西藏南部若干变质橄榄岩体橄榄石的组构特征

藏南变质橄榄岩的橄榄石组构可划分为三个主要类型:100]、010]和001]组构。橄榄石100]组构反映洋壳下部—上地幔上部的高温粘性流变和高温塑性流变,橄榄石010]和001]组构基本上是构造侵位阶段陆壳中低温塑性流变结果。变质橄榄岩中橄榄石组构转化具有明显的规律性,在岩体变形过程中,总的显示由高温的100]组构逐渐转化为低温的001]、010]组构。高温塑性流变组构影响和制约低温塑性流变组构的发育,叠加变形有利于橄榄石100]极密的加强和100]组构向010]、001]组构的转化。

Fabric Characteristics of Olivine in Some Metaperidotite Massifs in Southern Tibet

Metaperidotite occurring at the bottom of the Yaluzanbujiang ophiolite suite has extensively experienced strong deformation. According to main characteristics of plastic deformation in the studied massifs and X-ray fabric analysis, the fabrics of olivine can be classified into three main types: 100], 010] and 001], which all assume the maximum pattern and are respectively parallel to lineation, The development of fabrics closely related to deformation conditions (such as flow stress, temperature and strain rate), deformation mechanism and deformation evolution results from dislocation movement.The fabric transformation of olivine in metaperidotite shows obvious regularity. In general, there is a progressive transition from high temperature 100] fabric to low temperature 010] and 001] fabrics in the process of deformation. The high temperature plastic flow fabrics affect and restrict the development of low temperature ones, and the overprinted deformation is favorable for the formation of 100] preferred orientation and the transformation from 100] fabric to 001] and 010] fabrics.