Re-Os Age of Molybdenite from the Mengku Iron Deposit in Altay,Xinjiang and Its Implication for Metallogeny

The Mengku large-size iron deposit occurs in metavolcanic-sedimentary sequence of the Upper Silurian-Lower Devonian Kangbutiebao Formation in the Maizi Basin of south Altay,with the host rocks being garnet skarn,granulitite,leucogranulitite and marble.Ore bodies are largely concordant with the bedding of the strata,and the distribution of the ore bodies is spatially related to skarn.Precise Re-Os dating of molybdenite from the pyrite-molybdenite-quartz large vein in the No.1 orebody of the Mengku iron deposit has been carried out in this study.The results show that the Re-Os model ages of seven samples rang from(261.6±3.7)Ma to(264.0±3.6)Ma,weighted mean ages of(262.9 1.4)Ma with a Re-Os isochron age of(261±6.9)Ma.Re-Os dating of molybdenite suggests that the hydrothermal activity and Cu-Mo mineralization in the Mengku deposit occurred in the late Middle Permian.The ages of 261±6.9 Ma of molybdenite provide the latest time of mineralization ages and the iron main mineralization perhaps took place in the Early Devonian.The rhenium contents of molybdenite samples range from(22.74～35.69)μg/g,which indicate that Mo-Cu was derived from both mantle and crust.