Advances in composition and dating methods of fault gouge and weakening mechanisms of earthquake faults in bedrock area

Fault gouges result from the sliding of brittle faults and can be used to determine the deformational characteristics, formation ages and weakening mechanisms of earthquake faults, which are of great significance for structural geology and earthquake geology. Therefore, the comprehensive understanding of the research findings and its advances in fault gouges will contribute to palaeoseismic investigations. On the basis of collected and absorbed data, we introduced comprehensive advances in the components of fault gouges, surface textures of quartz grains from fault gouges, dating methods of fault gouges and weakening mechanisms of earthquake faults. The fault gouge is mainly composed of clay minerals and powder and debris of wall rocks. The clay minerals mainly consist of montmorillonite, illite, kaolinite and chlorite. The powder and debris of wall rocks are mainly composed of quartz, feldspar, mica, calcite and dolomite. Quartz, illite and calcite selected from fault gouges could be used to distinguish the polysstages of faulting and date its formation ages. Geochronological methods include surface texture analysis of quartz grains, electron spin resonance (ESR) and optically stimulated luminescence (OSL)dating of quartz, K-Ar or 40Ar/39Ar dating of illite, and U-Pb dating of calcite. The weakening mechanisms of earthquake faults consist of the powder of minerals, the formation of new minerals and fabric development in fault gouges, and frictional heating, frictional melting and thermal pressurization after fault initialization.