GEOCHEMICAL CHARACTERISTICS OF THE KEZILEZHAYILAO BATHOLITH IN WEST TIANSHAN

The Kezilezhayilao batholith, located in the west of Alataw Pass in Xinjiang, belongs to Carboniferous mixed source sequence granite, including eight intrusive sequences. Geochemically, the contents of SiO₂ and K₂O+Na₂O tend to increase gradually from early to late sequences, while those of Mg, Fe, Ca and TiO tend to decrease. Among trace elements, the siderophile, chalcophile and lithophile elements each have different evolutional laws in the evolution process of magma. In general, major radius lithophile elements are relatively concentrated while high field strength elements are relatively depleted. The total amount of rare earth elements tends to increase from early to late sequence, with LREE enriched and HREE depleted relatively. The fractional distillation of LREE is strong while that of HREE is relatively weak. Comprehensive analysis of lithogeochemical data suggests that the emplacement depth becomes shallower from early to late sequence. The source of magma is mainly from basaltic differentiation, mostly with characteristics of Itype granite. The early sequences were formed in the extension-convergence stage of the Late Paleozoic Alataw continental margin basin; while the late sequences, in the closure-collision stage.