喜马拉雅造山带中段麻粒岩构造侵位过程中变质变形演化

喜马拉雅造山带中段麻粒岩绝大多数呈透镜状、布丁体等弱应变域断续产出,强应变带围岩往往发育糜棱面理和构造片理。部分麻粒岩经历了强烈的韧性剪切构造变形,形成剪切透镜体,并且明显受韧性剪切带控制,显示成带分布、局部集中的特点。根据矿物组合可将产出的麻粒岩分为4种麻粒岩,其主要组成矿物如斜方辉石、单斜辉石、斜长石、角闪石以及石榴石等均不同程度地发生扭折、压扁、拉长扭曲、亚颗粒化及边缘强烈动态重结晶等强烈塑性显微构造变形特征。研究分析表明,麻粒岩的产出与重熔花岗岩的侵位及藏南伸展拆离断层活动有关,在喜马拉雅造山带强烈伸展快速抬升造山的绝热降压大陆动力学过程中,下地壳基性麻粒岩以较快的速率上升到地表,而下地壳层流作用、造山带伸展-隆升-造山导致麻粒岩相变质作用。

Evolution of Deformation and Metamorphism During the Tectono-Emplacement of the Granulite in the Middle Himalaya Orogen

In the middle section of the Himalaya belt,lenticular or pudding granulites are exposed intermittently in some weak strained areas,while the country rocks have been strongly deformed,as indicated by their mylonite foliations and schistosity.Due to the strongly ductile shear deformation and obviously controlled by the ductile shear zone,some mylonite occurs with the characteristics as shear lens shaped,stripy distributing and local concentrating.The granulite can be sorted into four types according to the mi...