SHRIMP U-Pb Dating of Zircon from Quartz Porphyry in the Yaguila Pb-Zn-Mo Deposit,Gongbujiangda County,Tibet and Its Geological Implication

Located in Gongbujiangda County, Tibet, the Yaguila Pb-Zn, Mo deposit is a porphyry Mo-skarn-hydrothermal vein type deposit, which belongs to the eastern part of the Gangdese belt. This study provides the high-precision magmatic zircon SHRIMP dating of the quartz porphyry from the Yaguila deposit. SHRIMP U-Pb dating analyses for 56 zircon grains from the quartz porphyry present 206Pb/238U concordant ages from 110.2±6.8 Ma to 140.9±1.9 Ma. The weighted mean ages of the three rocks are 128±1.0 Ma (n=20, MSWD=1.3), 129.3±1.3 Ma (n=14, MSWD=1.12), 127.8±1.1 Ma (n=22,MSWD=1.4) respectively. Based on the former study, and the results of zircon dating mentioned above, it is proposed that: (1)Crystallization of the quartz porphyry occurred between 126.7～130.6 Ma, during the Late Yenshanian period. (2)The Yaguila-Sharang deposit is not a SEDEX type deposit but a porphyry Mo-skarn-hydrothermal vein type deposit. (4)The mineralization related to the crystallization of the quartz porphyry during the Late Yenshanian period to the early himalayan period. There are mineralization movements during main Indian-Asian collision period (41~65 Ma)in the Gangdese belt, which means a lot for the mineral resource prospecting of this area.