A STUDY OF DYNAMIC THIN SHELL OF FAULT STRUCTURE
Sun Yan, Shen Suzi, Liu Shuhe
The dynamic thin shell on the surface of the structural plane of fault is formed in dynamic metamorphism. It is very prevalent on the compressive, compresso-shear and shear structural planes, but on the surface of a tensile structural plane it develops into a secondary thin shell. In the present paper, ten examples of fractures from Anhui, Szechuan, Kiangsu and Shantung are chosen for investigation.Usually there are five kinds of lineations on the structural planes, they are caused by slippage, solid flowage, rotation, or growth of minerals during structural movements, and their orientation is closely related to the movement direction.Though the dynamic thin shell is very thin and only of several millimetres to several centimetres thick, but the layer texture is quite clear. Generally speaking, it can be devided into layers of tectonite, of stress minerals and of superficial secondary minerals.In the dynamic thin shell of sedimentary rocks, there are many kinds of stress minerals,among them calcite,quartz, feldspar, mica and chlorite are constantly found in the field. Both quartz and calcite are abundant and sensitive to stress, therefore they are known as mobile or pressure-sensitive minerals. The (0112) plane of the deformation twin crystals in calcite and the (1010) cleavage in quartz are well developed.The dynamic thin shell as a product of thermo-dynamic metamorphism shows various Phenomenon of dedolomitization, dewatering and slip-differentiation, etc.The segregation banding of mylonite of dynamic thin shell is related to the slip-differentiation.