糜棱岩化作用中角闪石变形结构的透射电子显微镜研究

THE CHARACTERISTICS OF DEFORMED HORNBLENDE IN THE PROCESS OF MYLONIZATION

石英的显微结构是判别含石英岩石变形程度的重要标志。为了认识角闪石在岩石变形过程中的特征，笔者对糜棱岩化闪造者中普通用闪石的变形显微结构进行了光学和透射电子显微镜研究。研究的角闪石都与石英共生，因而以石英的变形结构作为角门石变形研究的参照系。笔者发现，当石英呈明显波状消光时，普通角闪石未显示变形结构；当石英变形达到亚颗粒化和重结晶阶段时，普通角闪石的变形显微结构主要表现为单一方向的位错，其伯格斯矢量b=[0o1]，位借平行[001]，属于螺位错，有时它们排列成纯扭折壁。此外，还发育（010）面缺陷，缺陷两端的不全位错与螺位错平行。对照石英显微结构特征，估计上述角闪石的变形发生于数十万至数千万Pa的应力条件下。

The deformed micro-structure of quartz is an indicator of the deforming degree of a quartz-bearing rock. In order to understand the deforming behavior of hornblende in the course of rock deformation, the deformed micro-structure of hornblendes from mylonized diorites was studied by means of optical and TEM methods. The deformed micro-structure can be regarded as the reference system inasmuch as all the hornblendes studied coexist with quartz. It is found that the horn-blendes show no micro-structure while their coexisting quartz displays apparent undulatory extinction. The micro-structures are basically identical when the quartz exhibits subgrain and recrystallization structures, respectively. Their structures mainly show free dislocations and a sort of (010) plane defects. The Burges vector bis [001], and also the dislocations run parallel to [001] so that they are screw dislocations. Sometimes the dislocations are organized as twist dislocation walls. The partial dislocations of the plane defects are parallel to and have the sathe characteristics with the free dislcoations. By comparing the micro-structures of hornblende with those of quartz,it is estimated that there is no significant difference for the micro-structures of hornblendes in the range of the archeo-stress from several hundred thousands Pa to several ten million Pa.