Broken "Western China Craton".

Abstract

Similarities are shown to exist among the Tarim, Qaidam and Alashan blocks including their cratonized Neoproterozoic basement, the Sinian drift sheet and Yangtze type lower Paleozoic cover. It is therefore proposed that they are derived from a unique Craton - the "Western China Craton" of identical evolution, but not micro-continental blocks of Mesozoic age separated by oceans with small islands. The Craton is, during Sinian through early Paleozoic and together with the south China sub-plate and Australian sub-plate, part of the eastern Gondwana supercontinent, and has, similar to the Yangtze-South China Craton, characteristics of complicatedly broken unstable Craton. The North Qilian-Manji'er depression is the largest Aulacogen formed during Cambrian through mid-Ordovician. Aulacogens were also formed along different zones during late Ordovician, late Devonian and early Permian, respectively, while the main part remained stable craton with different degrees of sedimentation in cratonic basins during Paleozoic, providing important clues to the oil-gas exploration in the Paleozoic in the area. The Western China Craton is tectonically localized at the southwest of the Paleao-Asian continent due to the closing of the Tethys. The juxtaposition of the Qiangtang and Lahsa plates onto the Asian plate resulted in Indosinian-Yanshanian intraplate deformation. The most important broken event in the Western China Craton occurred during the Himalayan stage with large-scale displacements by strike-slip and thrusting owing to the collision between the Indian plate and the Asian plate. Then the present tectonic framework was formed.