Formation and its geological environment of the permian magmatic rocks in Donggou county, Daban city, southern margin of Bogeda orogenic belt
GUO Wei1,2, ZHOU Ding-wu3, OUYANG Zheng-jian4, ZHOU Xiao-hu1
(1 Department of Geology, Northwest University, Xi′an 710069, Shaanxi, China;2 School of Earth Sciences and Resources Management, Chang′an University, Xi′an 710054, Shaanxi, China;3 Geoinformation Science & Engineering College, Shandong University of Science and Technology,Qingdao 266510, Shandong, China；4 Changqing Petroleum Company, China National Petroleum Corporation, Xi′an 710021, Shaanxi, China)
Abstract:
The Permian magmatic rocks of Bogeda orogenic belt are characterized with REE distribution model for LREE enrichment, Eu weak abnormal or no-abnormal. The ion lithophile elements (LILE),such as Ba, K and Rb are intensively enrich, and Th, Sr, Ce and P are appropriately enrich.High field strength elements (HFSE), such as Ta, Nb and Ti show negative abnormity of “TNT” obviously,and Zr and Hf are moderate losses. These features indicated the magmatic rocks had the geochemistry property related to the subduction zone environment. However, the overall characteristics of trace elements and the characteristics of key elements of the magmatic rocks show that the magma was influenced by the process of mixture of continental crust during rising. The magma source was relatively shallow crust or environment of continent tension or initial crack valley mixed with continental crust. It indicated that the Bogeda orogenic belt experienced postorogenic regional extension without adjustment process.
KeyWords:
Bogeda； permian； magmatic rocks； geological environment
