Zircon U-Pb Ages, Hf Isotopes and Geochemistry of the Rhyolite in the Dianzhong Formation from the Qieqiong Area, Xietongmen County, Tibet

The Qieqiong area is located in the middle Lhasa block, Tibet, where volcanic rocks of the Linzizong Group are widespread. The Linzizong volcanic succession is regarded as the magmatism response to the continent collision between India and Asia, which is essentially important in discovering the initial collisional time and processes. This paper reports the whole-rock geochemical, Hf isotope and zircon U-Pb geochronological results of the rhyolite in this area. Tthe dating results show that the age of the rhyolite in the study area is 67.1±0.1 Ma and belongs to the volcanic rock of the Dianzhong Formation of the Linzizong Group. Chemical analyses show that the rhyolites in this area have high Si, high K, and low Ti, with peraluminous nature; they are characterized by LREE enrichment and obvious REE differentiation (Gd/Yb)N=0.57-1.16, with significant negative Eu anomalies (δEu=0.05-0.08), they are enriched in LILEs (Pb, Rb, Th and U), depleted in HFSEs (P and Ti), and obviously depleted in Ba and Sr, thus belong to calc-alkalic and peraluminous series with characteristics of continental margin arc volcanic rocks. Zircon grains from the rhyolite have 176Hf/177Hf values in the range of 0.282673 to 0.282804, εHf(t) values in the range of -2.1 to +2.3, and two-stage model ages (t2DM) of 875 Ma to 1117 Ma. Overall, the rhyolite in the Dianzhong Formation from the Qieqiong area was formed in a subduction tectonic setting, derived mainly from recycled crustal material, and mixed with a small amount of mantle-derived magma. Considering the related deposits in the area and the discovered ore spots in the Qieqiong area, we suggest that the volcanic rocks of the Dianzhong Formation in the Qieqiong area have promising potential for epithermal and skarn deposits prospecting. © 2022, Science Press. All right reserved.