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

First cycle or polycyclic? Combining apatite and zircon detrital U-Pb geochronology and geochemistry to assess sediment recycling and effects of weathering 第一周期还是多周期？结合磷灰石和锆石碎片U-Pb地质年代和地球化学评估沉积物循环和风化作用的影响

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-23 DOI: 10.1016/j.epsl.2024.119131

Emily S. Finzel , Stuart N. Thomson , David M. Pearson , L．Kenneth Horkley , Kacey Garber , Cole Gardner

Even with the advent of multiple new geochronologic provenance techniques in recent decades, almost all provenance studies are still hampered by a fundamental limitation: recycling of older strata is often a significant concern but cannot be adequately addressed using current techniques. Detrital zircon is the dominant mineral used in provenance studies, but zircons are robust and almost always represent both first-cycle and polycyclic sediment contributions in a sandstone. To overcome these issues, we implement two relatively novel applications of detrital geochronology – U-Pb geochronology and trace and rare earth element geochemistry of detrital apatite – to take a multi-method approach of analyzing both mineral phases from the same sandstone. Our results indicate that zircon and apatite detrital age distributions from the same sandstone that are nearly identical, paired with apatite TREE geochemistry denoting an igneous source, are a key diagnostic indicator of sediment derived from shallowly-emplaced (<∼500 °C) or extrusive igneous rocks. Detrital age distributions that are similar but offset from one another such that the apatite peaks are younger than the zircon peaks and also young up-section, paired with apatite TREE geochemistry denoting an igneous source, implies exhumation of a deep igneous source through the apatite U-Pb closure temperature. The combination of detrital zircon and apatite U-Pb geochronology and TREE geochemistry also permits detection of recycled versus first-cycle components from metamorphic basement terranes. This study signifies a significant advance in provenance research by demonstrating the facility of combining detrital apatite and zircon U-Pb geochronology and geochemistry to decipher first-cycle versus polycyclic sediment from various types of igneous and metamorphic rocks. Our results show this methodology has potential applications and implications for all types of sedimentary systems, paleogeographic reconstructions, provenance interpretations, and tectonic reconstructions.

即使近几十年来出现了多种新的地质年代出处技术，几乎所有的出处研究仍然受到一个基本限制的阻碍：老地层的再循环往往是一个重要问题，但使用现有技术却无法充分解决。碎屑锆石是来源研究中使用的主要矿物，但锆石是坚固的，几乎总是代表砂岩中第一周期和多周期沉积物的贡献。为了克服这些问题，我们采用了两种相对新颖的非铁质地质年代学应用--U-Pb地质年代学以及非铁质磷灰石的痕量和稀土元素地球化学--采用多种方法分析同一砂岩中的两种矿物相。我们的研究结果表明，来自同一砂岩的锆石和磷灰石的碎屑年龄分布几乎完全相同，同时磷灰石的TREE地球化学特征表明其来源于火成岩，这是沉积物来源于浅成岩（500 °C以下）或外成火成岩的一个关键诊断指标。残积物年龄分布相似但相互偏移，磷灰石峰值比锆石峰值年轻，而且上段也年轻，再加上磷灰石 TREE 地球化学特征表明火成岩来源，通过磷灰石 U-Pb 闭合温度暗示了深部火成岩来源的出露。将锆英石和磷灰石 U-Pb 地质年代学与 TREE 地球化学相结合，还可以检测出来自变质基底陆相的再循环成分和第一周期成分。这项研究表明，将非铁质磷灰石和锆石 U-Pb 地球地质年代学与地球化学结合起来，可以解读来自各类火成岩和变质岩的第一周期沉积物与多周期沉积物，从而在原产地研究方面取得了重大进展。我们的研究结果表明，这种方法对所有类型的沉积系统、古地理重建、出处解释和构造重建都有潜在的应用和影响。

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引用次数: 0

Ocean crustal veins record dynamic interplay between plate-cooling-induced cracking and ocean chemistry 大洋地壳脉络记录了板块冷却引起的开裂与海洋化学之间的动态相互作用

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-22 DOI: 10.1016/j.epsl.2024.119116

Aled D. Evans , Rosalind M. Coggon , Michelle Harris , Elliot J. Carter , Elmar Albers , Gilles M. Guérin , Thomas M. Belgrano , Mallika Jonnalagadda , Lewis J.C. Grant , Pamela D. Kempton , David J. Sanderson , James A. Milton , Timothy J. Henstock , Jeff C. Alt , Damon A.H. Teagle

As ocean crust traverses away from spreading ridges, low-temperature hydrothermal minerals fill cracks to form veins, transforming the physical and chemical properties of ocean crust whilst also modifying the composition of seawater. Vein width and frequency observations compiled from the International Ocean Discovery Program (IODP) South Atlantic Transect (∼31°S) and previous scientific ocean drilling holes show that vein width distributions progressively broaden and observed strain

(Σ m_{veins} / m_{core})

increases with crustal age, whereas vein densities

(#_{veins} / m_{core})

remain approximately constant. Elemental mapping and textural observations illuminate multiple precipitation and fracturing episodes that continue as the ocean crust ages. This challenges the existing notion that ocean crustal veins are passively filled; rather, they are dynamic features of ocean crust aging. These data, combined with thermal strain modelling, indicate a positive feedback mechanism where cooling of the ocean plate induces cracking and the reactivation of pre-existing veins, ultimately resulting in further cooling. Waning of this feedback provides a mechanism for the termination of the global average heat flow anomaly. Sites with total vein dilation greater than expected for their age correspond with crustal formation during periods of high atmospheric CO₂. The amount of vein material thus reflects the changing balance between ocean plate cooling, ocean chemistry, and the age of the ocean crust. Our results demonstrate that ocean crust endures as an active geochemical reservoir for tens of millions of years after formation.

当大洋地壳远离扩张脊时，低温热液矿物填充裂缝形成矿脉，改变了大洋地壳的物理和化学性质，同时也改变了海水的成分。从国际大洋发现计划（IODP）南大西洋横断面（南纬 31°）和以前的科学大洋钻探孔中收集的矿脉宽度和频率观测结果表明，矿脉宽度分布逐渐扩大，观测到的应变（Σmveins/mcore）随着地壳年龄的增加而增加，而矿脉密度（#veins/mcore）则大致保持不变。元素绘图和纹理观测表明，随着大洋地壳年龄的增长，会发生多次沉淀和断裂。这对现有的洋壳矿脉是被动填充的观点提出了挑战；相反，它们是洋壳老化的动态特征。这些数据与热应变建模相结合，表明了一种正反馈机制，即大洋板块的冷却会诱发开裂，并重新激活先前存在的矿脉，最终导致进一步冷却。这种反馈的减弱为全球平均热流异常的终止提供了一种机制。总矿脉扩张程度大于其年龄预期的地点，与大气中二氧化碳含量较高时期的地壳形成相吻合。因此，矿脉物质的数量反映了大洋板块冷却、海洋化学和大洋地壳年龄之间不断变化的平衡。我们的研究结果表明，大洋地壳在形成后的数千万年里一直是一个活跃的地球化学库。

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引用次数: 0

Context matters: Modeling thermochronologic data in geologic frameworks using the Great Unconformity as a case study 背景很重要：以大不整合带为例，在地质框架中建立热时序数据模型

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-21 DOI: 10.1016/j.epsl.2024.119061

R.M. Flowers, B.A. Peak

The critical importance of sample context and geologic information for interpreting geochronologic data has long been fundamental to the Earth sciences. However, the lack of quantitative uncertainties associated with contextual, observational information means that much geologic data cannot be statistically treated in computational models using the same approaches as quantitative datasets. This challenge is showcased by the current debate over whether and how geologic data should be used when modeling thermochronologic results, which has important implications for deriving time-temperature (tT) paths from which burial and exhumation histories are interpreted. Holistically leveraging observational data to test hypotheses and determine the set of geologically reasonable thermal histories that can explain thermochronologic results has a longstanding history, but some recent studies have criticized this approach as one that arbitrarily limits tT solutions. Here, a geologic context approach to thermal history modeling, in which observational and thermochronologic datasets are combined to design geologically valid models and reach the most geologically likely interpretation, is illustrated using an example of constraining Great Unconformity exhumation in Colorado where this modeling philosophy has been questioned. Although the quality of geologic data and their applicability to modeled samples can vary and be debated, this does not mean that all geologic data are inherently unreliable and therefore discardable. Exploring models with varying or minimal constraints can be useful to test different hypotheses and determine the resolving power of the data, but using an endmember context-blind approach to interpret thermochronologic results can produce outcomes that violate fundamental aspects of the geology. The strategy outlined here is not the only valid approach to modeling thermochronologic data, but if the purpose of the modeling is to derive meaningful interpretations about sample tT paths in order to better illuminate the geologic history, then critical thinking about the sample context, first order geologic observations, and primary relationships should be integral components of the modeling process.

长期以来，样本背景和地质信息对于解释地质年代数据至关重要，是地球科学的基础。然而，由于缺乏与背景和观测信息相关的定量不确定性，这意味着许多地质数据无法在计算模型中使用与定量数据集相同的方法进行统计处理。目前关于在建立热时学结果模型时是否以及如何使用地质数据的争论就体现了这一挑战，这对得出时间-温度（tT）路径并据此解释埋藏和掘起历史具有重要影响。全面利用观测数据来检验假说并确定一套能够解释热时学结果的地质合理热历史由来已久，但最近的一些研究批评这种方法任意限制了时间-温度（tT）解决方案。在这里，以科罗拉多州大不整合隆起为例，说明了热历史建模的地质背景方法，即结合观测数据集和热时学数据集来设计地质上有效的模型，并得出地质上最可能的解释。尽管地质数据的质量及其对模型样本的适用性可能各不相同并存在争议，但这并不意味着所有的地质数据本质上都是不可靠的，因此都是可以放弃的。探索具有不同或最小约束条件的模型，对于测试不同的假设和确定数据的解析能力是有用的，但使用终结者背景盲法解释热时序学结果，可能会产生违反地质学基本方面的结果。本文概述的策略并不是唯一有效的热时学数据建模方法，但如果建模的目的是对样本 tT 路径进行有意义的解释，以更好地阐明地质历史，那么对样本背景、一阶地质观察和主要关系的批判性思考就应该是建模过程中不可或缺的组成部分。

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引用次数: 0

Seismic radial anisotropy in southeastern Tibetan Plateau and its implications for regional geodynamic evolution 青藏高原东南部地震径向各向异性及其对区域地球动力演化的影响

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-21 DOI: 10.1016/j.epsl.2024.119122

Shaoqian Hu , Huajian Yao , Jikun Feng , Hui Huang , Qiyuan Liu , Robert D. van der Hilst

The southeastern Tibetan Plateau exhibits intricate crustal tectonics, encompassing recent seismic megathrust events. Previous research suggested the presence of north-south-oriented channelized viscous flow within the crust. However, recent investigations have unveiled a notable northeast-southwest-oriented geological structure, potentially rigid, intersecting with the presumed crustal channelized flow. Several questions persist regarding the composition of the northeast-southwest-oriented structure, the continuity of crustal channelized flow, and the interplay between them. In this study, dispersion data from a dense seismic array are employed to significantly refine regional crustal models for shear wave velocity and radial anisotropy through ambient noise tomography. The resulting high-resolution model further reveals the style of the crustal deformation and supports the interpretation that the northeast-southwest structure, which shows higher velocity and significant negative radial anisotropy, results from mafic material at the base of crust, obstructing the crustal channelized flow. However, the northeast-southwest structure is not as rigid as the Sichuan Block and exhibits depth-dependent deformation. The interpretation proves useful in further understanding regional earthquake focal mechanisms and strain distribution. Additionally, this research identified a region of generalized negative radial anisotropy in the crust of the western Chuan-Dian fragment, suggesting a reduced horizontal channel crustal flow in this area. Drawing upon various geophysical and geological evidence, we present a geodynamic evolution model, proposing a sequence of events: Permian plume activity resulting in mafic material at the base of the crust near Anninghe-Zemuhe fault, northward advancement of the east Himalayan syntaxis inducing crustal compressional stress field, reduced lower crustal channel flow in the western Chuan-Dian fragment leading to the regional east-west extension, and initiation of the Xianshuihe fault causing shift of strain concentration and depth-dependent deformation near the Anninghe-Zemuhe fault. The geodynamic model provides valuable insights into the regional distribution of crustal strain and the underlying mechanisms of large seismic events.

青藏高原东南部呈现出错综复杂的地壳构造，包括近期发生的地震大断裂事件。以前的研究表明，地壳内存在南北走向的渠化粘性流。然而，最近的调查揭示了一个显著的东北-西南走向地质结构，它可能是刚性的，与假定的地壳通道流相交。关于东北-西南向结构的组成、地壳通道化流动的连续性以及它们之间的相互作用，仍然存在一些问题。在这项研究中，利用密集地震阵列的频散数据，通过环境噪声层析成像，极大地完善了剪切波速度和径向各向异性的区域地壳模型。由此产生的高分辨率模型进一步揭示了地壳变形的风格，并支持了以下解释：东北-西南构造显示出较高的速度和显著的负径向各向异性，是地壳底部的岩浆物质阻碍地壳渠化流动的结果。然而，东北-西南构造并不像四川地块那样坚硬，而是表现出随深度变化的变形。这一解释有助于进一步了解区域地震的焦点机制和应变分布。此外，该研究还在川滇西部地块的地壳中发现了一个普遍的负径向各向异性区域，表明该区域的水平通道地壳流动减弱。根据各种地球物理和地质证据，我们提出了一个地球动力演化模型，提出了一系列事件：二叠纪羽流活动导致安宁河-则木河断层附近的地壳基底出现黑云母物质，喜马拉雅山东侧合成系北进引起地壳压缩应力场，川滇西部片区下地壳通道流减弱导致区域东西向延伸，咸水河断层的启动引起安宁河-则木河断层附近应变集中和深度变形的移动。该地球动力学模型对地壳应变的区域分布和大地震事件的内在机制提供了宝贵的见解。

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引用次数: 0

Fluid-mediated transition from dynamic rupturing to aseismic slip at the base of the seismogenic continental crust 流体介导的大陆地壳底部从动态破裂到无震滑动的过渡

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-21 DOI: 10.1016/j.epsl.2024.119117

Alberto Ceccato , Giorgio Pennacchioni

Chemo-mechanical fluid-rock interactions are critical in controlling the frictional-viscous transition in the continental crust and the competition between seismic and aseismic deformation in fault zones. In this study, we provide quantitative constraints on the timing and magnitude of weakening, and associated changes in slip rates, due to fluid-rock interactions at the base of the seismogenic continental crust. Integrating field, microstructural analyses, and micromechanical modelling we constrain the microstructural and mechanical evolution of phyllosilicate-rich, carbonate-bearing brittle-ductile faults/shear zones developed in the Rieserferner granitoid pluton (Eastern Alps). Here, transient overpressure of (H₂O + CO₂)-rich fluids triggered dynamic rupturing in the strong host rock (>100 MPa), and promoted the development of weak phyllonites through long-term fluid-mediated feldspar-to-mica reactions. These phyllosilicate-rich fault rocks accommodated frictional-viscous aseismic creep at very low differential stresses (<10 MPa) and near-lithostatic fluid pressure conditions. Microscale vein networks overprinting the phyllonite indicate cyclical embrittlement related to increased creep rates (up to 10⁻⁷ s⁻¹) that occurred over a timeframe of days to months and potentially related to slow earthquakes (slip rates of 10⁻⁸ m/s). These findings offer new constraints on the development and seismogenic potential of phyllosilicate-rich fault zones and on the effect of fluid chemistry on fault zone rheology. Fluid-mediated fault weakening can occur in rather short time (months-to-years) comparable to the interseismic period, progressively promoting long-term, viscous aseismic creep on a previously strong fault zone developed by dynamic rupturing. The combined effect of strain localization, the low permeability of the phyllonitic cores, as well as of fluid chemistry evolution and CO₂-enrichment, may lead to the development of brittle-frictional instabilities during transient accelerated-creep events. Therefore, the fluid-mediated microstructural evolution of phyllosilicate-rich fault rocks controls their seismogenic behaviour, potentially leading to accelerated creep, slow earthquakes and slow slip on otherwise aseismically creeping faults.

化学机械流体-岩石相互作用是控制大陆地壳摩擦-粘性转变以及断层带地震变形和非地震变形竞争的关键。在这项研究中，我们提供了关于成震大陆地壳底部流体-岩石相互作用导致的弱化时间和幅度以及相关滑动速率变化的定量约束。综合实地分析、微观结构分析和微观力学建模，我们对富含植物硅酸盐、含碳酸盐的脆性-韧性断层/剪切带的微观结构和力学演化进行了约束，这些断层/剪切带发育于雷塞尔费纳花岗岩岩体（东阿尔卑斯山）。在这里，富含（H2O + CO2）流体的瞬时超压引发了坚固主岩（100 兆帕）的动态破裂，并通过长期流体介导的长石-云母反应促进了软弱辉长岩的发育。这些富含长石硅酸盐的断层岩在极低的差应力（10 兆帕）和近基性流体压力条件下可承受摩擦粘性地震蠕变。覆盖在辉绿岩上的微尺度矿脉网络表明，周期性脆化与蠕变速率（高达 10-7 s-1）的增加有关，蠕变速率的增加发生在几天到几个月的时间内，可能与慢地震（滑动速率为 10-8 m/s）有关。这些发现为富含植物硅酸盐断层带的发展和致震潜力以及流体化学对断层带流变学的影响提供了新的约束条件。流体介导的断层弱化可在与地震间歇期相当的短时间内（数月至数年）发生，逐渐促进先前由动态破裂形成的坚固断层带的长期粘性地震蠕变。应变局部化、辉绿岩岩芯的低渗透性以及流体化学演化和二氧化碳富集的共同作用，可能会导致瞬态加速蠕变事件期间脆性摩擦不稳定性的发展。因此，富含辉绿硅酸盐的断层岩由流体介导的微结构演化控制着它们的致震行为，有可能导致加速蠕变、慢震和在无震蠕变断层上的慢滑。

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引用次数: 0

Methane sealed due to the formation of gas hydrate system in the South China Sea 南海天然气水合物系统的形成导致甲烷封存

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-21 DOI: 10.1016/j.epsl.2024.119114

Limin Gou , Zijian Zhang , Xianjun Zeng , Yulin He , Canping Li , Xuewei Liu

Although the release of methane into oceans and potentially the atmosphere could accelerate climate change, detailed investigations on the gas source from deep-buried strata and its migration through the gas hydrate stability zone (GHSZ) to the seafloor are limited. These studies are often hindered by the presence of diffracted waves and inaccuracies in seismic velocity models, leading to poor seismic imaging that hampers the understanding of gas sources, migration pathways, and gas hydrate accumulation. In the study, we utilize the technique of common scatter point (CSP) gathers to build an accurate velocity model and obtain high-quality images for a complex gas-hydrate and natural-gas petroleum system. The CSP processing enables the accurate migration of reflected and diffracted waves, resulting in improvements in signal-to-noise ratio and lateral resolution. The improved seismic images offer clearer visualization of various petroleum elements. Specifically, we can identify the top of the hydrate zone and base of the free gas zone within a shallow-buried hydrate system, fault geometries within the free gas zone, a middle-buried natural gas reservoir, gas chimneys as migration pathways, and the deep-buried source rock strata beneath the intrusive volcanic rocks. As a result, we reveal a joint prospect of natural-gas reservoir and gas-hydrate system in the deep-water region of the South China Sea. Our results suggest that methane in the natural gas reservoir has migrated upwardly into the hydrate system, and it is unlikely to leak into the water column.

虽然甲烷释放到海洋和大气中可能会加速气候变化，但对来自深埋地层的气体来源及其通过气体水合物稳定区（GHSZ）迁移到海底的详细调查却很有限。由于衍射波的存在和地震速度模型的不准确，这些研究往往受到阻碍，导致地震成像效果不佳，妨碍了对气体来源、迁移路径和气体水合物积累的了解。在这项研究中，我们利用共同散点（CSP）采集技术，为复杂的天然气水合物和天然气石油系统建立精确的速度模型，并获得高质量的图像。CSP 处理实现了反射波和衍射波的精确迁移，从而提高了信噪比和横向分辨率。改进后的地震图像能更清晰地显示各种石油元素。具体来说，我们可以识别浅埋水合物系统中的水合物区顶部和游离气区底部、游离气区内的断层几何形状、中埋天然气储层、作为迁移通道的天然气烟囱以及侵入火山岩下的深埋源岩层。因此，我们揭示了南海深水区天然气储层和天然气水合物系统的共同前景。我们的研究结果表明，天然气储层中的甲烷已向上迁移到水合物系统中，不太可能泄漏到水体中。

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引用次数: 0

Chondrites as thermal and mechanical archives of accretion processes in the Solar protoplanetary disk 作为太阳原行星盘吸积过程热档案和机械档案的软玉体

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-20 DOI: 10.1016/j.epsl.2024.119066

Anthony Seret , Guy Libourel

As some of the most ancient materials in our Solar System, chondritic meteorites offer a valuable window into the early stages of planetary formation, particularly the accretion processes that built the most primitive asteroids. Until now, high energy shocks and collisions have been invoked to explain the deformation and fragmentation of chondrules, the main component of chondrites. However, simulating the cooling of chondrules using continuum mechanics and finite elements, we demonstrate that plastic deformation of chondrules can occur at low collision velocities of just a few meters per second and with kinetic energies less than tenths of a millijoule when temperatures exceed the glass transition temperature

. Conversely, below

T_{g}

, spontaneous chondrule cracking occurs due to differential thermal contraction between phases and is more pronounced in larger chondrules. Counterintuitively, our findings suggest that both ordinary and carbonaceous chondrites formed through similar low-energy processes, with varying degrees of ductility and brittleness depending on the amount of processed material. This implies that the environments where chondrites formed were likely less turbulent and more thermally active than previously thought.

作为太阳系中一些最古老的物质，软玉陨石为了解行星形成的早期阶段，特别是建造最原始小行星的吸积过程提供了一个宝贵的窗口。迄今为止，高能冲击和碰撞一直被用来解释软玉的变形和碎裂，而软玉是软陨石的主要成分。然而，通过使用连续介质力学和有限元模拟软玉的冷却过程，我们证明了当温度超过玻璃转化温度时，软玉的塑性变形可以在每秒几米的低碰撞速度下发生，其动能小于十分之一毫焦。相反，当温度低于玻璃化温度时，由于各相之间的热收缩不同，会发生自发的软玉开裂，而且在较大的软玉中更为明显。与直觉相反，我们的研究结果表明，普通软玉和碳质软玉都是通过类似的低能过程形成的，其延展性和脆性程度因加工材料的数量而异。这意味着，形成软玉的环境很可能比以前认为的更少湍流和更多热能。

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引用次数: 0

Poroelastic effects on rupture propagation across fault stepovers 断层阶跃对断裂传播的挤弹性效应

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-19 DOI: 10.1016/j.epsl.2024.119103

Luyuan Huang , Elías Rafn Heimisson , Luca Dal Zilio

The role of poroelasticity in influencing the frequency of ruptures jumping through strike-slip stepovers remains unclear. To understand how poroelastic effects govern long-term rupture behavior in strike-slip fault systems with stepovers, we conduct earthquake sequence simulations incorporating undrained pore pressure responses across the full spectrum of Skempton's coefficient. Our findings reveal that Skempton's coefficient significantly affects the effective normal stress, which can either cause fault clamping or unclamping, and ultimately influences rupture propagation across fault stepovers. The likelihood of rupture jumping is predominantly determined by Skempton's coefficient and the width of the stepover, with Skempton's coefficient showing an approximately linear relationship to the critical jumpable step size. Specifically, a higher Skempton's coefficient facilitates rupture jumping across fault segments, even over larger stepover distances. Analytical solutions involving dislocation and Skempton's coefficient provide practical methods for evaluating pore pressure changes and associated seismic hazards near fault stepovers. Our statistical analysis identifies a critical jumpable width of 4.4–5.1 km due to static stress transfer, assuming a typical range of Skempton's coefficient for compressional stepovers, beyond which ruptures are unlikely to propagate. This study underscores the potential of using physics-based earthquake sequence models to reflect statistical fault rupture behaviors. Given that multi-segment earthquake ruptures present challenges in assessing maximum rupture lengths, our findings offer crucial insights into the role of poroelastic effects and the conditions that facilitate or limit rupture propagation across fault stepovers.

目前还不清楚孔弹性在影响通过走向滑动台阶的断裂频率方面所起的作用。为了了解孔弹性效应是如何影响具有台阶的走向滑动断层系统的长期破裂行为的，我们进行了地震序列模拟，其中包含了整个斯肯普顿系数频谱的排水孔隙压力响应。我们的研究结果表明，Skempton 系数会显著影响有效法向应力，从而导致断层夹紧或松开，并最终影响跨断层台阶的破裂传播。断裂跳跃的可能性主要由斯肯普顿系数和台阶宽度决定，斯肯普顿系数与临界可跳跃台阶大小呈近似线性关系。具体来说，Skempton 系数越高，越有利于跨断层段的断裂跳跃，即使跨步距离较大也是如此。涉及位错和斯肯普顿系数的分析解决方案为评估断层台阶附近的孔隙压力变化和相关地震危险提供了实用方法。我们的统计分析表明，假设斯肯普顿系数在典型的压缩性跨步范围内，由于静态应力传递，临界可跳跃宽度为 4.4-5.1 千米，超过这一宽度，断裂不太可能扩展。这项研究强调了使用基于物理学的地震序列模型来反映统计断层破裂行为的潜力。鉴于多区段地震破裂给评估最大破裂长度带来了挑战，我们的研究结果为了解孔弹性效应的作用以及促进或限制跨越断层台阶的破裂传播的条件提供了重要见解。

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引用次数: 0

Sound velocities and thermal equation of state of fcc-iron-nickel alloys at high pressure and high temperature: Implications for the cores of Moon and several planets 高压高温下 fcc 铁镍合金的声速和热状态方程：对月球和几颗行星内核的影响

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-18 DOI: 10.1016/j.epsl.2024.119118

Siheng Wang , Sibo Chen , Man Xu , Tony Yu , Yanbin Wang , Baosheng Li

Fcc-Fe-Ni alloy is believed to be the most dominant solid constitute of moderate-sized terrestrial planetary cores. Investigating the physical properties, especially the density and sound velocity of Fe-Ni alloys and comparing them with seismic observations is an indispensable approach to constructing compositional models for planetary interiors. In this study, we conducted sound velocity measurements on Fe-Ni alloys with 10 wt.% and 20 wt.% Ni up to ∼13.5 GPa and 1073 K, using the ultrasonic interferometry technique in a multi-anvil apparatus in conjunction with synchrotron radiation. By fitting the experimental data to finite strain equations, the bulk and shear moduli and their pressure and temperature derivatives are derived, yielding K_S0 =145.8(14) GPa, G₀ = 73.2(7) GPa, K_S0’ = 5.89(24), G₀’ = 2.89(8), (∂K_S/∂T)_P = -0.0181(12) GPa/K and (∂G/∂T)_P = -0.0393(10) GPa/K for fcc-Fe₈₀Ni₂₀. An examination of the density-velocity relationship shows that compressional wave velocity is insensitive to temperature within the current pressure and temperature range, while shear wave velocity exhibits a large reduction with increasing temperature. Extrapolation of the sound velocities following the finite strain theories suggests that much slower Vs should be expected at pressure and temperature conditions corresponding to those of the lunar core. Possible core density and velocity profiles for other moderate planets and satellites, such as Mars, Mercury, and Ganymede are also calculated.

Fcc-Fe-Ni合金被认为是中等大小的地球行星内核最主要的固体构成。研究Fe-Ni合金的物理性质，尤其是密度和声速，并将其与地震观测结果进行比较，是构建行星内部成分模型不可或缺的方法。在这项研究中，我们在同步辐射的配合下，利用多天线仪器中的超声干涉测量技术，对含 10 wt.% 和 20 wt.% Ni 的 Fe-Ni 合金进行了高达 ∼13.5 GPa 和 1073 K 的声速测量。通过将实验数据拟合到有限应变方程，得出了体积模量和剪切模量及其压力和温度导数，得出 KS0 =145.8(14) GPa, G0 = 73.2(7) GPa, KS0' = 5.89(24), G0' = 2.89(8), (∂KS/∂T)P = -0.0181(12) GPa/K 和 (∂G/∂T)P = -0.0393(10) GPa/K。对密度-速度关系的研究表明，在当前压力和温度范围内，压缩波速度对温度不敏感，而剪切波速度则随着温度的升高而大幅降低。根据有限应变理论对声速进行的推断表明，在与月核相应的压力和温度条件下，Vs 的速度应慢得多。此外，还计算了其他中等行星和卫星（如火星、水星和木卫三）可能的内核密度和速度曲线。

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引用次数: 0

Local sedimentary effects shaped key sulfur records after the Great Oxidation Event 当地沉积作用塑造了大氧化事件后的主要硫记录

IF 4.8 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Earth and Planetary Science Letters

Pub Date : 2024-11-16 DOI: 10.1016/j.epsl.2024.119113

Roger N. Bryant , Jordan P. Todes , Jocelyn A. Richardson , Tara C. Kalia , Anthony R. Prave , Aivo Lepland , Kalle Kirsimäe , Clara L. Blättler

Our understanding of Earth's surface oxidant budget following the Great Oxidation Event (GOE) relies heavily on interpretations of carbon (δ¹³C) and sulfur (δ³⁴S) isotope ratios. Isotopic data have been used to argue that a rise in marine sulfate concentrations to >10 mM during the GOE was followed by a sulfate reservoir ‘collapse’. However, carbonate δ³⁴S and δ¹³C values often reflect conditions specific to depositional setting and diagenetic alteration. To assess the relative importance of global vs. local/diagenetic controls, we present δ³⁴S, δ²⁶Mg, δ^44/40Ca, and trace-metal data coupled with existing δ¹³C data from the ca. 2.1–2.0 Ga Tulomozero Formation and the overlying Zaonega Formation in the Onega Basin (Karelia, Russia). Over this transitional interval, δ³⁴S and Sr/(Ca+Mg) values increase whereas δ¹³C and δ^44/40Ca values decrease. X-ray absorption spectroscopy shows that the dominant form of sulfur within the rocks concomitantly shifted from mineralized sulfate and carbonate-associated sulfate (CAS) to variable mixtures of sulfide, sulfonate, and CAS. Those changes are associated with a depositional shift from shallow-marine to deeper-marine slope settings. δ^44/40Ca and Sr/(Ca+Mg) data indicate that depositional environmental changes drove a shift from seawater- to sediment-buffered carbonate recrystallization. Consequently, we interpret δ³⁴S trends that closely match those reported by previous workers as reflecting changing local environmental and diagenetic conditions, a finding that renders equivocal the use of such trends to assess sulfur cycle changes following the GOE. Our work establishes a blueprint for how to obtain deeper insight into the evolution of Earth's surface oxidation from stable isotope records.

我们对大氧化事件（GOE）之后地球表面氧化剂预算的了解主要依赖于对碳（δ13C）和硫（δ34S）同位素比值的解释。同位素数据被用来证明，在大洋环流期间，海洋硫酸盐浓度上升到 10 毫摩尔之后，硫酸盐储层 "崩溃"。然而，碳酸盐δ34S和δ13C值通常反映了沉积环境和成岩蚀变的具体条件。为了评估全球控制与局部/成因控制的相对重要性，我们将δ34S、δ26Mg、δ44/40Ca和痕量金属数据与来自约2.1-2.0 Ga T.C.的现有δ13C数据结合起来。在奥涅加盆地（俄罗斯卡累利阿）的 2.1-2.0 Ga Tulomozero 地层和上覆的 Zaonega 地层。在这一过渡区间，δ34S 和 Sr/（Ca+Mg）值上升，而 δ13C和 δ44/40Ca 值下降。X 射线吸收光谱显示，岩石中硫磺的主要形式从矿化硫酸盐和碳酸盐相关硫酸盐（CAS）同时转变为硫化物、磺酸盐和 CAS 的可变混合物。这些变化与沉积环境从浅海向深海斜坡转变有关。δ44/40Ca和Sr/（Ca+Mg）数据表明，沉积环境的变化推动了从海水缓冲碳酸盐再结晶到沉积缓冲碳酸盐再结晶的转变。因此，我们将与前人所报道的趋势非常吻合的δ34S趋势解释为反映了当地环境和成岩条件的变化，这一发现使利用这种趋势来评估GOE之后的硫循环变化变得模糊不清。我们的工作为如何从稳定同位素记录中更深入地了解地球表面氧化作用的演变提供了一个蓝图。

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引用次数: 0