Double stage evolution model for the Altyn Tagh fault in China (3)

During the double stage extrusion, the Alxa–East Mongolia fault became inactive, and additional offset along the Altyn Tagh fault has been mainly accommodated by shortening of the Qilian Shan and the Qaidam basin. People infer that the first stage of movement along the Altyn Tagh–Alxa–East Mongolia fault system may have begun around Oligocene time; the region transformed to the second stage of fault movement ca. 13–16 Ma, probably because of thinning of the lithospheric mantle beneath northern Tibet. The proposed model suggests that the Derbur fault in northernmost China and beyond is an extension of the Alxa–East Mongolia fault, and has a history of strike-slip movement. The nearly 400 km of offset on the Alxa–East Mongolia fault may have been accommodated mainly by subduction in the Sea of Okhotsk.