Geochemistry and Sr-Nd-Pb Isotopes of Late Paleozoic Intrusive Rocks in Balikuntage, Xinjiang

The intrusive rocks of late Carboniferous and early Permian in the Balikuntage area mainly include diorite, granodiorite, granite and diabase.They show intrusive contact relationships and their ages are similar within the error range. All the intrusive rocks belong to peraluminous calc-alkaline and high-K calc-alkaline series. They are rich in LREE, LILE and incompatible elements, but deficient in HFSE, which are characteristics of the volcanic arc granite. Besides, isotopic composition characteristics of high Nd, low Sr and Pb content suggest that the intrusive rocks come from the depleted mantle.Based on the analysis of the regional geological evolution, the tectonic environment of Balikuntage region is the intercontinental rift valley between late Carboniferous and early Permian, and its island arc characteristics may be induced by the early subduction in magma source. The T_DM value(1076—806 Ma) reflects that the intermediate-acid intrusive rocks have same source area which is given priority to the partial melting of the juvenile crust, and the source of the young crust is derived from the depleted mantle. It can be deduced that Balikuntage and its adjacent area Bogda and Haerlike fully entered into the intraplate environment in late Carboniferous and early Permian.