Tectonophysics最新文献_第7页

Complex seismic anisotropy beneath the North China Craton from long-term shear wave splitting analysis 华北克拉通地下复杂地震各向异性的长期横波分裂分析

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-30 DOI: 10.1016/j.tecto.2025.231031

Wen Meng , Yonghua Li , Xiaoyu Yang

We investigate a contrast in the anisotropic complexity beneath different blocks of the North China Craton (NCC) using shear wave splitting measurements from teleseismic SKS, SKKS, and PKS phases recorded at 113 permanent stations over fifteen years. The systematic variations of splitting parameters with back azimuth observed at stations across various blocks have been modeled using two-layers anisotropic structure. The observed ENE-WSW-oriented fast polarization direction (FPD) in the upper layer beneath the Ordos Block is interpreted as frozen-in lithospheric anisotropy, likely inherited during cratonic formation. The FPD of the upper layer across the Circum-Ordos Rifts is consistent with the rift strike, which may be the result of a combined effect of pre-rift orogenic-related lithospheric fabric, oriented melt pockets or/and simple shear deformation associated with the counterclockwise rotation of the Ordos Block. The FPD in the upper layer beneath the Taihang Orogenic Belt is consistent with the strike of the orogenic belt, suggesting a possible association with past lithospheric orogenic deformation. In the lower layers of all regions modeled with two-layers anisotropic structure, FPDs are consistent with the direction of absolute plate motion (APM), reflecting the flow in the asthenosphere. However, in regions where the lithospheric thickness changes rapidly, such as along the margins of the Ordos Block and around the Datong Volcanic area, there are significant directional deviations between FPDs and APM. This suggests that lithospheric heterogeneity and upwelling mantle flow have a significant modulating effect on the asthenospheric flow.

本文利用华北克拉通（NCC） 113个永久台站近15年的远震SKS、SKKS和PKS相横波分裂测量数据，研究了华北克拉通不同地块各向异性复杂性的对比。利用两层各向异性结构，模拟了各测点观测到的分裂参数随反方位角的系统变化。鄂尔多斯地块下上层观测到的ene - wsw定向快速极化方向（FPD）解释为冻结岩石圈各向异性，可能是在克拉通形成时期继承的。环鄂尔多斯断陷上部的FPD与裂谷走向一致，这可能是与裂陷前造山作用相关的岩石圈结构、定向融袋或与鄂尔多斯地块逆时针旋转相关的单纯剪切变形共同作用的结果。太行造山带下上层FPD与造山带走向一致，可能与过去岩石圈造山变形有关。在所有采用两层各向异性结构模拟的区域的低层，FPDs与绝对板块运动（APM）方向一致，反映了软流层的流动。然而，在岩石圈厚度变化较快的地区，如鄂尔多斯地块边缘和大同火山区周围，FPDs和APM之间存在明显的方向性偏差。这表明岩石圈非均质性和地幔上升流对软流圈流动具有显著的调节作用。

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引用次数: 0

Escape tectonics 逃避构造

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-28 DOI: 10.1016/j.tecto.2025.231029

Donna L. Whitney , Maximiliano Bezada , Lars N. Hansen , Christian Teyssier , Ikuko Wada , Xin Zhou

Tectonic escape is the movement of large, strike-slip fault-bounded blocks of lithosphere obliquely away from collision zones. The process of escape has occurred in its current form since the inception of plate tectonics and likely operated as ‘soft escape’ in the hotter, early Earth.

Escape is driven by collision of a smaller, stronger continent or terrane with a larger, weaker continent. The collider acts as an indenter following consumption of oceanic lithosphere at its leading edge, when collision commences between the indenter and the larger, overriding plate. Owing to heterogeneities in the strength of the escape system and the dynamics of neighboring regions, escape occurs in a preferred direction: escaping lithosphere moves as a wedge-shaped block away from rheologically strong domains and towards weaker, thinner, and/or extending domains.

Insights from active escape systems and thermo-mechanical models indicate that pre- to syn-collision factors that drive or facilitate escape likely include (1) the presence or development of localized weak zones in the overriding plate and along the indenter-ocean boundary, and (2) the continuation of a driving force for escape following slab break-off downdip of the indenter. In large-scale active escape systems, the bounding strike-slip fault closest to the collisional plate boundary is more seismically active than the escape fault further from the collision zone.

Escape has been a significant contributor to heat and mass transfer over geological time, and it affects the lithosphere from mantle to surface. It is a mechanism for the formation of new plates from existing ones and has had a major role in the tectonic history of the planet; e.g., during supercontinent assembly and dispersal. Although escape involves profound strain localization along the bounding seismically-active strike-slip faults, the effects of the escape system encompass processes within and beyond the escaping block or plate.

构造逃逸是大型的走滑断界岩石圈块体斜向远离碰撞带的运动。自板块构造开始以来，这种逃逸过程就以目前的形式发生了，并且可能在较热的早期地球上以“软逃逸”的方式运作。逃逸是由一个更小、更强的大陆或地形与一个更大、更弱的大陆碰撞造成的。当压痕与较大的覆盖板块之间开始碰撞时，在其前缘海洋岩石圈的消耗之后，碰撞器充当压痕。由于逃逸系统的强度和邻近区域的动力学的非均质性，逃逸发生在一个优先的方向：逃逸岩石圈作为一个楔形块体从流变学强的区域向较弱、较薄和/或延伸的区域移动。主动逃逸系统和热力学模型表明，驱动或促进逃逸的碰撞前后因素可能包括：(1)上覆板块和压头-海洋边界上局部弱带的存在或发育，以及(2)压头板块断裂下倾后逃逸驱动力的延续。在大型活动逸出系统中，最靠近碰撞板块边界的边界走滑断层比远离碰撞带的逸出断层更具有地震活动性。在地质时期，逸出一直是热量和质量传递的重要贡献者，它影响着从地幔到地表的岩石圈。它是现有板块形成新板块的机制，在地球的构造史上起着重要作用；例如，在超大陆组合和分散期间。虽然泄漏涉及沿边界地震活动走滑断层的深刻应变局部化，但泄漏系统的影响包括泄漏块体或板块内部和外部的过程。

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引用次数: 0

Corrigendum to ‘Virtual earthquakes in a numerical granular rock box experiment’ [Tectonophysics Volume 874 (2024) 230230] “数值颗粒岩石箱实验中的虚拟地震”的勘误表[构造物理学卷874 (2024)230230]

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-28 DOI: 10.1016/j.tecto.2025.231010

Mikito Furuichi , Jian Chen , Daisuke Nishiura , Ryuta Arai , Yuzuru Yamamoto , Satoshi Ide

引用次数: 0

Seismogenic and rheological behaviours from time-dependent analysis of earthquake depth distribution in the Corinth Rift 科林斯裂谷地震深度分布时变分析的发震和流变特征

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-27 DOI: 10.1016/j.tecto.2025.231008

A. Septier , J. Déverchère , J. Perrot , A. Renouard

Understanding earthquake depth distribution is critical for improving seismogenesis models. While the spatiotemporal pattern of earthquakes is well studied, transient changes in depth distribution remain poorly explored. In this study, we investigate how crustal rheological parameters influence the depth of earthquakes through time, focusing on the Corinth rift, a well-monitored region experiencing a high-level seismic activity in a homogeneous extensional stress field.

To calculate crustal yield strength profiles, we compile geophysical and geological data, including heat flow, rock compositions and properties, Moho depth and strain rate. These estimates are then compared to a high-quality 11-year seismic catalogue of the region. An inversion approach is applied to identify crustal layers associated with persistent versus sporadic seismicity defined here instead of the conventional background versus clustered seismicity.

Our time analysis reveals that the persistent seismicity nicely matches the theoretical brittle–ductile transition and allows us to confidently define the seismogenic thickness, while sporadic seismicity is clustered at depths associated with swarm occurrences. Both distributions are subject to kilometre-scale changes after magnitude 4.0 – 5.5 earthquakes, evidencing a relaxation process even after moderate magnitude events. We conclude that in specific case studies aiming to compare depth distribution and yield strength in the crust, the application of declustering methods may not be optimal for examining the potential rheological controls on earthquake depth distribution and their temporal variations. Instead, the analysis of persistent and sporadic seismicity defined in this study is more accurate and reliable than a declustering approach and offers new and valuable insights for this comparison.

了解地震深度分布对改进地震发生模型至关重要。虽然地震的时空格局研究得很好，但深度分布的瞬态变化仍未得到充分探讨。在这项研究中，我们研究了地壳流变参数如何随时间影响地震深度，重点关注科林斯裂谷，这是一个在均匀伸展应力场中经历高水平地震活动的良好监测区域。为了计算地壳屈服强度剖面，我们收集了地球物理和地质数据，包括热流、岩石成分和性质、莫霍深度和应变率。然后将这些估计与该地区11年的高质量地震目录进行比较。应用反演方法来识别与这里定义的持续地震活动和零星地震活动相关的地壳层，而不是传统的背景地震活动和聚集地震活动。我们的时间分析表明，持续的地震活动与理论的脆性-韧性转变很好地匹配，使我们能够自信地定义发震厚度，而零星的地震活动聚集在与群发生相关的深度。在4.0 - 5.5级地震后，这两个分布都受到公里尺度变化的影响，表明即使在中等震级事件后也存在松弛过程。我们的结论是，在旨在比较地壳深度分布和屈服强度的具体案例研究中，应用聚类方法可能不是检验地震深度分布及其时间变化的潜在流变控制的最佳方法。相反，本研究中定义的持续和零星地震活动的分析比聚类方法更准确和可靠，并为这种比较提供了新的和有价值的见解。

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引用次数: 0

Receiver function and gravity inversion of the Moho depth beneath the Baltic states 波罗的海海底莫霍深度的接收函数和重力反演

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-27 DOI: 10.1016/j.tecto.2025.231012

Viesturs Zandersons, Jānis Karušs

We present a detailed analysis of crustal thickness across the Baltic States using two geophysical methods: receiver function (RF) analysis and gravity inversion. We calculate P-wave RFs for sixteen broadband seismic stations and estimate Moho depths using both standard and sedimentary layer corrected H-k stacking. RF results show crustal thicknesses in the range from 35.5 km in northern Latvia to 55.7 km in southeastern Lithuania and northern Estonia, with corresponding

V_{p} / V_{s}

ratios between 1.70 and 1.86. These results are broadly aligned with established Proterozoic tectonic domains and prior deep seismic sounding (DSS) profiles.

Gravity inversion is performed using a terrain-corrected and spectrally filtered Bouguer anomaly field derived from WGM2012, constrained by DSS and RF-derived Moho depths. A two-layer crust-mantle tesseroid model is optimised using cross-validation and grid search. The resulting gravity-derived Moho depth varies from 44 to 49 km, with a standard deviation of 4.39 km compared to seismic estimates. Major residuals of over 10 km are observed over the Kurzeme Batholith and the West Estonian domain, highlighting the limitations of the two-layer model in regions with complex crustal architecture.

We argue for a cautious interpretation of tectonic boundaries derived solely from potential field data. Our findings support the need for a new DSS transect and integrated gravity-seismic modelling to better constrain intra-crustal structure, especially in central Latvia, southern Lithuania and northwestern Estonia where current models show significant discrepancies.

我们使用两种地球物理方法：接收函数（RF）分析和重力反演对波罗的海国家的地壳厚度进行了详细分析。我们计算了16个宽带地震台站的p波rf，并使用标准层和沉积层校正的H-k叠加来估计莫霍深度。RF结果显示，拉脱维亚北部的地壳厚度为35.5 km，立陶宛东南部和爱沙尼亚北部的地壳厚度为55.7 km，对应的Vp/Vs比值为1.70 ~ 1.86。这些结果与已建立的元古代构造域和先前的深地震测深剖面基本一致。重力反演使用WGM2012反演的地形校正和频谱滤波布格异常场，受DSS和rf反演的莫霍深度约束。利用交叉验证和网格搜索对两层壳幔曲面模型进行优化。由此得到的重力导出的莫霍深度从44到49公里不等，与地震估计值相比，标准差为4.39公里。在Kurzeme Batholith和西爱沙尼亚域观测到超过10公里的主要残差，突出了两层模型在地壳结构复杂地区的局限性。我们主张仅从位场数据推导构造边界的谨慎解释。我们的研究结果支持需要一个新的DSS样带和综合重力-地震模型来更好地约束地壳内部结构，特别是在拉脱维亚中部，立陶宛南部和爱沙尼亚西北部，目前的模型显示显着差异。

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引用次数: 0

Seismic properties of lawsonite blueschist in cold subduction zones 冷俯冲带蓝片岩的地震性质

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-25 DOI: 10.1016/j.tecto.2025.231028

Seungsoon Choi , Junha Kim , Haemyeong Jung

Anomalous seismic low-velocity layers (LVLs) have been observed at the top of subducting slabs in cold subduction zones. However, their origins remain unclear. Here, based on experimentally derived crystal preferred orientation (CPO) data of lawsonite blueschists, we demonstrate that the LVLs can be caused by the alignment of glaucophane and lawsonite. The data were obtained from general shear experiments conducted at the pressures of 1.0–2.5 GPa, temperatures of 230–400 °C, and shear strains of up to 4. The seismic velocities of deformed lawsonite blueschists were calculated based on the CPOs and elastic properties of glaucophane and lawsonite. Our results show that the average P- and S-wave velocities of deformed lawsonite blueschists are 7.69–7.85 km/s and 4.35–4.36 km/s, respectively, which are approximately 7–11 % and 10–12 % lower than surrounding mantle rocks such as peridotite and eclogite. The velocity reduction varies with the wave propagation direction and volume fraction of glaucophane and lawsonite. The P-wave velocity decreases when the wave propagates along the subduction zone strike and when the glaucophane content is high. In contrast, the S-wave velocity decreases with increasing lawsonite content, with minimal difference between the strike-parallel and along-dip propagations. These findings highlight the influence of the CPOs of minerals in deformed lawsonite blueschists on LVL formation, particularly in directional P-wave velocity variation. Since guided waves are often used to analyze subduction zone LVLs, strike-parallel ray paths may provide better constraints on low-P-wave velocity layers associated with deformed lawsonite blueschists.

在冷俯冲带俯冲板块顶部发现了异常地震低速层（LVLs）。然而，它们的起源仍不清楚。本文基于实验得出的蓝片岩晶体优先取向（CPO）数据，证明了蓝片岩的llvls可能是由蓝片岩和蓝片岩的排列引起的。数据来源于1.0 ~ 2.5 GPa压力、230 ~ 400℃温度、4 ~ 4剪切应变条件下的一般剪切实验。根据蓝闪石和蓝闪石的cpo和弹性特性，计算了变形蓝闪石的地震速度。研究结果表明，变形长粒蓝片岩的平均纵、横波速度分别为7.69 ~ 7.85 km/s和4.35 ~ 4.36 km/s，比周围的橄榄岩、榴辉岩等地幔岩石低约7 ~ 11%和10 ~ 12%。速度降低随波的传播方向和蓝透石和lawsonite的体积分数而变化。当横波沿俯冲带走向传播时，横波速度减小，且当蓝透素含量高时，横波速度减小。相反，横波速度随滑石含量的增加而减小，沿走向平行和沿倾角传播的差异很小。这些发现强调了变形lawsonite蓝片岩中矿物的CPOs对LVL形成的影响，特别是对定向纵波速度变化的影响。由于导波通常用于分析俯冲带lls，因此走向平行射线路径可以更好地约束与变形lawsonite蓝片岩相关的低纵波速度层。

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引用次数: 0

Corrigendum to ‘The fine structure and seismogenic mechanism of the Yangjiang intraplate seismic zone in Guangdong Province, South China’ [Tectonophysics 914 (2025) 230904] 华南广东省阳江板内地震带精细构造与孕震机制勘误[构造物理学报914 (2025)230904]

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-24 DOI: 10.1016/j.tecto.2025.231006

Changrong Zhang, Shaohong Xia, Tao Gou, Chaoyan Fan

引用次数: 0

Geophysical evidence of mantle upwelling associated with slab tearing below Central Greece: Geodynamical implications 希腊中部以下与板块撕裂相关的地幔上涌的地球物理证据：地球动力学意义

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-23 DOI: 10.1016/j.tecto.2025.231025

Clarisse Kercret , Christel Tiberi , Frédéric Gueydan , Rodolphe Cattin , Eleni Karagianni

The tectonic evolution of the eastern Mediterranean region is largely influenced by two geological processes: subduction along the Hellenic arc and the westward extrusion of the Anatolian plate via the North Anatolian Fault. The interaction between these features, particularly at the termination of the North Anatolian Fault, has been widely studied but remains debated, largely due to the uncertain geometry of the African slab in the westernmost Hellenic arc. Here, we combined seismological and gravity datasets, revealing a complex deformation zone characterized by slab tearing, fault termination, and mantle upwelling. We processed two receiver function profiles, each about 500 km long and oriented perpendicular to the Hellenic trench, framing the southern tip of the North Anatolian Fault. These profiles reveal new slab geometry consistent with recorded seismicity, confirming slab break-off propagation. However, slab tearing alone cannot account for the regional mantle gravity field. Our findings indicate that asthenospheric upwelling at the slab tear location is necessary to explain the observed asymmetrical and bimodal gravity anomaly, coinciding with the North Anatolian Fault's termination and elevated surface heat flow. These insights enhance our understanding of deformation mechanisms in central Greece, suggesting that the slab tearing may have facilitated recent north-south extension in the Corinth rift, while asthenospheric flow concentrated strike-slip deformation on the North Anatolian Fault.

东地中海地区的构造演化在很大程度上受两个地质过程的影响：沿希腊弧的俯冲作用和通过北安纳托利亚断层向西挤压安纳托利亚板块。这些特征之间的相互作用，特别是在北安那托利亚断层的末端，已经被广泛研究，但仍然存在争议，主要是由于希腊弧最西端非洲板块的不确定几何形状。在此，我们结合地震和重力数据，揭示了一个以板块撕裂、断层终止和地幔上涌为特征的复杂变形带。我们处理了两个接收函数剖面，每个剖面长约500公里，垂直于希腊海沟，构成了北安那托利亚断层的南端。这些剖面揭示了与记录的地震活动相一致的新板的几何形状，证实了板的断裂传播。然而，单靠板块撕裂不能解释区域地幔重力场。研究结果表明，软流圈上升流在板块撕裂位置是解释观测到的不对称和双峰重力异常的必要条件，与北安那托利亚断层终止和地表热流升高相吻合。这些发现增强了我们对希腊中部变形机制的理解，表明板块撕裂可能促进了最近科林斯裂谷的南北伸展，而软流圈流动则集中了北安纳托利亚断层的走滑变形。

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引用次数: 0

Early Cretaceous shortening event recorded by the emplacement of the Tiantai pluton, Eastern South China Block 华南地块东部天台岩体侵位记录的早白垩世缩短事件

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-22 DOI: 10.1016/j.tecto.2025.231007

Ran An , Wei Wei , Wei Lin , Chao Song , Yang Chu

The Cretaceous tectonic activity of the East Asia Continental Margin (EACM), in response to Paleo-Pacific subduction, has long attracted attention for its effects on topography, climate, and biological evolution. However, competing hypotheses suggested that, under a dominantly NW-SE extensional background, the Cretaceous tectonic regime experienced NW-SE shortening, NE-striking sinistral or dextral strike-slip events due to different geodynamic processes. Located near the subduction zone, the Southeast Coastal Magmatic Belt (SECMB) is a tectonically sensitive area reflecting plate-boundary geodynamic processes. Considering that the magnetic fabric (Anisotropy of Magnetic Susceptibility, AMS) of a pluton is an effective tool to record the tectonic regime during emplacement, the SECMB, widely intruded by Cretaceous plutons, is an ideal zone to reconstruct the Cretaceous tectonic regime of the EACM. Therefore, a multidisciplinary study including field/microstructural observations, AMS measurements, and U-Pb zircon dating was conducted to investigate the Tiantai pluton in the northern SECMB. Results show that zircon U-Pb dating yields crystallization ages of ∼120–115 Ma. Magmatic to submagmatic fabrics revealed by field and microscopic observations, together with clustered, steeply dipping NE–SW-striking magnetic foliations and predominant NE- or SW-plunging magnetic lineations, suggest a syn-emplacement NW–SE shortening regime. This shortening event coincides with Early Cretaceous crustal thickening in the SECMB indicated by geochemical proxies and is further supported by a magmatic lull and unconformities between upper and lower volcanic sequences in the eastern South China Block. This discovery sheds light on the Cretaceous collision between the Dangerous Grounds-West Philippine Block and the South China Block.

白垩纪东亚大陆边缘（EACM）的构造活动是对古太平洋俯冲的响应，其对地形、气候和生物进化的影响一直受到人们的关注。然而，相互竞争的假设认为，在以NW-SE为主的伸展背景下，由于不同的地球动力学过程，白垩纪构造体系经历了NW-SE缩短、ne走向的左旋或右旋走滑事件。东南沿海岩浆带（SECMB）位于俯冲带附近，是反映板块边界地球动力学过程的构造敏感区。考虑到岩体的磁结构（磁化率各向异性）是记录侵位期间构造制度的有效工具，白垩系岩体广泛侵入的东南太平洋中生代是重建东洋中生代白垩系构造制度的理想带。为此，本文采用野外/微结构观测、AMS测量、U-Pb锆石定年等多学科研究方法，研究了中侏罗统北段天台岩体。结果表明，锆石U-Pb定年得到结晶年龄为~ 120 ~ 115 Ma。野外和显微观察显示，岩浆-次岩浆构造，以及密集的北东—西向陡倾磁片理和主要的北东—西向陡倾磁线，显示出北西—东西向的同位缩短机制。这一缩短事件与地球化学指标所显示的早白垩世东南中生代地壳增厚一致，并进一步得到了华南地块东部岩浆静息和上下火山层序不整合的支持。这一发现揭示了白垩纪危险地-西菲律宾地块与华南地块之间的碰撞。

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引用次数: 0

Prolonged early cretaceous crustal extension in the eastern Lhasa Terrane: A multiphase magmatic record (∼134–103 Ma) from the Bomi-Chayu batholith 拉萨地体东部早白垩世延长的地壳伸展：波米-察峪岩基多期岩浆记录(~134 ~ 103 Ma

IF 2.6 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2025-11-21 DOI: 10.1016/j.tecto.2025.231011

Yihu Zhang , Dongliang Liu , Xuxuan Ma , Haibing Li , Guilong Mi , Xunzhang Zhu , Wang Li

The Early Cretaceous (133–109 Ma) Bomi-Chayu batholith in the easternmost Lhasa terrane provides key insights into crustal growth and tectonic evolution, yet its petrogenesis and geodynamic setting remain contentious. Integrated petrographic, geochronological, geochemical, and isotopic analyses of three granitic suites identify crystallization ages of 134.3 Ma, 116.7–118.0 Ma, and 102.6–102.8 Ma, extending the known duration of regional magmatism. The ∼134 Ma and ∼103 Ma granites are classified as A2-type, formed under high-temperature, low-pressure settings. The ∼134 Ma biotite monzogranites show enriched isotopic compositions, suggesting derivation from ancient crustal sources. In contrast, the ∼103 Ma monzogranites exhibit decoupled ε_Nd(t)-ε_Hf(t) values, consistent with dehydration remelting of ancient crust. The ∼117 Ma granitoid suit is synchronous with a regional magmatic flare-up. The granodiorites in this stage display I-type affinities, with enriched Sr-Nd but relatively depleted zircon Hf isotopes. Geochemical and isotopic trends indicate hybridization between mantle-derived melts (represented by coeval gabbrodiorites and basalts) and crustal components (represented by coeval biotite monzogranites), followed by fractional crystallization and minor upper-crustal contamination. Magmatic types and isotopic compositions correlate the Bomi-Chayu batholith with the magmatic belt in the central Lhasa terrane. The two-stage A-type granites, together with synchronous I-S-type granitoids and bimodal volcanism, provide robust evidence for prolonged crustal extension in the eastern Lhasa terrane (at least the Bomi-Chayu area) during ∼134–103 Ma. We interpret this extensional regime as the result of slab rollback of the northward subducted Neo-Tethyan oceanic lithosphere.

拉萨地体最东端早白垩世（133-109 Ma） Bomi-Chayu基为研究地壳生长和构造演化提供了重要线索，但其岩石成因和地球动力学背景仍存在争议。综合岩石学、年代学、地球化学和同位素分析，确定了三套花岗岩的结晶年龄分别为134.3 Ma、116.7 ~ 118.0 Ma和102.6 ~ 102.8 Ma，延长了已知的区域岩浆活动持续时间。~ 134 Ma和~ 103 Ma花岗岩为a2型，形成于高温低压环境。~ 134 Ma黑云母二长花岗岩显示出丰富的同位素组成，表明其来源于古代地壳。而~ 103 Ma二长花岗岩的εNd(t)-εHf(t)值不耦合，与古地壳脱水重熔相一致。~ 117 Ma花岗岩套装与区域性岩浆爆发同步。该阶段花岗闪长岩呈i型亲和，Sr-Nd富集，锆石Hf同位素相对富集。地球化学和同位素趋势表明，幔源熔体（以同代辉长闪长岩和玄武岩为代表）和地壳成分（以同代黑云母二长花岗岩为代表）之间存在杂交，然后是分馏结晶和轻微的地壳上污染。岩浆类型和同位素组成与拉萨地体中部波米-察峪岩浆岩带相对应。两期a型花岗岩与同步的i- s型花岗岩和双峰火山作用为拉萨地体东部（至少是波米-察峪地区）在~ 134-103 Ma期间的地壳伸展提供了有力的证据。我们认为这种伸展状态是新特提斯洋岩石圈向北俯冲的板块回退的结果。

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引用次数: 0