内蒙古固阳地区太古宙乌拉山群构造变形分析

DEFORMATION OF ARCHAEAN WULASHAN GROUP IN GUYANG REGION OF INNER MONGOLIA

乌拉山群的变质 -变形问题一直有不同的认识[1～ 3] 。该文以固阳地区 3幅 1∶5万区调资料为基础 ,结合 90年代以来周边地区 1∶ 5万区调成果 ,提出晚太古宙乌拉山群经历了两期主要的构造变形。第一期为伸展体制下近水平分层剪切形成的固态流变褶皱和高温顺层韧性剪切带 ,属高角闪岩相 -麻粒岩相 ,变形时间为太古代末 ;第二期构造变形为地壳抬升之后的挤压体制下 ,中、浅层次的紧闭同斜相似褶皱——主期褶皱和低温韧性剪切带 ,形成时代为早元古代。

There have existed different views on the metamophism deformation of the Wulashan Group. It is pointed in this paper that the late Archaean Wulashan Group has experienced two major deformation events on the basis of recent results obtained from 3 sheets of 1:50000 geological mapping and other regional studies since 90's. The first deformation event is characterized by solid flow fold and high temperature ductile shear zone resulting from nearly horizontal shearing by extension. The metamorphism is of high amphibolite granulite facies. The deformation took place at the end of Archaean. The second deformation even is characterized by shallow tight homoclinal similar fold main fold and low temperature ductile shear zone arising from post crustal uplifting compression. The event occurred in the early Proterozoic.