青海可可西里北缘韧性剪切带的显微构造特征

MICROSTRUCTURE OF THE DUCTILE SHEAR ZONE IN THE NORTHERN MARGIN OF HOH XIL REGION QINGHAI PROVINCE

在可可西里北缘发现的糜棱岩化带，经显微构造研究确定为韧性剪切带。此带发育流劈理及拉伸线理。糜棱岩化花岗岩和糜棱岩化石英脉中的石英发育亚晶粒构造、位错构造和动态重结晶，长石主要发育机械双晶。石英ｃ轴组构属韧性剪切带中的典型形式，石英变形以位错蠕变机制和位错滑移机制共存为特征，石英的动态重结晶作用是由亚晶粒旋转机制形成。长石的变形主要是通过机械双晶实现的。此韧性剪切带形成时的温度约４００℃，差异应力约３０ＭＰａ，应变速率约１．９×１０－１３ｓ－１。

A ductile shear zone charaterized by well-developed foliation and streaching lineation is discovered in the northern margin of Hob Xil region, Qinghai province in 1990 for the first time. The quartz grains within mylonitized granites and quartz veins in the zone are characterized by well-developed subgrain structures, dislocation substructures and dynamic recrystallization, while the feldspars are characterized by mechanical twinning. The quartz c-axis displays a typical preferred orientation of ductile shear zone. The ductile shear zone was formed under a temperature of about 400℃, differential stress of about 30 MPa, and strain rate of1.9×10-13s-1.