Geochemistry Geophysics Geosystems最新文献

{"title":"Fault-Related Carbonates as Quaternary Seismotectonic and Paleoclimate Archives (Monte Marine Fault, Central Apennines)","authors":"Giorgio Arriga,&nbsp;Federico Rossetti,&nbsp;Marta Marchegiano,&nbsp;Marion Peral,&nbsp;Domenico Cosentino,&nbsp;Paolo Ballato,&nbsp;Hsun-Ming Hu,&nbsp;Chuan-Chou Shen,&nbsp;Simone Racano,&nbsp;Irene Puliti,&nbsp;Alberto Pizzi,&nbsp;Philippe Claeys","doi":"10.1029/2026GC013053","DOIUrl":"https://doi.org/10.1029/2026GC013053","url":null,"abstract":"<p>Seismogenic faults shape continental landscapes, drive crustal deformation and influence fluid exchange between the lithosphere and atmosphere. Yet, quantitative links between fault activity, exhumation and near-surface environmental evolution remain poorly understood. Here, structural (meso- and micro-scale) investigations are integrated with carbonate geochemistry and geochronology to reconstruct the long-term spatio-temporal evolution of seismogenic faulting along the Monte Marine normal fault (MMNF) in the central Apennines, Italy. Field investigations and sampling of exhumed fault zones were complemented by analyses of faults exposed in paleoseismological trenches, together preserving carbonate mineralizations and cataclasites formed at different crustal depths and during successive stages of fault evolution. Carbon and oxygen stable isotope analyses (δ¹³C, δ¹⁸O), clumped isotope thermometry (Δ₄₇) and carbonate geochronology (U-Th, ¹⁴C dating) distinguish three structural and geochemical groups, spanning deeply exhumed fault zones, shallow fault-related carbonates, and near-surface carbonate concretions. Meteoric-derived footwall mineralizations along the MMNF record structurally controlled fluid flow from at least ∼481 ka, up to the Holocene surface-rupture record preserved in paleoseismological trenches (ca. 5.3–4.0 ka cal BC), pointing to long-lived, spatially distributed seismogenic activity. These data also constrain a maximum average exhumation rate of ∼1.57 ± 0.30 mm/yr across the fault system since ∼0.5 Ma. By linking fault-zone carbonate archives from exhumed structures with those exposed in paleoseismological trenches, this study provides a quantitative framework for reconstructing long-term fluid circulation, seismogenic fault activity and paleoclimatic conditions, tracing the evolution of fault–fluid systems across structural levels, from deeply exhumed fault zones to active surface ruptures in extensional mountain belts.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013053","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145995","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unraveling the Evolution of Silicic Volcanism in a Distributed Volcanic Field: Insights From Harrat Khaybar, Western Saudi Arabia","authors":"Abdullah Alohali,&nbsp;Shanaka de Silva,&nbsp;Charles Lewis,&nbsp;Suhail S. Alhejji,&nbsp;Shane J. Cronin,&nbsp;Chris J. Russo","doi":"10.1029/2026GC013186","DOIUrl":"https://doi.org/10.1029/2026GC013186","url":null,"abstract":"<p>Distributed basaltic volcanic fields commonly host minor but significant silicic magmas, the origin of which remains debated. At Harrat Khaybar (western Saudi Arabia; ca. 1.7 Ma to present), volcanic activity erupted compositions range from alkali olivine basalt to trachyte and comendite. Here, we integrate petrography, geochemistry, Sr–Nd–Pb isotopes, and petrogenetic modeling in the context of existing geochronology to investigate the origin of the silicic magmas. Geochemical data define continuous, non-linear differentiation trends from basalt to comendite, accompanied by progressive incompatible element enrichment, increasingly negative Eu anomalies and increasingly radiogenic isotopic ratios; characteristics that cannot be fully explained by closed-system processes alone. Radiogenic isotope systematics exclude bulk melting of Arabian crust, instead supporting assimilation–fractional crystallization (AFC). AFC modeling supports a two-stage differentiation history: early basaltic evolution in the lower to middle crust dominated by olivine–clinopyroxene fractionation, followed by &gt;90% feldspar-dominated fractional crystallization in the upper crust coupled with minor assimilation (<i>r</i> &lt; 0.05), involving a prominent role for incongruent melting of biotite. Distinct geochemical and isotopic signatures among temporally associated volcanoes indicate multiple contemporaneous, short-lived, upper-crustal reservoirs sustained by continued basaltic input. Greater eruptive output of evolved volcanism in the center of the field connotes more efficient thermal conditioning of the crust enabled prolonged differentiation and production of comendite. Harrat Khaybar exemplifies distributed basaltic volcanic fields where silicic magmas arise through AFC rather than crustal anatexis or source-controlled enrichment and reveals a spatially and temporally distributed magmatic plumbing alternative to models invoking long-lived, static reservoirs.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013186","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Wilson Cycle of the North Altyn Ocean: A Record of Subduction Initiation, Slab Rollback, and Final Closure","authors":"Long Chen,&nbsp;Jinlong Yao,&nbsp;Guochun Zhao,&nbsp;Yigui Han,&nbsp;Qian Liu,&nbsp;Donghai Zhang,&nbsp;Xijun Zhao,&nbsp;Hang Yang,&nbsp;Wei Li","doi":"10.1029/2026GC013308","DOIUrl":"https://doi.org/10.1029/2026GC013308","url":null,"abstract":"<p>The North Altyn ophiolitic belt was formed by the subduction–closure of the Altyn segment of the Proto–Tethys Ocean and recorded the accretion of Tarim to northern Gondwana, but the timing of initial subduction and detailed tectonic transition processes remain poorly constrained. This study reports the oldest Phanerozoic magmatic record of 537 Ma juvenile I–type granodiorite for the Altyn belt, which was formed under high oxygen fugacity (−14.51 ≤ log<i>f</i>O₂ ≤ −10.96) and water–rich (6.92–9.50 wt%) arc condition. The southward subduction of the North Altyn Ocean thus initiated a priori to about 537 Ma. Coupled I– and S–type granitoids dated at ca. 505–478 Ma, which were generated in subduction - related but relatively reduced and reworked conditions, have also been observed. Moreover, a review of zircon Hf isotopes, crustal thickness, geobarometry and oxygen fugacity of magmas across the belt also argues for the advancing and retreating subduction of the North Altyn Ocean at ca. 537–500 Ma and ca. 500–470 Ma, respectively. The slab rollback event at 500–470 Ma triggered upwelling of reduced low oxygen fugacity mantle materials and also led to crustal thinning, which overlapped well with regional extensional magmatic activities. In addition, renewed increases in these proxies suggest resumed advancing subduction until ocean closure at ca. 450–440 Ma. Thus, magmatic records across the belt suggest a prolonged 100 Ma subduction cycle from initial, advancing and retreating subduction to final closure for the North Altyn Ocean.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013308","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Full-Waveform Seismic Tomography of the Upper Mantle Beneath the Arabia-Eurasia Collision Zone","authors":"Edward J. Clennett,&nbsp;Chujie Liu,&nbsp;Stephen P. Grand,&nbsp;Thorsten W. Becker","doi":"10.1029/2026GC013003","DOIUrl":"https://doi.org/10.1029/2026GC013003","url":null,"abstract":"<p>Despite being one of the most recent major orogenic events, the timing of the Arabia-Eurasia collision is still debated. Much of the discrepancy arises due to uncertainties over the amount of continental subduction of the Arabian passive margin and the timing of a hard collision of cratonic Arabian lithosphere with Eurasia. Subducted continental lithosphere and underthrusted cratons can be imaged using high resolution seismic tomography, which can be used to improve understanding of the tectonic history of the region. In this study, we perform a full waveform inversion of seismic wave velocity beneath the Turkish-Iranian plateau, using regional earthquakes, which provide good horizontal and vertical resolution in the upper 500 km of the mantle. We use a normalized cross-correlation misfit function, which fits both the phase and relative amplitude of multi-path arrivals, allowing us to extract additional information from complex triplicated waves that provide relatively good coverage of the upper mantle. Our results reveal that 250 km thick Arabian lithosphere extends horizontally beneath Eurasia. When reconstructed back in time, these results indicate that continental underthrusting and collision initiated at ∼22 Ma, which is consistent with accelerated deformation observed at this time in the geological record.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013003","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145838","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stratigraphic Signals and Cloudy Band Chemistry in Ice Cores Revealed by Large-Area Elemental Mapping","authors":"Pascal Bohleber,&nbsp;Piers Larkman,&nbsp;Remi Dallmayr,&nbsp;Martin Šala,&nbsp;Nicolas Stoll","doi":"10.1029/2026GC013241","DOIUrl":"https://doi.org/10.1029/2026GC013241","url":null,"abstract":"<p>Mapping the impurity distribution in 2D with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) has provided valuable insights into the micro-chemistry of a broad range of environmental samples. However, technical limitations have largely restricted mapping to millimeter-sized maps as “snapshots.” Especially for stratigraphic archives with layers on the cm to mm scale and finer, much could be gained from increasing the map size to encompass the layer scale. Polar ice cores are a prime example of this: They are invaluable climate archives, but detecting impurity-related climate signals in highly thinned ice is a state-of-the-art frontier. Here we introduce a new methodology using LA-ICP-MS that allows chemical mapping over large areas (cm × cm) within a feasible measurement time (&lt;1 h). For validation, we used “cloudy bands” from Greenland and central Antarctica: visual stratigraphic layers characterized by high impurity concentrations. Our large-area maps show clear bands of high intensities at positions of cloudy bands. The large maps let us take advantage of the merit of 2D data for feature recognition: Stratigraphic layers can be identified at sub-mm detail that would be missed by standard 1D meltwater analysis. Large-area mapping delivers important new insights for both understanding ice-impurity interactions and reliably detecting climate signals in highly deformed deep ice. As such, it will be a key component for future high-throughput analysis of hundreds of meters of ice cores. Ultimately, the new methodology provides a vital “bigger picture” in LA-ICP-MS mapping, opening important new applications for the study of other environmental samples.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013241","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LIPOTHERM: A Calibration Framework for GDGT Paleothermometry Based on Machine Learning","authors":"Vikash Kumar,&nbsp;Manish Tiwari,&nbsp;Biswajit Roy","doi":"10.1029/2026GC013071","DOIUrl":"https://doi.org/10.1029/2026GC013071","url":null,"abstract":"<p>SST reconstruction from glycerol dialkyl glycerol tetraethers (GDGT) preserved in marine sediments is an important tool in quantitative paleoclimatology. These reconstructions require calibration frameworks that provide mapping between sediment GDGT data and temperature values. Improvements in modeling and data coverage can reduce bias in existing calibrations, such as those based on the univariate TEX₈₆ index and other multivariate frameworks. GDGT cyclization is also known to be affected by nutrient stress as a non-thermal control. In this study, we present LIPOTHERM (Lipid Paleothermometry), a new GDGT-SST calibration trained on an extensive collection of globally distributed core-top GDGT data using supervised machine learning. LIPOTHERM features substantially lower calibration root mean square error than existing forms. Inclusion of core-top nutrient conditions as auxiliary predictors further lowers the calibration error. LIPOTHERM demonstrates that robust paleothermometry frameworks can be constructed by accumulating incremental improvements over different methodological refinements involving algorithm selection, feature space representation, expanding data coverage, and adding auxiliary non-thermal covariates.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013071","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145756","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Provenance of the Middle-Upper Triassic Songpan-Ganzi Flysch of Western China Revealed by Anisotropy of Magnetic Susceptibility Measurements: Implications for the Tectonic-Paleogeographic Evolution of the Paleo-Tethys Ocean","authors":"Yuhan Yang,&nbsp;Yong Cao,&nbsp;Xiaozhou Ye,&nbsp;Zhenyu Yang,&nbsp;Zhiming Sun,&nbsp;Haibing Li","doi":"10.1029/2026GC012964","DOIUrl":"https://doi.org/10.1029/2026GC012964","url":null,"abstract":"<p>The Triassic Songpan-Ganzi turbidite complex (SGC) on the eastern Tibetan plateau is one of the largest flysch turbiditic complexes on Earth. However, the provenance of its extremely thick turbidites is hotly debated. We conducted the measurement of anisotropy of magnetic susceptibility (AMS) of Triassic turbidites from nine profiles in Ruo'ergai, Aba, Ganzi, Seda, and Xiaojin counties in the Songpan-Ganzi Basin. The AMS of 937 samples from 130 sampling sites shows a very low anisotropy degree (<i>P</i> &lt; 1.07), and an oblate shape with the minimum axis (<i>k</i>₃) of the magnetic susceptibility ellipsoid being nearly perpendicular to the bedding plane. These findings reveal the primary sedimentary magnetic fabric in these rocks. The paleocurrent system during the Middle to Late Triassic was constructed based on the direction of the maximum axis (<i>k</i>₁) of the magnetic susceptibility ellipsoid. The results indicate that the SGC has a multi-source provenance, including the Qinling-Dabie orogenic belt, the Yidun arc and the North Qiangtang orogenic belt, and the East Kunlun-Qaidam block. The deposition of the great thick Upper Triassic flysch is genetically linked to the syn-collisional uplift of the surrounding orogenic belts. Therefore, we conclude that the Upper Triassic turbidites in the SGC were derived from surrounding collisional orogen sources, rather than only distant Dabie-Qinling sources eroded after the North China-South China collision. This challenges the traditional model that interprets the Triassic Songpan-Ganzi Basin as a simple, large-scale submarine fan system similar to the Cenozoic Bengal-Indus fans.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC012964","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145757","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Aurora Vent Field at the Transition From Magmatic Accretion to Tectonic Extension on Gakkel Ridge: Constraints From Microseismicity and Aeromagnetic Observations","authors":"Matthias Pilot,&nbsp;Mechita C. Schmidt-Aursch,&nbsp;Graeme Eagles,&nbsp;Vera Schlindwein","doi":"10.1029/2025GC012799","DOIUrl":"https://doi.org/10.1029/2025GC012799","url":null,"abstract":"<p>The Aurora hydrothermal vent field (AVF) is the first confirmed active vent system on the Arctic Ocean seafloor, located at the western end of the ultraslow spreading Gakkel Ridge. It marks a distinctive endmember among ridge-axis hydrothermal systems, where volcanic construction and ultramafic influence co-exist. The region's perennial ice cover and remoteness have left the crustal and lithospheric structure, including the underlying subseafloor processes, largely unconstrained. In 2023, the RV Polarstern PS137 expedition investigated how lithosphere forms in this region and how it interacts with the AVF's hydrothermal system. Here, we present results from a ∼11-month passive seismic data set, recorded by a network of eight ice-going ocean bottom seismometers and complemented by a coincident aeromagnetic survey. Together, these data reveal a transition from magmatic to non-volcanic spreading between the Western Volcanic Zone and the Lena Trough. With the AVF located at its onset, seismicity and magnetic anomaly patterns are consistent with progressively thicker and colder lithosphere and reduced melt supply toward the Lena Trough. A localized and likely thermally controlled gap in seismicity may indicate a small gabbroic intrusion northeast of the AVF that could provide a heat source for the hydrothermal system. Abundant seismicity surrounding the AVF indicates that tectonic processes continuously influence the lithosphere, whereas evidence for transient magmatic activity near the vent field is limited. These findings suggest that the AVF represents a long-lived hydrothermal system and provide new insights into the geological controls on hydrothermal systems at ultraslow spreading ridges.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GC012799","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149145752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Apatite as a Proxy for Reconstructing Magma Mixing Histories in Granitoids","authors":"Xiaowen Lin,&nbsp;Jiahao Zheng,&nbsp;Wanyi Feng","doi":"10.1029/2026GC013143","DOIUrl":"https://doi.org/10.1029/2026GC013143","url":null,"abstract":"<p>Apatite is a common accessory mineral in granites and mafic microgranular enclaves (MMEs), and its textural and compositional characteristics can record dynamic magmatic evolution processes. Apatites from the Early Cretaceous Sanguliu granite and its MMEs in the Liaodong Peninsula exhibit pronounced compositional heterogeneities. In this study, we systematically analyzed textures, in situ trace elements, and O isotopes of apatites in the Sanguliu granite and MMEs to reveal magma mixing processes. Cathodoluminescence (CL) images reveal clear core-rim textures and compositional zoning in apatites, defining four types: Ap1(G) and Ap2(G) in granite as well as Ap1(M) and Ap2(M) in MMEs. From core to rim, these apatites show abrupt changes in REE, Si, and Sr contents, suggesting their formation involved multiple episodes of magma mixing. In situ oxygen isotope analyses yield relatively high δ¹⁸O values of 7.19–8.45‰, 6.97–7.81‰, 5.32–8.75‰, and 7.77–8.86‰ for Ap1(G), Ap2(G), Ap1(M), and Ap2(M), respectively. Integrating the high Mg# values (53–56), consistent Sr-Nd isotopic compositions (I_Sr = 0.7145–0.7148; <i>ε</i>_Nd(<i>t</i>) = −18.6 to −18.3), and zircon Hf isotopes (<i>ε</i>_Hf(<i>t</i>) = −21.5 to −19.6) of both the granite and MMEs, our geochemical data indicate crust-mantle mixing and cognate magma mixing. Modeling calculations suggest that the crust-mantle mixing involved approximately 71% lower crustal melt and 29% mantle-derived melt, followed by 50% fractional crystallization of lower crustal melts and subsequent mixing with 28% hybrid magma. This study highlights that apatite serves as a sensitive petrogenetic proxy and provides critical insights into the petrogenesis of MME-bearing granitoids.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013143","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149146905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"OIB-Type Garnet Amphibolites From the Xuerongzangbu Area, Central Lhasa Terrane, Tibet: Implications for Songduo Paleo-Tethys Ocean Evolution and Permian Mantle Activity Along North Gondwana","authors":"Yuan-Bo Ma,&nbsp;Xin Jin,&nbsp;Yu-Xiu Zhang,&nbsp;Zhi-Wu Li,&nbsp;Shahbaz Bin Khalid,&nbsp;Ji-Heng Zhang,&nbsp;Wen-Guang Yang,&nbsp;Li-Dong Zhu,&nbsp;Gang Tao,&nbsp;Kai-Jun Zhang","doi":"10.1029/2026GC013127","DOIUrl":"https://doi.org/10.1029/2026GC013127","url":null,"abstract":"<p>Whether the Songduo metamorphic belt represents an in situ Paleo-Tethyan suture within the Lhasa Terrane or far-traveled allochthonous high-pressure slices, and how Permian mantle activity along the North Gondwana margin relates to subsequent Tethyan evolution, remain central questions in Tibetan tectonics. We investigated retrogressed garnet amphibolites from the Xuerongzangbu area of the Central Lhasa Terrane using petrography, mineral and whole-rock geochemistry, Sr–Nd isotopes, SHRIMP zircon U–Pb geochronology, ⁴⁰Ar/³⁹Ar thermochronology, and phase-equilibrium modeling. The rocks record prograde burial, peak high-pressure amphibolite-facies metamorphism, and fluid-assisted retrogression during exhumation. Modeling of a weakly retrogressed Type I amphibolite yields peak conditions of 15.4–16.0 kbar and 600–660°C, whereas more strongly retrogressed Type II amphibolites preserve relict kyanite, high-Si amphibole, phengite, and rutile. The amphibolites' OIB-type trace-element patterns, initial ⁸⁷Sr/⁸⁶Sr ratios of 0.7050–0.7057, ε_Nd(t) values of −1.59 to +0.16, and Nd model ages of 0.97–1.08 Ga indicate derivation from an enriched intraplate mantle source with limited crustal contamination. Zircon U–Pb dating gives a protolith crystallization age of 271.0 ± 3.0 Ma, whereas hornblende and mica ⁴⁰Ar/³⁹Ar ages of 232.9–216.9 Ma record Late Triassic cooling and exhumation. Integrated with regional geological evidence, the protoliths are interpreted as seamount or ocean-island basalts formed on the Songduo oceanic lithosphere. Together with regional Permian plume-affinity mafic magmatism, these data suggest sustained mantle heating beneath North Gondwana and a possible temporal and geodynamic link between Songduo Ocean closure and the development of younger Tethyan branches.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"27 10","pages":""},"PeriodicalIF":3.3,"publicationDate":"2026-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2026GC013127","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149068318","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}