Repeated seismic slips recorded in ultracataclastic veins along active faults of the Arima-Takatsuki Tectonic Line, southwestern Japan
Repeated seismic slips recorded in ultracataclastic veins along active faults of the Arima-Takatsuki Tectonic Line, southwestern Japan
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日本西南部有马-高槻构造线沿活动断层的超碎裂岩脉中记录到的重复地震滑动
DOI：
10.1016/j.jsg.2013.01.005
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发表时间：
2013
影响因子：
3.1
通讯作者：
A.)
中科院分区：
文献类型：
--
作者：
Lin;A.;Yamashita;K.;and Tanaka;M. (Lin;A.)
结合细观和微观构造分析，在日本西南部有马-高月构造线活动断层的断裂带（宽度<150 m）内，以简单脉、复杂透镜体和网络的形式广泛发育了大量的超碎屑脉。这些脉体主要由假粗灰岩样脉体和弱胶结到松散断层泥组成，颜色为黑色、深棕色、棕色、灰色和棕红色。细观和显微结构特征表明，这些假粗灰岩状和断层泥状脉网的形成是多阶段的，早期的脉网通常被较年轻的脉网切割和叠加，表明脉网形成事件是反复发生的，超塑性物质被注入断裂带的断裂和裂缝网络中。伪岩状和断层泥脉的特征是由超细到细粒的基质和亚微米到毫米不等大小的角状到亚角状花岗岩组成。SEM-EDS（扫描电子显微镜-能量色散x射线）和粉末x射线衍射分析表明，所有超碎屑脉体均以石英和长石为主的晶体物质为特征，与寄主花岗岩相似。目前的研究结果支持了已有的假设，即在地震滑动过程中，由粉碎形成的超细至细粒物质可以流化并快速注入远离源断层面的固-流-气系统裂缝网络中；因此，这些材料提供了发震断裂带内反复发生的古地震断裂事件的记录。
Field investigations, combined with meso- and microstructural analyses, reveal that numerous ultracataclastic veins are widely developed within a fault zone (<150 m wide) as simple veins, complex lenses, and networks, along active faults of the Arima–Takatsuki Tectonic Line, southwest Japan. These veins comprise mainly pseudotachylyte-like vein and weakly consolidated to unconsolidated fault gouge that is black, dark-brown, brown, gray, and brownish-red in color. Meso- and microstructural features show that these pseudotachylyte-like and fault gouge veins and networks formed during multiple stages, as earlier veins are generally cut and overprinted by younger veins, indicating that the vein-forming events occurred repeatedly and that ultracataclastic material was injected into networks of faults and fractures in the fault zone. The pseudotachylyte-like and fault gouge veins are characterized by an ultrafine- to fine-grained matrix and angular to subangular fragments of host granitic rocks of various sizes, ranging from submicron to millimeters. SEM–EDS (Scanning Electronic Microscope-Energy Dispersive X-ray) and powder X-ray diffraction analyses show that all the ultracataclastic veins are characterized by crystalline materials composed mainly of quartz and feldspar, similar to the host granitic rocks. The present results support the existing hypothesis that ultrafine- to fine-grained materials formed by comminution can be fluidized and injected rapidly into fracture networks located far from the source fault plane in a solid–fluid–gas system during seismic slip; therefore, such materials provide a record of paleoseismic faulting events that occurred repeatedly within the seismogenic fault zone.