Tectonophysics最新文献

The improved Moho depth imaging in the Arabia-Eurasia collision zone: A machine learning approach integrating seismic observations and satellite gravity data 阿拉伯-欧亚大陆碰撞带莫霍深成像的改进：整合地震观测和卫星重力数据的机器学习方法

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-11-07 DOI: 10.1016/j.tecto.2024.230553

Vahid Teknik

The Arabia-Eurasia convergences created one of the earth's topographic highs on the Central Tethys collisional belt. Despite the area's geological significance, a comprehensive and high-resolution map of Moho depth has been lacking due to the sparse and uneven distribution of seismically constrained Moho depth data. This study addresses this deficiency by compiling an extensive dataset of nearly 2500 seismically measured Moho depth points from 68 seismic local scale studies, resulting in the development of an updated seismically constrained Moho depth model (S-Moho) at a 0.5° × 0.5° spatial resolution. Despite some coverage gaps in the remote areas, the S-Moho model offers a more detailed view than previously available. To further improve the coverage of the S-Moho depth model, an incremental data-driven approach was employed. Initially, a gravity-based regression Moho depth model (SB-Moho) was developed by correlating S-Moho depth points with corresponding Bouguer anomalies. However, its accuracy was constrained by unaccounted isostatic and non-isostatic components. To address this limitation, a sliding window approach was applied to derive a windowed SB-Moho model (WSB-Moho). Additionally, a machine learning-based Moho model (ML-Moho) was developed using seismic Moho depth points along with 11 predictive variables. Both WSB-Moho and ML-Moho models demonstrated consistent and smooth Moho depth variations. The Zagros region reveals a prominent NW-SE oriented Moho depression (45-60 km thick), attributed to the underthrusting of the Arabian Plate beneath the Iranian Plateau. The models suggest that crustal thickening extends beyond tectonic boundaries, likely influenced by the dip of suture zones. In contrast, the crustal thickening in eastern Anatolia, northwest of the Zagros, is less pronounced, indicating different geodynamic processes. Strike-slip faulting and magmatic activity in this area contribute to a broader distribution of deformation compared to the more localized crustal thickening in the Zagros. In southeastern Zagros, strike-slip faults in central Iran accommodate much of the northward convergence of the Arabian Plate, thereby limiting the extent of crustal thickening.

阿拉伯-欧亚大陆的汇聚形成了特提斯碰撞带中部的地形高地之一。尽管该地区具有重要的地质意义，但由于地震约束莫霍深度数据稀少且分布不均，一直缺乏全面、高分辨率的莫霍深度图。本研究针对这一不足，汇编了来自 68 个地震局部尺度研究的近 2500 个地震测量莫霍深度点的广泛数据集，从而建立了 0.5° × 0.5° 空间分辨率的最新地震约束莫霍深度模型（S-Moho）。尽管在偏远地区存在一些覆盖缺口，但 S-Moho 模型提供了比以前更详细的视图。为了进一步提高 S-Moho 深度模型的覆盖范围，采用了数据驱动的渐进方法。最初，通过将 S-Moho 深度点与相应的布格尔异常点相关联，建立了基于重力的回归莫霍深度模型（SB-Moho）。然而，其准确性受到了等静力和非等静力成分的制约。为解决这一局限性，采用了滑动窗口法，得出了一个窗口 SB-Moho 模型（WSB-Moho）。此外，利用地震莫霍深度点和 11 个预测变量，开发了基于机器学习的莫霍模型（ML-Moho）。WSB-Moho 和 ML-Moho 模型都显示出一致而平滑的莫霍深度变化。扎格罗斯地区显示出明显的西北-东南走向莫霍凹陷（厚 45-60 公里），这是由于伊朗高原下的阿拉伯板块发生了下推作用。这些模型表明，地壳增厚延伸到了构造边界之外，很可能受到缝合带倾角的影响。相比之下，扎格罗斯山脉西北部安纳托利亚东部的地壳增厚没有那么明显，这表明了不同的地球动力过程。与扎格罗斯地区较为局部的地壳增厚相比，该地区的走向滑动断层和岩浆活动导致了更广泛的变形分布。在扎格罗斯东南部，伊朗中部的走向滑动断层容纳了阿拉伯板块向北辐合的大部分，从而限制了地壳增厚的范围。

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引用次数: 0

Crustal silica content of East China: A seismological perspective and its significance 华东地壳硅含量：地震学视角及其意义

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-11-06 DOI: 10.1016/j.tecto.2024.230554

Ziwen Bao , Xiaohui Yuan , Wei Li , Yuan Gao , Xianliang Huang , Dequan Hong , Hongyu Ni

East China has experienced multiple periods of tectonic movements, which have contributed to the composition and rheological properties of its present crust. Estimating the composition of the crust is crucial for understanding the tectonic processes. Based on the teleseismic receiver functions with data from the National Seismic Network of China, we applied the H-κ-c method to obtain the crustal bulk V_P/V_S ratio and to constrain the SiO₂ content in the crust. We estimated the SiO₂ content to range from 50.89 wt% to 73.51 wt%, with an average value of 65.87 wt%, indicating a predominant felsic composition of the East China's crust. Our study suggests that the North-South Gravity Lineament (NSGL) is an approximate delimitator of the felsic and mafic crust in East China, hinting at a widespread deficiency of mafic lower crust in the east of the NSGL. The mafic crust is extensively distributed in the Taihang orogenic region (TSR) and WuLingshan gravity gradient belts (WLG), particularly in the Datong volcanic area, which manifests the mantle materials intraplating. The scatteredly distributed mafic crust at the east of the NSGL is mainly concentrated in the southeast coast of China and in the intersection region of the Tanlu Fault (TLF) and Sulu region. In Sulu region, the TLF may primarily provide a channel for the thermal intrusion from the underlying mantle lithosphere, which has increased the mafic content. The Pacific/Philippine Sea plate subduction has triggered a significant amount of crust-mantle material exchange below southeast China that resulted in a high degree of mafic crustal composition.

华东地区经历了多个时期的构造运动，形成了现在的地壳成分和流变特性。估算地壳的组成对于了解构造过程至关重要。基于中国国家地震台网数据的远震接收函数，我们应用H-κ-c方法获得了地壳体积VP/VS比，并对地壳中的SiO2含量进行了约束。我们估计地壳中SiO2的含量范围为50.89 wt% 至 73.51 wt%，平均值为65.87 wt%，表明华东地壳的主要成分为熔岩。我们的研究表明，南北重力线是华东地区长岩地壳和黑云母地壳的近似分界线，暗示南北重力线以东地区普遍缺乏黑云母下地壳。黑云母地壳广泛分布于太行造山带和武陵山重力梯度带，特别是大同火山区，表现为地幔物质内镀。国家南极重力梯度带东侧零星分布的黑云母地壳主要集中在中国东南沿海和郯庐断裂（TLF）与苏禄地区的交汇区。在苏禄地区，郯庐断层可能主要为来自下伏地幔岩石圈的热侵入提供了通道，从而增加了岩浆岩的含量。太平洋/菲律宾海板块俯冲在中国东南部下方引发了大量的地壳-地幔物质交换，造成了高度的岩浆地壳成分。

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引用次数: 0

Geophysical characterization of an alkaline‑carbonatite complex using gravity and magnetic methods at Magnet Cove, Arkansas, USA 在美国阿肯色州磁湾使用重力和磁力方法确定碱性碳酸盐岩复合体的地球物理特征

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-11-02 DOI: 10.1016/j.tecto.2024.230545

Chelsea M. Amaral , Andrew P. Lamb , Gregory Dumond

The Magnet Cove alkaline‑carbonatite complex (MCC), located in the Ouachita Mountains of south-central Arkansas in the United States, hosts an extensive variety of rare rock types and critical mineral resources with physical properties (density and magnetization) that contrast significantly with the sedimentary rocks into which they have intruded. Newly acquired ground-based gravity and magnetic data were used to develop two-dimensional and three-dimensional geophysical models of the Cretaceous-aged Magnet Cove intrusive complex. The models reveal that the MCC: (1) widens out at middle crustal depths to as much 22 km across, and may reach a depth of 20 km; (2) has a total volume (exposed and subsurface) that may be over 800 km³; (3) is likely connected at depth to other intrusions in the Arkansas alkaline province; and (4) has a geometry that is aligned with pre-existing structures such as the Reelfoot rift and the Ouachita orogenic belt, some of which were likely structurally controlled by the Precambrian crystalline basement and the continent-ocean transition zone buried beneath the Ouachita orogen. For the first time, the magnetic models of the MCC account for the presence of strong remanent magnetization. This results in a geophysical workflow necessary to accurately interpret magnetic anomalies over the much larger Arkansas alkaline province, its geologic and structural framework, and critical mineral potential.

磁湾碱性碳酸盐岩复合体（MCC）位于美国阿肯色州中南部的瓦奇塔山脉，拥有种类繁多的稀有岩石类型和重要的矿产资源，其物理性质（密度和磁化率）与其侵入的沉积岩形成鲜明对比。新获得的地基重力和磁力数据被用于开发白垩纪时期磁湾侵入复合体的二维和三维地球物理模型。模型显示，磁性海湾侵入体(1) 在中地壳深度扩大到 22 千米宽，深度可能达到 20 千米；(2) 总体积（裸露和地下）可能超过 800 千立方米；(3) 在深度上可能与阿肯色碱性矿带的其他侵入体相连；(4) 其几何形状与里尔富特裂谷和瓦奇塔造山带等先前存在的构造相一致，其中一些构造可能受前寒武纪结晶基底和埋藏在瓦奇塔造山带下的大陆-海洋过渡带的结构控制。MCC 的磁性模型首次考虑到了强剩磁的存在。这就产生了一个地球物理工作流程，它是准确解释更大的阿肯色碱性省的磁异常、其地质和结构框架以及关键矿产潜力所必需的。

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引用次数: 0

Subsurface basement structures of the Usangu basin, East African rift system, with implications for basin structural configuration and hydrocarbon potential 东非裂谷系统乌桑古盆地的地下基底结构及其对盆地结构构造和油气潜力的影响

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-26 DOI: 10.1016/j.tecto.2024.230544

Edward Pastory , Gabriel D. Mulibo , Isaac M. Marobhe

The Usangu basin is a rift basin developed along the Eastern arm of the East African rift system trending in the NE-SW direction. Although the general structures of the basin have been well studied, the structural configuration of the basin and the spatial and depth variations of sediment thickness are still not well known. This study investigates the structures related basement configuration and the variation of sediment thickness within the basin using the Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM), aeromagnetic and gravity data. Results from DEM data indicate a few lineaments on the basin flanks representing the Usangu and Chimala border faults with no structures in the central part of the basin. The aeromagnetic and gravity data highlight three sets of normal and strike-slip faults, most of which trend NE-SW and others NNE-SSW, while a few trends WNW-ESE or NW-SE. Structures on the southwest of the basin reveal complex patterns attributed to the concentration of important tectonic and seismic activities in the study area. The Euler deconvolution and gravity models used to calculate the depth to the basement show that the basement is shallow in the north and south to southwest, and the basin deepens in the northeastern, northwestern and western parts. The findings also reveal that the basin has two grabens, troughs, depression and intrabasinal basement trending in the same direction as the basin configuration. The general thickness of sediments filling the basin ranges from 3 to 4.5 km, with the maximum accumulation of sediments reaching up to 4.8 km in the two depocenters at the south and southwest of the basin. The depth range of the sediments obtained implies that the basin has potential for hydrocarbon exploration with the possibility of natural gas occurrence.

乌桑古盆地是一个裂谷盆地，沿东非裂谷系统东臂发育，呈东北-西南走向。虽然对该盆地的总体结构已有深入研究，但对盆地的结构构造以及沉积厚度的空间和深度变化仍不甚了解。本研究利用航天飞机雷达地形图任务（SRTM）数字高程模型（DEM）、航空磁力和重力数据，对盆地内与基底构造相关的结构和沉积厚度变化进行了研究。数字高程模型数据结果表明，盆地两侧有几条代表乌桑古断层和奇马拉边界断层的线状构造，盆地中部没有构造。气磁和重力数据突出显示了三组正断层和走向滑动断层，其中大部分呈东北-西南走向，其他呈东北-西南走向，少数呈西北-东南走向或西北-东南走向。盆地西南部的构造显示出复杂的模式，这归因于研究区域集中了重要的构造和地震活动。用于计算基底深度的欧拉解卷积和重力模型显示，基底在北部和南部至西南部较浅，盆地在东北部、西北部和西部加深。研究结果还显示，盆地内有两个地堑、地槽、洼地和盆地内基底，其走向与盆地构造一致。充填盆地的沉积物一般厚度为 3 至 4.5 千米，在盆地南部和西南部的两个沉积中心，沉积物的最大堆积厚度达 4.8 千米。所获得的沉积物深度范围意味着该盆地具有油气勘探的潜力，有可能出现天然气。

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引用次数: 0

When did the Dead Sea fault become a transform? 死海断层是何时形成的？

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-25 DOI: 10.1016/j.tecto.2024.230543

Amit Segev , Nadav Wetzler , Uri Schattner

This study re-evaluates the ∼20 Myr development of the Dead Sea Fault System (DSFS) and its tectonic definition as a transform plate boundary. The DSFS conveys sinistral displacement between the Arabian-Sinai plates: ∼105 km along its ∼400 km-long southern segment (Gulf of Aqaba-Eilat to the Hula basin); ∼90 km and 4–16 km along the central and northern segments (∼190 km long each, across Lebanon, western Syria, and southern Turkey). A review of previous studies, combined with new seismological data analysis, associates the northward displacement decline with obstacles along the DSFS propagation path. During the Miocene, DSFS propagated up to the NW-trending Irbid rift (1st obstacle) and splayed NW towards the Mediterranean and NE along the Late Cretaceous Palmyra fold-thrust belt (2nd obstacle). Its reactivation uplifted the Hermon and the Anti-Lebanon mountain ranges. Northward DSFS propagation into the cold and rigid Aleppo plateau lithosphere (3rd obstacle) was stalled until the early Pliocene (∼5 Ma), when volcanism and ongoing regional tectonic forcing enabled the DSFS to shift to the Yammouneh fault and rupture through the Missyaf-Ghab branch farther north (central and northern segments, respectively). During the Pleistocene-recent, connection of the DSFS with the ophiolite belt and East Anatolian Fault System (EAFS) along the Bitlis suture zone (4th obstacle) has not yet been established. Seismological data show a clear separation between the EAFS and the DSFS, while seismicity is scattered across the Aleppo plateau and the central and northern DSFS segments. In contrast, seismicity is localized along the southern DSFS segment. Our findings suggest that, at present, the DSFS has still not made a structural, seismologic, and tectonic connection with the EAFS. Hence, we redefine the DSFS as a pre-transform and suggest its interaction with the EAFS is a world-class example of a fault-fault-fault triple junction in the making.

本研究重新评估了死海断裂系统（DSFS）20∼Myr的发展及其作为板块转换边界的构造定义。死海断裂系统传达了阿拉伯-西奈板块之间的正弦位移：沿其长达 400 公里的南段（亚喀巴湾-埃拉特到胡拉盆地）有 105 公里；沿中部和北部（各长 190 公里，横跨黎巴嫩、叙利亚西部和土耳其南部）有 90 公里和 4-16 公里。对以往研究的回顾，结合新的地震数据分析，将向北位移的下降与 DSFS 传播路径上的障碍联系起来。在中新世时期，DSFS 传播到西北走向的伊尔比德裂谷（第一道障碍），并向西北向地中海延伸，沿晚白垩世帕尔米拉褶皱推覆带向东北延伸（第二道障碍）。它的重新激活抬升了赫尔蒙和反黎巴嫩山脉。直到上新世早期（∼5 Ma），火山活动和持续的区域构造作用使得DSFS转移到Yammouneh断层，并在更北的Missyaf-Ghab分支断裂（分别为中部和北部地段）。在更新世晚期，DSFS 与蛇绿混杂岩带和东安纳托利亚断层系统（East Anatolian Fault System，EAFS）沿比特利斯缝合带（第 4 个障碍）的联系尚未确定。地震学数据显示，东安纳托利亚断裂带与东安纳托利亚断裂系统之间有明显的分隔，而地震活动则分散在阿勒颇高原以及东安纳托利亚断裂系统的中部和北部地段。相比之下，地震活动则集中在 DSFS 南部地段。我们的研究结果表明，目前，DSFS 仍未与 EAFS 在结构、地震学和构造上建立联系。因此，我们将 DSFS 重新定义为转型前，并认为其与 EAFS 的相互作用是正在形成的断层-断层-断层三重交界的世界级范例。

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引用次数: 0

Seismic lithospheric model across Ukrainian Shield from the Carpathians to the Dnieper-Donets Basin and its tectonic interpretation 从喀尔巴阡山脉到第聂伯河-顿涅茨盆地的整个乌克兰地盾的地震岩石圈模型及其构造解释

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-24 DOI: 10.1016/j.tecto.2024.230540

V. Starostenko , T. Janik , A. Murovskaya , W. Czuba , P. Środa , T. Yegorova , P. Aleksandrowski , O. Verpakhovska , K. Kolomiyets , D. Lysynchuk , T. Amashukeli , T. Burakhovych , D. Wójcik , V. Omelchenko , O. Legostaeva , D. Gryn , S. Chulkov

The SW-NE directed wide-angle reflection-refraction (WARR) SHIELD’21 profile crosses entire width of Ukraine. It targeted the structure of the crust and uppermost mantle in the southwestern part of the East European Craton (EEC), between Carpathians and Voronezh Massif, across Ukrainian Shield and Dnieper-Donets Basin. The ∼660 km-long profile is an extension of the RomUkrSeis profile in Romania and Ukraine. SHIELD’21 experiment, using TEXAN and DATA-CUBE short-period seismic stations, provided high-quality seismic sections from 10 shot points. This allowed construction of a ray-tracing P-wave velocity model, supplemented by V_p/V_s ratio, for the upper part of the lithosphere in the Sarmatia segment of the EEC and constraining geodynamic processes that led to the formation of the Ukrainian Shield and its margins since Archean times.

The velocity distribution in the crystalline crust indicates a rather uniform structure, with velocity changing from 6.0 km/s near the surface to 6.8 km/s at the Moho. The entire section shows the lack of a high-velocity lower crust (V_p > 6.8 km/s), presumably resulting from delamination of the primitive mafic lower crust during early evolution of a juvenile continental crust. The seismic boundaries in the upper crust reflect a Paleoproterozoic extensional detachment system below the SW flank of Dnieper-Donets rift basin, initiated in the Devonian. At larger depths, a wide dome of the lower crust with velocities of 6.5–6.8 km/s in the SW-central segment of the profile, probably represents an enormous Palaeoproterozoic(?) granitoid batholith. In the southwesternmost part of the profile, the crystalline crust shows exclusively low velocities. The prominent Moho is undulating and varies in depth between 32 and 50 km. It is underlain by high-velocity bodies (V_p: 8.36–8.40 km/s), against the background of 8.16–8.25 km/s in the mantle. The velocity model corresponds with the anomalies of potential fields and zones of high electric conductivity.

西南-东北定向广角反射-折射（WARR）SHIELD'21剖面横跨乌克兰全境。它的目标是东欧克拉通（EEC）西南部，喀尔巴阡山脉和沃罗涅日山丘之间，横跨乌克兰地盾和第聂伯河-顿涅茨盆地的地壳和最上层地幔的结构。该剖面长达 660 公里，是 RomUkrSeis 剖面在罗马尼亚和乌克兰的延伸。SHIELD'21 试验使用 TEXAN 和 DATA-CUBE 短周期地震台，提供了 10 个测点的高质量地震剖面。这就为欧洲经济共同体萨尔马特区段岩石圈上部构建了一个射线追踪 P 波速度模型，并辅以 Vp/Vs 比值，从而对自 Archean 时代以来导致乌克兰地盾及其边缘形成的地球动力过程进行了约束。整个剖面显示缺乏高速的下地壳（Vp > 6.8 km/s），这可能是在幼年大陆地壳早期演化过程中原始岩浆下地壳分层的结果。上地壳的地震边界反映了第聂伯河-顿涅茨河断裂盆地西南侧下方的古新生代延伸剥离系统，该系统始于泥盆纪。在剖面的中西南部，下地壳有一个宽大的圆顶，其速度为 6.5-6.8 公里/秒，这可能是一块巨大的古新生代（？）花岗岩熔岩。在剖面的最西南部，结晶地壳只显示出较低的速度。突出的莫霍面起伏不定，深度在 32 至 50 千米之间。其下是高速岩体（Vp：8.36-8.40 千米/秒），而地幔的背景速度为 8.16-8.25 千米/秒。该速度模型与电位场异常和高电导率区相吻合。

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引用次数: 0

Present-day incipient fault coalescence at a relay zone (Jiloca extensional basin, Spain): Evidence from instrumental seismicity 中继带（西班牙吉洛卡伸展盆地）现今萌生的断层凝聚：来自仪器地震的证据

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-22 DOI: 10.1016/j.tecto.2024.230541

Alba Peiro , Lucía Lozano , Luis E. Arlegui , Juan V. Cantavella , Sandra Ruiz-Barajas , José L. Simón

The relay zones between NW-SE to NNW-SSE striking faults of the Jiloca graben (Iberian Chain) mostly show distributed along-strike fault and fracture patterns. The latter are chiefly controlled by the Late Pliocene-Quaternary regional stress field, and secondarily respond to local controls from inherited structures. Such fracture patterns contrast with the classical models of transverse connecting faults controlled by relay kinematics. North of the Concud fault trace, at the relay zone with the Sierra Palomera fault, an unusually high seismic activity has been noticed since 2014, with magnitudes up to M = 3.5. Upgrading of the National Seismic Network allowed obtaining such new detailed records, while the installation of a new seismometer by the IGN within the study area has improved the reliability of focal depth data since 2017. A high-precision absolute relocation of seismicity from 01/01/2000 to 30/05/2022 has been carried out. The results show that (i) the epicentres are significantly clustered along a nearly N-S trending band, and (ii) the focal depths range from 0 to 14 km, in good agreement with the thickness of the brittle crust. This 3D spatial distribution of seismicity is interpreted as a consequence of activation of either a single fault or a fault zone, nearly vertical and N-S striking. Such structural setting is consistent with the surficial fracture patterns observed at both map and outcrop scale: NNW-SSE and NNE-SSW oriented faults and fractures, orthogonal to the ENE-WSW to ESE-WNW regional σ₃ trajectories, together with NW-SE trending ones controlled by inherited contractive faults. The present-day seismic activity suggests that along-strike, incipient fault propagation at the relay zone between the Concud and Sierra Palomera faults is currently operating under the control of the remote stress field.

吉洛卡地堑（伊比利亚地链）西北-东南至西北-东南走向断层之间的中继带大多呈现分布式沿走向断层和断裂形态。后者主要受晚渐新世-第四纪区域应力场的控制，其次是受继承结构的局部控制。这种断裂模式与由中继运动学控制的横向连接断层的经典模式形成鲜明对比。Concud 断层以北，在与 Sierra Palomera 断层的中继区，自 2014 年以来，地震活动异常频繁，震级最高达 M = 3.5。国家地震台网的升级使我们得以获得这些新的详细记录，而 IGN 在研究区域内安装的新地震仪则提高了自 2017 年以来焦点深度数据的可靠性。对 2000 年 1 月 1 日至 2022 年 5 月 30 日的地震活动进行了高精度的绝对重新定位。结果表明：(i) 震中明显集中在近南北走向的带状区域；(ii) 震源深度在 0 至 14 千米之间，与脆性地壳的厚度十分吻合。这种地震的三维空间分布被解释为一个近乎垂直和 N-S 走向的单一断层或断层带被激活的结果。这种结构设置与在地图和露头尺度上观察到的表层断裂模式一致：NNW-SSE 和 NNE-SSW 走向的断层和断裂与 ENE-WSW 至 ESE-WNW 的区域 σ3 轨迹正交，同时还有由继承性收缩断层控制的 NW-SE 走向的断层和断裂。目前的地震活动表明，Concud 断层和 Sierra Palomera 断层之间中继带的沿走向、初生断层扩展目前正在远程应力场的控制下运行。

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引用次数: 0

Upper mantle shear velocity structure of the Cathaysia Block and surrounding areas: New insight into deep geodynamics 国泰岛地块及周边地区的上地幔剪切速度结构：对深部地球动力学的新认识

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-22 DOI: 10.1016/j.tecto.2024.230542

Yao Xu , Qingtian Lü , Dapeng Zhao , Jiayong Yan , Danian Shi , Yongqian Zhang , Shuai Ruan , Zhiwu Xu , Changxin Chen , Wenwen Zhang , Xu Wang

The Cathaysia Block (CAB) and its surrounding areas experienced intensive magmatism and mineralization in the Yanshanian period (ca. 200–90 Ma), but their mechanism and deep geodynamics are still debated. In addition, the origin and structures of the Hainan mantle plume are still unclear. To resolve these issues and investigate the large-scale lithospheric thinning and extension in the eastern South China Block, we determine a detailed 3-D S-wave velocity (Vs) model down to 700 km depth by collecting 24,190 S-wave teleseismic data recorded at 164 permanent stations and 125 portable stations deployed in the CAB and surrounding areas. Our results show that high-Vs anomalies exist separately in the study volume. Two high-Vs anomalies appear in the shallow upper mantle and the mantle transition zone, which may reflect the present thin lithosphere and the stagnant Paleo-Pacific slab, respectively. Two other high-Vs anomalies exist in the upper mantle, which may reflect the detached lithosphere and subducting slabs. In contrast, low-Vs anomalies appear widely beneath the CAB, which reflect a tilting magmatic conduit beneath the Wuyishan metallogenic belt (WYMB) and magmatic chambers beneath the Nanling metallogenic belt (NLMB). In addition, our results show that the Hainan plume has a double-layered appearance. Combining our tomographic results with previous multidisciplinary findings, we consider that (1) the subduction and rollback of the Paleo-Pacific Plate may have played different roles in the Yanshanian mineralization of the WYMB and the NLMB; (2) the double-layered appearance of the Hainan plume may be formed due to the influence of plume self-evolution dynamics and pre-existing deep structures; and (3) lithospheric delamination triggered by gravity instability may have occurred beneath the Xuefengshan Mountain in the late Mesozoic.

在燕山期（约200-90Ma），华夏地块（Cathaysia Block）及其周边地区经历了密集的岩浆活动和成矿作用，但其机制和深部地球动力学仍存在争议。此外，海南地幔羽流的起源和结构仍不清楚。为了解决这些问题并研究华南东部块体的大尺度岩石圈减薄和延伸，我们通过收集部署在CAB及周边地区的164个永久台站和125个便携式台站记录的24190个S波远震数据，确定了一个详细的三维S波速度（Vs）模型，其深度可达700千米。结果表明，研究区内分别存在高 Vs 异常。两个高 Vs 异常点出现在浅上地幔和地幔过渡带，可能分别反映了目前较薄的岩石圈和停滞的古太平洋板块。另外两个高 Vs 异常出现在上地幔，可能反映了脱离的岩石圈和俯冲板块。相反，低Vs异常广泛出现在CAB下方，反映了武夷山成矿带下方的倾斜岩浆导管和南岭成矿带下方的岩浆腔。此外，我们的研究结果表明，海南羽流具有双层外观。结合我们的层析成像结果和之前的多学科研究结果，我们认为：（1）古太平洋板块的俯冲和回滚可能在西洋大洋带和南岭成矿带的燕山期成矿过程中扮演了不同的角色；(2)海南羽流的双层外观可能是由于羽流自我演化动力学和原有深部构造的影响而形成的；(3)雪峰山下可能在中生代晚期发生过重力不稳定引发的岩石圈分层。

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引用次数: 0

Tectonomagmatic evolution of Pune – Nasik Deccan Dykes: Insights from structure and dimension scaling 普纳-纳西克德干堤坝的构造地貌演化：从结构和尺寸缩放中获得的启示

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-19 DOI: 10.1016/j.tecto.2024.230539

Ragini Kumari, Jyotirmoy Mallik, Garima Shukla

The Deccan Continental Flood Basalt of the Indian Peninsula is characterized by extensive basaltic eruptions ornamented with three spectacular distinct dyke swarms: the Pune – Nasik, Narmada – Tapi, and Western Coastal dyke swarms. Our study area is the Pune – Nasik dyke swarm, which has ∼465 mappable dykes. These dykes exhibit different orientations with a predominant trend of N101° and vary in length from less than 1 km to ∼64 km. These dykes are massively jointed and occasionally contain vesicles filled with secondary minerals like quartz and calcite. The host rock is weathered basalt of various older Deccan flows. In this study, we have calculated magmatic overpressures and magma chamber depths using the aspect ratios (length/thickness) of the dykes. The average estimated source depth is ∼13 km, based on an average Young's modulus for the host rock basalt (E_avg, 7.5 GPa). Additionally, we compared the inferred magma source depths of the Pune – Nasik, and Narmada-Tapi dyke swarms which include the Nandurbar – Dhule, and Pachmarhi dykes of the Deccan Flood Basalt Province. Our findings indicate that the magma chamber source depth is greater in the Pune – Nasik dyke swarm compared with other dyke swarms. The variation in strike distribution of the Pune-Nasik dyke swarm may be attributed to several factors, including a larger magma chamber, local stress fields generated by shallow magma chamber, or the superimposition of tectonic stress fields (N-S and E-W extension) during the emplacement of dykes. This contrasts with the commonly held belief that the dykes are solely connected to a central edifice of the Reunion hotspot.

印度半岛德干大陆洪积玄武岩的特点是广泛的玄武岩喷发，并以三个壮观独特的堤坝群为装饰：普纳-纳西克堤坝群、纳尔马达-塔皮堤坝群和西部海岸堤坝群。我们的研究区域是普纳-纳西克堤坝群，该堤坝群有 465 个可标注的堤坝。这些堤坝的走向各不相同，主要走向为 N101°，长度从不足 1 千米到 64 千米不等。这些堤坝具有大量节理，偶尔含有充满石英和方解石等次生矿物的囊泡。主岩是各种较古老的德干岩流的风化玄武岩。在这项研究中，我们利用堤坝的长宽比（长度/厚度）计算了岩浆超压和岩浆腔深度。根据主岩玄武岩的平均杨氏模量（Eavg，7.5 GPa），估计岩浆源的平均深度为 13 千米。此外，我们还比较了推断的普纳-纳西克和纳尔马达-塔皮堤群（包括德干洪水玄武岩省的南杜尔巴尔-杜勒和帕赫马希堤群）的岩浆源深度。我们的研究结果表明，与其他堤群相比，普纳-纳西克堤群的岩浆室源深度更大。普纳-纳西克堤坝群走向分布的变化可归因于多种因素，包括岩浆腔较大、浅岩浆腔产生的局部应力场或堤坝形成过程中构造应力场（N-S 和 E-W 向延伸）的叠加。这与人们普遍认为堤坝仅与留尼汪热点的中心结构有关的观点形成了鲜明对比。

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引用次数: 0

Remagnetisation of the Caerfai Group (lower Cambrian, SW Wales) in hot geothermal fluids during Caledonian (pre-Acadian) metamorphism 在喀里多尼亚（前阿卡迪亚）变质过程中，热地热流体对 Caerfai 组（下寒武统，威尔士西南部）的重磁作用

IF 2.7 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Tectonophysics

Pub Date : 2024-10-18 DOI: 10.1016/j.tecto.2024.230532

Peter Turner , Rob Ixer , Duncan Pirrie , Matthew Power

Palaeomagnetic data from the Lower Cambrian red beds of the Caerfai Group in Pembrokeshire, South Wales have been revisited. Original studies all produced closely similar directional data with the combined results yielding a palaeomagnetic pole at 21.8^oS; 355.5°E corresponding to a time of ∼430 Ma when compared with the APWP of Stable Europe and Baltica. The results of this study indicate that remagnetisation occurred during Caledonian metamorphism, prior to Acadian deformation in the area. The magnetic remanence is carried by fine grained hematite distributed throughout the sequence and which appears to have been acquired during the duration of a single chron. This time zone is traditional early Silurian (late Llandovery) and corresponds to the docking of Baltica and east Avalonia with the Laurentian continent. The proposed age of the remagnetisation event is consistent with radiometric ages from epizonal authigenic illites in overlying Middle Cambrian bentonites at Porth-y-Rhaw and elsewhere in the Welsh Basin and other parts of Avalonia including Charnwood block and Brabantia. The Caerfai Group comprises texturally immature litharenites with a mineral assemblage including chlorite, biotite, muscovite, graphite, and epidote consistent with a greenschist facies source area which remains unidentified. A key component of the Caerfai mineral assemblage are magnetite crystals (typically 30–60 μm) deposited during contemporaneous volcanic activity. Deep burial during the drift of Avalonia, indicated by clay transformations and overpressure in the Caerfai Bay Mudstone, was associated with the alteration of iron-bearing minerals and the dissolution of magnetite. During collision of Avalonia/Baltica with Laurentia a geothermal cell with epizonal metamorphic conditions (>300 °C) and fluids enriched in iron, probably in the form of iron chloride complexes was established. The remagnetisation event was triggered when the geothermal cell was cooled, most likely by the infiltration of meteoric water, and the reaction of iron chloride with water produced the widespread precipitation of fine-grained hematite and the formation of a chemical remanent magnetisation (CRM).

我们重新研究了南威尔士彭布罗克郡凯尔法伊组下寒武统红色岩床的古地磁数据。最初的研究都得出了非常相似的方向数据，综合结果得出古地磁极位于 21.8oS; 355.5°E 与稳定的欧洲和波罗的海的 APWP 相比，对应的时间为 ∼430 Ma。这项研究的结果表明，在该地区阿卡迪亚变形之前的喀里多尼亚变质过程中发生了再磁化。磁性剩磁由分布在整个序列中的细粒赤铁矿携带，似乎是在一个纪元期间获得的。该时区是传统的志留纪早期（兰德发现晚期），与波罗的海和东阿瓦隆尼亚与劳伦大陆的对接相吻合。所提出的再磁化事件的年龄与 Porth-y-Rhaw 和威尔士盆地其他地方以及阿瓦鲁尼亚其他地区（包括 Charnwood 区块和 Brabantia）上覆中寒武纪膨润土中的外生自生伊利石的放射性年龄一致。Caerfai 组由质地不成熟的石英岩组成，矿物组合包括绿泥石、黑云母、白云母、石墨和绿帘石，与绿帘石面源区一致，该源区仍未确定。凯尔法伊矿物组合的一个重要组成部分是在同期火山活动中沉积的磁铁矿晶体（通常为 30-60 μm）。阿瓦隆尼亚漂移期间的深埋（由卡埃尔费湾泥岩中的粘土转化和超压表明）与含铁矿物的蚀变和磁铁矿的溶解有关。在阿瓦鲁尼亚/波罗的海与劳伦提亚碰撞期间，建立了一个地热单元，该单元具有表层变质条件（>300 °C）和富含铁的流体，可能以氯化铁复合物的形式存在。地热池冷却时（很可能是流星水的渗入）引发了再磁化事件，氯化铁与水的反应产生了细粒赤铁矿的广泛沉淀，并形成了化学剩磁（CRM）。

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引用次数: 0