GEOTECTONIC EVOLUTION AND ITS CHARACTERISTICS IN QILIANSHAN REGION
HUANGR Ruihua (Changsha Institute of Geotectonics, Academia Sinica,Changsha 41001 3)
In geotectonic evolution Qilianshan region has gone through geosynclinal stage from Proterozoic to earlier Palaeozoic era, platform stage in latter Palaeozoic era and diwa stage in Meso-Cenozoic era,Proterozoic era of geosynclinal stage is the period of foundation , growth and development of landmass. Earlier Palaeozoic era is the periods of plate margin tectonism of crust-oceanization and intercontinental collision tectonism. Large sedimentary basins are developed in the platform stage. Intracontinental orogenesis and basin-making prossesses, and block-faulting nappe tectonism are structural features in the diwa stage.Qilianshan region has been undergone three importent orogenesises of different natures:compression-folding orOgenesis of landmass of Tuolai orogeny in last Proterozoic era, intercontinental collision orogenesis of Qllian otogeny in latter Caledonian period and intracontinental block-faulting orugenesis in Meso-Cenozoic era.From the above it can been seen that tectonic units of Qllianshan and its adjacent regions are divided from north to south into following: Zoulang diwa, North Qilian geodome, Centre Qilian depression, South Qiliang geodome and Qaidam diwa.