The nature and importance of phyllonite development in crustal-scale fault cores: an example from the Median Tectonic Line, Japan
The nature and importance of phyllonite development in crustal-scale fault cores: an example from the Median Tectonic Line, Japan
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DOI：
10.1016/j.jsg.2005.10.008
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发表时间：
2006-01-01
影响因子：
3.1
通讯作者：
Lloyd, GE
中科院分区：
文献类型：
--
作者：
Jefferies, SP;Holdsworth, RE;Lloyd, GE
像许多大型地壳断层一样，日本西南部的中央构造线（MTL）有着悠久的运动历史，自白垩纪中期以来一直以走滑断层为主。断层岩暴露在核心的MTL保留了变形的历史，在一个范围内的中，浅地壳深度。在主接触面以北1- 4km处的Ryoke糜棱岩记录了更深层次的白垩纪自上而下的左旋运动。断裂带核心的其余部分是令人惊讶的狭窄，展示了各种各样的断层岩，说明了在一系列变形条件下同构造流体流入的相互作用和影响。在中央滑动带50 m范围内的出露显示了断层岩演化的渐进序列：超糜棱岩->碎裂岩->片理碎裂岩->千屈岩->角砾岩/断层泥。这一序列的发生是因为断裂核附近的碎裂作用为化学活性流体进入断裂带创造了可渗透通道。这导致承载相（如长石）被本质上较弱的层状硅酸盐（如白色云母和云母）的细粒片理化聚集体取代。与碎裂和矿物蚀变相关联的粒度减小为流体辅助的、应力诱导的扩散传质机制的操作创造了理想的条件。与最近的实验研究结果的比较表明，在MTL的核心观察到的断层带过程将导致长期的削弱，提供的层状硅酸盐丰富的断层岩网络能够形成一个相互连接的薄弱材料层公里至数十微米的长度尺度。(C)2006爱思唯尔有限公司保留所有权利。
Like many large, crustal-scale faults, the Median Tectonic Line (MTL) in SW Japan has a long history of movement, having been active predominantly as a strike-slip fault since the mid-Cretaceous. Fault rock exposures in the core of the MTL preserve a history of deformation at a range of mid- to shallow-crustal depths. Ryoke mylonites 1-4 km north of the main contact record deeper level, Cretaceous top-to-the-south sinistral movements. The remainder of the fault zone core is surprisingly narrow, exhibiting a wide variety of fault rocks that illustrate both the interaction and effects of syn-tectonic fluid influx over a range of deformation conditions. Exposures within 50 m of the central slip zone display a progressive sequence in fault rock evolution from ultramylonite -> cataclasite -> foliated cataclasite -> phyllonite -> breccia/gouge. This sequence occurs because cataclasis in the vicinity of the fault core creates permeable pathways for the ingress of chemically active fluids into the fault zone. This leads to the replacement of load-bearing phases, such as feldspar, by fine-grained, foliated aggregates of intrinsically weaker phyllosilicates such as white mica and chlorite. The grain size reduction associated with both cataclasis and mineral alteration creates conditions ideal for the operation of fluid-assisted, stress-induced diffusive mass transfer mechanisms. Comparison with the findings of recent experimental studies suggest that the fault zone processes observed in the core of the MTL will lead to long-term weakening, provided the network of phyllosilicate-rich fault rocks are able to form an interconnected thin layer of weak material on kilometre- to tens of kilometre-length scales. (C) 2006 Elsevier Ltd. All rights reserved.