CHARACTERISTICS AND TECTONIC SETTING OF THE PERMIAN VOLCANIC ROCKS IN BOLE AREA, XINJIANG

The volcanic rocks of Wulang formation are scattered in the Late Paleozoic Alataw continental marginal basin near the contact between Ili micro-plate and Junggar micro-plate of the Kazakhstan-Junggar plate. The volcanic activities are relatively weak, with basic, intermediate and acid magma. The tectonic environment of the tephrite in the area is intraplate; while that of the andesite and rhyolite is intracontinental collision orogenic belt. The alkalinity of the tephrite of Wulang formation is strong. The andesite, rhyolite and rhyolite porphyry are sub-alkaline. The Rb-Sr isotopic age of the intermediate andesite is 282.5±2.6 Ma, in Early Permian. It can be inferred that, in Alataw area, the Ili micro-plate and Junggar micro-plate have been sutured since Early Permian, forming intracontinental fault basin, with the development of continental volcanic-clastic rock formation.