Genesis and tectonic significance of Late Permian Qimulaike intrusive rocks in the west of East Kunlun Mountains, Xinjiang

Zircon U-Pb dating of Qimulaike granitic stocks shows that the age of the granodiorite is 274.6 ±1.2Ma and that of diatomite granitic diorite is 271.2±0.6Ma, implying the formation time of Late Permian. The geochemical characteristics of the rocks show that they have calc-alkaline and weak aluminum (A/CNK being 0.99~1.1)characteristics; the chondrite-normalized REE patterns show steepness on the left and smoothness on the rightwith weak negative anomaly of the δEu; the trace elements exhibit depletion of high field strong elements such as Nb, Ta, Ti and P.Combined with the structural environment, the authors hold that the rocks were formed in an island arc environment and belong to the I-type granite. In combination with regional tectonic evolution, it is shown that ancient Tethys in the Late Permian began subducting to the Tarim plate, while the mid-ocean ridge was still continuing to expand, indicating that the ancient Tethys at that time had been in the dying period.