Structural inheritance is common in fold-and-thrust belts, but the conditions under which inherited faults are reactivated or bypassed remain poorly constrained. Here, we employ two-dimensional elastoplastic numerical models to investigate how cover thickness (Hc), proto-wedge taper (α0), and fault dip (θ) control wedge growth and inherited-fault utilization. Because the inherited structure is represented as a 0.5-cm-wide finite-width weak zone, we quantify its contribution using a fault-zone accommodation ratio (Rv), rather than treating it as discrete fault slip. Our results show that regional overburden and localized topographic loading exert mechanically distinct effects. Increasing Hc from 2 to 7 cm enlarges the wedge, with the maximum wedge height (Hmax) increasing from 8.1 to 13.8 cm and frontal propagation distance increasing from 29.0 to 47.5 cm. At the same time, Rv decreases from all fault dips, most strongly for steep faults, with the θ=90∘ case declining from 4.17% to 3.02%. This behavior suggests how elevated lithostatic stress suppresses the reactivation of high-angle pre-existing faults, thereby favoring distal strain localization. Superimposed on this regional control, localized topographic loading induces a dip-dependent response. Increasing α0 from 5∘ to 20∘ enhances reactivation in optimally oriented faults (θ≈30∘, Rv rising from 6.67% to 8.54%), whereas steep faults (θ=60∘–90∘) remain largely inhibited (Rv≈3.75%). This contrast suggests a dip-dependent strain partitioning, where vertical loading redistributes strain according to fault dip rather than uniformly suppressing slip. These results indicate that regional overburden acts mainly through uniform lithostatic loading, whereas localized topographic loading selectively partitions strain based on fault dip. The models provide a possible mechanical framework for interpreting why steep inherited basement faults may remain viable under limited cover, whereas low-angle master thrusts can remain active beneath strong topographic loading.

The acceleration of climate change has led to an increase in the frequency of glacial lake outburst floods (GLOFs) in the Himalayas, resulting in significant devastation. InSAR data indicate that Qiangzongke Co, located in southwestern Tibet, China near the China-Nepal border, experienced considerable deformation of the adjacent terrain over recent decades, implying a potential landslide. Landslide entry into a glacial lake typically initiates surge waves that propagate forward, eroding the moraine dam and ultimately inducing a GLOF disaster. This study integrated multi-source data and hydrodynamic models to assess the potential GLOF process chain and downstream impact. The results indicate that the surface area of Qiangzongke Co has increased by 194

Transpressional deformation in the overriding plate is a prevalent mechanism along convergent margins that critically impacts geodynamics and seismogenesis. The northern Tibetan Plateau formed through the closure of the Proto-Tethys and subsequently underwent significant Cenozoic shortening driven by far-field stress from the Indo-Asian collision. The existence of Mesozoic crustal-scale structures in this region underscores a more complex geological evolution that remains insufficiently understood. We herein document the presence of four subparallel Triassic ductile transpressional strike-slip shear zones (the North Wulan shear zones-NWZs), in the Wulan area of the North Qaidam Mountains, northern Tibet. Deformation temperatures in these shear zones progressively increase from similar to 400 degrees C in the northernmost zone (NWZ-1) to similar to 590 degrees C in the southernmost zone (NWZ-4). Meanwhile, each shear zone exhibits a general plane strain type, accompanied by kinematic vorticity (W m) values gradually decreasing from 0.84 to 0.92 in NWZ-1 to 0.32-0.39 in NWZ-4. These spatial variations suggest that strain partitioning and subsequent crustal thickening in transpressional settings may play a critical role in modulating deformation conditions and shear zone rheology. Combined zircon U-Pb and biotite 40Ar/39Ar geochronological data constrain the timing of transpressional shearing to the Early Triassic (252-235 Ma). We propose that the deformation style, kinematics, and dynamics of these shear zones, formed within a thickened continental arc setting, were predominantly controlled by the northward oblique subduction of the Paleo-Tethyan Ocean prior to its final closure.

With ongoing global climate warming, rock-ice avalanches in cold, high-mountain regions are becoming increasingly frequent, posing severe threats to the cryospheric environment and human society. This study examines a large rock-ice avalanche that occurred on 25 July 2024 at Yanzigou Glacier on Mount Gongga and reconstructs the cascade hazard evolution from rock-ice avalanche to debris flow and subsequent flooding based on multi-source observations. At 11:58:07 local time, a rock-ice mixture with an estimated volume of approximately 4.58 & times; 105 m3 became unstable at an elevation of about 4900 m. Based on seismic inversion, the alongpath evolution of velocity and equivalent friction coefficient of the rock-ice avalanche was reconstructed. The results show that the equivalent friction coefficient exhibits an anomalous and abrupt decrease at approximately 1.95 km, indicating a phase transition from a rock-ice avalanche to a debris-flow state. Subsequently, the failure of a temporary landslide dam triggered flooding, constituting a second phase transition. Time-frequency analysis of high-frequency seismic signals reveals systematic differences in spectral characteristics between the debrisflow and flood stages, with the evolution of peak frequencies reflecting a transition in flow mechanisms from particle-fluid coupling to hydraulically dominated flood flow. From a seismological perspective, this study provides key constraints on the dynamic evolution and phase transitions of cascading hazards in glacierized regions, and offers new insights into process identification and risk mitigation of multi-hazard coupling in cold, high-mountain environments.

Surface heat flow (SHF) is a crucial indicator of Earth interior thermal processes and crust-mantle interactions, and its precise evaluation is paramount for understanding regional geothermal systems and potential energy development. Eastern China, featured by its distinctive high heat flow and complex tectonic background, presents unique challenges and significant opportunities for geothermal study. The various geological controls governing its heterogeneous SHF patterns, however, remain inadequately quantified. Traditional geophysical methods face limitations in elucidating the intricate, nonlinear relationships inherent in such complex geological settings. This study introduces an innovative hybrid machine learning model, specifically Random Forest Weighted Neural Networks (RFWNNs), to decipher the complex, nonlinear relationships between SHF and multi-scale geological and geophysical parameters across Eastern China. We integrated diverse datasets, including crustal thickness, lithosphere-asthenosphere boundary (LAB) depth, Moho depth, Bouguer gravity anomaly, elevation, fault density, and other tectonic features, to construct a comprehensive geological context. The RFWNNs model demonstrated exceptional predictive performance, achieving a coefficient of determination (R2) of 0.815, and successfully identified three major geothermal anomalies domain: Northeast China, North China, and South China. Through feature importance analysis and SHAP interpretability assessment, elucidated distinct deep thermal controlling mechanisms for these high-flow regions. Feature importance analysis and SHAP interpretation reveal distinct dominant mechanisms: lithospheric thinning and mantle upwelling in Northeast China, rift-related crustal architecture in North China, and subduction-driven magmatism in South China. This work provides a robust, data-driven framework for interpreting regional geothermal anomalies and offers novel insights into deep thermal processes within convergent continental margins.

Several continental-scale strike-slip faults in the southeastern Tibetan Plateau developed during the Cenozoic eastward growth of the plateau. However, geodynamic mechanisms driving plateau growth and their relationship to intracontinental deformation remain poorly resolved, primarily because the brittle deformation histories of major fault systems-such as the >1000-km-long Xianshuihe-Xiaojiang (XSH-XJ) fault system-are inadequately constrained and difficult to reconstruct. To address this gap, we performed thermochronological analyses of samples from the highest mountains (i.e., Jiaozi Shan and Dahaicao Shan) flanking the XJ segment of the fault system, including apatite (U-Th)/He, apatite fission track, and zircon (U-Th)/He dating, complemented by thermal history modeling. Results reveal differential exhumation and cooling across the XJ fault between ca. 26 Ma and 22 Ma, with greater cooling in the Jiaozi Shan (30-50 degrees C) than the Dahaicao Shan (<5 degrees C), implying an exhumation offset of 1-2 km. Since ca. 13 Ma, rapid cooling (50-70 degrees C) has occurred synchronously on both sides of the XJ fault, corresponding to similar to 2 km of accelerated exhumation. Together with structural analyses, it is interpreted that the two phases of exhumation and cooling were kinematically linked to a transition of deformation from late Oligocene east-vergent thrusting to late Miocene left-slip faulting. Integrating structural and geophysical data along the XSH-XJ fault system, we propose that the Oligocene shortening caused crustal thickening and in situ anatexis. These processes produced thermally and mechanically weakened lower crust, facilitating the late Miocene initiation of left-lateral slip. Our work highlights a dynamic linkage between the two phases of deformation, providing new insights into how kinematic inversions of major faults operate in the southeastern Tibetan Plateau.

The southeastern Tibetan Plateau represents a critical transition zone between the high plateau interior and the surrounding region with moderate elevation. Its topographic uplift history provides key constraints on the geodynamic mechanisms driving plateau growth, serving as an ideal natural laboratory for exploring the coupled effects of tectonics, monsoon dynamics, and biodiversity. However, the spatiotemporal patterns of regional uplift across distinct tectonic domains remain debated, primarily due to the limited resolution and accuracy of existing geochronological and paleo-elevation proxies. To resolve these uncertainties, we synthesize sedimentary archives from 16 Cenozoic basins across the southeastern plateau. We integrate high-resolution paleoelevation proxies, including stable and clumped isotopes, with multi-proxy paleoclimate records derived from palynological assemblages and leaf physiognomy. This multi-basin comparison reveals that the southeastern Tibetan Plateau experienced a major phase of regional uplift during the Late Eocene to Early Oligocene, characterized by a systematic decrease in uplift magnitude from the plateau interior toward the outer margins. A second phase of localized uplift occurred along the southeastern margin during the Middle to Late Miocene, progressively establishing the modern topographic configuration. Throughout the Cenozoic, this surface uplift was accompanied by distinct stages of climatic evolution. The region was predominantly arid during the Early Eocene, followed by a transition toward more humid conditions in the Late Eocene that persisted throughout the Late Oligocene. From the Middle to Late Miocene onward, the southeastern margin generally experienced a warm and humid subtropical climate, with regional variability reflecting the episodic reorganization and strengthening of the monsoon system. During the Pliocene, intensified global cooling and the expansion of Northern Hemisphere glaciation drove a shift toward cooler climatic conditions across the southeastern Tibetan Plateau. These findings clarify the spatiotemporal uplift history of the southeastern plateau margin and highlight its fundamental role in regional climate reorganization.

To address global climate change and meet carbon neutrality goals, CO2 hydrate sequestration in marine reservoirs offers extensive geological potential for carbon sinks. Based on phase equilibrium analysis, this study proposes a pathway for injecting CO2 into submarine reservoirs depleted by methane hydrate extraction. Using a self-developed multi-field coupling simulator and constructing a heterogeneous three-dimensional horizontal well model, we investigated the feasibility of CO2 hydrate sequestration in Site W11 of the GMG53 expedition in the South China Sea. A systematic analysis of sequestration efficiency, formation subsidence, and injection optimization was conducted. The results show that prior depressurization to create low-temperature and lowpressure conditions effectively mitigates CO2 migration toward the seafloor, thereby increasing the safety distance (vertical gap between the hydrate top and the seafloor) between the hydrate top and the seabed. Subject to this safety distance constraint, the maximum single-well CO2 sequestration capacity in the study area is 25,550 t; exceeding this threshold may pose environmental risks. An injection rate of 40 kg/day/m sustained for 17.5 years balances sequestration efficiency with a minimum 25 m safety distance. This study confirms the feasibility of integrating methane hydrate production with CO2 sequestration and offers a new analytical paradigm for marine carbon storage engineering.

Understanding the in situ stress field is crucial for hydraulic fracturing and efficient development of low-permeability reservoirs. The Enping Formation in the Huizhou Oilfield of the Pearl River Mouth Basin is a key yet challenging target. However, a systematic high-resolution investigations of its in situ stress field are lacking. In this study, we constructed the first high-resolution three-dimensional (3D) stress field model for the Huizhou Oilfield. This model integrates rock mechanics and acoustic emission experiments, well-log interpretation, amplitude versus angle simultaneous inversion and finite-element simulations. Compared with previous localized studies, this integrated basin-scale approach provides a more comprehensive and advanced framework. The direction of the maximum horizontal stress, derived from image logs, six-arm caliper logs, and multipole array acoustic logs, varies from NWW-SEE to NNW-SSE. Stress magnitude calculations from eight wells indicate a normal faulting regime in the Enping Formation. Numerical simulations reveal that the vertical stress, maximum horizontal stress, minimum horizontal stress, and horizontal differential stress range from 68.3 to 92.6, 45.4 to 58.7, 38.9 to 52.3, and 3.3 to 7.1 MPa, respectively. The distribution of in situ stress is primarily controlled by regional plate-tectonic forces and tectonic architecture such as anticlines and faults, while lithological and rock-mechanical heterogeneities exert localized secondary influences. Hydraulic fracturing sweet spots were identified, characterized by high brittleness, low fracturing pressure, and small horizontal stress difference. Horizontal wells are recommended to be oriented approximately parallel to the minimum horizontal stress direction (NE-SW) to enhance fracture complexity. Stress simulations for the proposed horizontal well quantitatively predict maximum and minimum horizontal stresses of 48.5-53.1 MPa and 43.2-46.9 MPa, respectively, with a differential stress of 3.7-8.6 MPa and an estimated fracturing pressure of 50.2-60.8 MPa. These results offer novel insights into the 3D in situ stress field and provide practical guidance for optimizing hydraulic fracturing design and enhancing efficient hydrocarbon recovery in low-permeability reservoirs of the Pearl River Mouth Basin and similar settings worldwide.

The cause of mare asymmetry between the lunar nearside and farside remains a long-lasting conundrum. Due to scarcity of directly sourced deep samples, the formation mechanism of this phenomenon has not been well constrained. Here we characterized a class of rare impact glass beads with extremely high TiO2 (16-25 wt%) and FeO (25-35 wt%) in the Chang'e-5 regolith. Petrological modeling indicates that the precursor rock of these glass beads cannot be formed through normal magmatic evolution, but rather has a deeper mantle origin. Phase diagram calculations show that the precursor rock has a typical mineral assemblage similar to ilmenite-bearing cumulates. Based on different residual anorthite proportions, the restored Lunar Magma Ocean (LMO) original crystalline mineral assemblage is predicted to contain similar to 15-20 vol% ilmenite, significantly higher than the average predicted levels. Therefore, the nearside ilmenite-bearing cumulates may have higher ilmenite abundance than farside, causing increased partial melting and more abundant volcanism.

Subsurface fault structures are generally difficult to delineate, particularly in areas covered by thick sediments. Soil-gas geochemical surveys can provide useful constraints on concealed structures after major earthquakes and complement conventional geophysical methods in sediment-covered basins. This study investigates the 2023 Jishishan M6.2 earthquake as a representative case. Previous studies have suggested that the nearby Lajishan fault alone cannot fully account for the seismogenic structure of this earthquake, while no obvious surface rupture has been identified within the epicentral basin, complicating post-earthquake reconstruction planning and fault-avoidance measures. The spatial distribution of coseismic damage suggests the possible presence of previously unrecognized concealed structures. To investigate post-seismic soil-gas degassing and its spatial relationship with these structures, we measured Rn, Hg, H2, and CO2 along two profiles across the severely damaged area. Two prominent gas-anomaly zones were identified and showed spatial correspondence with the inferred concealed structures. Integration of the soil-gas anomalies with aftershock relocation, shallow seismic reflection, and ambient-noise surface-wave tomography provides preliminary constraints on the location and geometry of a concealed active structure spatially associated with the broader seismogenic fault system. Hg and H2 anomalies were more closely associated with the inferred major structural zone than those of Rn and CO2, suggesting that their distributions may be preferentially influenced by permeable fault-related pathways. These findings provide new constraints on concealed active structures associated with the Jishishan earthquake sequence and highlight the potential value of integrating soil-gas geochemistry with geophysical observations as a complementary approach for post-earthquake concealed-fault investigation in sediment-covered basins.

Space weathering extensively transforms the materials on the lunar surface due to solar wind irradiation and micrometeorite impact. However, the spatial variability of space weathering across the lunar surface is not yet well understood. The recently returned Chang'e-6 samples from the Apollo Basin provide a new perspective for exploring space weathering on the lunar farside. In this study, we report the space weathering characteristics of the Chang'e-6 samples from the farside of the Moon. All mineral phases exposed on the surface of a single basaltic clast exhibit a typical phase-dependent, solar wind irradiation-damaged zone, but lack a vapordeposit layer. The nanophase iron (npFe0) particles produced by solar wind H+ are observed as spheres in the pyroxene amorphous rim, elongated in ilmenite, and absent from Fe-poor plagioclase. Compared with samples from the nearside, the Chang'e-6 samples show deeper solar wind damage in a shorter exposure time, while the npFe0 particles are concentrated in the shallow part. Stopping and Range of Ions in Matter (SRIM) ion implantation modeling results indicate that the solar wind on the farside may be dominated by high-energy ion (He+) effects, while the penetration depth of low-energy ions (H+) is limited due to the shielding of local magnetic anomalies. These observations suggest significant differences in space weathering effects between the lunar nearside and farside, which may be attributed to the presence of local magnetic anomalies on the lunar farside.

Subsea sediments may provide a promising pathway for carbon neutrality by storing carbon dioxide as solid hydrate. Here we use a self-developed numerical multiphysics simulator to examine hydrate-based carbon storage over 100,000 years, capturing coupled multiphase flow, heat transfer and phase transitions in marine sediments. The sequestration process can be divided into three sequential stages. Under the homogeneous baseline model and reference injection schedule, the theoretical single-well storage capacity is estimated to be 41,975 tonnes of liquid carbon dioxide while maintaining the prescribed safety criterion. Permeability enhances early-stage storage at higher values but reduces vertical buffering. High thermal conductivity restores temperatures more rapidly to hydrate-stable conditions, increasing storage efficiency and safety margins. A two-parameter map integrating permeability and thermal conductivity identifies distinct storage regimes and helps screen offshore reservoirs for safe and efficient carbon dioxide sequestration.

How and when the Bangong–Nujiang Ocean closed—and whether collision was followed by extension or continued convergence—remains central to understanding how the Tibetan Plateau was built prior to India–Asia collision. We combine growth-strata architecture, U–Pb geochronology, and provenance from four fault-bounded basins along a ~ 150 km transect in the central Bangong–Nujiang suture zone. Growth wedges and thrust kinematics record a northward-propagating contractional system active during ~104–83 Ma, with successive thrust fronts generating flexural foredeep and wedge-top depocenters rather than rift fills. Conglomerate compositions, sandstone petrography, and detrital-zircon age spectra show coeval, time-transgressive provenance shifts from Lhasa-affinity arc sources to recycled Precambrian basement within Qiangtang domains, tracking the northward advance of deformation. Together these data document a > 20 Myr Albian–Santonian contractional basin archive in the studied central Bangong–Nujiang corridor, indicating a substantial pre–India–Asia collision contribution to plateau growth. Central Tibet likely experienced significant shortening before the India-Asia collision, contributing to crustal thickening and suggesting that plateau growth occurred over multiple tectonic stages rather than during a single collisional event, according to geological and geochronological analysis of syntectonic basins in central Tibet. Primary Handling Editors: Maria Laura Balestrieri and Alireza Bahadori.

Abstract The cause of the observed mare basalt asymmetry between the lunar nearside and farside remains a long‐lasting conundrum. In this study, we characterized the petrology and geochemistry of the Chang'e‐6 low‐Ti basalts from the lunar farside, performed petrological modeling of major elements and conducted Monte Carlo simulation of trace elements, for Chang'e‐6 and Chang'e‐5 basalts. The results from multiple approaches indicate that the young Chang'e‐6 (2.8 Ga) and Chang'e‐5 (2.0 Ga) basalts both originated from shallow, depleted ilmenite‐bearing cumulate (IBC). Based on remote sensing and thermodynamic constraints, we estimated the mantle source ilmenite abundance for young shallow‐source basalts (<3.0 Ga) globally. The modeling results indicate that the mantle sources of these basalts on the nearside generally contains ∼16–32 wt% ilmenite, especially beneath the PKT, whereas the mantle sources of these basalts beneath the farside SPA basin only has ∼13–24 wt% ilmenite. The phase equilibrium calculations show that the nearside mantle sources with higher ilmenite abundance leads to a significant decrease in melting point and tends to produce more melt compared to farside mantle sources. Therefore, asymmetric IBCs may play a key role in accounting for asymmetric nearside/farside volcanism.

The supercritical carbon dioxide Brayton cycle offers the advantages of high power generation efficiency and near-zero pollutant emissions, whereas oxy-fuel combustion technology leads to a reduction in power generation efficiency due to the need for high-energy-consuming air separation and flue gas treatment units. To compensate for this drawback, this paper constructs a novel oxy-fuel coal-fired power generation system based on the supercritical carbon dioxide Brayton cycle. Through parametric sensitivity analysis of this coupled system, the impact of key operational parameters on system energy efficiency and exergy efficiency was quantified. Local optimization results indicate that the system performance reaches its optimum when the economizer bypass ratio is 11%, the dry cycle flue gas ratio is 50%, and the high-pressure turbine inlet pressure is 29 MPa. Furthermore, a multiple quadratic regression equation was established based on the response surface methodology. By analyzing the interactions among influencing factors, the global optimal performance indicators of the system were obtained: a power supply standard coal consumption of 124.87 t·h⁻¹, a boiler thermal efficiency of 99.21%, a net electrical efficiency of 42.93%, and an exergy efficiency of 46.44%.

Iron-rich particles, including nanophase metal iron (npFe(0)) and iron sulfide, are generated from multi-process space weathering effects such as micrometeorite impact and solar wind. However, their post-formation behaviors, especially preservation and transport during reworking, remain poorly constrained. This study presents the microstructures of iron-rich particles on the surface and inside the glass beads in the Chang'e-5 regolith sample. The surface and internal iron-rich particles have similar morphology but significant differences in number density, indicating a consistent formation mechanism but not contemporaneous products. The major element data shows that glass beads containing iron-rich particles generally have higher volatile elements, suggesting that these particles tend to form under the mild low-energy impact, which causes melting without extensive volatilization. The proportion of glass beads records the information of source materials, which with iron-rich particles gradually decreases from ancient mare units to young mare units and then to highlands. In this case, the main factors controlling the formation of iron-rich particles are the FeO content in the material; however, impact intensity and exposure time could also play roles, especially under similar FeO content. The oxygen isotope analysis and calculation results show that the contribution of iron-rich particles formed by thermal decomposition is smaller than that of the disproportionation reaction, but the total production exceeds the abundance obtained from the regolith sample. These observations suggest that pre-existing independent iron-rich particles in the regolith are necessary, which are generated from mare units and can be widely transported to highlands and bonded to the surface of glass beads.

[Objective]The Eastern Himalayan Syntaxis and its southeastern region serve as a critical channel for the eastward extrusion or/and expansion of Tibetan Plateau material.The deformation/rheology mechanisms and seismic anisotropy of the lithosphere provide key insights into plateau uplift and lateral growth.[Methods]This study investigates lower-crustal garnet pyroxenites(27-44 km depth)and lithospheric mantle spinel lherzolites(50-78 km depth)from the Ailao Shan-Red River shear zone and adjacent regions.This study integrates petrographic analysis,microstructural observations,measurements of crystallographic preferred orientations(CPOs),metamorphic-deformation thermobarometry,and whole-rock seismic velocity modeling to constrain the lithospheric seismic anisotropy and its tectonic implications.[Results]Our key findings include:(1)Microstructural analysis reveals that garnet in lower-crustal pyroxenites behaves as a rigid phase with rotational deformation,while clinopyroxene accommodates strain via dislocation creep.In the lithospheric mantle,olivine exhibits both A-type(high-temperature,low-pressure simple shear)and AG-type(melt-present)CPOs;orthopyroxene and clinopyroxene also deform predominantly by dislocation creep,indicating polyphase plastic deformation and static recrystallization.(2)Seismic velocities show distinct layering:garnet pyroxenites exhibit VP=8.01-8.07 km/s and VS=4.54-4.57 km/s with weak anisotropy(AVP=0.6%-1.4%,AVS=0.7%-1.1%),whereas spinel lherzolites display higher velocities(VP=8.03-8.08 km/s,VS=4.60-4.61 km/s)and stronger anisotropy(AVP=3.8%-8.0%,AVS=3.0%-6.6%).(3)The velocity controls differ between lithologies:in pyroxenites,the garnet content dominates the bulk seismic velocity,while the anisotropy correlates with the clinopyroxene content;in lherzolites,the seismic properties are primarily controlled by olivine,while orthopyroxene and clinopyroxene exert a diluting effect,and the deformation intensity significantly influences the anisotropy.(4)From the middle crust to the lithospheric mantle,a vertical velocity model reveals stepwise increases:mica schist(VP=6.12-6.46 km/s)→granodiorite(VP=6.69-6.78 km/s)→amphibolite(VP=6.30-6.69 km/s)→ garnet pyroxenite(VP=8.01-8.07 km/s)→ spinel lherzolite(VP=8.03-8.08 km/s),with the amphibolite layer(VS=3.59-4.01 km/s)acting as a key interface for crust-mantle velocity transitions.[Conclusion]Integrated with published geophysical data,we propose a tectonic model wherein:(1)mid-lower crustal amphibolites and partial melts are the primary sources of crustal anisotropy;(2)mantle anisotropy reflects southeastward lithospheric extrusion driven by asthenospheric upwelling,with clear crust-mantle decoupling.[Significance]Our new data provide critical constraints on the lithospheric deformation and crust-mantle decoupling beneath the Eastern Himalayan Syntaxis and its southeastern region by linking mineral-scale deformation mechanisms with large-scale seismic anisotropy.This enhances our understanding of the uplift and lateral growth of the Tibetan Plateau in the Cenozoic.

In the southeastern Tibetan Plateau, a series of region-scale dextral strike-slip shear zones play important roles in accommodating the continental collision and continental subduction during India-Asia convergence. This study provides structural, kinematic and geochronological data along the Dulongjiang shear zone, a newly recognized region-scale dextral strike-slip zone around the Eastern Himalayan Syntaxis (EHS) region. The structures and kinematic indicators record dextral lateral shearing within the zone in the Dulongjiang and Nabang regons of western Yunnan, China. The temperature range for dextral ductile shearing is estimated to be between 550 and 450 ℃, based on ductile feldspar deformation and CPO patterns of quartz in the granitic mylonites. Zircon U-Pb dating of syn-shearing leucogranites indicateds a period of dextral strike-slip movement between 30 and 18 Ma. The 40Ar/39Ar dating results from the mica fragments in mylonitic granites suggest rapid cooling since approximately 17-14 Ma. Combining these findings with previously published data on other dextral strike-slip faults/shear zones around the EHS and southeastern Asia, it is concluded that the Dulongjiang shear zone is connected with the Parlung shear zone in Tibet, the Nabang shear zone in western Yunnan and Sagaing Fault in the southeastern Asia. The Parlung-Dulongjiang-Nabang shear zone, along with other dextral strike-slip zones, forms a regional-scale Cenozoic dextral shear system around the EHS, extending into southeastern Asia. In addition, our study, in conjuncation with high wavespeed tomographic anomalies beneath the India-Asia collision zone, emphasizes the distinct evolution at lithospheric scales in the southeastern and eastern parts of the collision zone. The intracontinental continuous strike-slip shearing indicates a tectonic transformation from extension in Tibet to block rotation around the EHS. From 30 to 18 Ma, the slab tear is associated, spatially and temporally, with a clockwise rotation and dextral strike-slip shearing around the EHS. These characteristics suggest a warmer geodynamic setting during the rotation and the influence of a hot mantle flow associated with the tear in ongoing India lithosphere subduction. The Oligocene-Miocene dextral strike-slip shearing around the EHS and their linkage southwards with the dextral Sagaing Fault may correspond to the rotation required for the slab to bend, stretch and eventually tear beneath the EHS region.