Structure of large-displacement, strike-slip fault zones in the brittle continental crust
Structure of large-displacement, strike-slip fault zones in the brittle continental crust
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脆性陆壳中大位移走滑断裂带的结构
DOI：
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发表时间：
2004
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通讯作者：
James P. Evans
中科院分区：
文献类型：
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作者：
F. Chester;J. Chester;D. Kirschner;S. Schulz;James P. Evans
确定断裂带的结构特征对于理解岩石圈的力学、流体流动和地球物理性质是必要的。本文详细描述了加州南部圣安德烈亚斯系统的两个大位移走滑断层带，Punchbowl和北分支圣加布里埃尔断层。断层切割结晶和充分石化的沉积岩，并包括广泛的断裂和断层岩石（损伤区），其中包含一个或多个狭窄的高度剪切岩石（断层核）的板状区。在与滑动相关的应力循环作用下，形成了损伤带的次级断层和裂缝。断层核是由非常细粒度的蚀变断层岩组成，反映了高剪切应变、极端粉碎和增强的流体-岩石反应。这些大位移断层的特征和相对有序的结构与断层寿命期间的渐进损伤累积一致。断层核内含有介观滑动面的超碎屑岩层记录了宏观和介观尺度上的滑动极端局部化。在整个断裂历史中，超碎屑岩由磨粒磨损沿着滑动面逐渐堆积，可以解释超碎屑岩层的粒度分布、层状结构和尖锐边界。滑动面的寿命和相对稳定性由朝向滑动面逐渐年轻的超碎屑岩的积累证明。尽管这不是一个常见的特征，但将围岩薄片纳入超碎屑岩层记录了断层核内滑动面的偶尔分支。损伤带和断核表征可用于描述陆壳结晶和良好石化沉积岩中脆性断裂带的地球物理、力学和流体流动特性。
Characterizing the structure of fault zones is necessary to understand the mechanical, fluid flow and geophysical properties of the lithosphere. This paper provides a detailed characterization of two large-displacement, strike-slip fault zones of the San Andreas system in southern California, the Punchbowl and North Branch San Gabriel faults. The faults cut crystalline and well-lithified sedimentary rocks, and consist of broad zones of fractured and faulted rock (damage zone) containing one, or more, narrow, tabular zones of highly sheared rock (fault core). Subsidiary faults and fractures of the damage zone formed in response to stress cycling associated with slip. The fault core is composed of very fine-grained, altered fault-rocks that reflect high shear strain, extreme comminution, and enhanced fluid-rock reactions. The characteristic and relatively ordered structure of these large-displacement faults is consistent with progressive damage accumulation over the lifetime of the fault. Layers of ultracataclasite containing mesoscopic slip surfaces within fault cores record extreme localization of slip at the macroscopic and mesoscopic scale. Progressive accumulation of ultracataclasite from abrasive wear along a slip surface throughout faulting history can explain the particle size distribution, layered structure, and sharp boundaries of the ultracataclasite layer. The longevity and relative stability of the slip surface is evidenced by the accumulation of progressively younger ultracataclasite towards the slip surface. Although not a common feature, the incorporation of slivers of wall rock into the ultracataclasite layer document occasional branching of the slip surface within fault cores. The damage-zone and fault-core characterization may be used to describe the geophysical, mechanical, and fluid-flow properties of brittle fault zones in crystalline and well-lithified sedimentary rocks of the continental crust.