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

Coupled tectonic and surface processes in the Guerrero forearc, Mexico: Insights from the basin-averaged erosion rates 墨西哥Guerrero前弧的耦合构造和地表过程：来自盆地平均侵蚀速率的见解

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-02-06 DOI: 10.1016/j.epsl.2026.119896

Krzysztof Gaidzik , María-Teresa Ramírez-Herrera

The complex interactions among erosion, tectonic uplift, and climate are fundamental to understanding the mechanisms that drive landscape evolution and govern the recycling of crustal materials. In this study, we used basin-averaged erosion rates based on ¹⁰Be concentrations in river sediments from eight medium- to large-sized drainage basins across the Guerrero forearc to investigate the interplay between lithology, climatic conditions, and tectonic factors in shaping the topography above the flat-slab subduction zone. The calculated erosion rates range from <0.5 to >0.8 mm/yr and show an apparent eastward increase. This spatial pattern appears to be primarily controlled by the tectonic processes associated with the subduction of the Cocos Plate beneath the North American Plate, particularly the seismogenic activity of crustal faults, with climate variability exerting a secondary influence and limited lithology impact. The eastward increase in erosion rates across the Guerrero forearc appears to correspond to the activity of trench-parallel, W-striking crustal faults, most notably the La Venta Fault, and aligns with observed patterns of exhumation rates, increasing convergence rate, and roughness of the subducting Cocos Plate. The relatively low erosion rates may be attributed to the flat-slab subduction observed in the Guerrero sector of the Mexican subduction zone, consistent with global observations that associate forearc regions above flat slabs with reduced erosion rates. A secondary climatic influence on erosion patterns is indicated by correlations with mean annual discharge and the potential impact of extreme precipitation events at the individual basin scale.

侵蚀、构造隆起和气候之间复杂的相互作用是理解驱动景观演化和控制地壳物质循环的机制的基础。在这项研究中，我们使用了基于格雷罗前弧8个大中型流域河流沉积物中10Be浓度的盆地平均侵蚀速率，来研究岩性、气候条件和构造因素在塑造平板俯冲带上方地形方面的相互作用。计算得到的侵蚀速率在0.5 ~ 0.8 mm/年之间，呈明显的向东增加趋势。这种空间格局似乎主要受与科科斯板块俯冲到北美板块之下有关的构造过程控制，特别是地壳断层的发震活动，气候变化起次要影响，岩性影响有限。东侵格雷罗前弧的侵蚀速率增加似乎与沟平行的w向地壳断层（最显著的是La Venta断层）的活动相对应，并与观测到的挖掘速率、不断增加的收敛速率和俯冲的Cocos板块的粗糙度模式一致。相对较低的侵蚀速率可能归因于在墨西哥俯冲带的Guerrero板块观测到的平板俯冲作用，这与全球观测结果一致，即平板上方的弧前区域侵蚀速率较低。在单个流域尺度上，气候对侵蚀模式的次生影响与年平均流量和极端降水事件的潜在影响相关。

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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 : 2026-02-05 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

Spatial variability and mechanics in aeolian ripples: A case study in Chilean Patagonia 风成波纹的空间变异性和力学：以智利巴塔哥尼亚为例

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-02-04 DOI: 10.1016/j.epsl.2026.119892

Tyler R. Gough , Chris H. Hugenholtz , Paul R. Nesbit , Thomas E. Barchyn

The transport capacity, sediment supply, and sediment availability in an aeolian landscape exert control on its bedforms. In this work, we use a 200 m long megaripple field forming on the 400 m high El Chingue escarpment in Chilean Patagonia as a case study in evaluating how spatial differences in these factors affect bedforms. Strong westerly winds encounter the steep escarpment of El Chingue, which creates a speed-up effect and increased transport capacity at the ridgeline followed by a trend of decreasing wind speed and transport capacity across the megaripple field. We describe and analyze the morphological, granulometric, and structural responses of the megaripples to this spatial trend. Results indicate that upwind megaripples are smaller, have poor sorting, thin armor layers, and no cross-bedding. In the middle of the field, the megaripples are larger, have thicker armor layers, a distinct bimodal distribution, and well-developed cross-bedding. At the downwind margin, megaripples are increasingly vegetated, generally flatter, and lose the distinct cross-bedding and bimodality. This transition of morphology, granulometry, and structure through the megaripple field reflects the spatial trend in transport capacity and aligns with current understanding of megaripple morphodynamic regimes. However, it highlights that different regimes may occur simultaneously within the same field. Broadly, these results emphasize the dynamic nature of megaripples and encourages the further application of a spatial analysis and sediment state understanding for ripple-scale bedforms to improve understanding of similar features across environments.

风成景观的输沙能力、泥沙供给和泥沙可利用性对其床型起着控制作用。在这项工作中，我们以智利巴塔哥尼亚400米高的El Chingue悬崖上200米长的巨型雷波场形成为例，评估这些因素的空间差异如何影响地层。强烈的西风遇到El chinue陡峭的陡坡，在山脊线上产生加速效应和运输能力增加，随后在整个巨ariple区风速和运输能力呈下降趋势。我们描述和分析了形态、粒度和结构对这一空间趋势的反应。结果表明，逆风巨型水波较小，分选差，护甲层薄，无交叉层理。在野地中部，巨核果较大，甲壳层较厚，双峰分布明显，交错层理发育良好。在下风边缘，巨果被越来越多的植被覆盖，通常是平坦的，失去了明显的交叉层理和双峰。这种形态、粒度和结构的转变通过巨果场反映了运输能力的空间趋势，并与目前对巨果形态动力学机制的理解一致。然而，它强调在同一领域内可能同时出现不同的制度。总的来说，这些结果强调了巨涟波的动态性质，并鼓励进一步应用空间分析和沉积物状态理解涟波尺度的河床，以提高对不同环境相似特征的理解。

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引用次数: 0

Interannual to multidecadal climate oscillations occurred during Cryogenian glaciation 在冰川期发生了年际到多年代际气候振荡

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-02-04 DOI: 10.1016/j.epsl.2026.119891

Chloe Griffin , Thomas M. Gernon , Minmin Fu , Elias J. Rugen , Anthony M. Spencer , Geoffrey Warrington , Thea K. Hincks

During the two Cryogenian snowball Earth glaciations, the Sturtian (ca. 717–658 Ma) and Marinoan (ca. 639–635 Ma), ice persisted in the tropics for millions of years. Previous analyses of varves deposited before and after these glaciations have revealed climate variability linked to solar, oceanic, and atmospheric dynamics. However, to our knowledge, no evidence of sub-Milankovitch scale climatic variability has been documented during the glaciations themselves. The proposition of reduced solar luminosity in the Cryogenian, an attenuated hydrological cycle, and an expected hiatus in atmosphere-ocean interactions due to ocean freezing, raises questions regarding whether solar-ocean-atmospheric interactions continued during these glaciations. We analyze a unit of 2,640 laminites within the Sturtian Port Askaig Formation on the Garvellach Islands, Scotland, to better understand climate variability during a discrete interval of the Sturtian. Our study indicates the laminites most likely represent annual varves, reflecting seasonal freeze-thaw cycles in a deep, quiescent waterbody. Spectral analysis of laminae thickness reveals decadal and centennial periodicities consistent with present-day Schwabe and Gleissberg solar cycles, alongside interannual periodicities, likely tied to ocean-atmospheric climate modes, resembling the modern El-Niño Southern Oscillation. Our coupled Cryogenian climate simulations under varying degrees of ice coverage produce similar interannual periodicities in surface temperatures near the paleo-coordinates of the Garvellach Islands and in the tropics. This evidence reveals that solar-ocean-atmospheric interactions generated a wider range of climatic variability than expected during snowball Earth and hints at the possibility of transient unfrozen tropical waters during the Sturtian, or other yet unexplored modes of internal climate variability.

在两次冰冻期雪球地球冰期，斯图亚特期（约717-658 Ma）和马里诺期（约639-635 Ma），冰在热带地区持续存在了数百万年。先前对这些冰期前后沉积的碎屑的分析表明，气候变化与太阳、海洋和大气动力学有关。然而，据我们所知，在冰期期间没有记录亚米兰科维奇尺度气候变化的证据。低温期太阳亮度降低、水文循环减弱以及由于海洋冻结而导致大气-海洋相互作用预期中断的主张，提出了在这些冰期期间太阳-海洋-大气相互作用是否继续的问题。我们分析了苏格兰Garvellach群岛上的Sturtian Port Askaig组内的2640个层叠岩单元，以更好地了解Sturtian离散间隔期间的气候变化。我们的研究表明，纹层岩最有可能代表年度变化，反映了一个深的、静止的水体中的季节性冻融循环。层叠厚度的光谱分析显示，年代际和百年周期与当今的Schwabe和Gleissberg太阳周期一致，年际周期可能与海洋-大气气候模式有关，类似于现代El-Niño南方涛动。我们在不同冰覆盖程度下的低温期气候耦合模拟，在Garvellach群岛古坐标附近和热带地区产生了类似的年际周期性地表温度。这一证据表明，太阳-海洋-大气相互作用在雪球地球期间产生的气候变化范围比预期的要大，并暗示在斯图蒂亚时期可能存在短暂的未冻结的热带水域，或者其他尚未探索的内部气候变化模式。

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引用次数: 0

Multi-pulse and crystal-laden emplacement of the Tunnel Dike: implications for flood basalt volcanism 隧道堤防的多脉冲和含晶就位：对洪水玄武岩火山作用的启示

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-02-03 DOI: 10.1016/j.epsl.2026.119895

Ryan M. Currier , Paulo J. Hidalgo , Tushar Mittal , Jada Nimblett , Lucian Bitner , Taiylor Williams , Bil Schneider

Flood basalt provinces, like the Columbia River Basalts (CRB), signify vast volcanic activity capable of inducing paleoclimatic shifts and extinction events via extensive volatile emissions. Two competing models exist for their rates of emplacement: one argues for slow, prolonged eruption based on lava flow morphology, while the other argues for rapid emplacement based on thermally constrained modeling of dikes, assuming crystal-poor, low-viscosity magmas fed through wide conduits. We test these assumptions by investigating the Tunnel Dike, a Chief Joseph Dike Swarm dike thought to be the feeder for several significant CRB flows. Thermal modeling indicates the dike was emplaced as relatively cool, crystal-laden magma, assembling incrementally to its final thickness. Crystal size distributions across the dike exhibit aphanitic margins which transition sharply into a porphyritic interior, where plagioclase commonly displays high-temperature deformation, with spatial distributions suggesting granular flow. These lines of evidence point to a multi-pulse, crystal-rich mush emplacement of the Tunnel Dike. Under these conditions, magmatic flux would have been orders of magnitude slower than previous estimates, aligning with flux rates based upon lava flow morphology of flood basalts and with peak effusion rates of the 1783 Laki fissure eruption. Although based on a single dike, the textures observed in the Tunnel Dike appear to be widespread across the CJDS, suggesting that crystal-rich, incremental dike emplacement may be more broadly characteristic of Columbia River Basalt magmatism. These findings carry implications for estimates of volatile emissions, and, consequently, paleoclimate modeling.

洪水玄武岩省，如哥伦比亚河玄武岩（CRB），表明巨大的火山活动能够通过大量挥发性排放物引起古气候变化和灭绝事件。关于喷发速度存在两种相互竞争的模型：一种是基于熔岩流形态的缓慢而持久的喷发，而另一种是基于热约束的岩脉模型的快速喷发，假设结晶性差、低粘度的岩浆通过宽管道注入。我们通过调查隧道堤防来检验这些假设，这条约瑟夫酋长堤防群堤防被认为是几个重要的CRB流的馈线。热模拟表明，岩脉的就位是相对较冷的、富含晶体的岩浆，逐渐聚集到最终的厚度。沿岩脉的晶体尺寸分布呈隐晶边缘，边缘向斑岩内部急剧过渡，其中斜长石通常表现为高温变形，空间分布呈粒状流动。这些证据表明隧道堤防有多脉冲，富含晶体的糊状掩体。在这些条件下，岩浆通量将比先前的估计慢几个数量级，与基于洪水玄武岩熔岩流形态的通量率和1783年拉基裂缝喷发的峰值流出率一致。虽然基于单一岩脉，但在隧道岩脉中观察到的结构似乎在CJDS中广泛存在，这表明富含晶体的渐进式岩脉侵位可能是哥伦比亚河玄武岩岩浆活动的更广泛特征。这些发现对挥发性排放物的估计以及古气候模型都有影响。

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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 : 2026-02-03 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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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 : 2026-02-02 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

Low δ30Si values in olivine-hosted melt inclusions trace sediment contributions to subduction zone melts 含橄榄石的熔体包裹体δ30Si值低，微量沉积物对俯冲带熔体有贡献

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-02-01 DOI: 10.1016/j.epsl.2026.119884

Anne-Sophie Bouvier , Martin Guitreau , Clémence Le Lay , Muriel Laubier , Estelle F. Rose-Koga

This study reports the first high-precision silicon isotope (δ³⁰Si) measurements of olivine-hosted melt inclusions (OHMIs) and their host olivine crystals using laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS). We analyzed samples from two contrasting tectonic settings: three mid-ocean ridge basalts (MORB) and four island arc volcanic rocks. Our results reveal systematic differences in silicon isotope compositions between these two environments. MORB samples show internally consistent δ³⁰Si values in both melt inclusions and host olivine crystals, with isotopic fractionation between phases suggesting equilibrium crystallization processes in MORB magmas. In contrast, arc samples display greater heterogeneity and systematically lower δ³⁰Si values that deviate from equilibrium fractionation factors between olivine and melt. The absence of a correlation with the degree of polymerization of the silicate melt (NBO/T) indicates that these isotopic signatures are not controlled by melt structure. The coupling of low δ³⁰Si and high δ¹⁸O values suggests significant contributions from subducted sedimentary materials, particularly siliceous components, to the arc magma source. Our results demonstrate that OHMIs preserve small-scale Si isotope heterogeneities which are invisible at the bulk rock scale. This work highlights the potential of in situ silicon isotope analysis of melt inclusions and their host crystals to trace magmatic processes and source contributions in different tectonic environments, hence providing new insights into the geochemical evolution of arc magmas and the role of subducted materials in mantle heterogeneity.

本研究首次利用激光烧蚀多集电极电感耦合等离子体质谱（LA-MC-ICP-MS）对橄榄石包裹体（OHMIs）及其宿主橄榄石晶体进行了高精度硅同位素（δ30Si）测量。我们分析了两种不同构造背景的样品：三种洋中脊玄武岩（MORB）和四种岛弧火山岩。我们的研究结果揭示了这两种环境中硅同位素组成的系统性差异。MORB样品中熔体包裹体和寄主橄榄石晶体的δ30Si值内部一致，相间同位素分馏表明MORB岩浆中存在平衡结晶过程。相比之下，电弧样品表现出更大的非均质性，δ30Si值偏离橄榄石和熔体之间的平衡分馏因子。与硅酸盐熔体聚合度（NBO/T）没有相关性表明这些同位素特征不受熔体结构的控制。低δ30Si值和高δ18O值的耦合表明，俯冲沉积物质，特别是硅质成分对弧岩浆源有重要贡献。我们的研究结果表明，OHMIs保留了在大块岩石尺度上不可见的小尺度Si同位素非均质性。本工作强调了熔融包裹体及其寄主晶体原位硅同位素分析在不同构造环境下追踪岩浆过程和来源贡献的潜力，从而为弧岩浆的地球化学演化和俯冲物质在地幔非均质性中的作用提供了新的见解。

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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 : 2026-01-31 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

Low temperature brine formation by serpentinization on asteroid (162,173) Ryugu 小行星（162173）Ryugu的蛇纹岩作用形成低温卤水

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2026-01-30 DOI: 10.1016/j.epsl.2026.119885

Guy Libourel , Marc Portail , Vincent Guigoz , Virginie Brändli , Cyrille Collin , Nathalie Vigier , Tomoki Nakamura , Hikaru Yabuta , Shogo Tachibana , Cecile Engrand

Secondary mineral prevalence in Ryugu samples, similar to primitive carbonaceous-Ivuna type (CI) chondrites, suggests that aqueous alteration was a key factor in its formation. However, this general consensus masks our limited understanding of the specific mechanisms and environmental conditions involved in water-rock interactions on primitive asteroids. High-resolution cathodoluminescence (CL) analysis of the ubiquitous dolomite crystals in Ryugu samples reveals concentric epitaxial overgrowths with varying levels of Mn²⁺-activated luminescence. CL panchromatic images and spectral deconvolution provide compelling evidence for the evolution of aqueous fluids toward highly saturated brines. Given the close association of dolomite with widespread intergrowths of serpentine and saponite in the matrix, we propose that brine formation occurs as a byproduct of serpentinization. Unlike large-scale evaporation or freezing, this process can locally cause the hydrothermal fluid to dry out, significantly increasing its salinity over time. This leads to the sporadic precipitation of an evaporite mineral sequence, with dolomite forming at an early stage. This serpentinization-driven brine formation model offers a convincing alternative to a purely prograde alteration history for Ryugu. It may also provide a better explanation for the alteration processes of Bennu and other CI chondrite parent bodies.

与原始碳-伊武那型（CI）球粒陨石相似，Ryugu样品中的次生矿物普遍存在，表明水蚀变是其形成的关键因素。然而，这种普遍共识掩盖了我们对原始小行星上水岩相互作用的具体机制和环境条件的有限理解。高分辨率阴极发光（CL）分析了龙谷样品中普遍存在的白云石晶体，发现了不同水平的Mn2+活化发光的同心外延过度生长。CL全色图像和光谱反褶积为含水流体向高饱和盐水的演化提供了令人信服的证据。鉴于白云岩与基质中广泛的蛇纹石和皂石共生关系密切，我们认为卤水形成是蛇纹石化的副产物。与大规模蒸发或冻结不同，这一过程会局部导致热液变干，随着时间的推移，其盐度会显著增加。这导致蒸发岩矿物序列的零星沉淀，白云岩形成于早期阶段。这种蛇纹岩驱动的盐水地层模型为Ryugu提供了一种令人信服的替代方案，而不是纯粹的递进蚀变历史。这也可能为贝努和其他CI球粒陨石母体的蚀变过程提供更好的解释。

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引用次数: 0