Internal structure, fault rocks, and inferences regarding deformation, fluid flow, and mineralization in the seismogenic Stillwater normal fault, Dixie Valley, Nevada
Internal structure, fault rocks, and inferences regarding deformation, fluid flow, and mineralization in the seismogenic Stillwater normal fault, Dixie Valley, Nevada
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DOI：
10.1016/j.jsg.2010.03.004
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发表时间：
2010-11
影响因子：
3.1
通讯作者：
J. Caine;R. Bruhn;C. Forster
中科院分区：
文献类型：
--
作者：
J. Caine;R. Bruhn;C. Forster
内华达州迪克西山谷斯蒂尔沃特正断层带的露头测绘和断层岩石表征用于记录和解释古热液流及其与地震变形的可能关系。断裂带由不同的构造和水文地质组成。以前对断层岩的研究被扩展到地图尺度，其中一个独特的断层核显示了一系列不同的断层相关角砾岩。这些包括主要由碎屑支撑的角砾岩和角状碎屑，这些角砾岩被含有角砾岩的区域切割，角砾岩和圆形碎屑也由碎屑支撑。这些被角砾岩进一步切割，角砾岩主要是由角状和圆形碎屑支撑的基质。断层核角砾岩被不均匀破裂的损伤带所包围。角砾岩以主要的硅化滑动面为界，形成大的豆荚状结构，系统地定向，长轴平行于滑动。基质支撑的角砾岩有多重角砾，角和圆形碎屑揭示幕式变形和流体流动。这些角砾岩有一个富含石英的基质，具有微晶上反角、等轴和普遍整合的镶嵌结构。角砾岩豆荚被解释为形成减压沸腾和快速沉淀的热液流体，其流动引起同震，混合剪切变形和水力连接到一个地热储。在地图尺度上，在岩芯中局部化的热液硅质胶结物的添加导致断层带加宽、局部封闭和机械不均匀性，这些不均匀性影响了整个地震周期中断层带的演化。
Outcrop mapping and fault-rock characterization of the Stillwater normal fault zone in Dixie Valley, Nevada are used to document and interpret ancient hydrothermal fluid flow and its possible relationship to seismic deformation. The fault zone is composed of distinct structural and hydrogeological components. Previous work on the fault rocks is extended to the map scale where a distinctive fault core shows a spectrum of different fault-related breccias. These include predominantly clast-supported breccias with angular clasts that are cut by zones containing breccias with rounded clasts that are also clast supported. These are further cut by breccias that are predominantly matrix supported with angular and rounded clasts. The fault-core breccias are surrounded by a heterogeneously fractured damage zone. Breccias are bounded between major, silicified slip surfaces, forming large pod-like structures, systematically oriented with long axes parallel to slip. Matrix-supported breccias have multiply brecciated, angular and rounded clasts revealing episodic deformation and fluid flow. These breccias have a quartz-rich matrix with microcrystalline anhedral, equant, and pervasively conformable mosaic texture. The breccia pods are interpreted to have formed by decompression boiling and rapid precipitation of hydrothermal fluids whose flow was induced by coseismic, hybrid dilatant-shear deformation and hydraulic connection to a geothermal reservoir. The addition of hydrothermal silica cement localized in the core at the map scale causes fault-zone widening, local sealing, and mechanical heterogeneities that impact the evolution of the fault zone throughout the seismic cycle.