DISCUSSION ON THE FORMING ENVIRONMENT AND ORIGIN OF THE INTRUSIVE ROCKS IN XIFENG AREA, LIAONING PROVINCE

The intrusive rocks in Xifeng area, Liaoning Province, formerly called Xifeng intrusive body, are component parts of the Bureya-Zhangguangcailing giant granite belt, which recorded the essential information of evolution process of the orogenic belt from the Paleo-Asian oceanic plate subduction, through ocean basin closure to accretion orogeny. Presently, the Xifeng intrusive body has been disintegrated and reassigned into four intrusion stages, including 11 intrusion orders, and referred to as the intrusive rocks in Xifeng area. On the basis of the new division, forming temperature-pressure condition, tectonic environment, material sources and origin of the rocks are further discussed. The intrusive rocks of the first- and second-order of Early Permian and the first-order of Middle Jurassic Epoch belong to I-type granite. The intrusive rocks (diorite porphyry) of the third-order of Late Cretaceous are also I-type. Their material source is mainly from the remelting of magmatic rocks in the crust. The intrusive rocks of the other orders are S-type granite, with main material source from the remelting of sedimentary rocks in the crust. The intrusive rocks of the first-order of Early Permian are plutonic rocks of the volcanic arc; while those of the second-order are the transition type between volcanic arc and syn-collisional. The intrusive rocks after that are syn -collision or post -collision type granites. These characteristics are basically consistent with the evolution sequence of subduction, closure and accretion orogeny of the Paleo-Asian ocean plate.