TECTONIC CHARACTERISTICS OF NORTHERN XINJIANG AND OIL AND GAS PROSPECTS OF CARBONIFEROUS TO PERMIAN SYSTEMS

Northern Xinjiang which had been a single entity during Precambrian time, was splitted up in early Palaeozoic time. From north to south, there were three tectonic units,i.e. Allay Plate, Zhungaer Plate and North Tianshan Plate. Zhungaer Plate was a Palaeozoic oceanic plate evolved on Pre-cambrian basement, and it was basically an eugeogycline during Ordovician and early Carboniferous times. The oceanic crust became closed during middle Carboniferous, and gradually transformed into a newly formed plat-form. By late Middle-Carboniferous time,sediments on the plate were largely laid down under stable regime. For Altay Plate in the north, the Or-dovician-Silurian sediments of miogeosyncline were deposited on Precam-brian basement. Once in Devonian, it became an eugeosyncline, but it was uplifted during early Carboniferous. In the south, North Tianshan Plate with its typical properties of continental crust had been covered by sediments of platform type, and was transformed into an eugeosyncline during Devonian-early Carboniferous. The middle-late Carboniferous sediments are of transitional type, and those of Permian time are of depression type. After Permian, the three plates merged into a single plate, entering a new period of evolution, i.e. the stage of intraplate basin. Depending on the studies of the evolution of regional structure, depositional construction, and oil generation conditions in the northern Xinjiang, it is thought that oil/gas propects may be bright in TulufanHami, Chaiwo-bao,Santanghu and Yili basins, except in Zhungaer Basin.