MIDDLE PROTEROZOIC TECTONIC DEFORMATION AND EVOLUTION OF THE LANGSHAN-ZHARTAI MOUNTAINS IN INNER MONGOLIA

The Langshan and Zhartai Groups of extensional transitional crust nature formed on the basis of the Changchengian（Middle Proterozoic）taphrogeny at the northern margin of the North China platform underwent solid rheologic folding and bedding ductile shear sliding at the early stage,folding-thrusting in the main stage and superimposition and reworking in the late stage in the middle-late Proterozoic folding and orogeny,thus giving rise to the Langshan normal fan-shaped nappe structure and the isoclinal folding-frac- turing structure.By using voluminous statistical data obtained by field sur- eying,this paper deals with the features of tectonic deformation of various vstages and then discusses the sequence of tectonic evolution of the middle and late Proterozoic fold belt in the Langshan-Zhartai Mountains at the northern margin of the North China platform.