Geochemistry and tectonic significance of Buya granite in southwestern margin of Tarim, NW China
Zhu Yanfei1, Li Ping2, Zhu Zhixin1,2, Jin Liuyuan2, Liu Xin1, Chen Bangxue3
1. College of Geology and Mining Engineering, Xinjiang University, Ürümqi 830046;
2. Geological Research Academy of Xinjiang, Ürümqi 830011;
3. The No.11 Geological Brigade of Xinjiang Geology and Mineral Bureau, Changji Xingjiang 831100
Buya granites emplaced into Ailiankate Group which located in Tiekelike tectonic belt of the southern margin of Tarim, which mainly consists of Monzonitic granite. Zircon LA-ICP-MS U-Pb dating results show that Buya granite formation in the Late Ordovician(457.03~445.07 Ma)and belongs to the product of Early Paleozoic magmatism. Rock geochemistry indicates that its features with high-K calc-alkaline series, with aluminum Ⅰ-type granites, and have geochemical characteristics of high Ba-Sr granites, namely high Ba, Sr and LREE content, high Sr/Y, La/Yb values, low Y(5.9×10-6~8.0×10-6), Yb(0.41×10-6~0.72×10-6)and HREE(4.01×10-6~5.02×10-6), LREE and HREE strongly differentiation, without significantly negative Eu anomaly, low Nb, P, Ti high field strength elements. According to the rock geochemical characteristics and high Ba-Sr granite genesis of previous research, I believe that the rock partial melting may cause by delamination and thinning of the lithosphere of mantle lithosphere, and formed Buya high Ba-Sr granites accompanied by fractional crystallization of hornblende, biotite and accessory mineral. Its source material is likely to mixed source including enriched mantle which contains ocean sediments(including carbonate rocks)subducted slab precipitate fluid/melt and substances of Early Proterozoic Ailiankate Group.