Abstract Silica gel has been proposed as a fault weakening mechanism that may offer a solution to the stress paradox of faulting and be important in promoting seismic slip. Evidence that a gel was present in a fault zone during displacement has proven elusive owing to the unstable nature of a gel and its descendants. Examination of faults in the Middle Silurian Tuscarora Sandstone and other quartz-rich rocks in the region has shown that the microcrystalline quartz in bands and cement in cataclasites was derived from a silica gel. The presence of comminuted grains, silica nanospheres, flow features, amorphous silica, and polygonal crystal domains of low dislocation density within microcrystalline quartz on and adjacent to the fault surfaces is interpreted as evidence of a mobile silica gel precursor. Brecciated microbreccias and mutually crosscutting relationships between microfractures, microcrystalline quartz bands, and microveins along and adjacent to fault surfaces suggest that formation of these features was cyclic. Mutually overprinting textures between brittle and fault creep microstructures (stylolites) indicate alternating episodic brittle deformation and pressure solution. As silica-rich rocks are common, understanding the process of silica gel formation on fault surfaces and its behavior may provide new insights into the mechanics of faulting in the brittle crust.

中文翻译：

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硅胶的证据及其在 Tuscarora 砂岩断层中的作用

摘要 硅胶被认为是一种断层弱化机制，可以解决断层作用的应力悖论，并在促进地震滑动方面发挥重要作用。由于凝胶及其后代的不稳定性质，证明在位移期间断层带中存在凝胶的证据难以捉摸。对该地区中志留统 Tuscarora 砂岩和其他富含石英的岩石中的断层的检查表明，条带中的微晶石英和碎裂岩中的胶结物来自硅胶。在断层表面和断层表面附近的微晶石英中存在粉碎的颗粒、二氧化硅纳米球、流动特征、无定形二氧化硅和低位错密度的多边形晶体域，被解释为可移动硅胶前体的证据。角砾微角砾岩和微裂缝、微晶石英带和沿断层表面和邻近断层表面的微脉之间的相互交叉关系表明这些特征的形成是循环的。脆性和断层蠕变微观结构（针柱石）之间的相互叠印纹理表明交替的偶发脆性变形和压力解决方案。由于富含二氧化硅的岩石很常见，了解断层表面硅胶的形成过程及其行为可能会为脆性地壳中的断层力学提供新的见解。脆性和断层蠕变微观结构（针柱石）之间的相互叠印纹理表明交替的偶发脆性变形和压力解决方案。由于富含二氧化硅的岩石很常见，了解断层表面硅胶的形成过程及其行为可能会为脆性地壳中的断层力学提供新的见解。脆性和断层蠕变微观结构（针柱石）之间的相互叠印纹理表明交替的偶发脆性变形和压力解决方案。由于富含二氧化硅的岩石很常见，了解断层表面硅胶的形成过程及其行为可能会为脆性地壳中的断层力学提供新的见解。