摘要 超高压变质岩的发现导致了人们对大别山构造格架的重新认识。最近的研究表明,超高压变质岩只产于大别山南部(Wang et al., 1992),而北部为古生代岛弧杂岩所占据,晓天-磨子潭断裂即为这些杂岩的北界(Wang et al., 1994)。晓天-磨子潭断裂作为左行走滑断裂已经得到公认,但笔者对该断裂南侧糜棱岩的研究表明,其并非左行走滑产物,而是早期变形的构造形迹。本文旨在分析这些糜棱岩中石英的显微构造,进而揭示其早期构造变形特征。
The well-known sinistral strike-slip Xiaotian-Mozitan Fault is the northern boundary of the Northern Dabie Paleozoic island arc complex. The present study shows that there existed an earlier mylonite zone south to the Xiaotian-Mozitan Fault.Quartz grains in the mylonite zone developed extensively hasal subgrain boundary (0001). A high temperature (>650℃) strain of slipping along the c-axis in quartz grains is manifested by the point maximum parallel to the stretch lineation in polar diagram of c-axis fabric. A top-to-the-north shear sense is also indicated. In the context of the regional geology, this shear sense might imply the northwards subduction of the Northern Dabie Paleozoic island arc complex. On the other hand.prismatic subgrain boundary (hklO) parallel to the c-axis is observed in the quartz grains from the mylonite zone. It reflects a low temperature strain of slip along a-axis in quartz grain, that could result from the late sinistral strike-slip.