Evolution of the Median Tectonic Line fault zone, SW Japan, during exhumation
Evolution of the Median Tectonic Line fault zone, SW Japan, during exhumation
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日本西南部中央构造线断裂带在折返过程中的演化
DOI：
10.1016/j.tecto.2016.12.017
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发表时间：
2017-01
期刊：
影响因子：
2.9
通讯作者：
N. Shigematsu;M. Kametaka;Noriyuki Inada;M. Miyawaki;A. Miyakawa;J. Kameda;T. Togo;K. Fujimoto
中科院分区：
文献类型：
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作者：
N. Shigematsu;M. Kametaka;Noriyuki Inada;M. Miyawaki;A. Miyakawa;J. Kameda;T. Togo;K. Fujimoto
像许多地壳规模的断裂带一样，日本的中构造线（MTL）断裂带保留了在各种物理条件下形成的断层岩石。为了了解不同地壳水平下的断层行为，我们在一个大的新露头上检查了MTL的结构。这里的MTL走向几乎是东西向，向北倾斜，并与南部的三巴川变质岩和北部的泉群沉积物并置。断核主要由三川衍生的断层泥组成。断裂带可划分为若干构造单元，包括两个滑动带（上滑带和下滑带），其中下滑带较为明显。构造和运动学之间的横切关系表明，断裂带经历了四个变形阶段。显微组织和粉末x射线衍射（XRD）分析表明，在不同温度条件下发生了四个阶段的变形。最古老的变形（第1阶段）分布广泛，在发震区深部具有自顶向东（右向）滑动感。具有相同滑动感的变形，然后在较低的滑动区局部化（阶段2）。随后，下滑动带的滑动方向转变为顶向西（正弦-正向）（阶段3）。变形的最后阶段（第4阶段）涉及沿浅层地壳内（接近地表）的两个滑动带自上而下向北的正断层。广泛分布的第1阶段破坏带是孕震带较深部的特征，而第4阶段的局部主滑带和分支断裂则是孕震带较浅的特征。本文所描述的断裂带结构使我们认为，在不同的地壳水平上，断裂带表现出不同的行为。
Like many crustal-scale fault zones, the Median Tectonic Line (MTL) fault zone in Japan preserves fault rocks that formed across a broad range of physical conditions. We examined the architecture of the MTL at a large new outcrop in order to understand fault behaviours under different crustal levels. The MTL here strikes almost E–W, dips to the north, and juxtaposes the Sanbagawa metamorphic rocks to the south against the Izumi Group sediments to the north. The fault core consists mainly of Sanbagawa-derived fault gouges. The fault zone can be divided into several structural units, including two slip zones (upper and lower slip zones), where the lower slip zone is more conspicuous. Crosscutting relationships among structures and kinematics indicate that the fault zone records four stages of deformation. Microstructures and powder X-ray diffraction (XRD) analyses indicate that the four stages of deformation occurred under different temperature conditions. The oldest deformation (stage 1) was widely distributed, and had a top-to-the-east (dextral) sense of slip at deep levels of the seismogenic zone. Deformation with the same sense of slip, then became localised in the lower slip zone (stage 2). Subsequently, the slip direction in the lower slip zone changed to top-to-the-west (sinistral-normal) (stage 3). The final stage of deformation (stage 4) involved top-to-the-north normal faulting along the two slip zones within the shallow crust (near the surface). The widely distributed stage 1 damage zone characterises the deeper part of the seismogenic zone, while the sets of localised principal slip zones and branching faults of stage 4 characterise shallow depths. The fault zone architecture described in this paper leads us to suggest that fault zones display different behaviours at different crustal levels.