Journal of Structural Geology最新文献_第2页

Ultracataclastic vein evolution within a granodiorite along the Naxos-Paros Detachment System 纳克索斯-帕罗斯滑脱系花岗闪长岩内超碎屑脉演化

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-30 DOI: 10.1016/j.jsg.2025.105613

O. Rolfe , R. Dubosq , D.A. Schneider , S. Zaefferer , B. Grasemann

Ultracataclastic and pseudotachylytic veins are interpreted as direct evidence of coseismic slip, reflecting the conditions and mechanisms associated with fault rupture. Although the Naxos granodiorite, Greece, is known for its pristine pseudotachylyte exposures, these features remain largely understudied in terms of their microstructural evolution and implications for upper and middle crustal seismicity. We examine a suite of well-preserved veins hosted in the deformed Miocene granodiorite, historically described as examples of melt-origin pseudotachylytes, but here are re-interpreted as dominantly ultracataclasites, produced from the comminution of host rock. The veins occur in the immediate footwall of the fluid-rich, low-angle Naxos-Paros Detachment System, active between c. 20-10 Ma, and possess a similar composition as the surrounding host rock of primarily albite (35%), quartz (25%), orthoclase (16%), and biotite (12%). Structural field observations from the highest strain zone reveal three distinct crosscutting vein sets. Electron backscatter diffraction mapping of host rock porphyroclasts of albite, orthoclase, and quartz crosscut by ultracataclastic veins demonstrates that cataclasis is the dominant deformation mechanism. Variations in microstructural maturity of vein fragments suggest episodic emplacement, with rupture exploiting pre-existing slip planes. Cuspate phase boundaries between orthoclase and albite, initially observed in optical and scanning electron microscopy, are confirmed by electron microprobe analyses as a result from dissolution-precipitation reactions. These features indicate deformation by dissolution-precipitation creep. The results suggest that fluid-mediated reactions localized at vein tips contributed to weakening, generating a mechanical-chemical feedback loop that promoted ultracataclastic vein propagation along the detachment.

超碎裂和伪碎裂脉被解释为同震滑动的直接证据，反映了断层破裂的相关条件和机制。尽管希腊纳克索斯花岗闪长岩以其原始的伪长岩暴露而闻名，但就其微观结构演化及其对上、中地壳地震活动的影响而言，这些特征仍未得到充分研究。我们研究了一组保存完好的矿脉，这些矿脉位于变形的中新世花岗闪长岩中，在历史上被描述为熔体成因的伪长岩的例子，但在这里被重新解释为主要是由宿主岩石粉碎产生的超碎屑岩。脉体赋存于富流体、低角度的纳克索斯-帕罗斯滑脱系的直接下盘，活动时间为约20 ~ 10 Ma，其组成与围岩相似，主要为钠长石（35%）、石英（25%）、正长石（16%）和黑云母（12%）。从最高应变区进行的构造现场观测显示出三个不同的横切脉组。利用超碎裂岩脉对钠长石、正长石和石英等围岩斑状碎屑进行电子背散射成像，结果表明碎裂作用是主要的变形机制。微观结构成熟度的变化表明静脉碎片是幕式就位的，破裂利用了先前存在的滑动面。在光学和扫描电子显微镜中观察到的正长石和钠长石之间的尖形相界，通过溶解-沉淀反应的电子探针分析得到了证实。这些特征表明变形是由溶解-沉淀蠕变引起的。结果表明，位于静脉尖端的流体介导的反应有助于减弱，产生了一个机械-化学反馈回路，促进了超塑性静脉沿着脱离体传播。

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引用次数: 0

Investigating the generation of transport-parallel gradients in ductile strain and kinematic vorticity in the footwalls of metamorphic core complexes: Insights from the Northern Snake Range, Nevada, USA 研究变质岩心杂岩下盘韧性应变和运动涡度的输运平行梯度的产生：来自美国内华达州北蛇岭的见解

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-26 DOI: 10.1016/j.jsg.2025.105611

Aurora E. Rosenberger , Sean P. Long , Nolan Blackford , Johannes Haemmerli , Kyle P. Larson , Brianna Dowler , Scott Jess

Several metamorphic core complexes exhibit structural asymmetry in their exhumed footwalls, with ductile strain, crystallographic preferred orientation (CPO) intensity, and/or mean kinematic vorticity (W_m) increasing in the direction of detachment fault displacement. Here, we investigate the Northern Snake Range metamorphic core complex in Nevada, to explore the processes that are the most influential for generating transport-parallel strain gradients in detachment fault footwalls. Eocene-Oligocene tectonic strain (Rs), lineation-parallel extension, and foliation-normal thinning in the Northern Snake Range increase eastward from 1.5–1.6 to 240–820, 25–30 % to 1400–2400 %, and 15–21 % to 93–95 %, respectively (assuming no volume change). CPO intensity parameters (cylindricity and J_PF index) increase eastward from 0.45 to 0.90–0.95 and 1.40 to 2.64–6.40, respectively, and average W_m increases eastward from 0.26–0.40 (72–82 % pure shear) to 0.77–0.83 (56–63 % simple shear). Restoration of a strain model supported by a range-wide cross-section defines 17.9 km (470 %) of Eocene-Oligocene ductile extension. Published footwall cooling histories demonstrate an eastward progression of exhumation-related cooling, driven by unroofing via top-down-to-ESE displacement on the master detachment. This progressive unroofing resulted in an eastward increase in the residence time of quartz-rich footwall rocks at temperatures above ∼300 °C (and thus a longer ductile strain history on the eastern side of the range), which we interpret was a 1st-order factor for generating the eastward increases in strain, CPO intensity, and W_m. The Northern Snake Range is an excellent case study that demonstrates the potential for generation of pronounced transport-parallel structural asymmetry in metamorphic core complexes that are exhumed by high-displacement detachment faults.

一些变质岩心杂岩体在其下盘表现出结构不对称性，韧性应变、晶体优选取向（CPO）强度和/或平均运动涡量（Wm）沿滑脱断层位移方向增大。本文以美国内华达州北蛇岭变质核杂岩为研究对象，探讨对滑脱断层下盘形成输运平行应变梯度影响最大的过程。北蛇岭始新世—渐新世构造应变（Rs）、线—平行伸展和片理—正常减薄分别从1.5 ~ 1.6增加到240 ~ 820、25 ~ 30%增加到1400 ~ 2400、15 ~ 21%增加到93 ~ 95%（假设体积没有变化）。CPO强度参数（圆柱度和JPF指数）分别从0.45增加到0.90-0.95和1.40增加到2.64-6.40，平均Wm从0.26-0.40（72 - 82%纯剪切）增加到0.77-0.83（56 - 63%单纯剪切）。由全范围截面支持的应变模型的恢复确定了17.9公里（470%）的始新世-渐新世延展性延伸。已发表的下盘冷却历史表明，与挖掘相关的冷却过程是向东推进的，这是由主分离层自上而下至ese位移的拆顶所驱动的。这种渐进式去顶导致富石英下盘岩石在温度高于~ 300°C时的停留时间向东增加（因此在该范围的东侧有更长的韧性应变历史），我们解释这是导致应变、CPO强度和Wm向东增加的一级因素。北蛇岭是一个很好的研究案例，它证明了在高位移脱离断层挖掘出的变质岩心杂岩中可能产生明显的输运平行构造不对称。

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引用次数: 0

Pre-Neogene tectonics and early broken foreland basin stages in the Bermejo basin 贝尔梅霍盆地前新近纪构造与早期破碎前陆盆地阶段

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-23 DOI: 10.1016/j.jsg.2025.105612

Marcelo Gonzalez , Federico Lince Klinger , Cinthya Moreno , Franco Clavel , Federico Morales , Cristian Ortiz , Guido Gianni , Miguel Ramos

Broken foreland basins develop in response to far-field compressional stresses from active margins, resulting in deep-seated intraplate contractional structures that fragment the original foreland basin. This study investigates the tectono-sedimentary evolution of the Bermejo Basin, the first recognized broken foreland basin in South America, situated between the Eastern Precordillera and Western Pampean Ranges. Through the reprocessing of seismic data and gravity analyses, we identify three main tectono-sedimentary stages: Stage 1 (Pre-Neogene), Stage 2 (19-4 Ma), and Stage 3 (4–2.5 Ma to Present). Stage 1 generated structures that were buried and subsequently reactivated during Stage 2. This latter stage marked a significant reconfiguration of the basin with progressive northward propagation of compressional structures and a major shift in basin polarity around 6-5 Ma. These stages correspond to varying configurations of the Andean subduction zone, with strong foreland compression linked to flat subduction. However, the mild initial compression of a key structure active since 19-17 Ma, as evidenced by syntectonic strata, suggests that the foreland remained responsive to compressional forces transmitted from the plate margin during episodes of normal subduction. Our findings underscore the previously unrecognized role of inherited (or pre-Andean) compression in the evolution of the Bermejo Basin and provide evidence for a hybrid deformation style affecting the Eastern Precordillera, impacting the western margin of this basin. This study emphasizes the need for updated regional kinematic models that account for the interplay of ancient and more recent tectonic processes in the Bermejo Basin. Finally, our observations indicate that inherited compressional structures, such as the Carboniferous-Permian faults and the early Miocene Alto del Jumeal Range, have played a significant role in guiding subsequent deformation and sedimentation within the Bermejo basin.

破碎前陆盆地是在活动边缘的远场挤压应力作用下发育的，形成了将原始前陆盆地破碎的深层板内收缩构造。本文研究了Bermejo盆地的构造-沉积演化。Bermejo盆地是南美洲第一个被发现的破碎前陆盆地，位于东部Precordillera山脉和西部Pampean山脉之间。通过对地震资料的再处理和重力分析，我们确定了三个主要的构造沉积阶段：第1阶段（前新近纪）、第2阶段（19-4 Ma）和第3阶段（4-2.5 Ma至今）。第一阶段产生了埋藏的结构，随后在第二阶段重新激活。这一阶段标志着盆地的重大重构，挤压构造向北扩展，盆地极性在6-5 Ma左右发生重大转变。这些阶段对应于安第斯俯冲带的不同构造，强烈的前陆挤压与平坦的俯冲有关。然而，同构造地层表明，19-17 Ma以来活跃的关键构造的轻微初始压缩表明，在正常俯冲期间，前陆仍然对板块边缘传递的挤压力作出反应。我们的发现强调了继承（或前安第斯）挤压在Bermejo盆地演化中的作用，并为影响东部前科迪勒拉的混合变形样式提供了证据，影响了该盆地的西缘。这项研究强调需要更新的区域运动学模型，以解释贝尔梅霍盆地古代和近代构造过程的相互作用。结果表明，石炭-二叠纪断裂和早中新世Alto del Jumeal山脉等挤压构造对Bermejo盆地的后续变形和沉积起着重要的指导作用。

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引用次数: 0

Deformation evolution of the rifting and positive inversion in the Central African Shear Zone: Insights from Analogue Modelling 中非剪切带裂陷和正反转的变形演化：来自模拟模拟的启示

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-18 DOI: 10.1016/j.jsg.2025.105605

Lirong Dou , Xinshun Zhang , Chuanbo Shen , Yebo Du , Li Wang , Xiang Ge , Huahua Gao , Yu Yang

Investigating the deformation evolution of rifting, strike-slip faulting, and positive inversion within the Central African Shear Zone (CASZ) is crucial for understanding regional tectonic evolution, dynamic processes, and improving the exploration of hydrocarbon-rich basins. To better understand the deformation evolution of the CASZ, three brittle/ductile analog models with different block angles were tested. The results indicate that under NE–SW extensional stress: (1) rifting intensity in the CASZ decreases progressively from west to east, with the Doba Basin experiencing the strongest rifting, followed by the Doseo Basin, and the weakest rifting occurring in the Salamat Basin; (2) significant strike-slip deformation is concentrated primarily in the Doseo Basin, followed by the Salamat Basin, with minimal strike-slip deformation in the Doba Basin; and (3) strong positive inversion occurs near boundary regions of the CASZ—predominantly along the basin boundaries in the Doba Basin, whereas in the Doseo and Salamat Basins, it is more pronounced in the central depression areas.

研究中非剪切带内裂陷、走滑断裂和正反转的变形演化，对于认识区域构造演化和动力过程，提高油气勘探水平具有重要意义。为了更好地了解CASZ的变形演变，测试了3种不同块体角度的脆性/韧性模拟模型。结果表明，在NE-SW张拉应力作用下：(1)CASZ内裂陷强度自西向东逐渐减弱，其中断陷最强的是Doba盆地，其次是Doseo盆地，最弱的是Salamat盆地；(2)走滑变形主要集中在多西盆地，其次是萨拉马特盆地，多巴盆地走滑变形最小；(3)强正反转发生在casz边界附近，在Doba盆地以沿盆地边界为主，而在Doseo和Salamat盆地，在中央坳陷区更为明显。

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引用次数: 0

Clayrock deformation and permeability: insights from natural observations and experimental tests 粘土岩石变形和渗透性：来自自然观察和实验测试的见解

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-17 DOI: 10.1016/j.jsg.2025.105610

Adrien Damon , Roger Soliva , Jean Busson , Christopher Wibberley , Céline Fliedner , Frédéric Bourgeois , Frédéric Ego

We propose a model of the permeability behavior of clayrocks based on a review of plastic deformation observed in the field and permeability measurements in reactivation tests of fractures and faults. Firstly, we classify structures observed in the field according to their deformation mode and propose a model of clayrock deformation relative to usual mechanical concepts described in the literature. Secondly, we evidence controls on clayrock fracture/fault permeability by the stress conditions of the reactivated structures, the amount of shear displacement along them, and the mechanical properties of the clayrock. Finally, we formulate our model based on similarities in the concepts of clayrock deformation and the experimental evolution of clayrock fracture/fault permeability. This model links quantitative data on permeability evolution to deformation mechanisms, defining the permeability behavior of clayrocks, which was lacking in the literature until now. We highlight the dependence of this behavior on the stress and shear conditions, and demonstrate that the ratio of effective normal stress (

σ_{n}^{'}

) to the Unconfined Compressive Strength (UCS) of the clayrock can be used to describe this behavior. This model can be used in the assessment of clayrock formation sealing capacity in the context of geological storage. Particularly, the use of the UCS has the advantage of integrating important geological parameters in this assessment, such as the clay content or consolidation history. According to this model, we recommend to preserve a

σ_{n}^{'} / U C S

level larger than 0.5 in order to avoid a significant permeability increasing behavior associated with reactivation.

我们在回顾了现场观察到的塑性变形和裂缝和断层再激活试验中的渗透率测量的基础上，提出了粘土岩渗透行为的模型。首先，我们根据变形模式对现场观察到的结构进行分类，并相对于文献中描述的通常力学概念提出了粘土岩变形模型。其次，通过活化构造的应力条件、沿构造的剪切位移量和粘土岩的力学性质来证明对粘土岩破裂/断层渗透性的控制。最后，基于粘土岩变形概念的相似性和粘土岩裂缝/断层渗透率的实验演化，建立了我们的模型。该模型将渗透率演化的定量数据与变形机制联系起来，定义了粘土岩的渗透率行为，这是迄今为止文献中所缺乏的。我们强调了这种行为对应力和剪切条件的依赖性，并证明了有效正应力（σn’）与粘土岩的无侧限抗压强度（UCS）的比值可以用来描述这种行为。该模型可用于地质储层条件下粘土岩储层封闭性评价。特别是，使用UCS具有在评估中整合重要地质参数的优势，例如粘土含量或固结历史。根据该模型，我们建议保持σn′/UCS大于0.5，以避免与再活化相关的显著渗透率增加行为。

{"title":"Clayrock deformation and permeability: insights from natural observations and experimental tests","authors":"Adrien Damon , Roger Soliva , Jean Busson , Christopher Wibberley , Céline Fliedner , Frédéric Bourgeois , Frédéric Ego","doi":"10.1016/j.jsg.2025.105610","DOIUrl":"10.1016/j.jsg.2025.105610","url":null,"abstract":"<div><div>We propose a model of the permeability behavior of clayrocks based on a review of plastic deformation observed in the field and permeability measurements in reactivation tests of fractures and faults. Firstly, we classify structures observed in the field according to their deformation mode and propose a model of clayrock deformation relative to usual mechanical concepts described in the literature. Secondly, we evidence controls on clayrock fracture/fault permeability by the stress conditions of the reactivated structures, the amount of shear displacement along them, and the mechanical properties of the clayrock. Finally, we formulate our model based on similarities in the concepts of clayrock deformation and the experimental evolution of clayrock fracture/fault permeability. This model links quantitative data on permeability evolution to deformation mechanisms, defining the permeability behavior of clayrocks, which was lacking in the literature until now. We highlight the dependence of this behavior on the stress and shear conditions, and demonstrate that the ratio of effective normal stress (<span><math><mrow><msubsup><mi>σ</mi><mi>n</mi><mo>′</mo></msubsup></mrow></math></span>) to the Unconfined Compressive Strength (UCS) of the clayrock can be used to describe this behavior. This model can be used in the assessment of clayrock formation sealing capacity in the context of geological storage. Particularly, the use of the UCS has the advantage of integrating important geological parameters in this assessment, such as the clay content or consolidation history. According to this model, we recommend to preserve a <span><math><mrow><msubsup><mi>σ</mi><mi>n</mi><mo>′</mo></msubsup><mo>/</mo><mi>U</mi><mi>C</mi><mi>S</mi></mrow></math></span> level larger than 0.5 in order to avoid a significant permeability increasing behavior associated with reactivation.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"204 ","pages":"Article 105610"},"PeriodicalIF":2.9,"publicationDate":"2025-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145771939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Comparative studies of salt pillows in proximity to the Ringkøbing-Fyn High, Denmark 丹麦Ringkøbing-Fyn高地附近盐枕的比较研究

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-15 DOI: 10.1016/j.jsg.2025.105609

Cecilia E.B. Nielsen, Ole R. Clausen

The salt structures in Denmark have become of increased interest for the current Carbon Capture and Storage (CCS) investigations, with most of the prospecting areas being in close relation to the structures. In this study we have investigated three salt pillows located on both sides of the Ringkøbing-Fyn High (RFH), Denmark, with focus on the timing and direction of salt movement. With the use of interpretation and restoration software, we have interpreted multiple 2D seismic lines and made a structural restoration of a defining line for each structure to determine the evolution of the salt movement. Our results show that the structures closest to the RFH have been created by Triassic gravitational gliding of the salt away from the high, while the salt further north most likely initiated by a combination of differential loading and local tectonics during the same period. Salt reactivation is more pronounced for the structures located north of the RFH, especially showing salt reactivation after the deposition of the late Cretaceous Chalk Group indicating a Cenozoic process only affecting the salt structures north of the high. However, the overall deformation of the three structures shows similar patterns, indicating that they all might represent structures located at the border zone of the Permian Zechstein salt basins, thus pushing the influence of the Sorgenfrei-Tornquist Zone in the Norwegian-Danish Basin much further west in the Norwegian-Danish basin than formerly understood.

丹麦的盐结构已成为当前碳捕集与封存（CCS）调查中日益增加的兴趣，大多数勘探区都与盐结构密切相关。在这项研究中，我们调查了位于丹麦Ringkøbing-Fyn高地（RFH）两侧的三个盐枕，重点研究了盐运动的时间和方向。利用解释和恢复软件，我们解释了多条二维地震线，并对每个结构的定义线进行了结构恢复，以确定盐运动的演变。我们的研究结果表明，最接近RFH的构造是由三叠纪盐远离高点的重力滑动造成的，而更北的盐很可能是由同一时期的差异荷载和局部构造共同形成的。盐的再激活作用在RFH以北的构造中更为明显，特别是在晚白垩世白垩群沉积后，表明新生代的盐的再激活作用只影响到高北的盐构造。然而，三个构造的整体变形模式相似，表明它们都可能代表了位于二叠纪Zechstein盐盆地边界带的构造，从而将挪威-丹麦盆地的Sorgenfrei-Tornquist带的影响推到了挪威-丹麦盆地的西部，比以前认识的要远得多。

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引用次数: 0

Quantifying finite strain in the poly-deformed Lansdowne Klippe, Garhwal Himalaya, India: An appraisal of popular strain estimation techniques 定量有限应变在多变形的Lansdowne Klippe， Garhwal喜马拉雅，印度：流行的应变估计技术的评价

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-11 DOI: 10.1016/j.jsg.2025.105585

Sayandeep Banerjee , Sayan Maity , Ashish Rawat , Virendra Rana , Yaspal Sundriyal , Hari B. Srivastava

Understanding finite strain in poly-deformed terranes remains a challenge due to multiple deformation phases, impacting accurate estimation. This study presents a comparative analysis of four distinct techniques (Rf/Φ, Fry's, Panozzo, and AMS-based strain estimation) to estimate the finite strain in the Lansdowne Klippe of the Garhwal Himalaya, India. In the estimation of strain, complexities might arise due to the inherent difficulties in assessing the original shape of strain indicators in areas with a history of multiple deformations. Such challenges significantly affect the precision of finite strain estimation, leading to inconsistencies in the obtained values. By analysing the quantitative and qualitative differences among the methodologies, this study reveals the discrepancies in determining 2-D finite strain and respective strain ellipses. The present attempt is the first rigorous multi-method comparison for quantifying strain within a poly-deformed klippe in the Himalayan orogen. In our comparative analysis, Rf/Φ and Fry methods yielded the highest finite strains (Rs ∼1.7–2.3), whereas the Panozzo method gave lower values (Rs ∼1.1–2.0). AMS-derived anisotropy (Pj ∼1.05–1.2) corresponds to only low finite strain. These systematic method-dependent differences underscore that strain magnitudes in a polyphase terrane are strongly influenced by the chosen technique. Our findings also highlight the inherent inconsistencies and limitations in estimating finite strain in regions with polyphase deformation.

在多变形地形中，由于存在多个变形阶段，因此理解有限应变仍然是一个挑战，影响了准确的估计。本研究提出了四种不同的技术（Rf/Φ， Fry's， Panozzo和基于ams的应变估计）的比较分析，以估计印度Garhwal喜马拉雅地区Lansdowne Klippe的有限应变。在应变估计中，由于在具有多次变形历史的区域中评估应变指标的原始形状存在固有的困难，可能会产生复杂性。这些挑战严重影响了有限应变估计的精度，导致所得值不一致。通过分析这些方法在定量和定性上的差异，揭示了在确定二维有限应变和各自的应变椭圆时的差异。目前的尝试是第一次对喜马拉雅造山带多变形断裂带的应变进行定量的严格的多方法比较。在我们的比较分析中，Rf/Φ和Fry方法产生了最高的有限应变（Rs ~ 1.7-2.3），而Panozzo方法给出了较低的值（Rs ~ 1.1-2.0）。ams衍生的各向异性（Pj ~ 1.05-1.2）只对应于低有限应变。这些系统的方法相关的差异强调了多相岩层中的应变大小受到所选技术的强烈影响。我们的研究结果还强调了在多相变形区域估计有限应变的固有不一致性和局限性。

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引用次数: 0

Numerical modeling of young-beneath-old subduction and implications for Taiwan-Luzon double volcanic arc in East Asia 东亚台湾-吕宋双火山弧年轻下老俯冲的数值模拟及其意义

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-09 DOI: 10.1016/j.jsg.2025.105608

Shaohua Yang , Haibing Li , Jiawei Pan , Yaolin Shi

While the initiation mechanisms, patterns, and effects of subduction involving an old oceanic plate beneath a younger plate (old-beneath-young subduction) are well established, the dynamics of young-beneath-old subduction, such as that observed at the Manila Trench in East Asia, remain poorly understood. The influence of key parameters, including oceanic plate age and convergence rate, on the geometry of young-beneath-old subduction, and how these factors differ from those in old-beneath-young subduction, has yet to be fully explored. Furthermore, the role of young-beneath-old subduction in modulating subduction-related volcanism, exemplified by the double volcanic arc between Taiwan and Luzon, is not well characterized. In this study, we present ocean-ocean subduction numerical models to investigate these issues. Our results reveal that when the overriding plate is older or the subducting plate is younger, the subduction angle is smaller. Additionally, for a constant age difference between the plates, younger subducting plates are associated with shallower subduction angles. Faster convergence rates tend to promote low-angle subduction. These findings provide new insights into the formation of the Taiwan-Luzon double volcanic arc. We propose that the initial low-velocity convergence between the Philippine and South China Sea plates caused high-angle subduction, leading to the formation of the West Volcanic Chain (WVC). Subsequently, the acceleration of the Philippine Plate in the north-westward direction resulted in a decrease in subduction angle, halting WVC activity and facilitating the formation of the East Volcanic Chain (EVC). Latitudinal lithospheric age gradients drive WVC-EVC divergence through differential subduction angles, inducing contrasting mantle wedge dynamics and volcanic chain spacing.

虽然一个古老的大洋板块在一个年轻板块之下的俯冲的起始机制、模式和影响已经很好地确立了，但是年轻板块在古老板块之下的俯冲动力学，比如在东亚马尼拉海沟观察到的，仍然知之甚少。包括大洋板块年龄和收敛速度在内的关键参数对年轻-老下俯冲几何形状的影响，以及这些因素与年轻-老下俯冲几何形状的差异，尚未得到充分探讨。此外，以台湾和吕宋之间的双火山弧为例，还没有很好地描述年轻下老俯冲对俯冲相关火山活动的调节作用。在这项研究中，我们提出了洋-洋俯冲的数值模型来研究这些问题。结果表明，上覆板块年龄越大，俯冲板块年龄越小，俯冲角度越小。此外，由于板块之间年龄差异恒定，较年轻的俯冲板块与较浅的俯冲角有关。较快的收敛速度倾向于促进低角度俯冲。这些发现为台湾-吕宋双火山弧的形成提供了新的认识。我们认为，菲律宾板块与南海板块之间的低速初始辐合导致了高角度俯冲，导致了西火山链的形成。随后，菲律宾板块向西北方向加速运动，导致俯冲角减小，WVC活动停止，有利于东部火山链的形成。纬向岩石圈年龄梯度通过不同的俯冲角驱动WVC-EVC的辐散，形成对比鲜明的地幔楔动力学和火山链间距。

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引用次数: 0

A new mode of syn-depositional folding in the Zechstein Supergroup due to differential loading and diagenetically induced density inversion 一种由差异载荷和成岩诱导的密度反转导致的Zechstein超群同沉积褶皱新模式

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-03 DOI: 10.1016/j.jsg.2025.105606

Ben Aldridge , Simon Stewart , Dan Phillips , Martino Foschi , Joe Cartwright

This study examines short-wavelength folding within the Zechstein Supergroup in the Southern Permian Basin by focusing on the Z3 anhydrite (Z3a) stringer, documenting a previously unrecognised mode of deformation that occurred during evaporite deposition in the Late Permian. Three-dimensional mapping of the Z3a reveals a network of irregularly shaped and oriented folds that pre-date Late Palaeocene magmatic intrusions, indicating an early deformation phase (F1) distinct from regional salt tectonics (F2). The observed fold geometries cannot be readily explained by buckling; instead, they are interpreted to result from vertical simple shear driven by differential loading in addition to density increases caused by the diagenetic transformation of gypsum to anhydrite. These density increases influenced deformation most notably across the recently identified basin-scale network of anomalously thick Z3a, causing these sections of the Z3a to sag into the underlying halite units and produce characteristic dome- and bowl-shaped folds without lateral shortening. The stiffness of the Z3a prevented sections from sinking to the base of the Zechstein and preserved early forming structures through the subsequent episode of regional salt tectonics in regions of modest salt structure. Our findings challenge traditional models of intra-salt fold formation that emphasize regional salt tectonics as the primary driver, highlighting the active role that mechanical heterogeneity and diagenesis exert on evaporite deformation. These findings have implications for understanding the mechanical behaviour of layered evaporite sequences for a variety of subsurface applications.

本研究通过关注Z3硬石膏（Z3a）弦线，研究了南二叠纪盆地Zechstein超群中的短波褶皱，记录了一种以前未被认识到的变形模式，这种变形模式发生在晚二叠纪蒸发岩沉积期间。Z3a的三维制图显示，在晚古新世岩浆侵入之前，Z3a发育了一个形状不规则、定向的褶皱网络，表明其早期变形阶段（F1）与区域盐构造（F2）不同。观察到的褶皱几何形状不能轻易地用屈曲来解释；相反，它们被解释为除了石膏向硬石膏的成岩转化引起的密度增加外，还受到不同载荷驱动的垂直单纯剪切作用的影响。这些密度的增加对最近发现的异常厚的Z3a盆地尺度网络的变形影响最为显著，导致Z3a的这些部分凹陷到下伏的岩盐单元中，并产生了典型的圆顶和碗状褶皱，没有横向缩短。Z3a的刚度阻止了剖面下沉到Zechstein的底部，并通过随后在适度盐构造区发生的区域性盐构造事件保存了早期形成的构造。我们的发现挑战了强调区域盐构造是主要驱动因素的传统盐内褶皱形成模型，强调了机械非均质性和成岩作用对蒸发岩变形的积极作用。这些发现对于理解层状蒸发岩序列在各种地下应用中的力学行为具有重要意义。

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引用次数: 0

Veining style and size-scaling behavior throughout the generation and exhumation of subduction mélange: Evidence from Japan and Alaska 贯穿于俯冲带形成和发掘的脉纹样式和尺度行为：来自日本和阿拉斯加的证据

IF 2.9 2区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of Structural Geology

Pub Date : 2025-12-02 DOI: 10.1016/j.jsg.2025.105607

J.N. Hooker , S. Luciano , D.M. Fisher , A.J. Smye , Y. Hashimoto , T. Hosokawa , S.J. Elliott

We document patterns of cemented opening-mode fractures (veins) across the thickness of subduction mélanges, focusing on the Shimanto belt of SW Japan with ancillary observations from the Kodiak accretionary complex, Alaska, USA. We interpret at least two distinct phases of vein formation at seismogenic depths in Cretaceous mélanges of the Shimanto belt. Early veins (Set 1) can be ptygmatically folded, indicating formation prior to the completion of sedimentary compaction. Set 1 is crosscut by pervasive mélange foliation. Cement deposits within Set 1 comprise wall-lining, blocky quartz cement having blue cathodoluminescence (CL) cores and orange rims; calcite generally overgrows quartz, filling fracture pore space left between quartz crystals. Both minerals contain abundant fluid inclusions. Set 1 aperture sizes are power-law distributed, with most strain associated within the largest veins. Late veins (Set 2) crosscut Set 1 and mélange foliations. Set 2 veins have relatively planar walls, crack-seal texture, blue CL, a low density of fluid inclusions, and only sparse overgrowing calcite. Set 2 is numerically dominated by microfractures, likely a consequence of rapid healing at high temperature during fracture opening. Vein intensity is heterogeneous at outcrop and thin-section scales, with veins of both generations preferentially forming within brittle, sand-silt dominated facies, as opposed to intervening shales. Vein and host rock geometries indicate that the mélange deforms by early pure shear that evolves to simple shear as subduction proceeds. Vein formation accommodates plate convergence throughout numerous earthquake cycles on the subduction interface and comprises opening-mode fractures whose formation and cementation reflect long-term, interseismic fluid conditions.

我们记录了贯穿俯冲带厚度的胶结张开型裂缝（脉）模式，重点研究了日本西南部的Shimanto带，并辅以美国阿拉斯加Kodiak增生杂岩的观测结果。我们解释了石曼托带白垩纪msamulanges发震深度至少两个不同的脉体形成阶段。早期脉（第1组）可呈典型褶皱，表明沉积压实作用完成前形成。集合1是由普遍的宽叶理切成的横切。第1组内的水泥沉积物包括壁衬、具有蓝色阴极发光（CL）岩心和橙色边缘的块状石英水泥；方解石一般生长在石英之上，填充石英晶体之间留下的裂隙孔隙空间。这两种矿物都含有丰富的流体包裹体。组1孔径尺寸呈幂律分布，最大的矿脉内应变最多。晚脉（组2）横切组1和宽叶理。2组脉壁相对平坦，裂隙封闭，CL呈蓝色，流体包裹体密度低，方解石稀疏过长。集合2在数值上以微骨折为主，这可能是骨折打开时在高温下快速愈合的结果。在露头和薄片尺度上，脉体强度是不均匀的，两代脉体都优先形成于脆性砂粉质为主的相中，而不是中间的页岩。矿脉和寄主岩石的几何形状表明，在早期的纯剪切作用下，随着俯冲作用的进行，其变形演化为单纯剪切作用。在俯冲界面的多个地震旋回中，脉状地层适应板块收敛，包括开口型裂缝，其形成和胶结反映了长期的地震间流体条件。

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引用次数: 0