发震断裂带内黏土矿物的纳微米变形

Nano/Micro-Scale Deformation of Clay Minerals in Seismogenic Fault Zone

断层泥是发震断裂最显著的物质标志之一,它保留着许多断层活动的信息.在野外宏观调查和显微视域观察基础上,利用SEM技术,从纳微米尺度,研究发震断裂带内黏土矿物的组合形态和变形样式,并对一些问题进行深入分析和讨论.黏土矿物在断层粘滑滑移过程中,出现定向排列,在正交偏光显微镜下表现为平行排列的消光带.在SEM视域下,可以观察到片状黏土矿物的定向排列,同时可以清晰地识别多次断层粘滑滑移事件.在断层泥中发现的蠕变滑移现象,带有普遍性.在显微视域下,黏土矿物表现为波状消光带.在SEM视域下,可以观察到片状黏土矿物的褶皱变形、流动变形、绕砾滑动、撕裂变形等.鉴于在同一个视域内,可以同时观察到粘滑滑移标志和蠕变滑移标志,通过分析其先后关系,发现蠕变滑移发生于粘滑滑移之前,对应于断层的亚失稳阶段的运动.

Fault gouge is one of the most obvious material indicators in seismogenic fault zone,and it retains a wealth of information of fault activities.Based on field investigation and observation under microscope,nano/micro-scale deformation styles of clay minerals in seismogenic fault zone were analyzed in detail and discussed in this paper by use of SEM technology.The clay minerals are arranged in alignment during stick-slipping,and exhibit parallel extinction zones under orthogonal polarization microscope.In the view of SEM,the directional arrangement of flake clay minerals can be observed,and multiple stick-slipping events on the principle sliding zone can be clearly identified.Moreover,it is found that the creep-slipping phenomena in fault gouges are universal.In the microscopic view,clay minerals exhibit wavelike extinction zones.In the view of SEM,fold deformation,wavelike deformation,sliding around the gravels and entangling deformation of flake clay minerals can be observed.As stick-slipping and creep-slipping indications can be observed in the same view,and by analyzing their temporal relationship,it is found that the creep-slipping occurs before the stick-slipping and corresponds to the movement in the metainstability stage of fault sliding.