Earth and Planetary Science Letters最新文献_第2页

Structural heterogeneity and anisotropy beneath Myanmar: Insights into the complex deformation of the Indo-Burma subduction zone 缅甸地下构造非均质性和各向异性：印缅俯冲带复杂变形的启示

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-29 DOI: 10.1016/j.epsl.2026.119879

Yiming Bai , Shengji Wei , Jing Chen , Tianjue Li , Bingfeng Zhang , Xiao Xiao , Shucheng Wu , Jiayuan Yao , Yu Wang , Ping Tong

The highly oblique Indo-Burma convergence has produced complex tectonic deformation along the Myanmar margin, and the depth-resolved anisotropy offers a valuable means to elucidate the mechanisms that drive this deformation. Here, we build a 3-D anisotropic body-wave velocity model in the upper 80 km using the adjoint-state traveltime tomography applied to an AI-assisted local earthquake catalog. The new model reveals pronounced azimuthal anisotropy and velocity heterogeneities. In the overriding Burma plate crust, a complex anisotropic structure is observed: fast velocity directions (FVDs) normal to the trench beneath the inner Indo-Burma Ranges while broadly parallel to the tectonic block boundaries and fault strikes beneath the Central Myanmar Basin. These patterns reflect transpressive deformation under oblique convergence. In the uppermost mantle, the observed ENE-WSW FVDs west of the Wuntho-Popa Arc are attributed to the fossil fabric in the subducting Indian plate, and the NNW-SSE FVDs farther east are associated with supra-slab along-strike flow, possibly shaped by the slab geometry complexity. Additionally, the segment of the Sagaing Fault near 21°N is likely infiltrated by crustal fluids originating from the adjacent Mogok Metamorphic Belt, potentially linked to recent asthenospheric melt upwelling. Evidence for fluid presence includes a near-fault crustal anomaly with ∼8% velocity reduction, high Vp/Vs of >1.85 and FVDs parallel to the maximum horizontal compressive stress. Fluid infiltration likely promotes partial creep in this fault segment, and, together with variations in lithology and deformation state, may affect earthquake nucleation along this portion of the Sagaing Fault, including the 2025 Mw 7.8 Mandalay event.

高度倾斜的印缅辐合带在缅甸边缘产生了复杂的构造变形，深度分辨各向异性为阐明这种变形的驱动机制提供了有价值的手段。在这里，我们利用伴随状态走时层析成像技术建立了80公里以上的三维各向异性体波速度模型，该模型应用于人工智能辅助的局部地震目录。新模型显示出明显的方位各向异性和速度非均质性。在上覆的缅甸板块地壳中，观察到一个复杂的各向异性结构：快速方向（FVDs）与印缅山脉内部的海沟垂直，而与缅甸盆地中部的构造块体边界和断层走向大致平行。这些模式反映了斜辐合作用下的压迫变形。在上地幔，Wuntho-Popa弧以西的ENE-WSW型fvd与俯冲的印度板块化石构造有关，而更以东的NNW-SSE型fvd与板块上沿走向流动有关，可能受板块几何复杂性的影响。此外，在21°N附近的实皆断裂段可能被来自相邻Mogok变质带的地壳流体渗透，这可能与最近的软流圈融化上涌有关。流体存在的证据包括近断层地壳异常，速度降低约8%，高Vp/Vs为>；1.85， fvd平行于最大水平压应力。流体渗透可能促进了该断裂带的部分蠕变，并与岩性和变形状态的变化一起，可能影响实皆断裂带这部分的地震成核，包括2025 Mw 7.8曼德勒事件。

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引用次数: 0

Two episodes of ultrahigh-temperature metamorphism within one orogenic cycle 一个造山旋回内的两期超高温变质作用

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-28 DOI: 10.1016/j.epsl.2026.119887

Jie Dong , Chunjing Wei , Shuguang Song , Guochun Zhao , Guibin Zhang

Ultrahigh-temperature metamorphism (UHTM) is significant for constraining the thermal-mechanical evolution of continental crust, which can periodically occur within one orogenic cycle involving subduction, collision and subsequent extension stages. However, multi-episode UHTM within one orogenic cycle has been rarely reported. Here, we performed a comprehensive investigation of petrography, phase equilibria modelling, and zircon U-Pb dating for felsic and Mg-Fe-Al granulites from the Kunlun-Qaidam Massif in north Qingzang Plateau. Three episodes of metamorphism were inferred, involving two episodes of low pressure (LP)-UHTM intervened by an episode of medium-pressure and high-temperature (MP-HT) metamorphism. The first episode LP-UHTM (I) exhibits peak P–T conditions of 0.5–0.8 GPa/930–1050 °C, occurring at >460 Ma. The second episode MP-HT metamorphism (II) was achieved by compressional cooling from the LP-UHT conditions to MP-HT conditions of >0.9–1.2 GPa/<820–900 °C. This was followed by decompressional heating to another episode of LP-UHTM (III) with conditions of 0.55–0.75 GPa/900–1070 °C at >410 Ma. Combining our metamorphic studies and other geological data, a three-stage tectonic model is proposed: (a) oceanic slab rollback inducing an arc-backarc extension and the LP-UHTM (I) during the late-stage subduction of the Proto-Tethys Ocean; (b) continental subduction-collision leading to the thickening of hot arc-backarc crust and the MP-HT metamorphism (II) after the closure of the Proto-Tethys Ocean, and (c) post-collisional crustal thinning and mantle upwelling related to lithosphere delamination resulting in the LP-UHTM (III). It is for the first time that we recognize two episodes of LP-UHTM occurring within < 50 Myr in one orogenic cycle.

超高温变质作用（UHTM）对大陆地壳热力学演化具有重要的制约作用，它可以周期性地发生在一个造山旋回内，包括俯冲、碰撞和随后的伸展阶段。然而，在一个造山旋回内发生多期超热热症的报道却很少。本文对青藏高原北部昆仑-柴达木地块长英质和Mg-Fe-Al麻粒岩进行了岩石学、相平衡模拟和锆石U-Pb定年研究。推断出三期变质作用，包括两期低压(LP)-UHTM变质作用和一期中压高温（MP-HT）变质作用。第一集LP-UHTM (I)表现出0.5-0.8 GPa/ 930-1050°C的峰值P-T条件，发生在>；460 Ma。第二阶段MP-HT变质作用（II）是通过从LP-UHT条件压缩冷却到>； 0.9-1.2 GPa/<； 820-900°C的MP-HT条件实现的。随后减压加热到另一段LP-UHTM (III)，温度为0.55-0.75 GPa/ 900-1070°C，温度为>；410 Ma。结合变质学研究和其他地质资料，提出了三阶段构造模式：(a)原特提斯洋晚期俯冲过程中，洋板回退引起弧后伸展和低-超热缩；(b)原特提斯洋关闭后大陆俯冲碰撞导致热弧-弧后地壳增厚和MP-HT变质作用（II）； (c)碰撞后地壳变薄和地幔上涌导致岩石圈拆沉，形成LP-UHTM （III）。这是我们首次发现在同一个造山旋回中，在50 Myr范围内出现两期LP-UHTM。

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引用次数: 0

Extended time delay and complex rupture behaviors of dynamically triggered earthquakes on gouge-filled fault 充泥断层动力触发地震的延迟性和复杂破裂行为

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-29 DOI: 10.1016/j.epsl.2026.119853

Yishuo Zhou , Ran Xu , Peng Dong , Kaiwen Xia

Seismic waves emitted by an earthquake can trigger other earthquakes over a variety of spatial and temporal scale, yet extended time delay and rupture behaviors associated with these events are not well understood. Here, we report on the experimental observation of earthquake rupture triggered by explosion-generated stress perturbations at different stress level, showing that the time delay of triggered events on gouge-filled fault is significantly higher than those on bare fault. Furthermore, we identify notable difference in rupture behaviors between the triggered events on gouge-filled and bare faults. For bare fault, the triggered events may be arrested or runaway, depending on the initial stress level at the onset of dynamic triggering. However, for gouge-filled fault, the rupture behaviors is more complex, manifested by scattered micro-ruptures, coalescent micro-ruptures, and runaway rupture. The extended time delay and complex rupture behaviors of triggered events on gouge-filled fault are attributed to the evolution of force chain within the fault gouge. Our results suggest that fault gouge plays an important role in earthquake dynamic triggering, which may provide new insights into the mechanism for extended time delay of dynamically triggered earthquakes on natural fault systems.

地震发出的地震波可以在不同的空间和时间尺度上引发其他地震，但与这些事件相关的延长时间延迟和破裂行为尚未得到很好的理解。本文报道了不同应力水平下爆炸应力扰动触发地震破裂的实验观测结果，结果表明，充填断层触发事件的时间延迟明显高于裸断层。此外，我们还发现了泥断层和裸断层在破裂行为上的显著差异。对于裸断层，触发事件可能被阻止或失控，这取决于动态触发开始时的初始应力水平。而对于泥质断层，其破裂行为更为复杂，表现为分散微破裂、聚结微破裂和失控破裂。断层泥内部力链的演化是充填断层触发事件时滞延长和破裂行为复杂的主要原因。研究结果表明，断层泥在地震动力触发中起着重要作用，为研究自然断层系统动态触发地震延时延长的机理提供了新的思路。

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引用次数: 0

Tracking deep mantle heat and volatiles in the Iceland plume from a high-density survey of helium isotopes along the Reykjanes Ridge 通过沿雷克雅内斯山脊的氦同位素高密度调查，追踪冰岛地幔深处的热量和挥发物

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-28 DOI: 10.1016/j.epsl.2026.119882

U. Balci , L. Di Nicola , J.G. Fitton , R.N. Taylor , F.M. Stuart

The upwelling mantle plume beneath Iceland flows southwest down the Reykjanes Ridge. Several prominent V-shaped ridges (VSRs) and troughs (VSTs) extend obliquely from the ridge that are believed to result from pulses of hotter plume mantle. The intimate connection between heat and primordial He in the deep mantle means that the mantle beneath the Reykjanes Ridge should have elevated ³He/⁴He. A new high resolution He isotope study of basaltic glasses from southernmost Iceland (63°N) to 55°N along the Reykjanes Ridge demonstrates a broad peak of ³He/⁴He (16.0 R_a) centred around 60°N that coincides with the first topographic high (VSR-1). The magnitude of the He isotope anomaly broadly scales with the excess temperature inferred from crustal thickness. This supports the hypothesis that thickened oceanic crust is a consequence of a pulse of hotter mantle within the upwelling plume that flows down the Reykjanes Ridge. The along-ridge ³He/⁴He peak at 59-62°N is significantly longer (320 km) than the thickened oceanic crust of VSR-1 (60-70 km). This can most simply be explained if the hot mantle blob is surrounded by a high ³He/⁴He mantle carapace that has a temperature similar to the surrounding mantle. As helium diffusion is orders of magnitude slower than heat, this relationship can be most simply explained if the outer region of the hot, He-rich blob has lost heat to the surrounding mantle during transit from the core-mantle boundary, yet retained the deep mantle He isotope fingerprint.

冰岛下方上升流的地幔柱沿着雷克雅内斯山脊向西南方向流动。几个突出的v形脊（VSRs）和槽（VSTs）从脊斜伸出，被认为是由较热的地幔柱脉冲造成的。热与地幔深处原始氦之间的密切联系意味着雷克雅内斯脊下的地幔应该升高了3He/4He。对冰岛最南端（63°N）至55°N的Reykjanes山脊玄武岩玻璃的高分辨率He同位素研究表明，在60°N附近有一个宽的3He/4He （16.0 Ra）峰，与第一个地形高点（VSR-1）一致。氦同位素异常的大小与地壳厚度推断出的过量温度大致一致。这支持了一种假设，即变厚的海洋地壳是由沿雷克雅内斯山脊上涌的羽流中较热的地幔脉冲造成的。沿脊3He/4He峰在59 ~ 62°N明显长于VSR-1增厚洋壳（60 ~ 70 km）（320 km）。最简单的解释是，热的地幔团被高3He/4He的地幔壳所包围，其温度与周围的地幔相似。由于氦的扩散速度比热慢几个数量级，这种关系可以最简单地解释为：热富氦团的外部区域在从核心-地幔边界转移的过程中向周围的地幔失去了热量，但保留了深部地幔的He同位素指纹。

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引用次数: 0

Permian mylonites in the footwall of a Miocene Cycladic core complex (Ios, Greece): Insights from (micro)structurally integrated apatite U-Pb petrochronology 希腊Ios中新世基克拉底岩心杂岩下盘二叠纪糜伦岩：来自（微观）结构整合磷灰石U-Pb岩石年代学的启示

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-24 DOI: 10.1016/j.epsl.2026.119857

Megan Elysia Flansburg , Daniel Fritz Stockli , Eirini Maria Poulaki , Konstantinos Soukis , Lisa Danielle Stockli

Oligo-Miocene large-magnitude extension and the formation of metamorphic core complexes accommodated exhumation of High Pressure/Low Temperature (HP/LT) rocks in the eastern Mediterranean. Previous studies on Ios Island in the southern Cyclades have associated mylonitic fabrics exposed within the crystalline Cycladic Basement and along its contact with the overlying Cycladic Blueschist Unit, termed the South Cycladic Shear Zone, with Oligo-Miocene extension in the backarc of the retreating Hellenic subduction zone. We utilized apatite U-Pb geo-thermochronology, combined with Ti-in-Quartz and quartz c-axis opening-angle thermometry and microstructural characterization of mylonitic fabrics, to constrain the timing of mylonitization preserved in the footwall of the South Cycladic Shear Zone. Apatite U-Pb ages of the high-temperature (> ca. 500°C) mylonites in the Basement Core are Permo-Carboniferous (ca. 302—270 Ma), with two samples yielding apparent Mesozoic apatite U-Pb ages and whose U-Pb and REE systematics may have been perturbed by Cenozoic tectonics. Despite lower-temperature (300—400°C) mylonitization within the South Cycladic Shear Zone, rocks there preserve exclusively Permo-Carboniferous (ca. 307–297 Ma) apatite U-Pb ages, corresponding to either relict high-temperature quartz domains (ca. >500°C) or a detrital age signature sourced from the Cycladic Basement, but not to Cenozoic movement along the interface. The dominance of Permian cooling ages suggests that significant exhumation of the Cycladic Basement occurred prior to and concurrent with deposition of the earliest Cycladic Blueschist Unit in the late Permian to early Triassic, and that Cycladic core complexes preserve high-temperature fabrics related to pre-Miocene extension. Importantly, this work advises caution when assuming the age of mylonitic fabrics in the footwalls of metamorphic core complexes across the globe without integrating deformation conditions within thermochronometric and geochemical context.

东地中海渐新世-中新世大尺度伸展和变质岩心杂岩的形成为高压低温（HP/LT）岩石的发掘提供了条件。先前对基克拉迪群岛南部的伊奥斯岛的研究将暴露在结晶基克拉迪基底内的糜棱岩结构及其与上覆基克拉迪蓝片岩单元（称为南基克拉迪剪切带）的接触与撤退的希腊俯冲带后弧的渐新世-中新世伸展联系起来。利用磷灰石U-Pb地球热年代学，结合ti -in-石英和石英c轴开角测温和糜棱岩组构的显微结构表征，对南基克拉底剪切带下盘保存的糜棱岩化时间进行了限定。基底核高温糜伦岩（>；约500℃）的磷灰石U-Pb年龄为二叠石炭系（约302 ~ 270 Ma），其中2个样品具有明显的中生代磷灰石U-Pb年龄，其U-Pb和REE系统可能受到了新生代构造的扰动。尽管南基克拉底剪切带的糜石化作用温度较低（300-400°C），但那里的岩石只保留了二石纪（约307-297 Ma）磷灰石U-Pb年龄，对应于残余的高温石英域（约500°C）或来自基克拉底的碎屑年龄，而不是新生代沿界面运动。二叠纪冷却时代的优势表明，基克拉迪基底的大量发掘发生在晚二叠世至早三叠世最早的基克拉迪蓝片组沉积之前和同时，基克拉迪岩心杂岩保存着与前中新世伸展有关的高温织物。重要的是，这项工作建议在假设全球变质岩心复合体下壁糜糜岩织物的年龄时要谨慎，而不考虑热时学和地球化学背景下的变形条件。

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引用次数: 0

Oxygen vacancy diffusion in davemaoite (CaSiO3 perovskite): Implications for the redox equilibrium and the electrical conductivity of Earth’s lower mantle 钙钛矿（CaSiO3）中的氧空位扩散：对地球下地幔氧化还原平衡和电导率的影响

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-27 DOI: 10.1016/j.epsl.2026.119861

Maximilian Schulze, Gerd Steinle-Neumann

Davemaoite (CaSiO₃), a major rock-forming mineral in the Earth’s lower mantle, adopts a perovskite structure, which is known for the rapid diffusion of extrinsic oxygen vacancies (OV). Here, we use molecular dynamics simulations in conjunction with a machine learning potential to systematically investigate extrinsic OV diffusion in davemaoite at lower mantle conditions. We determine diffusion coefficients (D_v) for a series of temperatures along isobars of 25, 50, 75, 100 and 125 GPa and find that computed diffusivities closely follow an Arrhenian behavior. The pre-exponential factor is pressure independent with

\log D_{v}^{\circ} =

-6.53  ±  0.06 and the activation enthalpy increases nonlinearly with pressure from 0.87 eV to 1.66 eV. On the basis of the Arrhenian model, we predict that D_v decreases throughout the lower mantle by at least one order of magnitude along geotherms representative of the ambient mantle and subducted lithosphere. We argue that despite the high OV diffusivities, the davemaoite component of subducted oceanic crust does not achieve complete redox equilibration with the surrounding mantle on its way to the core-mantle boundary, and that significant redox exchange is limited to the upper parts of the lower mantle. Finally, we provide arguments that the electrical conductivity of most parts of the lower mantle cannot be explained by ionic conductivity and that its electrical conductivity must therefore be determined by iron-induced polaron hopping.

钙钛矿（CaSiO3）是地球下地幔的主要造岩矿物，其结构为钙钛矿，具有快速扩散外在氧空位（OV）的特点。在这里，我们将分子动力学模拟与机器学习潜力相结合，系统地研究了下地幔条件下davemaoite中的外在OV扩散。我们确定了沿等压线25、50、75、100和125 GPa的一系列温度下的扩散系数（Dv），并发现计算得到的扩散系数密切遵循Arrhenian行为。指数前因子与压强无关，logDv°=-6.53 ± 0.06，激活焓随压强非线性增加，从0.87 eV增加到1.66 eV。在阿伦尼模型的基础上，我们预测沿代表环境地幔和俯冲岩石圈的地热，整个下地幔的Dv至少减少一个数量级。我们认为，尽管洋壳的OV扩散系数很高，但俯冲洋壳的橄榄橄榄岩组分在向核幔边界移动的过程中并没有与周围地幔实现完全的氧化还原平衡，明显的氧化还原交换仅限于下地幔的上部。最后，我们提出的论点是，下地幔大部分地区的电导率不能用离子电导率来解释，因此其电导率必须由铁诱导的极化子跳变来确定。

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引用次数: 0

Zircon thermal annealing ages determine a late Eocene birth for the First Bend of the Yangtze River 锆石热退火年龄确定了长江第一弯的始新世晚期形成

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-01-31 DOI: 10.1016/j.epsl.2026.119888

Yang Zhang , Rui Li , Guang-Yan Zhou , David Chew , Jian-Ping Zheng , Qing Xiong , Wei Wang

Understanding the evolution of the First Bend of the Yangtze River is essential in deciphering the Cenozoic tectonic dynamics of the Tibetan Plateau and the associated intricate interplay between surface uplift, river erosion and sediment deposition. Nevertheless, the precise timing and mechanisms for its formation remain a subject of debate, primarily stemming from the ambiguous interpretation of sediment provenance studies that solely rely on detrital zircon U-Pb ages. Here, we employ zircon Raman spectroscopy data integrated with a new developed support vector machine model to assess whether detrital zircons from the Eocene Jianchuan Basin underwent thermal annealing after crystallization. Combined with zircon depth profiling U-Pb age data, we show that the sediments in the lower to middle sequences of the Jianchuan Basin were predominantly sourced from the Qiangtang terrane and the western Yangtze region, implying paleo-Yangtze (Jinsha) River once flowed southwards through this basin. In contrast, the overlying Jianchuan Formation mainly received recycled detritus from the underlying Paleozoic sedimentary strata. This shift in sediment supply to the Jianchuan Basin was caused by the uplift within and surrounding the basin induced by a change in stress regime from extension to compression, which resulted in the reorganization of the paleo-Yangtze river and ultimately the formation of the First Bend and the modern Yangtze River during the late Eocene.

了解长江第一弯道的演化过程，对于解读青藏高原新生代构造动力学以及地表隆起、河流侵蚀和泥沙沉积之间复杂的相互作用具有重要意义。然而，其形成的精确时间和机制仍然是一个争论的主题，主要是由于仅仅依赖于碎屑锆石U-Pb年龄的沉积物物源研究的模糊解释。本文利用锆石拉曼光谱数据结合新建立的支持向量机模型，对建川盆地始新统碎屑锆石结晶后是否进行了热退火处理进行了评价。结合锆石深度剖面U-Pb年龄资料，认为建川盆地中下层序沉积物主要来源于羌塘地体和西扬子地区，暗示古扬子（金沙江）曾南下流经该盆地。上覆建川组主要接收下伏古生代沉积地层的再循环碎屑。始新世晚期，应力状态由伸展向挤压转变，导致盆地内部和周围隆升，形成了古长江的重组，最终形成了第一弯道和现代长江。

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引用次数: 0

Frictional weakening of gabbro faults after quasi-stationary contact under hydrothermal conditions 热液条件下辉长岩断层准静止接触后的摩擦减弱

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-02-05 DOI: 10.1016/j.epsl.2026.119893

Wei Feng , Lu Yao , Shengli Ma , Feng Shi , Jinyu Zheng , Giulio Di Toro

Quasi-stationary fault contacts are known to enhance static friction. However, its role in modulating dynamic friction remains poorly understood. Here, we investigate how quasi-stationary contacts influence subsequent fault slip. We perform slide-hold-slide experiments on simulated gabbro gouge with distilled water at temperatures ranging from 25 to 400 °C and a pore pressure of 30 MPa. At 300 °C, prolonged holds (≥ 3000 s) induce significant post-hold frictional weakening and enhanced fault stability (i.e., decrease of the magnitude of stress drop). The post-hold frictional weakening correlates with hold duration, fluids and ambient temperature, suggesting the involvement of thermally-activated, time-dependent processes on the contact surfaces. Microanalytical investigations reveal the formation of clay minerals via hydrothermal alteration in the experimental fault. Our findings demonstrate that short-term hydrothermal processes occurring during static holds may leave persistent mineralogical imprints, thereby modifying fault strength and slip behavior.

已知准静止故障接触可以增强静摩擦。然而，它在调节动态摩擦中的作用仍然知之甚少。在这里，我们研究了准平稳接触如何影响随后的断层滑动。我们用蒸馏水对模拟辉长岩泥进行了滑动-保持-滑动实验，温度范围为25至400°C，孔隙压力为30 MPa。在300°C时，长时间保持（≥3000 s）会导致保持后明显的摩擦减弱和断层稳定性增强（即应力降幅度减小）。保持后的摩擦减弱与保持时间、流体和环境温度有关，这表明接触面上存在热激活的、与时间相关的过程。微量分析表明，实验断层中黏土矿物是通过热液蚀变形成的。我们的研究结果表明，在静态保持期间发生的短期热液过程可能会留下持久的矿物学印记，从而改变断层强度和滑动行为。

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引用次数: 0

New early cretaceous paleomagnetic results from the Northern Lhasa Terrane and their tectonic implications 拉萨地块北部早白垩世古地磁新结果及其构造意义

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-02-02 DOI: 10.1016/j.epsl.2026.119859

Zijian Li , Yalin Li , Xiaodong Tan , Zhongpeng Han , Shuai Li , Xingduo Ma , Ying Liang , Xu Zhang , Jizheng Song , Zihao Zhou , Yuanxiang Li , Shuqing Miao , Chengshan Wang

The tectonic evolution of central Tibet was shaped by multiple collisions, notably the Cretaceous collision between the Lhasa and Qiangtang terranes and the subsequent India–Asia collision. Yet, uncertainties in the Early Cretaceous paleogeography of the Lhasa terrane still obscure their timing and mechanisms. Here we present new paleomagnetic data derived from Early Cretaceous sedimentary and volcanic sequences in the northern Lhasa terrane. Field tests, rock magnetic experiments, and petrographic analyses demonstrate that the characteristic remanent magnetizations are primary. Sedimentary rocks show shallower mean directions than volcanic rocks, but Elongation–Inclination analysis effectively corrects this bias, producing consistent paleomagnetic estimates. The combined dataset defines a paleomagnetic pole at 68.6°N, 348.7°E (A₉₅ = 1.4°), indicating a paleolatitude of 25.5° ± 1.4°N for the Bangoin region during the interval of 114–113 Ma. Comparison with the Asian apparent polar wander path suggests 560 ± 200 km of intracontinental shortening since the late Early Cretaceous. Integrated with published paleomagnetic data and geological evidence, these findings indicate that the central and eastern Lhasa terrane had already collided with the Qiangtang terrane at approximately 30°N by ∼114 Ma, with subsequent westward propagation of the collision. Moreover, during the late Early Cretaceous, the southern margin of Asia was situated at a paleolatitude exceeding 20°N, in contrast to the coeval low-latitude setting (≤10°N) of the Trans-Tethyan Subduction Zone. This significant paleolatitudinal disparity supports an intra-oceanic equatorial arc–continent collision at ∼55 Ma and provides new constraints on the timing and geodynamic mechanisms of the India–Asia collision.

西藏中部的构造演化受到多次碰撞的影响，特别是白垩纪拉萨和羌塘地块的碰撞以及随后的印亚碰撞。然而，拉萨地体早白垩世古地理的不确定性仍然使其时间和机制模糊不清。本文介绍了拉萨地体北部早白垩世沉积和火山层序的新古地磁资料。现场测试、岩石磁性实验和岩石学分析表明，特征残余磁化是主要的。沉积岩的平均方向比火山岩浅，但拉长-倾斜分析有效地纠正了这种偏差，产生了一致的古地磁估计。结合数据，确定了一个位于68.6°N, 348.7°E （A95 = 1.4°）的古磁极，表明在114 ~ 113 Ma区间，Bangoin地区的古纬度为25.5°±1.4°N。与亚洲的视极移路径比较表明，早白垩世晚期以来大陆内缩短了560±200 km。结合已发表的古地磁资料和地质证据，这些发现表明，拉萨地体的中东部在约30°N的位置已经与羌塘地体发生碰撞，碰撞随后向西传播。此外，早白垩世晚期，亚洲南缘位于古纬度超过20°N的地区，与同期特提斯外俯冲带的低纬环境（≤10°N）形成鲜明对比。这一显著的古纬度差异支持了在~ 55 Ma的洋内赤道弧-大陆碰撞，并为印度-亚洲碰撞的时间和地球动力学机制提供了新的约束。

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引用次数: 0

Triple oxygen isotope signatures of cherts record pore-fluid composition and temperature across the opal-CT to quartz transition 燧石的三氧同位素特征记录了整个蛋白石-石英过渡过程中的孔隙流体组成和温度

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-04-01 Epub Date: 2026-02-03 DOI: 10.1016/j.epsl.2026.119889

Oskar Schramm , Katharina Ebert , Patrick J. Frings , Andreas Pack , Tommaso Di Rocco , Volker Karius , Nils Keno Lünsdorf , Dieter Korn , Daniel Herwartz , Michael Tatzel

Sedimentary chert is the diagenetic end-product of amorphous silica that first transforms to opal-cristobalite/tridymite (CT) and subsequently to microcrystalline quartz via dissolution and reprecipitation reactions. The ¹⁸O/¹⁶O and ¹⁷O/¹⁶O ratios (i.e. triple oxygen isotope composition, δ¹⁸O, Δ’¹⁷O) of cherts record equilibration with the pore fluids at the diagenetic temperatures prevalent during the opal-CT to quartz transition. Pore fluid oxygen isotope gradients emerge when secondary minerals, e.g. clay minerals form during burial. Here, we demonstrate that chert triple oxygen isotope compositions not in equilibrium with modern like seawater can be explained by changes in pore water δ¹⁸O and Δ’¹⁷O without invoking any alteration or different paleo-seawater. We demonstrate this using a suite of Carboniferous cherts that we collected from the same stratigraphic level at five locations in the Rhenish Massif, Germany, spanning a range of inferred burial rates. The precursor sediments were deposited in the marine Rhenohercynian Basin and were subject to peak diagenetic temperatures of up to 279 ± 37 °C upon folding and thrusting. Their triple oxygen trajectory cannot be explained by any realistic paleo-seawater composition. Using our numerical silica diagenesis model, we find that the chert isotope signatures are explained by a formation temperature between 20–35 °C and a pore fluid composition of -7 to -14‰ δ¹⁸O consistent with a pore fluid gradient of -13.5 ‰ km^-1 across the Rhenohercynian Basin. This suggests that triple oxygen isotope compositions of chert systematically record near-surface conditions and therefore represent a valuable resource for paleoenvironmental research.

沉积燧石是无定形二氧化硅的成岩最终产物，它首先转化为蛋白石-方英石/钇石（CT），随后通过溶解和再沉淀反应转化为微晶石英。燧石的18O/16O和17O/16O比值（即三氧同位素组成Δ 18O， Δ’17O）记录了在蛋白石- ct -石英转变过程中普遍存在的成岩温度下与孔隙流体的平衡。次生矿物如粘土矿物在埋藏过程中形成时，孔隙流体氧同位素梯度就会出现。研究结果表明，与现代海水不平衡的燧石三氧同位素组成可以用孔隙水Δ 18o和Δ’17O的变化来解释，而不需要任何蚀变或不同的古海水。我们用一套石炭纪燧石来证明这一点，这些燧石是我们在德国莱茵山脉的五个地点从相同的地层水平收集的，跨越了一系列推断的埋葬率。前体沉积于海相雷诺西期盆地，在褶皱和逆冲作用下，成岩温度最高可达279±37℃。它们的三氧轨迹不能用任何现实的古海水成分来解释。利用数值硅石成岩模型，我们发现石英同位素特征可以解释为地层温度在20-35℃之间，孔隙流体组成为-7 ~ -14‰δ18O，与整个雷诺西期盆地的孔隙流体梯度为-13.5‰km-1相一致。这表明燧石的三氧同位素组成系统地记录了近地表条件，因此为古环境研究提供了宝贵的资源。

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