DID TARIM (+NORTH CHINA) COLLIDE WITH QIANGTANG (+SOUTH CHINA) IN BOTH THE DEVONIAN AND THE TRIASSIC?
COWGILL, Eric and KAPP, Paul, Department of Earth and Space Sciences, UCLA, Los Angeles, CA 90095, ecowgill@ess.ucla.edu

Structural mapping, integrated with 40Ar/39Ar thermochronology and U-Pb ion microprobe zircon geochronology indicate that the western Kunlun Shan and Altyn Mountains along the southern edge of Tarim experienced widespread middle to late Paleozoic contractional deformation, regional metamorphism, and calc-alkaline to peraluminous magmatism. In the western Kunlun Shan, contractional deformation and plutonism (i.e., 480-380 Ma 206Pb/238U zircon ages) was followed by regional unroofing and cooling (i.e., 370-320 Ma 40Ar/39Ar biotite total gas ages) during the development of an Upper Devonian to Upper Carboniferous angular unconformity. This unconformity is capped by widespread Upper Carboniferous (i.e., ~290 Ma) shelf carbonates which are in turn overlain by Lower Permian terrestrial siliciclastic deposits. The middle to late Paleozoic tectonic evolution of the western Kunlun Shan is broadly similar to that inferred for the Qiangtang terrane to the south, based on recent work. We propose that during the Late Devonian to Early Carboniferous the composite Tarim-North China block collided with the Qiangtang and South China terranes along the northern margin of Gondwana to form a supercontinent. Subsequent rifting of Tarim+North China from the north edge of Gondwana initiated opening of the Paleotethys Ocean and produced Upper Carboniferous through Permian passive margin sedimentation in both the Kunlun and Qiangtang terranes. The Qiangtang and South China terranes collided with Tarim+North China a second time in the Late Permian to Early Jurassic, following closure of the Paleotethys ocean basin. By allowing collision in both the Devonian-Carboniferous and Permo-Jurassic our model reconciles a long-standing debate over the timing of collision between the North and South China cratons.

Cordilleran Section - 97th Annual Meeting, and Pacific Section, American Association of Petroleum Geologists (April 9-11, 2001)
Session No. 13
Tectonics of Eastern Asia with Emphasis on Tibet and Adjacent Regions
Sheraton Universal: Studio I
1:20 PM-4:30 PM, Monday, April 9, 2001