东喜马拉雅南迦巴瓦地区区域地质特征及构造演化

Geological Features and Tectonic Evolution in the Namjagbarwa Area,Eastern Himalayas

研究区位于喜马拉雅造山带的东构造结。本文以区域地质填图成果为基础 ,结合前人资料 ,首先对研究区进行了构造单元划分 ,其次对各构造单元的地质特征进行了总结 ,最后对构造演化和有关问题进行了探讨。结论为 :1南迦巴瓦地区可以划分为冈底斯—拉萨陆块、雅鲁藏布江缝合带和印度陆块 3个一级构造单元。以蛇绿混杂岩为代表的雅鲁藏布江缝合带呈向 NE凸的马蹄状连续分布 ;印度陆块由被称为南迦巴瓦岩群的高喜马拉雅结晶岩系单独构成 ,南迦巴瓦岩群由以含高压麻粒岩透镜体为标志的直白岩组、派乡岩组和多雄拉混合岩组成。2印度—欧亚板块碰撞的时间早于 70 Ma;2 3Ma以来主要断层的运动性质以伸展拆离作用为主 ;大约 5 Ma时发生了大规模的混合岩化和深熔作用。3地幔上隆是本区快速隆升的关键因素 。

The study area is located in the eastern Himalayan syntaxis. In the paper, firstly, the tectonic units are divided; secondly the geological features of each tectonic unit are introduced; finally the tectonic evolution and related questions are discussed, according to the original data achieved by geological mapping and some conclusions drawn by other geologists. The following conclusions are reached: (1) The Namjagbarwa area can be divided into three first-order units: the Gandise—Lhasa block, the Yarlung Zangbo suture and the Indian block. The Yarlung Zangbo suture dominated by ophiolitic mélanges lies in a continued U type; the Indian block is formed individually by the Higher Himalayan crystalline rock series which is named the Namjagbarwa rock group. The Namjagbarwa group consists of the Zhibai Formation bearing high-pressure granulite lenses, Paixiang Formation and Duoxiongla migmatites. (2) The collision of the India plate with the Eurasian plate took place before 70 Ma. The movement of major faults has been dominated by detachment since 23 Ma; and large-scale migmatization and anatexis occurred at ca.5 Ma. (3) The rise of the mantle is the key factor for the rapid uplift of the area, but the action of the action of the river cannot be ignored either.