The Geological And Geochemical Characteristics Of The Wenquan Molybdenum Deposit In The West Qinling, And Its Metallogenetic Geodynamic Setting

The Wenquan Mo deposit occurred in coincidence with the late Triassic continental collisional orogenesis and magmatism in Qinling orogenic belt, so that the furthermore study on genesis and geodynamic setting of Wenquan Mo deposit will provide a useful insight into the genetic connections between mineralization with the tectonic regime transformation of Qinling orogenic belt and improve the Indonesian metallogenic theory in Qinling orogenic belt. Based on the previous studies on geological characteristics and prospecting information of Wenquan Mo deposit, ore geochemistry and isotope geochemistry were adopted on the study of ore- and granite-forming geochronology, genetic type of Mo-bearing granitoids, the source of ore-forming fluid, geodynamic setting and detailed ore-forming process for the Wenquan Mo deposit.This study obtained the LA-ICP-MS zircon U-Pb ages of porphyritic monzogranite, porphyry-like biotite monzogranite and MMEs are 216.2±1.7Ma,217.2±2.0Ma,217.0±2.0Ma, were formed in Late Triassic. Furthermore, Wenquan Mo deposit yield a weighted mean Os model age of 214.1±1.1Ma and Re-Os molybdenite isochron age of 214.4±7.1 Ma.The monlybdenite age consistent with the LA-ICP-MS zircon U-Pb dating yields crystallization ages, which suggest that the Mometallogenic episode is related to the late Triassic magmatism in the West Qinling Orogen.The study of the lithogeochemistry and Lu-Hf isotope geochemistry indicate the monzogranite derived form the partial melting of Neo-Mesoproterzoic ancient crust, and the MMEs derived from partial melts of the Neoproterozoic enriched lithosphere mantle that formed during rift magmatism in response to breakup of supercontinent Rodinia, and experience subsequent fractional crystallization and magma mixing process.The study of the Pb, S, C isotopic compositions and REE suggest that the ore-forming fluid is magmatic-hydrothermal fluid which derived from the magma of Wenquan Mo-bearing granite.As a result of the late Triassic intra-continental collisional orogenesis in China, the Wenquan Mo deposit formed during a period of tectonic setting transition from compression to extension in Qinling orogenic blet. During this period, the asthenosphere upwelling triggered partial melting of the Neoproterozoic enriched lithosphere mantle, which resulted in the generation of mafic magma. The thermal anomoly produced by the underplating of mafic magma resulted in the partial melting of Neo-Mesoproterozoic lower crust, and formed Mo-bearing granitoid. The ore-forming fluid generated during the late phases of magma crystallisation, filled the joints or replaced the host rocks to form the Late Triassic Wenquan Mo deposit. As a typical and rare magmatic-hydrothermal quartz vein-type Mo deposit in the West Qinling orogenic belt, Wenquan Mo deposit highlights the possibility of extensive Mo mineralization in the other Late Triassic granite of the West Qinling orogenic belt.