应变软化在甘肃红柳河辉长质糜棱岩形成中的作用

THE EFFECT OF STRAIN SORTENING ON THE FORMATION OF GABBRIC MYLONITE IN HONGLIUHE,GANSU

本文论述的辉长质糜棱岩发现于甘肃北山红柳河蛇绿岩套中。在简单说明了糜棱岩的地质背景及特征、描述了变形岩石的显微构造特征之后，重点对糜棱岩形成过在中的应变软化机制作了论述。探讨了软化岩的存在、组构调整、粒度缩小，长石的动态重结晶，水以及主导变形机制的不断调整与转化等应变软化机制，在应力作用下使岩石逐步软化过程中所起的作用，得出这种糜棱岩是在拆离剪切作用下，应力在蛇绿岩中的软化岩石辉长岩中集中，从而形成红柳河辉长质糜棱岩的结论。

Up to now, much attention and research words have been put on the felsic mylonite in Upper level of crust and on the ultra-mafic mylonite in Upper mantle level, little has been done on the gabbric mylonite which stands for the rock originating from mid-low level crust. This pa per just deals with the Problem in this field. The gabbric mylonite, discussed here, developed in the ophiolite from Hongliuhe area in in Gansu province which is the relic part of south Tianshan paleo-ocean crust.Based on the field observation and microstructural studing, it is show that the strong ductile deformation of gabbro layers in the ophiolite. The roles of strain softening mechanisms, such as the existence of soft rock layer,fabric adjusting, reduction of grain size , the dynamic recrystalization of feldspar minerals, water existiong and constinously adjusting and transforming of the main deformation mechanism etc. in the the strain softeing under stress are discussed in detailed. It is argued that the gabbric mylonite is only formed under shear stress, concentrating of stress in the relatively softer rock layer-accumulated gabbro layers in ophiolite.