GEOLOGICAL EVOLUTION AND OROGENY OF EAST KUNLUN TERRAIN ON THE NORTHERN QINGHAI—TIBET PLATEAU

GEOLOGICAL EVOLUTION AND OROGENY OF EAST KUNLUN TERRAIN ON THE NORTHERN QINGHAI—TIBET PLATEAU1　XuZQ ,YangJS ,ZhangJX ,etal.AcomparisonbetweenthetectonicunitsonthesidesoftheAltunsinistralstrike slipfaultandthemechanismoflithosphericshearingJ] :ActaGeologicaSinica,1999,73:193～ 2 0 5(inChinesewithEnglishabstract) . 2　YangJS ,XuZQ ,LiHB ,Wu ,etal.DiscoveryofeclogiteatthenorthernmarginofQaidambasin,NWChinaJ] .Chi neseScienceBulletin,1998,4 3…

Geological Evolution and Orogeny of East Kunlun Terrain on the Northern Qinghai-Tibet Plateau

The East Kunlun terrain is located on the northern Qinghai—Tibet plateau, composed of the East Kunlun Mountain and the Qaidam Basin and bounded by the Qilian terrain on the north and Bayanhar—Songpan Ganze terrain on the south. It is regarded as a composite orogenic belt characterized by having developed superimposed ductile tectonic regimes reflecting the collision orogeny during Early Paleozoic and Triassic periods. It has also experienced transformation from ductile to brittle deformation caused by the post orogeny, since Jurassic after the formation of the East Kunlun Mountain and the Qaidam Basin. A Paleozoic subduction complex zone was recently recognized along the north border of the East Kunlun terrain from Da Qaidam to Dulan (Xu,et al, 1 999). It is composed of ophiolite (of Early Paleozoic age?), tectonic melange and very high\|pressure metamorphic rocks with eclogite (\%p\%=2 2GPa, \%t\%=720℃) (Yang,et al.,1998) and garnet\|peridotite (\%p\%=2 5GPa, t =837℃). The Anyemaqin Triassic subduction complex zone trending in NWW\|SEE was developed along the eastern segment of the south border of the East Kunlun terrain. It is mainly composed of ultramafic and mafic rocks, pillow basalt, radiolaria\|bearing clastic rocks, tectonic melange and mylonite. The subduction complex zone contains a series of the southward overthrusting imbricated slices. Instead of this subduction complex zone, a 2 km\|wide sinistral strike\|slip ductile shear zone trending in E\|W was developed along the western segment. On the basis of macroscopic and microscopic studies on a series of structural sections, we divide the East Kunlun Mountain into four tectonic units as follows: (1) North Proterozoic Metamorphic Basement Zone; (2) South Early Paleozoic—Triassic Superimposed Fold Zone; (3) South Triassic Transpression Zone; (4) Anyemaqin Back\|Arc Decollement\|Thrust Zone.