THE WUTAISHAN OROGENIC BELT WITHIN THE SHANXI PROVINCE, NORTHERN CHINA - A RECORD OF LATE ARCHEAN COLLISION TECTONICS

The Archaean crust of northeastern Shanxi Province, northern China, is dominated by three distinct terranes: the high-grade gneiss terranes Hengshan in the north and Fuping in the southeast, and the intervening low-grade terrane of the Wutaishan belt. The 2.5 Ga Beitai are comple x which constitutes the major part of the Wutaishan belt is interprete d as a pre-collision magmatic are. There was a marginal-sea basin betw een the Beitai are and the Fuping terrane. At the fore-are collision s tage the passive margin deposits which occurred along the western marg in of the Fuping terrane became a foreland fold-thrust belt after the closure of the marginal-sea basin. The remnants of sea floor occur as a melange zone along the suture zone between the Beitai are and Fuping terrane. Nearly at the same time, at similar to 2.5 Ga, the back-are oceanic lithosphere started to subduct beneath the Hengshan terrane, t hen the Hengshan terrane came into collision with the are and the Fupi ng terrane. Some dismembered sea-floor rocks are preserved as a back-a re melange zone between the Hengshan terrane and the Beitai are. The t erm 'Wutaishan Orogeny' should be reserved for the processes which las ted from 2600 to 2450 Ma.