Geochronology, geochemical characteristics and Hf isotopic compositions of granite in the Hutouya deposit, Qimantag, East Kunlun

Abstract: The Hutouya Pb-Zn polymetallic ore deposit is located in Qimantag, East Kunlun. Intermediate-acid intrusive rocks occur widely in this area, and are closely related to iron polymetallic mineralization. The results of LA-ICP-MS zircon U-Pb isotope dating reval that the granodiorite in the periphery of No. Ⅴore belt was formed at (224.3±0.6) Ma and the orthoclase granite in No. Ⅷ ore belt was formed at (239.7±0.8) Ma. Petrogeochemistry shows that the granodiorite is rich in K and poor in Na, with no strong negative Eu anomalies (δEu=0.68-1.06), and is enriched in Rb, Th, U, K, but depleted in Nb, P, Ti, thus belonging probably to I-type granite series. The orthoclase granite is characterized by high SiO2, high alkali, low TFeO, MgO, CaO, P2O5 and TiO2, strong negative Eu anomalies (δEu 0.08-0.26), enrichment of Rb, Th, U, K，and depletion of P, Ti, Ba, Sr, belonging probably to highly fractionated I-type granite series. Both of them were formed at the post-collision stage. Variable Hf isotopic compositions of zircon indicate that it experienced magma mixing, which provided large quantities of ore-forming meterials for large-scale polymetallic mineralization.