Re-Os Isotope Dating of Molybdenite from the Shapoling Mo Deposit, East Qinling and Its Implication for Identification of Late Jurassic Mo Mineralization

The Shapoling Mo deposit is located in the Xiong'er rock mass of the southern margin of the North China Craton. The deposit is hosted in a contact zone between granite and wallrocks of the Taihua Soupergroup, which is a recently found discovered vein dissemination type deposit in East Qinling. The ore-bodies are associated with quartz veins and controlled by subsidiary faults. The mineralization styles include veinlet and disseminated types. In order to determine the age of the Shapoling Mo deposit, Re-Os isotopic dating of molybdenite was conducted. Six molybdenite samples yielded Re-Os ages ranging from 158.3±1.5 Ma to 160.7±1.2 Ma, with a weighted mean age of 160±1 Ma (2σ, MSWD=2.1). The Re-Os age shows that the Mo mineralization occurred during the late Jurassic, earlier than the formation of Huashan rock mass (about 30 Ma). In addition, one molybdenite sample in Huashan rock mass yielded a Re-Os age of 130.5±1.0 Ma, which is in accordance with the age of the Huashan pluton and molybdenite age (125.4-129.4 Ma) reported by a previous study. In conclusion, the Shapoling deposit contains two episodes of Mo mineralization from the early Cretaceous and late Jurassic periods. Combining this with geological characteristics and tectonic-metallogenic evolution, it is suggested that Huashan rock mass, granite porphyry, and related hydrothermal deposits in the Xiong'er terrain are the products of extrusion to extension transition during continent-continent collision in the Qinling orogenic belt.