沂沭断裂带中段基底韧性剪切带

在沂沭断裂带中段的泰山群结晶基底中,存在着一系列北东、北北东走向的左行韧性剪切带。对其中发育糜棱岩的韧性剪切带的结构构造、应变测量、变形岩石的显微构造、显微组构以及长石粒度和含量的变化规律进行了观测分析。讨论了韧性剪切带的变形条件和机制。及其递进发展的趋势。指出基底韧性剪切带是沂沭断裂带元古宙时期断裂活动时在地壳较深层次上形成的构造表象。在此基础上,讨论了地壳不同层次上的断裂变形及断裂岩石的综合分类问题

THE BASEMENT DUCTILE SHEAR ZONE OF THE MIDDLE YIHE-SHUHE FAULT BOET

The Yi-She fault system is located in Shandong province and lies on the middle section of the Tancheng-Lujiang fault zone. The ductile shear zone found on the crystalline basement of the middle Yi-Shu fault system provides evidence for its formation in Presinian periodDuctile shear zones have a NE or NNE trending and show a pattern of sinistral movement that turned Nw trending gneissosity in the west of the fault into NNE one. This great ductile shear deformation zone is about 20 km. in width. The distribution of the fault system may be controlled by the major shearing zone.The east part of the zone consists of the ductile shear zones in the lack of mylonite and original gneiss remnants, which suggests that it may result from gneissosity under the shearing at a relatively high temperature. However, the west part contains the shear zonet with various kinds of mylonite. They cut through and made original gneissosity move in such a way as sinistral movement, which reflects the result of displacesment under the condition of lower greenschist facies metamorphism.In this paper, the texture, deformation rocks and strain measurements of the shear zones with the mylonite are discussed. The deformation behavour of minerals in the matrix and mortar of mylonite, the fabric pattern and the preferred orientation of c-axis of the plastically deformed and syntectonic recrystallized quarz grains, and their evolution with progressive increase of the shear strain are described. The relationship of grain size and variation in content of feldspar with increasing strain in felsic mylonite is analysed. It is inferred that mylonite was formed at the crustal depth of 10-15 km. and had undergone a long time shearing at a strain rate of about 10-14/sec. and a stress of about 580-745 bars.Finally, the ideal model of the major fault zone and the synthetical classification of fault rocks are discusse