桂北上元古界－下古生界变质构造层中的韧性变形带

THE DUCTILE SHEAR ZONE WITHIN THE METAMORPHIC TECTONIC LAYER BETWEEN THE UPPER PROTEROZOIC ERATHEM AND THE LOWER PALAEOZOIC ERATHEM IN NORTH GUANGXI

桂北上无古界－下古生界变质构造层中发育有４类韧性变形带：丹洲群中的层状韧性变形带主要发育于中、下部，与丹洲群沿下不整合面的总体向东滑脱有关；三门街组基性－超基性岩中的韧性变形带是一种典型的透镜体型变形分解构造，是纯剪变形向单剪变形转化的产物；花岗岩体中的韧性剪切带主要发育于接触带的内侧，具有明显的左旋单剪效应；变质地层中的陡倾韧性剪切带则具有韧性向脆－韧性过渡特征。韧性变形带最早发育始于雪峰期，但其主变形期则与广西运动有关，是递进变形过程中顺序发展的结果，其变形变质相总体为低绿片岩相，花岗岩体中的部分剪切带可达高绿片岩相至低角闪岩相。

There are four type of ductile deformation zones within the metamorphic tectonic layer between the upper Proterozoic erathem and the lower Paineozoic erathem: The stratified ductile shear zone existing in the Dangzhou Group of the middle part and the lower part of the layer,has a close relation to the generally eastward decollement along the lower surface of the uncomformity of the Dangxhou Group. The ductile deformation zone in basic-ultrabasic rocks within the Sanmengjie Formation is a kind of typical lenticular deformational decomposition structure, as a result of the transition from pure shearing to simple shearing. The ductile shear zone within the granite body exists in the internal contact belt, demonstrating the obvious sinistral simple shearing effect The high-angle ductile shear zone of the metamorphic layer has the characteristics of transition from ductility to brittleness. The deformation episode of the ductile deformation zones developing gradually due to the progressive deformation, are formed initially during the Xuefeng episode, but the main deformation is related closely to the Guangxi Movement. The main metamorphic facies is generally the lower-graded greenschist facies, while some shear zones in the granite body are the upper-graded greenschist to the lower-graded amphibolite facies.