TECTONIC EVOLUTION OF THE LATE ARCHEAN WUTAISHAN COLLISION OROGEN

The Wutaishan collision orogen may be divided into three tectonic slices by applying the tectonic lithologic event method;from south to north they are the forearc mélange zone,paleoisland arc system and backarc mélange zone.Five stages are proposed for the tectonic evolution of the Late Archean Wutaishan collision orogen:the ocean basin spreading stage（＞2 600 Ma）,stage of subduction of the southern ocean basin beneath the microcontinental blok and transformation of the microcontinental block into an island arc （2 600～2 500 Ma）,stage of forearc collision backarc subduction（2 550～2 500 Ma）,continent continent collisison stage（2 550～2 450 Ma）,and extension stage（2 500～2 400 Ma）.