rare-earth element data further show that the melting for different basaltic episodes occurred at consistently shallow depths (40–60 km) and ambient mantle-like potential temperatures (1350–1400°C). Together with regional lithospheric seismic imaging and the orogenic evolution nearby, the southwestard younging trend likely records progressive erosion of the basal lithosphere from the northern margin of the Yangtze block to its interior; the lithospheric thinning was likely triggered by an inland propagating chain of mantle instabilities at lithosphere-asthenosphere boundary initiated by the delamination of the Dabie orogenic root. We suggest that the proposed model should have general relevance to many other intraplate diffuse basaltic fields with similar spatiotemporal features.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438797","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}

引用次数: 0

Metal-Silicate Partitioning of Si, O, and Mg at High Pressures and High Temperatures: Implications to the Compositional Evolution of Core-Forming Metallic Melts

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-19 DOI: 10.1029/2024GC011940

Chang Pu, Xiujin Gao, Zhengyang Wu, Zhixue Du, Zhicheng Jing

{"title":"Metal-Silicate Partitioning of Si, O, and Mg at High Pressures and High Temperatures: Implications to the Compositional Evolution of Core-Forming Metallic Melts","authors":"Chang Pu, Xiujin Gao, Zhengyang Wu, Zhixue Du, Zhicheng Jing","doi":"10.1029/2024GC011940","DOIUrl":"https://doi.org/10.1029/2024GC011940","url":null,"abstract":"High-pressure and high-temperature experiments were conducted to investigate the partitioning behaviors of Si, O, and Mg between molten Fe-alloys and silicate melts in the Fe-Si-O-Mg system under conditions of 2–72 GPa and 2000–5500 K, using both laser-heated diamond anvil cells and a multi-anvil press. Combing our new experimental results with previously published data, we evaluated the effects of pressure, temperature, and metallic compositions on the partitioning behaviors of Si, O, and Mg. A set of internally consistent interaction parameters between Si, O, and Mg were obtained by the simultaneous fitting of distribution coefficients for all three elements in the Fe-Si-O-Mg system. The composition-dependent distribution coefficients were applied in calculating the compositional evolution of metallic melts during multi-stage core formation. Our results suggest that the core-forming metallic melts would contain more Si and O than previously estimated due to the attractive interactions of light elements in the metal. Compared to the geophysically constrained core composition, these findings imply the exsolution of light elements, likely in the form of SiO2, from the outer core upon cooling.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011940","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438799","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}

引用次数: 0

Monospecific Diatom Cultures Suggest Potential Interspecies Variation of Diatom-Bound Nitrogen Isotope Signatures Associated With Silica Acquisition

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-19 DOI: 10.1029/2024GC011923

R. S. Robinson, C. A. Jones, I. A. Dove, R. P. Kelly, M. A. Brzezinski

{"title":"Monospecific Diatom Cultures Suggest Potential Interspecies Variation of Diatom-Bound Nitrogen Isotope Signatures Associated With Silica Acquisition","authors":"R. S. Robinson, C. A. Jones, I. A. Dove, R. P. Kelly, M. A. Brzezinski","doi":"10.1029/2024GC011923","DOIUrl":"https://doi.org/10.1029/2024GC011923","url":null,"abstract":"Tracking the supply and demand of nitrate in the past ocean can help to constrain the role of biology and circulation in regulating climate. The nitrogen isotopic composition of marine phytoplankton (δ15Nbiomass) tracks nitrate supply and demand but may not be well preserved in the sediments, while the isotopic composition of nitrogen contained within the frustules of diatoms (δ15NDB) is thought to be protected from alteration. Here we document the relationship between δ15Nbiomass and δ15NDB in cultures of seven Southern Ocean diatom species. Average δ15Nbiomass values are 1.8 ± 0.8‰ lower than δ15NDB values for 6 of the 7 species grown. The exception, Fragilariopsis rhombica, records δ15Nbiomass that are greater than δ15NDB values, opposite in sign from the other studied species and statistically significantly different from each other. Because most of the diatom species measured indistinguishable isotopic offsets between biomass and diatom-bound N, we assert that sedimentary δ15NDB values largely reflect surface ocean nitrate δ15N and therefore nitrate supply and demand. F. rhombica was not only different in terms of its relationship between δ15Nbiomass and δ15NDB but also in mean N:Si uptake and nitrogen content of cleaned frustules, suggesting a role for N allocation relative to Si in setting δ15NDB. While this result is largely based on only one species of diatom in culture, it is possible that significant contribution of groups with a similarly elevated εDB could decrease the overall value of the sedimentary δ15NDB signal.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011923","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143438798","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}

引用次数: 0

Formation of Miocene Authigenic Carbonates Within the Shimanto Accretionary Complex, Southwest Japan

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-17 DOI: 10.1029/2024GC011982

H. Hara, M. Utsunomiya, S. Tonai, H. Matsumoto, M. Satish-Kumar

{"title":"Formation of Miocene Authigenic Carbonates Within the Shimanto Accretionary Complex, Southwest Japan","authors":"H. Hara, M. Utsunomiya, S. Tonai, H. Matsumoto, M. Satish-Kumar","doi":"10.1029/2024GC011982","DOIUrl":"https://doi.org/10.1029/2024GC011982","url":null,"abstract":"Authigenic carbonates in the exhumed Miocene Shimanto accretionary complex (the Nabae carbonates) were studied in the Cape Muroto area to better constrain the formation mechanisms and tectonic setting during carbonate precipitation. Three main types of carbonates were recognized on the basis of morphology: nodular, bedded, and tubular. The δ13C values of the carbonates define two distinct groups with relatively low (−31.9‰ to −20.3‰) and relatively high values (−14.7‰ to −4.7‰). The former suggests carbonate precipitation from methane-enriched fluids, while the latter indicates mixing of fluid sources in a range of depositional settings. Most carbonates have REE + Y patterns characterized by well-defined positive Eu and Y anomalies, which we interpret to have formed by mixing between defused hydrothermal fluids and seawater. Other samples are enriched in MREE, a signature that is found in methane-derived cold seep carbonates. Additionally, the carbonates exhibit positive correlations between δ13C and various proxies for detrital input (e.g., REE + Y, Zr content, Y/Ho ratios). Based on comparing our observations with drill core and geophysical measurements from the active Nankai accretionary complex, we conclude that the Nabae carbonates were precipitated from relatively low-temperature hydrothermal fluids or as cold seeps near the deformation front at the toe of the Shimanto accretionary complex in a high heat flow environment. As the first onshore example of ancient authigenic carbonates from an accretionary complex, the Nabae carbonates have the potential to reveal important information regarding the characteristics and distribution of hydrothermal areas in active accretionary wedges.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011982","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431440","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}

引用次数: 0

European Arid Anomaly Explained With Southward Drift of Eurasia During the Late Jurassic Polar Shift

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-17 DOI: 10.1029/2024GC011730

Giovanni Muttoni, Edoardo Dallanave, Giovanna Della Porta

{"title":"European Arid Anomaly Explained With Southward Drift of Eurasia During the Late Jurassic Polar Shift","authors":"Giovanni Muttoni, Edoardo Dallanave, Giovanna Della Porta","doi":"10.1029/2024GC011730","DOIUrl":"https://doi.org/10.1029/2024GC011730","url":null,"abstract":"The sedimentary successions of several basins in Europe show evidence of widespread Late Jurassic aridification that is considered a long-standing conundrum in paleoclimate modeling. The distinctive feature of this event is that it appears concentrated in a discrete time interval between the Kimmeridgian (Late Jurassic) and the Berriasian (Early Cretaceous), and that it extended to eastern and southern-central Asia for a total of ∼10 Mkm2 in roughly the same time interval. Climate modeling has not provided a convincing explanation for this event. We compiled and reviewed paleomagnetic data from several continents including Adria, the African promontory, showing that this large-scale aridification was produced by an abrupt and transient southward migration of Eurasia toward arid tropical latitudes, while its demise coincided with a “retromotion” to more humid northern latitudes in the Early Cretaceous. This movement is part of a global plate motion event, most likely due to True Polar Wander, that profoundly affected the depositional environments, the ecosystems, and the architecture of sedimentary basins worldwide.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011730","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143431439","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}

引用次数: 0

Hydrogen Diffusion in Garnet: Insights From Atomistic Simulations

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-14 DOI: 10.1029/2024GC011951

Xin Zhong, Felix Höfling, Timm John

{"title":"Hydrogen Diffusion in Garnet: Insights From Atomistic Simulations","authors":"Xin Zhong, Felix Höfling, Timm John","doi":"10.1029/2024GC011951","DOIUrl":"https://doi.org/10.1029/2024GC011951","url":null,"abstract":"Garnet has been widely used to decipher the pressure-temperature-time history of rocks, but its physical properties such as elasticity and diffusion are strongly affected by trace amounts of hydrogen. Experimental measurements of H diffusion in garnet are limited to room pressure. We use atomistic simulations to study H diffusion in perfect and defective garnet lattices, focusing on protonation defects at the Si and Mg sites, which are shown to be energetically favored. Transient trapping of H renders ab-initio simulations of H diffusion computationally challenging, which is overcome with machine learning techniques by training a deep neural network that encodes the interatomic potential. Our results from such deep potential molecular dynamics (DeePMD) simulations show high mobility of hydrogen in defect-free garnet lattices, whereas H diffusivity is significantly diminished in defective lattices. Tracer simulations focusing on H alone highlight the vital role of atomic vibrations of heavier atoms like Mg on the release of H atoms. Two regimes of H diffusion are identified: a diffuser-dominated regime at high hydrogen content with low activation energies due to saturation of vacancies by hydrogen, and a vacancy-dominated regime at low hydrogen content with high activation energies due to trapping of H atoms at vacancy sites. These regimes account for experimental observations, such as a H-concentration dependent diffusivity and the discrepancy in activation energy between deprotonation and D-H exchange experiments. This study underpins the crucial role of vacancies in H diffusion and demonstrates the utility of machine-learned interatomic potentials in studying kinetic processes in the Earth's interior.","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011951","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143404345","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}

引用次数: 0

Strain Localization and Seismic Properties in the Heterogeneous Ailaoshan-Red River Shear Zone, Southeast Asia 东南亚艾劳山-红河异质剪切带的应变定位和地震特性

IF 2.9 2区地球科学

Geochemistry Geophysics Geosystems Pub Date : 2025-02-12 DOI: 10.1029/2024GC011929

Junyu Li, Shuyun Cao

{"title":"Strain Localization and Seismic Properties in the Heterogeneous Ailaoshan-Red River Shear Zone, Southeast Asia","authors":"Junyu Li, Shuyun Cao","doi":"10.1029/2024GC011929","DOIUrl":"https://doi.org/10.1029/2024GC011929","url":null,"abstract":"Strain localization is crucial in developing crustal-scale shear zones; however, a systematic analysis of deformation characteristics and their impact on seismic properties is still lacking. This study provides a comprehensive analysis of migmatites and granitic mylonites in the Ailaoshan-Red River shear zone (ASRR-SZ), incorporating detailed field observations, microstructure analysis, mineral crystallographic preferred orientations, rheological parameters, and seismic properties. Pre-existing compositional and mechanical anisotropies significantly influence strain localization in the ASRR-SZ. The southern part of the ASRR-SZ is primarily characterized by crustal anatexis, suggesting these regions as potential initiation sites for strain localization. Strain characteristics in the ASRR-SZ manifest in deformation temperatures (three ranges, ∼400–440°C, ∼470–500°C, and ∼730°C), differential stress (concentrated at 15.9–65.1 MPa), and strain rate (concentrated at 10−13–10−11 s−1). Notably, strain localization significantly alters the rock fabric and further affects the seismic properties of rocks. Significant differences in Vp values and orientations are noted between melanosomes (anisotropy of P-waves: AVp = 6.8%–17.9%, Max. Vp along the X-axis) and leucosomes (AVp = 3.4%–3.7%, Max. Vp along the Y-axis). The seismic velocities and AVp in granitic mylonites exhibit a linear correlation with quartz content, and deformation conditions strongly influence their orientation. For a middle to lower crust thickness of ∼25 km, the delay times between fast and slow polarized shear waves are 0.3–0.66 s for granitic mylonites, 0.37–0.7 s for melanosomes, 0.22–0.31 s for leucosomes, 0.27–0.58 s for amphibolites, and 0.57–2.7 s for schists. The average delay time (dt) of these rocks along the ASRR-SZ accounts for the observed delay time (dt = 0.58 s).","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 2","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011929","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143397067","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}

引用次数: 0