藏北中西部大地构造单元划分及地质意义

Division of the geotectonic units of the middle-western area of north Tibet and its geological significance

调研区位于冈瓦纳大陆北缘。中生代以来班公湖—怒江洋及雅鲁藏布江洋相向俯冲、消亡,形成多岛弧—盆系洋陆的转化和陆内汇聚—高原隆升,构成了极复杂的构造格局。根据藏北1∶25万邦多幅、措麦幅地质调查成果及区域前人资料综合分析,以多岛弧盆造山模式为理论,认为在Ⅰ级大地构造单元班公湖—怒江结合带及拉达克—冈底斯—拉萨—腾冲陆块上,由北至南可进一步划分晚侏罗世前陆盆地、白垩纪残余海盆、阿索构造混杂岩、燕山期岩浆弧、中生代复合弧后盆地、断隆带、晚燕山—喜马拉雅期岩浆弧带及新近纪—第四纪南北向地堑等Ⅱ级大地构造单元,将复杂的造山活动遗迹进行了有序的时空配置。

The research area is located in the north margin of Gondwana. Since Mesozoic , the Bangong Lake-Lu River ocean and the Yaluzangbu River ocean have subducted toward each other, leading to the transformation of poly-island arc-basin and the intracontinental convergence-the plateau uplift, and forming a extreme complex pattern of geological structure. On the basis of the 1∶250 000 Bangduo Chuomai geologic maps of North Tibet and the previous regional geological data in the theory of the poly-island arc-basin orogency model ,it is believed that geotectonic unit Ⅰ--the Banggong Lake-Lu River junction zone and Ladake-Gangdisi-Lasa-Tengchong continental block from north to south can be divided further into such geotectonic units Ⅱ such as the late Jurassic foreland basin, the Cretaceous residual sea basin, the Asuo tectonic mélange, the Yanshanian magma arc,the Mesozoic compound back-area basin and fault-uplift zone , late Yanshanian-Himalayan magma arc and the Neogene Quaternary S-N graben and so on.The result shows that complex orogenesis reminders are very well arranged in a time-space seqaence