Earth and Planetary Science Letters最新文献_第6页

A model for Cenozoic seawater chemistry and carbon cycling 新生代海水化学与碳循环模式

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-31 DOI: 10.1016/j.epsl.2025.119811

Laurence A. Coogan, Stan E. Dosso

We present a model for the evolution of seawater chemistry and carbon cycling over the Cenozoic forced by changes in global mean temperature, continental weatherability, ocean crust accretion and solid Earth CO₂ degassing. The model tracks fluxes from continental silicate and carbonate weathering, seafloor weathering, marine silicate diagenesis, high-temperature hydrothermal circulation and carbonate sediment formation. The carbon system in the ocean is tracked through alkalinity (ALK) and dissolved inorganic carbon (DIC) fluxes allowing the entire carbon system to be calculated. The model has 48 parameters that are treated as unknowns, and we use a Bayesian inversion to determine the probable range of parameter values. Reasonable fits to reconstructions of Cenozoic seawater compositions (e.g., Mg, Ca, δ⁷Li, ⁸⁷Sr/⁸⁶Sr) and pCO₂ records are achieved. Consistent with other studies that consider the carbon system in seawater, the model results have limited change in seawater DIC and ALK over the Cenozoic. Key results include that the: (i) decrease in pCO₂ over the Cenozoic is driven by changing ocean chemistry (increased ratio of ALK to DIC) without a systematic change in the total carbon content of the ocean-atmosphere system, and (ii) CO₂ degassing rate and pCO₂ are decoupled. These results are inconsistent with commonly used geological carbon cycle models (e.g., GEOCARB, COPSE) but are readily understood in terms of seawater carbon chemistry and carbon cycling. Decreasing the Ca content of seawater at the same time as deepening the carbonate compensation depth requires increasing the carbonate ion concentration in the deep ocean; in the models this results from an increased ratio of ALK to DIC.

我们建立了一个受全球平均温度变化、大陆气候、海洋地壳增生和固体地球CO2脱气影响的新生代海水化学和碳循环演化模型。该模型跟踪了大陆硅酸盐和碳酸盐风化、海底风化、海相硅酸盐成岩作用、高温热液循环和碳酸盐沉积形成的通量。通过碱度（ALK）和溶解无机碳（DIC）通量来跟踪海洋中的碳系统，从而计算出整个碳系统。该模型有48个参数被视为未知数，我们使用贝叶斯反演来确定参数值的可能范围。对重建的新生代海水成分（如Mg、Ca、δ7Li、87Sr/86Sr）和pCO2记录进行了较好的拟合。与其他考虑海水碳系统的研究结果一致，该模式的结果显示新生代海水DIC和ALK的变化有限。主要结果包括：(1)新生代pCO2的减少是由海洋化学变化（ALK / DIC比值增加）驱动的，而海洋-大气系统总碳含量没有系统变化；(2)CO2脱气速率与pCO2解耦。这些结果与常用的地质碳循环模型（如GEOCARB、COPSE）不一致，但在海水碳化学和碳循环方面很容易理解。在加深碳酸盐补偿深度的同时降低海水中Ca含量，需要增加深海中的碳酸盐离子浓度；在模型中，这是由于ALK与DIC的比值增加。

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引用次数: 0

Ancient, buoyant mantle under the Sierra Leone Ridge in the equatorial Atlantic 赤道大西洋塞拉利昂海岭下古老的浮力地幔

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-31 DOI: 10.1016/j.epsl.2025.119812

Camilla Sani , Alessio Sanfilippo , Felix Genske , Carlotta Ferrando , Daniele Brunelli , Anna Cipriani , Alexander Peyve , Sergey Skolotnev , Marco Ligi , Andreas Stracke

The Sierra Leone Ridge is the equatorial portion of the Mid-Atlantic Ridge (MAR) between the St. Paul (0–1°N) and Doldrums (7–9°N) Fracture Zones. At ∼80 Ma, a submarine plateau –the Sierra Leone Rise which is now located off-ridge on the African plate and the Céarà Rise on the South American plate– formed due to excess magma production. Incompatible element-enriched MORB with high Sr-Pb but low Nd isotope ratios suggests that the high magma production could result from the interaction of a mantle plume with the Sierra Leone Ridge, the so-called Sierra Leone mantle plume that may now be centered at ∼1.7°N along the MAR. In order to define the nature of the mantle source beneath the Sierra Leone Ridge, we present major-trace element concentrations and radiogenic isotope ratios from abyssal peridotites and MORB from 4 to 7°N along the MAR. High Hf isotope ratios are preserved in clinopyroxenes from abyssal peridotites (Ɛ_Hf = 12–54), indicating that the mantle beneath the Sierra Leone Ridge underwent extensive melting several 10⁸–10⁹ years before remelting under the present MAR. Most peridotites have high Ɛ_Hf, but low Ɛ_Nd similar to MORBs, although some extend to unusually low Ɛ_Nd of ∼-6. We argue that these peridotites not only melted, but were also re-enriched in compatible elements concurrent to melting in the past, and that such incompatible element re-enriched peridotites are now the main component of the sub-ridge mantle in the Sierra Leone area. Extensive remelting of ancient, incompatible element re-enriched peridotite that is compositionally buoyant, in addition to minor amounts of recycled crust, may therefore have caused the abundant magmatism that characterizes this portion of the MAR since formation of the Sierra Leone and Céarà Rise ∼80 Ma ago, and accounts for its elevated topography.

塞拉利昂海脊是中大西洋海脊（MAR）的赤道部分，位于圣保罗断裂带（0-1°N）和低潮断裂带（7-9°N）之间。在~ 80 Ma，海底高原——现在位于非洲板块的塞拉利昂隆起和南美洲板块的csamaracom隆起——由于过量的岩浆产生而形成。具有高Sr-Pb和低Nd同位素比率的不相容元素富集MORB表明，高岩浆产量可能是地幔柱与塞拉利昂山脊相互作用的结果，所谓的塞拉利昂地幔柱现在可能集中在沿mar的~ 1.7°N。我们从4 ~ 7°N的深海橄榄岩和MORB中获得了主要微量元素的浓度和放射性成因同位素比值。深海橄榄岩的斜斜辉石中保存了较高的Hf同位素比值（ƐHf = 12-54），表明塞拉利昂山脊下的地幔在10⁸-10⁹年的时间里经历了广泛的融化，然后在现在的mar下重新融化。大多数橄榄岩的ƐHf高，ƐNd低，与MORB相似，尽管有些橄榄岩的ƐNd低至~ -6。我们认为，这些橄榄岩在过去不仅熔融，而且在熔融的同时还被相容元素重新富集，并且这种不相容元素重新富集的橄榄岩现在是塞拉利昂地区次脊地幔的主要组成部分。古不相容元素再富集橄榄岩的大量重熔，以及少量的再循环地壳，可能导致了自塞拉利昂和csamuaros隆起形成以来的丰富岩浆活动，这些岩浆活动是MAR的这一部分的特征，并解释了其隆起的地形。

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引用次数: 0

Cascade reservoirs seismicity: a unique dynamical system 层叠储层地震活动性：一个独特的动力系统

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-30 DOI: 10.1016/j.epsl.2025.119815

Guangyao Yin , Huai Zhang , Lipeng He , Pei He , Yaolin Shi

China's unique cascade reservoir system employs coordinated scheduling to regulate water storage and discharge, significantly influencing regional dynamics. However, studies investigating the potential seismic hazards induced by the cascading effects of multiple reservoirs remain limited. The Xiangjiaba and Xiluodu cascade reservoirs, located downstream along the Jinsha River in southwestern China, a region characterized by significant tectonic activity, are geographically connected in series. In this work, we first examine the spatiotemporal distribution of seismicity in the vicinity of the reservoirs. Subsequently, we develop a three-dimensional poroelastic finite-element model of the cascade-reservoir region that explicitly incorporates fault geometries and typical geological features. This model is adopted to estimate the pore-pressure evolution in association with elastic Coulomb stress changes under a variety of impoundment scenarios. Our results reveal that these two reservoirs exhibit significant concurrent influences on each other, as well as the subsequent regional seismicity. In particular, the changes in Coulomb stress and pore pressure do not accumulate consistently with respect to time. Their interaction induces a redistribution of the crustal stress field through reservoir-reservoir coupling, suggesting that the cascade-reservoir system operates essentially as an independent and exclusive dynamic system. Notably, seismicity appears to be governed not merely by static pore-pressure magnitudes but by the rate of pore-pressure increase, underscoring the importance of dynamic pore-pressure evolution in seismic triggering processes. These findings enhance the understanding of how cascade reservoirs may perturb crust stress fields and seismic activity, providing a theoretical basis for future reservoir design, operation, and seismic risk assessment in complex and seismically active geological settings.

中国独特的梯级水库系统采用协调调度来调节储水量和排水量，对区域动态具有重要影响。然而，对多储层级联效应引起的潜在地震危害的研究仍然有限。向家坝和溪洛渡梯级水库位于中国西南金沙江下游，是一个构造活动明显的地区，在地理上是串联的。在这项工作中，我们首先研究了水库附近地震活动的时空分布。随后，我们建立了一个明确包含断层几何形状和典型地质特征的级联储区三维孔隙弹性有限元模型。采用该模型估计了不同蓄水情景下孔隙压力随弹性库仑应力变化的演化规律。研究结果表明，这两个储层具有明显的相互影响，并对后续的区域地震活动产生影响。特别是，库仑应力和孔隙压力的变化并不随时间累积一致。它们的相互作用通过储层-储层耦合导致了地壳应力场的重新分布，表明级联-储层系统本质上是一个独立的排他性动力系统。值得注意的是，地震活动性似乎不仅受静态孔隙压力大小的控制，而且受孔隙压力增加速度的控制，这强调了动态孔隙压力演化在地震触发过程中的重要性。这些发现增强了对级联储层如何干扰地壳应力场和地震活动的理解，为未来复杂和地震活跃地质环境下的储层设计、运行和地震风险评估提供了理论基础。

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引用次数: 0

Generation of large transient porosity at the brittle to semi-ductile transition 在脆性向半韧性转变时产生大的瞬态孔隙

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-30 DOI: 10.1016/j.epsl.2025.119805

Erina Prastyani , Benoît Cordonnier , François Renard

Fluid circulation within Earth’s crust is contingent on the presence of connected porosity. Yet, at depths near the brittle to ductile transition regimes, where the base of the seismogenic zone is located, high pressure compacts the rock, reducing porosity and inhibiting fluid circulation. At greater depths, plastic mechanisms during ductile deformation further reduce the likelihood of porosity generation. In this study, we experimentally simulated the brittle to semi-ductile transition in Carrara marble by performing triaxial deformation experiments coupled with time-lapse 3D synchrotron X-ray microtomography at five confining pressures, ranging from 5 MPa to 70 MPa at room temperature and tracked the evolution of porosity over time. Contrary to the prevailing belief, our results show that porosity increases with increasing axial stress at stresses corresponding to the brittle to semi-ductile transition, where fluid circulation is thought to be impeded. In both the semi-brittle and semi-ductile regimes, the total porosity (averaged over the entire sample) exhibits similar values, close to 18%, increasing from an initial porosity of approximately 1% at equivalent axial strain. Although the porosity is comparable, the dominant deformation mechanisms differ: localized shear zones and distributed microcracking characterize the semi-brittle regime, whereas distributed microcracking, without localization, becomes more prominent in the semi-ductile regime. Our findings reveal the formation of high porosity within the semi-brittle and semi-ductile regimes and offer new insight into how this porosity, interpreted as transient within the crust, may enable fluid circulation at the base of the seismogenic zone in Earth’s crust.

地壳内的流体循环取决于连通孔隙的存在。然而，在靠近脆性到韧性过渡区的深度，也就是孕震带底部的位置，高压会压实岩石，降低孔隙度，抑制流体循环。在更深的深度，塑性变形过程中的塑性机制进一步降低了孔隙产生的可能性。在本研究中，我们通过实验模拟了Carrara大理岩在5 MPa至70 MPa的室温围压下的三轴变形实验，并结合延时3D同步加速器x射线微断层扫描技术，模拟了大理岩脆性向半韧性转变的过程，并跟踪了孔隙度随时间的演变。与普遍的看法相反，我们的研究结果表明，在脆性到半韧性转变的应力中，孔隙度随着轴向应力的增加而增加，流体循环被认为受到阻碍。在半脆性和半延性状态下，总孔隙度（整个样品的平均值）显示出相似的值，接近18%，在等效轴向应变下的初始孔隙度约为1%。虽然孔隙度相似，但主要的变形机制不同：局部剪切带和分布微裂纹是半脆性的特征，而分布微裂纹在半延性中更加突出，而非局部化。我们的发现揭示了高孔隙度在半脆性和半韧性体系内的形成，并提供了新的见解，解释了这种孔隙度在地壳内的短暂性，如何使地壳地震带底部的流体循环成为可能。

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引用次数: 0

Climatic controls on erosional efficiency vary with lithology across the Himalaya 气候对侵蚀效率的控制因喜马拉雅地区的岩性而异

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-29 DOI: 10.1016/j.epsl.2025.119808

Kevin Shao , Seulgi Moon , Gen K. Li , Peter J. Haproff , An Yin , Lee B. Corbett , Paul R. Bierman , Marina O. Argueta , Alan J. Hidy

Although climate can strongly influence erosional efficiency (i.e., erosion rate for a given topography), demonstrating its impact in tectonically active areas has been challenging due to other confounding controlling factors, such as lithology. Here, we show that ¹⁰Be-derived erosion rates and efficiencies in the Himalayan orogen exhibit distinct relationships with climatic factors depending on lithology. We compile 173 ¹⁰Be-derived, basin-averaged erosion rates across the orogen, including 12 newly measured rates from the Dibang and Lohit valleys in the easternmost Himalaya, regions characterized by high precipitation magnitudes and variability. We group basins based on lithologies separated by orogen-scale thrust faults and quantify erosional efficiency coefficients based on the relationships between erosion rates and topographic metrics. Our results show that erosion rates and erosional efficiency from sedimentary and metasedimentary rocks along the Himalayan range front display a positive, nonlinear correlation with climatic factors, such as the number of extreme rainfall events and mean annual precipitation rates. In contrast, erosion rates from crystalline lithologies in the hanging wall of the Main Central thrust show a strong correlation with fluvial topography, whereas erosional efficiency shows no statistically significant correlation with climatic factors. Rapid erosion rates and high erosional efficiencies in the eastern Himalayan range front are likely driven by extreme precipitation on tectonically active, steep slopes composed of mechanically weak metasedimentary rocks. Our findings highlight the importance of the interplay between controlling factors, which include tectonics, lithology, and climate, that drive surface erosion and influence the topographic evolution of orogenic systems.

尽管气候可以强烈影响侵蚀效率（即给定地形的侵蚀速率），但由于其他混杂的控制因素（如岩性），证明其在构造活跃地区的影响一直具有挑战性。在这里，我们发现喜马拉雅造山带的10be侵蚀速率和效率与气候因素表现出明显的关系，这取决于岩性。我们编制了173个基于10be的盆地平均侵蚀速率，其中包括喜马拉雅最东端迪邦和洛希特山谷的12个新测量速率，这些地区以高降水强度和高变异性为特征。我们根据造山带规模逆冲断层分隔的岩性对盆地进行分组，并根据侵蚀速率与地形指标之间的关系量化侵蚀效率系数。研究结果表明，喜马拉雅山脉前缘沉积和变质沉积岩的侵蚀速率和侵蚀效率与极端降雨次数和年平均降水量等气候因子呈非线性正相关。相反，中央主冲断层上盘的结晶岩性侵蚀速率与河流地形有很强的相关性，而侵蚀效率与气候因素没有统计学上的显著相关性。东喜马拉雅山脉锋面的快速侵蚀速率和高侵蚀效率可能是由构造活跃的、由机械弱变质沉积岩组成的陡峭斜坡上的极端降水驱动的。我们的研究结果强调了构造、岩性和气候等控制因素之间相互作用的重要性，这些因素驱动地表侵蚀并影响造山系统的地形演化。

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引用次数: 0

Insights into the 3D structure and behaviour of Icelandic crystal mushes from gabbroic nodules 冰岛辉长岩结核晶体糊状物的三维结构和行为

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-28 DOI: 10.1016/j.epsl.2025.119791

Rahul Subbaraman , Margaret E. Hartley , Jonathan Fellowes , Margherita Polacci , Barbara Bonechi , Lucia Pappalardo , Gianmarco Buono , David A. Neave

Crystal mushes—porous yet cohesive frameworks of crystals interspersed with interstitial melts—form the plumbing systems of most active volcanoes. In Iceland, magmatic plumbing systems are inferred to be constructed from vertically stacked mushy magma reservoirs separated by subsolidus rock. Gabbroic nodules from Gígöldur in central Iceland provide a rare window into the structure, evolution, and degassing behaviour of upper crustal (6–10 km) mushy magma reservoirs. These plagioclase-rich nodules preserve recycled high-An plagioclase cores, rim overgrowths, and interstitial crystallisation of mafic phases, reflecting in situ modification within the final storage reservoir and roof cumulate formation via density-driven segregation. Oscillatory zoning and variable rim patterns indicate that crystals experienced non-steady-state growth and were incorporated into clusters at different times. Compositional similarities between carrier and interstitial melts demonstrate that the final stages of mush evolution occurred in relatively homogeneous melts. Volatile saturation pressures of  ∼ 2.0–2.8 kbar, together with high vesicularities (21–30 vol.%) and extensive connectivities ( > 93 %), are consistent with the presence of a CO₂-rich vapour phase within the mush. Nodules are erupted when a rigid crystal framework and a well-connected bubble network that enables effective degassing, preserve their integrity. When bubble networks fail to form, degassing disrupts the framework—even if initially rigid—causing disaggregation into plagioclase-phyric crystal cargoes, akin to plagioclase-ultraphyric basalts erupted in diverse settings. Nodules record the dynamics of stratified mushy magma reservoirs, the influence of volatiles on mush behaviour, and the transport of crystalline material in active volcanic systems, providing key insights into how crystal mushes shape the storage and mobilisation of magma in the Earth’s crust.

晶体浆糊——多孔但有凝聚力的晶体框架，点缀着间隙性的融水——构成了大多数活火山的管道系统。在冰岛，岩浆管道系统被推断为由由亚固体岩石隔开的垂直堆叠的糊状岩浆储层构成。冰岛中部Gígöldur的辉长岩结核为研究地壳上部（6-10 km）糊状岩浆储层的构造、演化和脱气行为提供了一个难得的窗口。这些富含斜长石的结核保存了回收的高安斜长石岩心、边缘生长物和基性相的间隙结晶，反映了最终储层和顶层积聚地层通过密度驱动的偏析发生的原位改变。振荡区带和可变边缘模式表明晶体经历了非稳态生长，并在不同的时间被合并成簇。载体熔体和间隙熔体的成分相似性表明，糊化演化的最后阶段发生在相对均匀的熔体中。挥发饱和压力为 ~ 2.0-2.8 kbar，具有较高的囊泡性（21-30 vol.%）和广泛的连通性（ >； 93%），这与浆料中富含co2的气相的存在相一致。当坚硬的晶体框架和连接良好的气泡网络能够有效脱气，保持其完整性时，结核就会爆发。当气泡网络无法形成时，脱气破坏了框架（即使最初是刚性的），导致分解成斜长石-物理晶体产物，类似于斜长石-超水玄武岩，在不同的环境中爆发。结核记录了层状糊状岩浆储层的动力学，挥发物对糊状行为的影响，以及活跃火山系统中结晶物质的运输，为晶体糊状如何形成地壳中岩浆的储存和动员提供了关键的见解。

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引用次数: 0

From seal to pathway: carbonate veins reveal fluid flow in the clay-rich strike-slip Yangsan Fault, South Korea 从封闭到通道：碳酸盐岩脉体揭示了韩国梁山富泥走滑断层的流体流动

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-27 DOI: 10.1016/j.epsl.2025.119807

Luca Smeraglia , Youngbeom Cheon , Chang-Min Kim , Andrea Billi , Chiara Boschi , Ilaria Baneschi , Stefano M. Bernasconi , Andrea Fiorini , Eugenio Carminati

Clay-rich fault cores are commonly considered low-permeability barriers to across-fault fluid flow. However, increasing field-based evidence revealed syn-tectonic mineralizations within such fault cores, raising questions about their long-term hydraulic behavior, particularly during seismic events. This study investigates calcite veins and slickenfibres from the clay-rich fault core and damage zone of the 200-km-long strike-slip Yangsan Fault in South Korea, the major intraplate active fault in this region, by integrating structural and microstructural analyses with stable and clumped isotope geochemistry. Our data reveal that meteoric fluids downward infiltrated the fault damage zone over long time periods (possibly since late Cretaceous time), heated with depth according to the geothermal gradient, mixed with local formation water, and laterally infiltrated (i.e. across-fault) through a network of foliation planes into the clay-rich fault core, possibly affecting fault strength. We also propose meteoric water mixing with hydrothermal fluids derived by Late Cretaceous and Paleogene granite emplacement. We infer that mineralizations precipitated during different stages of the seismic cycle. Slickenfibres along fault-parallel foliation and shear planes probably precipitated during post-seismic to interseismic creep. Precipitation of foliation parallel extensional veins and stockwork veins probably occurred during the co-seismic phase due to earthquake fracturing. We speculate that transient pressurized fluid release may have occurred during the co-seismic phase. These findings challenge the prevailing view of clay-rich fault cores as static fluid barriers, instead pointing to a dynamic sealing behavior that evolves with the seismic cycles and over long-term geological timescales. Both slow, long-term interseismic fluid infiltration and rapid, short-term co-seismic fluid flow must be accounted for modeling the permeability of clay-rich faults in risk assessments for CO₂ and H₂ storage sites or for resource (hydrocarbons, geothermal fluids) exploration, especially in seismically active areas.

富粘土断层岩心通常被认为是阻碍断层间流体流动的低渗透屏障。然而，越来越多的现场证据显示，在这些断层核心中存在同构造矿化，这就提出了关于它们长期水力行为的问题，特别是在地震事件期间。通过构造和微观构造分析，结合稳定和团块同位素地球化学，研究了该地区主要板内活动断裂——韩国梁山走滑断裂200 km长富粘土断裂核和损伤带的方解石脉和滑脱纤维。我们的数据表明，在很长一段时间内（可能从晚白垩世开始），大气流体向下渗透断层破坏带，根据地温梯度随深度加热，与当地地层水混合，并通过片理面网络横向渗透（即跨断层）进入富含粘土的断层核心，可能影响断层强度。我们还认为大气水与晚白垩世和古近纪花岗岩侵位形成的热液混合。我们推断矿化沉淀发生在地震旋回的不同阶段。顺滑纤维可能在震后至震间蠕变过程中沿断层平行片理面和剪切面沉积。片理平行张脉和网状脉可能在同震阶段由于地震破裂而形成。我们推测瞬态加压流体释放可能发生在同震阶段。这些发现挑战了富粘土断层核是静态流体屏障的主流观点，而是指出了一种随地震周期和长期地质时间尺度演变的动态密封行为。在对CO2和H2储存地点或资源（碳氢化合物、地热流体）勘探进行风险评估时，特别是在地震活跃地区，必须考虑到缓慢的、长期的地震间流体渗透和快速的、短期的同震流体流动，以模拟富粘土断层的渗透率。

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引用次数: 0

Strain rate concentration along the Niigata-Kobe tectonic zone, central Japan as explained by 2D collision numerical models with visco-elasto-plastic rheology 用粘弹塑性流变学的二维碰撞数值模型解释了日本中部新潟-神户构造带的应变率集中

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-26 DOI: 10.1016/j.epsl.2025.119806

Erika J. Moreno , Shoichi Yoshioka , Vlad C. Manea , Marina Manea , Nobuaki Suenaga

Unusual high strain rate concentration and WNW-ESE shortening along the Niigata-Kobe tectonic zone (NKTZ) are reported by GEONET (GNSS Earth observation network). The highest concentration of strain rate has been observed in the Niigata Prefecture, NE Japan, where earthquakes with magnitude M_j > 6 have been recorded. In order to explain the shortening along the NKTZ, different hypotheses are put forward. One of them relates the strain rate concentration near the Earth's surface to weakening of the lower crust caused by the interaction between the continental Amurian plate and the continental North American plate, or the oceanic PHS (Philippine Sea) plate/NA (North American) plate and the oceanic PAC (Pacific) plate/NA plate. Other studies suggest the existence of low-viscosity weak zones beneath the upper continental crust caused by upwelling dehydrated fluids, melts from the PHS and PAC plates, and presence of soft sediments. In this study, we employ two-dimensional high-resolution thermomechanical numerical models with visco-elasto-plastic rheology subject to simple horizontal compression, as well as a combination of horizontal extension and compression. We select three profiles across the SW, central, and NE parts of the NKTZ aligned with the direction of maximum contraction of the principal strain. Numerical models that incorporate hydrated lower crust, magmatic intrusions, and soft sediments are tested against the observations along these three profiles. Our numerical results indicate that significant surface strain concentration develops where low-viscosity weak zones, represented by fluids, magmatism, and soft sediments, are localized at different crustal levels. These weak zones consequently play a key role in fault development and in the Earth’s surface strain concentration along the NKTZ.

GEONET （GNSS地球观测网）报道了沿新潟-神户构造带（NKTZ）异常的高应变速率集中和WNW-ESE缩短。应变率的最高集中在日本东北部的新泻县，那里记录了6级地震。为了解释沿NKTZ的缩短，提出了不同的假设。其中一种理论认为，近地表应变速率的集中与阿姆里亚大陆板块与北美大陆板块或菲律宾海（PHS）板块/北美（NA）板块与太平洋（PAC）板块/北美（NA）板块相互作用引起的下地壳弱化有关。其他研究表明，由于上涌的脱水流体、PHS和PAC板块的熔体以及软沉积物的存在，在上大陆地壳下存在低粘度弱带。在这项研究中，我们采用二维高分辨率的热力学数值模型，包括简单水平压缩下的粘弹塑性流变，以及水平拉伸和压缩的组合。我们选择了与主应变最大收缩方向一致的NKTZ的SW、central和NE部分的三个剖面。结合水合下地壳、岩浆侵入和软沉积物的数值模型根据这三条剖面的观测结果进行了测试。数值结果表明，以流体、岩浆活动和软沉积物为代表的低黏度弱带在不同的地壳水平上具有显著的地表应变集中。因此，这些弱带在断层发育和地球表面应变沿NKTZ集中中起关键作用。

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引用次数: 0

Organic carbon burial and ocean redox modulated biotic recovery after the latest Ordovician crisis 最近一次奥陶纪危机后，有机碳埋藏和海洋氧化还原调节了生物恢复

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-24 DOI: 10.1016/j.epsl.2025.119794

Wei Tang , Mu Liu , Heng-Ye Wei , Li-Guang Wu , Kai Lu , Jian Wang , Xian-Hua Li

Widespread marine anoxia is considered a key impediment to recovery following the late Ordovician mass extinction (LOME), yet the spatiotemporal evolution of early Silurian ocean redox condition remains unresolved. Benthic ecosystem recovery on the South China inner shelf coincided with a global cooling trend during the Rhuddanian–Aeronian transition, but its drivers and links to redox dynamics remain poorly understood. Here we reconstruct redox conditions across a shelf transect in the Yangtze region using iron speciation, redox-sensitive trace elements (RSTEs), C_org/P ratios, and δ¹³C_org data from three sections spanning inner- to outer-shelf environments. Combined with a global compilation of 49 continental shelf sections and a new CA-ID-TIMS zircon U–Pb date of 439.51 ± 0.23 Ma, the data indicate that reducing conditions have persisted for ∼2.91 ± 0.39 million years on the inner shelf after the LOME, followed by progressive reoxygenation beginning in the late Rhuddanian and extending into the Aeronian. A sharp rise in global organic carbon burial rates—up to ∼23 times the Hirnantian baseline, together with coeval rises in ⁸⁷Sr/⁸⁶Sr ratios indicative of intensified continental silicate weathering, would have driven a drawdown of atmospheric CO₂ and global cooling. This climatic shift likely enhanced shelf ventilation and oxygen solubility, facilitating benthic metazoan recovery in shallow settings, while outer-shelf environments remained anoxic until the mid-Aeronian. These findings underscore the tight coupling among carbon cycling, climate regulation, redox evolution, and biotic recovery, highlighting continental shelves as key sites of carbon–climate feedback in the aftermath of mass extinction events.

广泛的海洋缺氧被认为是晚奥陶世大灭绝（LOME）后恢复的关键障碍，但早志留世海洋氧化还原条件的时空演变尚未解决。华南内陆陆架底栖生物生态系统的恢复与鲁达尼—aeronian过渡期间的全球降温趋势一致，但其驱动因素及其与氧化还原动力学的联系尚不清楚。本文利用铁形态、氧化还原敏感微量元素（RSTEs）、Corg/P比值和δ13Corg数据重建了长江地区陆架样带的氧化还原条件。结合49个大陆架剖面的全球汇编和新的CA-ID-TIMS锆石U-Pb测年（439.51±0.23 Ma），数据表明，LOME后，内大陆架的还原条件持续了~ 2.91±0.39万年，随后从晚鲁达尼世开始逐步再氧化，并延伸到Aeronian。全球有机碳埋藏率的急剧上升（达到希尔南提基线的23倍），以及87Sr/86Sr比值的同期上升（表明大陆硅酸盐风化加剧），将推动大气二氧化碳的减少和全球变冷。这种气候变化可能增强了大陆架的通风和氧的溶解度，促进了浅层环境中底栖后生动物的恢复，而大陆架外部环境直到aeronian中期仍处于缺氧状态。这些发现强调了碳循环、气候调节、氧化还原进化和生物恢复之间的紧密耦合，强调了大陆架是大规模灭绝事件后碳-气候反馈的关键场所。

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引用次数: 0

Eoarchean TTG formation via melt-solid interaction at the base of the Tanzania Craton inferred from multi-proxy detrital zircon data 根据多代碎屑锆石资料推断坦桑尼亚克拉通底部始太古代融固相互作用形成的TTG

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2025-12-22 DOI: 10.1016/j.epsl.2025.119701

Robert Bolhar , Axel Hofmann , Balz S. Kamber , Martin J. Whitehouse , Roland Maas , Jeffrey D. Vervoort , Heejin Jeon , Manuela Botero , Joas Kabete

Detrital zircon grains with U-Pb ages >3.8 Ga from the Tanzania Craton represent a rare, and so far understudied, record of early crust formation in Africa. Here we report microbeam-based isotopic (U-Th-Pb, Lu-Hf, O) and trace element (REE, U, Th, Ti) compositions for Eoarchean to Hadean grains from Tanzania and discuss this record in the context of early crust formation. Zircon, extracted from a pre-3.2 Ga quartzite sequence in the Simba-Nguru Hills of the Dodoma Basement Complex, has ²⁰⁷Pb/²⁰⁶Pb ages of 4013 to 3482 Ma. The most concordant analyses are spread between 4.0 and 3.6 Ga. Oscillatory-zoned zircons preserve magmatic REE patterns, and Ti-in-zircon model temperatures of 818 ± 33 °C suggest crystallisation from TTG-like magmas. Estimates of oxygen fugacity (fO₂) derived from zircon REE systematics (-3.4 to +1.8 ΔFMQ) match both modern and Archean mantle values. Zircon δ¹⁸O largely overlaps the ‘mantle’ range through the entire 400 Ma age span and initial ε_Hf values are near-chondritic, becoming slightly more juvenile with time. These signatures are difficult to reconcile with zircon parent rocks derived from strongly depleted (high-ε_Hf) mantle-like sources, from old and evolved continental crust, or from strongly hydrated sources with a low-temperature, high-δ¹⁸O signature. Thus, the data add to a growing body of evidence that the early Earth crust was formed from chondritic mantle. We propose zircon to have crystallised in TTG magmas that formed through reaction of underplated basalt with mafic granulite at the Moho of the proto-continental crust, likely in an intraplate setting.

来自坦桑尼亚克拉通的U-Pb年龄为>；3.8 Ga的碎屑锆石颗粒代表了非洲早期地壳形成的一种罕见的、迄今尚未得到充分研究的记录。本文报道了坦桑尼亚太古宙至古宙颗粒的微束同位素（U-Th- pb, Lu-Hf， O）和微量元素（REE， U, Th, Ti）组成，并在早期地壳形成的背景下讨论了这一记录。锆石提取自Dodoma基底杂岩Simba-Nguru山前3.2 Ga石英岩层序，其207Pb/206Pb年龄为4013 ~ 3482 Ma。最一致的分析分布在4.0和3.6 Ga之间。振荡带锆石保留了岩浆的REE模式，锆石中的ti -in模式温度为818±33℃，表明结晶来自ttg类岩浆。锆石REE系统估算的氧逸度（fO2）（-3.4 ~ +1.8 ΔFMQ）与现代和太古宙地幔值吻合。锆石δ18O在整个400 Ma年龄跨度内大部分重叠于“地幔”范围，初始εHf值接近球粒质，随着时间的推移略显年轻。这些特征很难与来自强烈衰竭（高ε hf）的幔状源、来自古老演化的大陆地壳或来自低温、高δ 18o特征的强水合源的锆石母岩相协调。因此，这些数据进一步证明了早期地壳是由球粒质地幔形成的。我们认为锆石在TTG岩浆中结晶，TTG岩浆是由下镀玄武岩与原大陆地壳莫霍处的基性麻粒岩反应形成的，可能是在板内环境中形成的。

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引用次数: 0