Geochronology, Geochemistry and Tectonic Significance of Miocene Quartz Monzonite from the Northern of Qitai Mountain in Western Kunlun

Qitai Mountain is located in Xinjiang−Xizang Highway 540 km west of Xinjiang Kunlun area, there are small−scale medium acid intrusive rocks distributed around it, the lithology is mainly composed of the quartz monzonite. Here we present bulk-rock geochemistry, zircon U-Pb geochronology of the Miocene quartz monzonite in Qitai Mountain in Western Kunlun in order to shed light on this issue. Zircon U–Pb dating yielded Miocene ages of (10.4 ± 0.3) Ma. Geochemically, this early Miocene quartz monzonite is A-type granites with high SiO₂ (63.16%～68.20%), K₂O (4.23%～5.24%), and low Al₂O₃ (13.39%～15.47%), MgO (1.06%～1.49%), TiO₂ (0.60%～0.83%). They are enriched in light rare earth elements (LREEs), large ion lithophile elements (LILEs, including K, Rb, Th, U, Ba and Sr), but depleted in high-field strength elements (Nb, Ta and Ti) and heavy rare earth elements (HREEs), and have obvious negative Eu anomalies. The geochemical characteristics of the rocks and the tectonic setting diagram indicate that the quartz monzonites may have been formed in an environment where the deep lithosphere was strongly extended, and a high temperature and low pressure environment was formed in the deep crust, which prompted a low degree of partial melting of the lower crust and rapid along deep and large faults. The uplift emplacement represents the magmatic response to the intraplate extensional background. We suggest that the Miocene magmas from the northern of Qita Mountain in Western Kunlun were likely sourced from low–degree partial melting of the lower crust with a high temperature and low pressure environment, there may have formed in the background of strong extension of the deep lithosphere, which promotes the magmas rapid uplift along deep and large faults.