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Unraveling progressive stages of formation and examining relative roles of proximity to fault, mechanical stratigraphy on fracturing in the leading-edge of thrust sheets: Insights from Ramgarh thrust, Darjeeling Himalaya 揭示形成的渐进阶段,研究断层附近的相对作用,机械地层学对逆冲片前缘破裂的影响:来自大吉岭-喜马拉雅拉姆加尔逆冲断层的见解
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-16 DOI: 10.1016/j.jsg.2025.105507
J.K. Ammu, Kathakali Bhattacharyya
We decipher the progressive stages of fracture formation and examine the competing effects of proximity to a thrust, lithology, and bed thickness on fracture abundance, orientation, mode, and length. We address this study in the interfoliated quartzite-phyllite sequence of the leading-edge (∼3.4 km) of the Ramgarh thrust (RT) sheet, the roof thrust of the lower Lesser Himalayan duplex in the Darjeeling Himalaya. Only ∼30 % of the total studied fractures (n = 884) preserve slickenlines and plumose structures. Due to favorable orientations relative to the vertical outcrop bearing, small displacement faults (shear fractures) (n = 236; ∼27 % of total fractures) with slickenlines are better exposed than opening-mode (n = 32; ∼4 %) with plumose structures. Further structural analyses reveal coexisting shear (∼59 %) and opening-mode (∼41 %) fractures. Through crosscutting, fold test, and intensity distribution, we establish fracturing initiated with low-angle, shear fractures during early layer parallel shortening. High-angle, shear, and opening-mode fractures formed post-folding. Fracture density fluctuates with perpendicular distance from the footwall contact due to variation in lithology and bed thickness. Fracture density most strongly depends on lithology (quartzitefractures > phyllitefractures), followed by bed thickness (thin bedsfractures > thick bedsfractures) and distance from the RT. Fracture mode and orientation, with respect to bedding, are similar across lithologies, only intensity differs. High-angle and Riedel shear fractures are localized proximal to the RT. Shear vs opening-mode proportions remain unchanged with increasing distance from the RT. Litho-boundaries and early-formed fractures constrain fracture lengths (ntraces = 10,758), irrespective of their mode and orientation. Fracture networks show more evolved length distributions close to the RT.
我们破译了裂缝形成的渐进阶段,并研究了与冲断的接近程度、岩性和层厚对裂缝丰度、方向、模式和长度的竞争影响。我们在Ramgarh逆冲(RT)薄片前缘(~ 3.4 km)的夹层石英岩-千层岩层序中进行了这项研究,该逆冲是大吉岭-喜马拉雅下部小喜马拉雅双相的顶板逆冲。在研究的所有裂缝中,只有约30% (n = 884)保留了丝状线和羽状结构。由于相对于垂直露头方位有利,小位移断层(剪切裂缝)(n = 236;约占总裂缝的27%)与开放模式相比,滑膜线的暴露效果更好(n = 32;~ 4%)具有羽状结构。进一步的结构分析显示,剪切裂缝(约59%)和张开型裂缝(约41%)并存。通过横切、褶皱试验和强度分布,确定了地层平行缩短早期以低角度剪切裂缝起裂。褶皱后形成高角度、剪切和开敞型裂缝。由于岩性和层厚的变化,裂缝密度随与下盘接触的垂直距离而波动。裂缝密度主要取决于岩性(石英岩裂缝);千层裂缝),其次是层厚(薄层裂缝);裂缝的模式和方向,就层理而言,在岩性上是相似的,只是强度不同。高角剪切裂缝和Riedel剪切裂缝位于rt附近。随着距离rt的增加,剪切模式与打开模式的比例保持不变。无论其模式和方向如何,岩石边界和早期形成的裂缝都约束着裂缝长度(ntraces = 10758)。裂缝网络的长度分布更接近RT。
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引用次数: 0
3D modeling and visualization of geological structures with python-implemented Bézier curves/surfaces 三维建模和可视化的地质结构与python实现的bsamzier曲线/表面
IF 2.9 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-15 DOI: 10.1016/j.jsg.2025.105508
Manuel Bullejos , Manuel Martín-Martín
Interactive 3D HTML models and visualizations of geological structures derived from classic surface geological information have been developed, for the first time, in a Python environment, using the key case of the tectonic Mula sheets in the Betic Cordillera (southern Spain). These models were performed through several steps: a geological 2D sketch map, creating equispaced geological cross-sections, 3D topography, a complete 3D model, and detailed 3D block diagrams. The result of the extrapolation of the equispaced geological cross-sections and their integration with the geological map into a 3D geological model shows the thrust-faulted and contractionally folded structure of the entire area, which affects the Cretaceous to Lower Miocene succession. The faults (strike-slip and normal) present in the tectonic thrust sheets are also represented. Three detailed 3D HTML blocks of illustrative regions within the modeled area were also created. For the 3D modeling, Bézier curves/surfaces as well as linear interpolation were used, as geological (stratigraphic and tectonic) contacts and surfaces between different stratigraphic units can be expressed geometrically with these tools. Compared to commercial alternatives, our software offers three key advantages: free user-friendly solutions, browser-compatible 3D models, and open-source software. The 3D visualization of stratigraphic-structural architecture enables predictive interpretations with applications in environmental and economic geology (e.g., groundwater, geotechnical studies, mining research, etc.). Moreover, 3D visualization and modeling provide valuable insights into geological phenomena, benefiting both the scientific community and society at large. Furthermore, advances in interactive 3D visualization bridge the gap between cutting-edge geological research and public understanding, enhancing social awareness.
基于经典地表地质信息的交互式3D HTML模型和地质构造可视化首次在Python环境中开发出来,以西班牙南部Betic Cordillera的Mula构造片为关键案例。这些模型是通过几个步骤完成的:一个地质2D草图,创建等距地质截面,3D地形,一个完整的3D模型,以及详细的3D方框图。对等步地质剖面进行外推,并将其与地质图整合成三维地质模型,显示了整个地区的逆冲断裂和收缩褶皱构造,影响了白垩纪至下中新世的演替。构造逆冲片上的断层(走滑断层和正断层)也有代表性。在建模区域内,还创建了三个详细的3D HTML块,用于说明区域。在三维建模中,由于不同地层单元之间的地质(地层和构造)接触和表面可以用这些工具进行几何表示,因此使用了bsamzier曲线/曲面和线性插值。与商业替代品相比,我们的软件提供了三个关键优势:免费的用户友好解决方案,浏览器兼容的3D模型和开源软件。地层构造的三维可视化使环境和经济地质学(如地下水、岩土工程研究、采矿研究等)的预测解释成为可能。此外,三维可视化和建模为地质现象提供了有价值的见解,有利于科学界和整个社会。此外,交互式三维可视化技术的进步弥合了前沿地质研究与公众理解之间的差距,增强了社会意识。
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引用次数: 0
A catalogue of calcite vein types in porous sandstone and their formation conditions (Huab Basin, Namibia) 纳米比亚Huab盆地多孔砂岩方解石脉类型及其形成条件
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-12 DOI: 10.1016/j.jsg.2025.105506
Eric Salomon , Anna Nele Meckler , Axel Gerdes , Richard Albert , Harald Stollhofen
We present a catalogue of calcite vein types in porous sandstone that have the potential to affect fluid flow properties in a reservoir. Host rock is the Lower Cretaceous aeolian Twyfelfontein Formation, covered by voluminous flood volcanic rock of the Paraná-Etendeka Large Igneous Province in the Huab Basin of NW Namibia. Since the host sandstone lacks carbonate components, these veins document advective fluid flow, where solutes were transported through the fractures from an external source. Crystal growth in veins vary from blocky, to radial, and micritic. Some veins exhibit an intergrowth with kaolinite, or show an initial dolomite and iron oxide precipitation. Deformation stages are evident in a number of veins from breccia to cataclasis and fault-slip slickenfibre generations. Some calcite generations underwent partial dissolution and replacement by chalcedony. U-Pb dating shows a predominant vein formation from 31 Ma to recent, with one outlier at ∼65 Ma. Pore-filling calcite cements of sandstone along veins and in contact with the covering volcanic rock show similar ages. Formation temperatures (16–47 °C) derived from clumped isotope analysis indicate precipitation at shallow burial depths (<1 km). An outlier of 59 °C stems from the vein dated to ∼65 Ma. Carbonate δ13CVPDB shows a trend from −8.3 ‰ to −1.3 ‰ between Oligocene to present and we argue this to be a reflection of the region's climatic shift from warm humid to (semi-)arid conditions in this time. We further discuss, that this shift is responsible for many of the observed vein characteristics.
我们提出了多孔砂岩中方解石脉类型的目录,这些方解石脉类型有可能影响储层中的流体流动特性。寄主岩为下白垩统风成Twyfelfontein组,被纳米比亚西北部Huab盆地Paraná-Etendeka大火成岩省的大量洪水火山岩覆盖。由于寄主砂岩缺乏碳酸盐成分,这些矿脉记录了流体的平流流动,溶质从外部来源通过裂缝输送。晶脉中的晶体生长从块状、放射状和微晶状不等。有些矿脉与高岭石共生,或显示白云石和氧化铁的初始沉淀。从角砾岩到碎裂岩和断滑滑脱纤维几代,许多矿脉的变形阶段都很明显。一些方解石发生了部分溶解并被玉髓取代。U-Pb测年显示,从31 Ma到最近,主要是静脉形成,在~ 65 Ma有一个异常值。砂岩沿脉状充填孔隙的方解石胶结物与覆盖的火山岩的接触年龄相近。团块同位素分析得出的地层温度(16-47°C)表明埋藏深度较浅(1 km)有降水。59°C的异常值来自年龄为~ 65 Ma的静脉。从渐新世至今,碳酸盐岩δ13CVPDB的变化趋势为- 8.3‰~ - 1.3‰,反映了该区气候从暖湿向(半)干旱的转变。我们进一步讨论,这种转变是负责许多观察到的静脉特征。
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引用次数: 0
Reconstructing the framework of the Paleo-Pacific Plate: A synthetic review 古太平洋板块格架的重建:综合评述
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-11 DOI: 10.1016/j.jsg.2025.105505
Sanzhong Li , Yong-Fei Zheng , Yanhui Suo
The Paleo-Pacific Ocean Basin would evolve from the Panthalassa and develop ancient plates such as Paleo-Pacific, Farallon and Phoenix. Multilines of geological and geophysical evidence indicate that a new-born plate, named the Pacific Plate, would initially develop at 190 Ma among these three plates in the Paleo-Pacific Ocean Basin, but it did not take shape until 55 Ma when the Paleo-Pacific Plate would finally disappear on the East Asian continental margin. Therefore, the Paleo-Pacific Plate and the Pacific Plate would co-evolve or co-exist from 190 Ma to 55 Ma in the Paleo-Pacific Ocean Basin. The ocean basin after the complete disappearance of the Paleo-Pacific Plate at 55 Ma is the Pacific Ocean Basin as presently seen. Geologically, the Pacific Ocean Basin is marked by the initial formation of the plate configuration on the current Pacific seafloor in the Mesozoic. Therefore, when did the Paleo-Pacific Plate begin in the Paleo-Pacific Ocean Basin? When was the Paleo-Pacific Plate subducted beneath the East Asian continental margin? How would its appearance and disappearance are spatiotemporally recorded in geology? What are its geological effects during its subduction beneath the East Asian continental margin? Although there are numerous studies dealing with the formation and evolution of the Paleo-Pacific Plate, the results have brought many big debates on its composition and structure. Some scholars refer to the Paleo-Pacific Plate differently, leading to some great difficulties in academic exchanges. There are three mainstream viewpoints: the Paleo-Pacific Plate is either the Kula Plate, or the Izanagi Plate, or a collage of many plates. Although the Paleo-Pacific Plate existed as a mysterious on Earth in the Mesozoic, a large number of geological observations indicate that its evolution is closely related to the tectonic evolution of the East Asian continental margin in this period. Therefore, it is necessary to recognize and reconstruct the configuration of the Paleo-Pacific Plate and its tectonic effects on the East Asian continental margin. This paper attempts to systematically summarize the previous observations and interpretations of the Paleo-Pacific Plate, to distinguish between the concepts of the Kula Plate, the Izanagi Plate and the Paleo-Pacific Plate in different study stages, and to systematically explore various differences in plate reconstruction since the proposal of the Paleo-Pacific Plate. Based on the current progresses on plate tectonics, this paper also summarizes the relevant geological records of the Paleo-Pacific Plate, including the continental margin accretion of oceanic plateaus, island arc basalt-like magmatic rocks and terrane-collage accretion. The time of its subduction initiation, geometric evolution and spatial range changes are explored, and its tectonic evolutionary history is reconstructed. Finally, remaining problems are presented for the future research.
古太平洋盆地将从泛海板块演化而来,并发展出古太平洋、法拉隆和凤凰等古板块。多种地质和地球物理证据表明,在古太平洋盆地的这三个板块中,一个新生的板块最初在190ma发育,但直到55ma古太平洋板块最终在东亚大陆边缘消失时才形成,并被命名为太平洋板块。因此,古太平洋板块与太平洋板块在190ma - 55ma期间在古太平洋盆地内共同演化或共存。55 Ma古太平洋板块完全消失后的洋盆就是现在看到的太平洋洋盆。在地质学上,太平洋盆地以中生代在现今太平洋海底初始形成板块构造为标志。那么,古太平洋板块是什么时候开始于古太平洋盆地的呢?古太平洋板块何时俯冲到东亚大陆边缘之下?它的出现和消失在地质中是如何记录时空的?它在东亚大陆边缘俯冲的过程中产生了怎样的地质效应?尽管关于古太平洋板块形成和演化的研究很多,但研究结果对古太平洋板块的组成和结构产生了许多大的争论。一些学者对古太平洋板块的说法不同,给学术交流带来了很大的困难。有三种主流观点:古太平洋板块要么是库拉板块,要么是伊扎那吉板块,要么是许多板块的拼贴。虽然古太平洋板块在中生代作为一个神秘的存在于地球上,但大量的地质观测表明,它的演化与这一时期东亚大陆边缘的构造演化密切相关。因此,有必要认识和重建古太平洋板块的形态及其对东亚大陆边缘的构造作用。本文试图系统总结前人对古太平洋板块的观测和解释,区分不同研究阶段的库拉板块、伊扎那吉板块和古太平洋板块概念,系统探讨古太平洋板块提出以来在板块重建上的各种差异。在板块构造学研究进展的基础上,总结了古太平洋板块的相关地质记录,包括海洋高原的大陆边缘增生、岛弧玄武岩样岩浆岩和地质体拼贴增生。探讨了其俯冲起始时间、几何演化和空间范围变化,重建了其构造演化史。最后,提出了今后研究中有待解决的问题。
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引用次数: 0
Kinematic interpretation of the Cañamares shear zone (central Iberian zone, Iberian Massif): from late Variscan strike-slip tectonics to Alpine deformation Cañamares剪切带(伊比利亚中部带,伊比利亚地块)的运动学解释:从晚瓦里斯坎走滑构造到阿尔卑斯变形
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-11 DOI: 10.1016/j.jsg.2025.105504
Diana Moreno-Martín , Carlos Fernández , Rubén Díez Fernández , Gerardo de Vicente
The Cañamares shear zone is located at the eastern end of the Spanish-Portuguese Central System, in the Central Iberian Zone of the Iberian Massif. It is a dextral transpressive structure, generated during the third Variscan deformation stage (D3: 318-300 Ma), which was later reworked during the Permian and by Alpine tectonics. Once the local effects of later phases have been eliminated, the kinematic analysis of the Cañamares shear zone shows that it is a structure due to a monoclinic to slightly triclinic flow, with a vorticity dominated by the simple-shearing component (Wk > 0.81). The convergence direction of the blocks separated by the shear zone would have been N160°E to N-S. The convergence direction calculated for the Cañamares shear zone differs from that of other D3 shear zones of the Iberian Massif. A comparison between these vectors would help to better understand the complexities of the final phases of the Variscan Orogeny in Iberia. However, the Cañamares shear zone lies at the core of an Alpine mega-fold and its current orientation does not probably reflect its primary geometry.
Cañamares剪切带位于西班牙-葡萄牙中央体系的东端,位于伊比利亚地块的伊比利亚中部地区。它是一个右向逆压构造,形成于第三个瓦里斯坎变形阶段(D3: 318-300 Ma),后来在二叠纪和高山构造中被改造。一旦排除了后期阶段的局部影响,Cañamares剪切带的运动学分析表明,它是一个由单斜到微三斜流动引起的结构,涡度由单剪切分量主导(Wk >;0.81)。被剪切带分隔的块体辐合方向为N160°E到N-S。Cañamares剪切带的辐合方向与伊比利亚地块其他D3剪切带的辐合方向不同。这些载体之间的比较将有助于更好地理解伊比利亚瓦里斯坎造山运动最后阶段的复杂性。然而,Cañamares剪切带位于阿尔卑斯巨型褶皱的核心,其目前的方向可能并不反映其原始几何形状。
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引用次数: 0
Deformation mechanisms of compressional overlapping area in strike-slip fault zone: Insights from experimental simulation 走滑断裂带挤压叠加区的变形机制:实验模拟的启示
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-10 DOI: 10.1016/j.jsg.2025.105503
Jingjing Zhang , Lingli Guo , Sanzhong Li , Wei Tao , Yuntao Ji , Yanshuang Guo , Shujuan Zhao , Jiaxuan Zhang , Guangzeng Wang
As an intense deformation region, the compressional overlapping areas of strike-slip faults play a crucial and significant role in influencing fault propagation, seismic activity, and the formation and distribution of hydrocarbon reservoirs. Hence, enhancing the comprehension of detailed microscopic deformation mechanisms lays the foundation for a better understanding of the macroscopic deformation, constituting the core issue of this study. Compressional en échelon fault model experiments were conducted, combining with acoustical and optical measurements to simulate fault interactions and mechanical coupling within fault systems. The experimental results manifest that three distinct episodes of derived faults were observed during the interaction of pre-existing faults. Firstly, a group of derived faults extends from the ends of the overlapping area, conjugating with the pre-existing en échelon faults. Secondly, the fault consisting of a series of secondary fractures propagates from the ends of the overlapping area towards the interior, leading to a complete destruction of the overlapping area. Thirdly, another group of faults extends from the ends of the overlapping area, forming a rhombic region in conjunction with the two pre-existing faults. Furthermore, the analysis of the strike-slip rate distribution along two en échelon faults showed significant heterogeneity. Specifically, the segments with relatively low strike-slip rate were inferred to be locked zones, which are likely to act as nucleation points for future emergent deformation events. These simulation results contributed to understanding the issues such as the mechanical coupling between Garlock and San Andreas fault systems, the linkage fault development in the branching zones of the North Anatolian Fault Zone, and the kinematic intersection geometry between the Danghenan Shan and Altyn Tagh faults.
走滑断层挤压叠合区作为一个强烈的变形区,对断层扩展、地震活动以及油气藏的形成和分布有着至关重要的影响。因此,加强对细观变形机理的理解,为更好地理解宏观变形奠定基础,是本研究的核心问题。结合声学和光学测量,进行了压缩en - cheon断层模型实验,模拟了断层相互作用和断层系统内的力学耦合。实验结果表明,在原有断层的相互作用过程中,观察到三次不同的派生断层。首先,一组衍生断层从重叠区域的末端延伸出来,与已有的en - samchelon断层相结合。其次,由一系列次生裂缝组成的断层从叠置区末端向内部扩展,导致叠置区完全破坏。第三,另一组断裂从叠置区末端向外延伸,与原有的两条断裂形成菱形区域。此外,沿两个en - samacheon断层的走滑速率分布分析显示出明显的非均匀性。具体而言,走滑速率相对较低的段被推断为锁定带,可能成为未来紧急变形事件的成核点。这些模拟结果有助于理解Garlock和San Andreas断裂系统之间的力学耦合、北安那托利亚断裂带分支带的联动断裂发育以及砀河南山和阿尔金塔格断裂之间的运动学相交几何等问题。
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引用次数: 0
Structural and stratigraphic control on fluid flow in the Mt. Conero anticline, Italy: An analog for offshore resource reservoirs in fold-and-thrust belts 意大利Conero山背斜流体流动的构造和地层控制:对褶皱冲断带海上资源储层的模拟
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-10 DOI: 10.1016/j.jsg.2025.105502
Luca Smeraglia , Luca Aldega , Stefano M. Bernasconi , Andrea Billi , Sabina Bigi , Eduardo di Marcantonio , Andrea Fiorini , Andrew Kylander-Clark , Eugenio Carminati
We investigate the structural control on paleofluid flow in the Mt. Conero anticline, Italy, located in the frontal part of the Apennines fold-and-thrust belt. This anticline can be considered as an exhumed analog for buried anticlines in the Adriatic offshore, currently exploited for hydrocarbons and potential geothermal reservoirs or CO2 storage sites in the future. By integrating field structural analyses, stable and clumped isotope geochemistry of carbonates, and U-Pb geochronology, we demonstrate that the structural evolution of the Mt. Conero anticline in a carbonate-siliciclastic succession is marked by: (1) pre-orogenic normal faulting and veining during foreland flexure, (2) layer-parallel shortening during early contraction, with the development of en-echelon bed-perpendicular conjugate veins and stylolites, (3) syn-folding thrusting and strike-slip faulting, and (4) transtensional faulting during fold exhumation and extensional collapse. Fluid circulation took place in a closed system, predominantly involving formation water, such as marine pore water trapped during diagenesis. Effective sealing by clay-rich formations overlying the fractured, permeable carbonates, coupled with low displacement strike-slip faults and thrusts, prevented the ingress of meteoric fluids and/or the upward migration of deep (hydrothermal) fluids. Limited mixing between formation and meteoric waters in a semi-closed system was observed during fold exhumation and extensional collapse. Our results show that folds in the frontal part of offshore fold-and-thrust belts are likely to retain fluids trapped during diagenesis due to the preservation of sealing layers. This suggests that such anticlines can preserve hydrocarbon reservoirs and are excellent candidates for CO2 storage due to their low leakage potential, offering also good storage capacity for geothermal fluids. These results may represent a benchmark for offshore anticlines in the frontal part of other offshore fold-and-thrust belts, particularly those with carbonate anticlines overlain by clay-rich sealing layers.
本文研究了位于亚平宁褶皱冲断带前缘的意大利Conero山背斜古流体流动的构造控制。这个背斜可以被认为是亚得里亚海近海埋藏背斜的一个被挖掘出来的模拟物,目前正在开发碳氢化合物和潜在的地热储层或未来的二氧化碳储存场所。综合野外构造分析、碳酸盐岩稳定和块状同位素地球化学、U-Pb年代学等资料,认为Conero山背斜的碳酸—硅屑演替过程具有以下特征:(1)前陆弯曲期的造山前正断裂和脉化作用;(2)收缩早期的层平行缩短作用,形成了成列的垂直层状共轭脉和柱面岩;(3)同褶皱逆冲和走滑断裂作用;(4)褶皱掘出和伸展崩塌期的张拉断裂作用。流体循环发生在一个封闭的系统中,主要涉及地层水,如成岩过程中圈闭的海相孔隙水。裂缝性、渗透性碳酸盐岩上覆的富粘土地层有效封闭,再加上低位移走滑断层和逆冲断层,阻止了大气流体的进入和/或深部(热液)流体的向上运移。在褶皱发掘和伸展崩塌过程中,观测到半封闭系统中地层与大气水的有限混合。研究结果表明,在近海褶皱冲断带前缘褶皱处,由于密封层的保存,可能会保留成岩过程中圈闭的流体。这表明,此类背斜具有保护油气藏的作用,由于其低泄漏潜力,是CO2储存的绝佳候选者,也为地热流体提供了良好的储存能力。这些结果可以为其他海上褶皱冲断带前缘的海上背斜,特别是覆有富粘土封层的碳酸盐岩背斜提供参考。
{"title":"Structural and stratigraphic control on fluid flow in the Mt. Conero anticline, Italy: An analog for offshore resource reservoirs in fold-and-thrust belts","authors":"Luca Smeraglia ,&nbsp;Luca Aldega ,&nbsp;Stefano M. Bernasconi ,&nbsp;Andrea Billi ,&nbsp;Sabina Bigi ,&nbsp;Eduardo di Marcantonio ,&nbsp;Andrea Fiorini ,&nbsp;Andrew Kylander-Clark ,&nbsp;Eugenio Carminati","doi":"10.1016/j.jsg.2025.105502","DOIUrl":"10.1016/j.jsg.2025.105502","url":null,"abstract":"<div><div>We investigate the structural control on paleofluid flow in the Mt. Conero anticline, Italy, located in the frontal part of the Apennines fold-and-thrust belt. This anticline can be considered as an exhumed analog for buried anticlines in the Adriatic offshore, currently exploited for hydrocarbons and potential geothermal reservoirs or CO<sub>2</sub> storage sites in the future. By integrating field structural analyses, stable and clumped isotope geochemistry of carbonates, and U-Pb geochronology, we demonstrate that the structural evolution of the Mt. Conero anticline in a carbonate-siliciclastic succession is marked by: (1) pre-orogenic normal faulting and veining during foreland flexure, (2) layer-parallel shortening during early contraction, with the development of <em>en-echelon</em> bed-perpendicular conjugate veins and stylolites, (3) syn-folding thrusting and strike-slip faulting, and (4) transtensional faulting during fold exhumation and extensional collapse. Fluid circulation took place in a closed system, predominantly involving formation water, such as marine pore water trapped during diagenesis. Effective sealing by clay-rich formations overlying the fractured, permeable carbonates, coupled with low displacement strike-slip faults and thrusts, prevented the ingress of meteoric fluids and/or the upward migration of deep (hydrothermal) fluids. Limited mixing between formation and meteoric waters in a semi-closed system was observed during fold exhumation and extensional collapse. Our results show that folds in the frontal part of offshore fold-and-thrust belts are likely to retain fluids trapped during diagenesis due to the preservation of sealing layers. This suggests that such anticlines can preserve hydrocarbon reservoirs and are excellent candidates for CO<sub>2</sub> storage due to their low leakage potential, offering also good storage capacity for geothermal fluids. These results may represent a benchmark for offshore anticlines in the frontal part of other offshore fold-and-thrust belts, particularly those with carbonate anticlines overlain by clay-rich sealing layers.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"200 ","pages":"Article 105502"},"PeriodicalIF":2.6,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144687535","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
Microstructure and CPO evolution of dynamically recrystallized olivine during complex deformation conditions: a full-field numerical modeling approach 动态再结晶橄榄石在复杂变形条件下的微观结构和CPO演化:一种全场数值模拟方法
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-05 DOI: 10.1016/j.jsg.2025.105500
Yuanchao Yu , Albert Griera , Enrique Gomez-Rivas , Paul D. Bons , Daniel Garcia-Castellanos , Baoqin Hao , Ricardo A. Lebensohn , Cassandra Seltzer , Maria-Gema Llorens
The rheological properties of mantle rocks are strongly dependent on their crystallographic preferred orientation (CPO). Olivine CPO, defined by the orientation of seismically fast [100] axes parallel to flow direction, is also thought to be a dominant contributor to seismic anisotropy in the Earth's upper mantle. However, the amount of deformation needed to overprint a new CPO on a pre-existing fabric and the impact of the inherited CPOs on the transient microstructure evolution, remain unknown. This study employs a full-field numerical approach (VPFFT-ELLE) to explore the dynamic recrystallization and microstructural evolution of olivine polycrystalline aggregates under complex deformation conditions. We test four combinations of successive pure shear and simple shear boundary conditions. Findings indicate that inherited CPOs influence subsequent deformation in a manner dependent on the kinematic relationship between successive stages. In all cases, a minor strain increment (ε ∼0.3–0.6) is sufficient to erase the previous microstructure and CPO. However, when deformation conditions change dramatically (e.g., stretching direction changes orthogonally), the intensity of the new CPO developed is significantly lower and strain distribution are specially altered. During a transient strain stage, pre-existing microstructures undergo extensive reworking, especially when deformation conditions are changed dramatically, such as switching from simple shear to a pure shear condition with a parallel shortening direction relative to the stretching direction. We estimate the significance of these results in interpreting observations of seismic velocity anisotropy, concluding that P-wave seismic anisotropy is significantly and positively correlated with the evolution of olivine CPO with deformation history. This research underscores the transient nature of microstructural rearrangement in olivine aggregates and the necessity for caution in interpreting seismic anisotropy in regions with complex deformation histories, as inherited CPOs can influence current fabric development and induce deviation to the present deformation conditions.
地幔岩石的流变性能在很大程度上取决于它们的晶体优先取向。橄榄石CPO,由平行于流动方向的地震快轴方向定义[100],也被认为是地球上地幔地震各向异性的主要贡献者。然而,在已有织物上叠印新CPO所需的变形量以及继承的CPO对瞬态微观结构演变的影响仍然未知。本研究采用全场数值方法(VPFFT-ELLE)研究复杂变形条件下橄榄石多晶聚集体的动态再结晶和微观组织演化。我们测试了连续纯剪切和简单剪切边界条件的四种组合。研究结果表明,遗传的CPOs以依赖于连续阶段之间的运动学关系的方式影响随后的变形。在所有情况下,微小的应变增量(ε ~ 0.3-0.6)足以消除先前的微观结构和CPO。而当变形条件发生显著变化(如拉伸方向发生正交变化)时,新形成的CPO强度明显降低,应变分布发生特殊变化。在瞬态应变阶段,原有的微观组织经历了广泛的重构,特别是当变形条件发生巨大变化时,例如从简单剪切状态切换到纯剪切状态,相对于拉伸方向平行缩短方向。我们估计了这些结果对解释地震速度各向异性观测的意义,认为纵波地震各向异性与橄榄石CPO随变形历史的演化显著正相关。这项研究强调了橄榄石聚集体中微观结构重排的短暂性,以及在具有复杂变形历史的地区解释地震各向异性的必要性,因为继承的CPOs会影响当前的结构发育并导致对当前变形条件的偏离。
{"title":"Microstructure and CPO evolution of dynamically recrystallized olivine during complex deformation conditions: a full-field numerical modeling approach","authors":"Yuanchao Yu ,&nbsp;Albert Griera ,&nbsp;Enrique Gomez-Rivas ,&nbsp;Paul D. Bons ,&nbsp;Daniel Garcia-Castellanos ,&nbsp;Baoqin Hao ,&nbsp;Ricardo A. Lebensohn ,&nbsp;Cassandra Seltzer ,&nbsp;Maria-Gema Llorens","doi":"10.1016/j.jsg.2025.105500","DOIUrl":"10.1016/j.jsg.2025.105500","url":null,"abstract":"<div><div>The rheological properties of mantle rocks are strongly dependent on their crystallographic preferred orientation (CPO). Olivine CPO, defined by the orientation of seismically fast [100] axes parallel to flow direction, is also thought to be a dominant contributor to seismic anisotropy in the Earth's upper mantle. However, the amount of deformation needed to overprint a new CPO on a pre-existing fabric and the impact of the inherited CPOs on the transient microstructure evolution, remain unknown. This study employs a full-field numerical approach (VPFFT-ELLE) to explore the dynamic recrystallization and microstructural evolution of olivine polycrystalline aggregates under complex deformation conditions. We test four combinations of successive pure shear and simple shear boundary conditions. Findings indicate that inherited CPOs influence subsequent deformation in a manner dependent on the kinematic relationship between successive stages. In all cases, a minor strain increment (ε ∼0.3–0.6) is sufficient to erase the previous microstructure and CPO. However, when deformation conditions change dramatically (<em>e.g.</em>, stretching direction changes orthogonally), the intensity of the new CPO developed is significantly lower and strain distribution are specially altered. During a transient strain stage, pre-existing microstructures undergo extensive reworking, especially when deformation conditions are changed dramatically, such as switching from simple shear to a pure shear condition with a parallel shortening direction relative to the stretching direction. We estimate the significance of these results in interpreting observations of seismic velocity anisotropy, concluding that P-wave seismic anisotropy is significantly and positively correlated with the evolution of olivine CPO with deformation history. This research underscores the transient nature of microstructural rearrangement in olivine aggregates and the necessity for caution in interpreting seismic anisotropy in regions with complex deformation histories, as inherited CPOs can influence current fabric development and induce deviation to the present deformation conditions.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105500"},"PeriodicalIF":2.6,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144579243","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
Fine geometric structures and characteristics of present-day activity of the Tianshui–Baoji segment of the West Qinling Fault, northeastern margin of the Tibetan Plateau 青藏高原东北缘西秦岭断裂带天水-宝鸡段精细几何构造及现今活动特征
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-05 DOI: 10.1016/j.jsg.2025.105499
Ruihuan Su , Daoyang Yuan , Zhao Wu , Jinchao Yu , Yunsheng Yao , Hong Xie , Lijun Zhang , Yameng Wen , Hao Sun , Yanwen Chen , Hongqiang Li
Accurately delineating the fine geometric structures of active faults and assessing their present-day activity are of paramount importance for studying regional fault tectonics and evaluating seismic risk. The West Qinling Fault (WQLF) is situated in a critical zone where material from the Tibetan Plateau is extruded towards the northeast, and the fine geometric structures, kinematic characteristics, and present-day activity of its eastern segment (Tianshui–Baoji segment) can provide important insights into the mechanisms of structural transition at the termination of strike-slip faults and the mode of material expansion in the plateau. In this study, the spatial distribution of the Tianshui–Baoji segment and the characteristics of present-day activity are systematically investigated through detailed interpretations of high-resolution satellite images, digital elevation models (DEMs), unmanned aerial vehicle (UAV) images, geological and geomorphological field surveys, and isotopic dating techniques. The results indicate that the Tianshui–Baoji segment, which begins as a single fault, gradually splays into multiple branching faults towards the east. Both the main fault and these branches have remained active since the Late Pleistocene and even during the Holocene, thus warranting attention to the seismic risk potential in the eastern segment of the WQLF, particularly at its termination. Moreover, the splay of the Tianshui–Baoji segment has led to the gradual divergence of the fault activity of the component to the east, reducing the maximum magnitude of seismic events at the fault terminus and resulting in significant differences in the seismic recurrence intervals between the eastern segment and the central segments of the WQLF (Zhangxian segment, Gangu–Wushan segment).
准确圈定活动断裂的精细几何结构并评估其现今活动性,对于研究区域断裂构造和评价地震危险性具有重要意义。西秦岭断裂位于青藏高原物质向东北挤压的关键地带,其东段(天水—宝鸡段)精细的几何构造、运动特征和现今活动特征,为研究走滑断裂末端的构造转换机制和高原物质扩张模式提供了重要依据。本文通过高分辨率卫星图像、数字高程模型(dem)、无人机(UAV)图像的详细解译、地质地貌野外调查和同位素测年技术,系统研究了天水-宝鸡段的空间分布和现今活动特征。结果表明,天水-宝鸡段以单条断裂开始,向东逐渐形成多条分支断裂。自晚更新世甚至全新世以来,主断层和这些分支都保持活跃,因此值得关注西qlf东段,特别是其末端的地震风险。此外,天水-宝鸡段的伸展导致该分量的断层活动向东逐渐分化,使断层末端地震事件的最大震级减小,导致WQLF东部段与中部段(张县段、甘谷-巫山段)的地震重现间隔存在显著差异。
{"title":"Fine geometric structures and characteristics of present-day activity of the Tianshui–Baoji segment of the West Qinling Fault, northeastern margin of the Tibetan Plateau","authors":"Ruihuan Su ,&nbsp;Daoyang Yuan ,&nbsp;Zhao Wu ,&nbsp;Jinchao Yu ,&nbsp;Yunsheng Yao ,&nbsp;Hong Xie ,&nbsp;Lijun Zhang ,&nbsp;Yameng Wen ,&nbsp;Hao Sun ,&nbsp;Yanwen Chen ,&nbsp;Hongqiang Li","doi":"10.1016/j.jsg.2025.105499","DOIUrl":"10.1016/j.jsg.2025.105499","url":null,"abstract":"<div><div>Accurately delineating the fine geometric structures of active faults and assessing their present-day activity are of paramount importance for studying regional fault tectonics and evaluating seismic risk. The West Qinling Fault (WQLF) is situated in a critical zone where material from the Tibetan Plateau is extruded towards the northeast, and the fine geometric structures, kinematic characteristics, and present-day activity of its eastern segment (Tianshui–Baoji segment) can provide important insights into the mechanisms of structural transition at the termination of strike-slip faults and the mode of material expansion in the plateau. In this study, the spatial distribution of the Tianshui–Baoji segment and the characteristics of present-day activity are systematically investigated through detailed interpretations of high-resolution satellite images, digital elevation models (DEMs), unmanned aerial vehicle (UAV) images, geological and geomorphological field surveys, and isotopic dating techniques. The results indicate that the Tianshui–Baoji segment, which begins as a single fault, gradually splays into multiple branching faults towards the east. Both the main fault and these branches have remained active since the Late Pleistocene and even during the Holocene, thus warranting attention to the seismic risk potential in the eastern segment of the WQLF, particularly at its termination. Moreover, the splay of the Tianshui–Baoji segment has led to the gradual divergence of the fault activity of the component to the east, reducing the maximum magnitude of seismic events at the fault terminus and resulting in significant differences in the seismic recurrence intervals between the eastern segment and the central segments of the WQLF (Zhangxian segment, Gangu–Wushan segment).</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105499"},"PeriodicalIF":2.6,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144596818","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
Numerical simulation of fault damage zones and their impact on the structural evolution of Pre-salt carbonate reservoirs 断裂破坏带数值模拟及其对盐下碳酸盐岩储层构造演化的影响
IF 2.6 2区 地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY Pub Date : 2025-07-03 DOI: 10.1016/j.jsg.2025.105498
Pedro A.L.P. Firme , Francisco C. Dias , Roberto Quevedo , Deane Roehl , Bruno R.B.M. Carvalho , Jorge A.B. Souza
Our work employs numerical models to investigate the impacts of the early and late faulting stages on the development of fault damage zones (DZs) in conditions analogous to Pre-salt. DZs exhibit contrasts in geomechanical and petrophysical properties compared to the surrounding host rock. Numerous studies have explored the characterization of DZs by modeling fault formation processes. Most Brazilian Pre-salt reservoirs have early faults associated with depositional tectonic development overprinted by late faults that formed at greater depths. Both faulting events can markedly affect the present-day DZ widths. Previous studies have investigated the development of DZ during the early faulting stage. However, the late faulting stage and its impact on DZs have not been explored. Thus, our goal is to investigate the impact of both the early and late faulting stages in the structural evolution of DZs in carbonate rocks through geomechanical analyses. The results indicate that burial during the late faulting stage increases confinement and enhances the integrity of the rock far from the DZ, while the DZs triggered during the early fault formation remains unchanged. In addition, for the late faulting stage, we assess the role of fault roughness on the DZ by adopting friction coefficients to represent smooth or rough surfaces. The results show that rough fault surfaces contribute to lower fault displacements.
我们的工作采用数值模型来研究在类似盐下条件下,早期和晚期断层阶段对断层破坏带(DZs)发育的影响。与周围的寄主岩石相比,DZs在地质力学和岩石物理性质上表现出明显的差异。许多研究通过对断层形成过程的建模来探索DZs的特征。大多数巴西盐下储层都有与沉积构造发育相关的早期断层,这些断层被更深的晚期断层所覆盖。这两个断裂事件对现今的DZ宽度都有显著影响。前人的研究主要集中在早断陷阶段。然而,断裂晚期及其对DZs的影响尚未深入研究。因此,我们的目标是通过地质力学分析来研究早、晚断裂阶段对碳酸盐岩DZs构造演化的影响。研究结果表明,断裂晚期的埋藏作用增加了远离断裂带的封闭性,提高了岩石的完整性,而断裂早期形成的断裂带则保持不变。此外,在断层后期,我们采用摩擦系数来表示光滑或粗糙的表面,以评估断层粗糙度对DZ的作用。结果表明,粗糙的断层面有助于减小断层位移。
{"title":"Numerical simulation of fault damage zones and their impact on the structural evolution of Pre-salt carbonate reservoirs","authors":"Pedro A.L.P. Firme ,&nbsp;Francisco C. Dias ,&nbsp;Roberto Quevedo ,&nbsp;Deane Roehl ,&nbsp;Bruno R.B.M. Carvalho ,&nbsp;Jorge A.B. Souza","doi":"10.1016/j.jsg.2025.105498","DOIUrl":"10.1016/j.jsg.2025.105498","url":null,"abstract":"<div><div>Our work employs numerical models to investigate the impacts of the early and late faulting stages on the development of fault damage zones (DZs) in conditions analogous to Pre-salt. DZs exhibit contrasts in geomechanical and petrophysical properties compared to the surrounding host rock. Numerous studies have explored the characterization of DZs by modeling fault formation processes. Most Brazilian Pre-salt reservoirs have early faults associated with depositional tectonic development overprinted by late faults that formed at greater depths. Both faulting events can markedly affect the present-day DZ widths. Previous studies have investigated the development of DZ during the early faulting stage. However, the late faulting stage and its impact on DZs have not been explored. Thus, our goal is to investigate the impact of both the early and late faulting stages in the structural evolution of DZs in carbonate rocks through geomechanical analyses. The results indicate that burial during the late faulting stage increases confinement and enhances the integrity of the rock far from the DZ, while the DZs triggered during the early fault formation remains unchanged. In addition, for the late faulting stage, we assess the role of fault roughness on the DZ by adopting friction coefficients to represent smooth or rough surfaces. The results show that rough fault surfaces contribute to lower fault displacements.</div></div>","PeriodicalId":50035,"journal":{"name":"Journal of Structural Geology","volume":"199 ","pages":"Article 105498"},"PeriodicalIF":2.6,"publicationDate":"2025-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144633298","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
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Journal of Structural Geology
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