关键词: 推覆构造, 断层泥, 显微球状砾

Abstract: The faulted rocks in the Sino-Mongolian Boundary Thrust are uncohesive gouges commenly a few or tens of centimeters in thickness (locally up to 3 meters). Analysis of 13gouge samples show that the content of clay minerals (grain size < 20 µm) are quite variable, ranging from 5 to 44 percent. The main clay minerals are illite and kaolinite; remaining claymaterial is montmorillonite and chlorite. These clay minerals appearas either angular fragments or rounded granulitic grains. Some micro-spheroclasts or microsphaeroidal fragments of clay minerals caused by mechanical grinding are found in the gouge. The illite fragments are not suitable for K-Ar model age determination. The fragments of clay minerals and micro-spheroclasts suggest that the thrusting occurred at least twice. The morphological features on the quartz grains are due to solution; these grains along with euhedral crystals of gypsum and calcite imply that the thrusting is inactive.

Key words: thrust, gouge, micro-spheroclast