Genesis of the Ore-related Granite Porphyry and Molybdenite Re-Os Age of Laomiaogou Porphyry-skarn Mo Deposit,Western Henan Province: Implications for Regional MineralizationEI北大核心CSCD

The newly discovered Laomiaogou porphyry-skarn Mo deposit is located south of the Machaoying fault in western Henan province. The ore-body is hosted in the contact between the Laomiaogou granite porphyry dyke and the Duguan Formation. LA-ICP-MS U-Pb analyses for zircons from the granite porphyry yield a weighted mean 206Pb/238U age of 152.1±0.6 Ma, and seven molybdenite separates yield a weighted mean age of 151.9±0.9 Ma and isochron age of 151.6±5.1 Ma. Thus, the granite porphyry dyke and Mo mineralization are contemporaneous. The ore-related granite porphyry dyke is a peraluminous I-type granite with high contents of SiO2 and K2O. The rocks are strongly depleted in P, Nb, Ta and Ti, indicative of intensive fractionation of apatite and Fe-Ti oxides, and characterized by low whole-rock εNd(t) (-20.6 to -17.6) and zircon εHf(t) values (-26.9 to -22.6). The old tDM2(Nd) ages (2.37 to 2.61 Ga) and zircon tDM2(Hf) ages (2.62 to 2.88 Ga) suggest that the granite porphyry was likely derived from an ancient crustal source. Considering the tectonic evolution and geochemical characteristics of the granite as well as other Mesozoic granites in the southern margin of the North China Craton, we suggest that the Laomiaogou granite porphyry dyke and Mo were most likely derived from partial melting of the Taihua Group metamorphic rocks under extensional tectonic regime related to the subduction of the paleo-pacific plate. © 2018, Science Press. All right reserved.