TECTONIC FRAMEWORK AND OROGENIC PROCESS OF HOH XIL OROGENIC BELT, QINGHAI PROVINCE, CHINA

摘要

The Hoh Xil Orogenic Belt is a composite one as it has both the Paleotethyin and Neotethyan orogenesis. It is composed, from south to north, of the foreland basin in northern North Qiangtang Block, Hoh Xil Accretional Wedge, Kunlun Island Arc and Qaidam Back-arc Basin. Creating the Hoh Xil Orogenic Belt, Paleotethyan ocean was almost closed at the end of Early Permian, which resulted in wide accretional wedge, with a slight orogeny called late Hercy-nian orogeny. The low mountain terrain formed during the orogeny was rapidly eroded, and a set of Late Permian-Early Triassic stable sediments was deposited on the erosion surface. During the Middle-Late Triassic period the region rapidly subsided and became a part of the Paleotethyan trough in which a great thickness of flysch was formed. By the end of Triassic, the most intense orogeny known as the late Indosinian orogeny took place, which resulted in the formation of the great orogenic belt. Later on it was affected by Neotethyan orogenesis.