Late Carboniferous intra-oceanic subduction and mineralization in western Junggar : Evidence from the petrology, geochemistry and zircon U-Pb geochronology of I # ore-bearing granite body in Suyunhe molybdenite orefield, Xinjiang

Porphyry-type molybdenite mineralization of Suyunhe in western Junggar is closely related to Late Carboniferous granitic magmatism. Rock samples of I-# ore-bearing granite body consisting of monzonitic granite-porphyry, porphyritic monzonitic-granite and biotite monzonitic granite porphyry are geochemically characterized by high SiO2, Al2O3 with Na2O/K2O ratios changing from 0.97 to 1.32 and A/CNK ratios ranging from 1.08 to 1.28, which synthetically display characteristics of calcalkaline peraluminous granitoids. Granite samples are rich in LREE and LILE (K, Rb, Th, U etc.), infertile in HREE and Ba, Sr, P, Ti, Nb, Ta etc., coupling with weakly Eu negative anomaly (delta Eu=0.62 similar to 0.92). Ore-bearing granite body intruded at 308.8 +/- 4.1Ma. Sr-Nd isotopic compositions indicate that I-# ore-bearing granite body is characterized by positive epsilon(Nd)(t) (3.64 similar to 6.33), low I-Sr (0.704000 similar to 0.705313) and relatively younger two-stage model ages (t(2DM)) ranging from 0.52Ga to 0.70Ga. In terms of both previous research results on regional tectonic setting and discrimination diagrams, I-# ore-bearing granite body in Suyunhe derived from partial melting of Late Proterozoic mafic rocks with the mixture of fluid and clastic sediments. Granitic intrusion formed at intra-oceanic arc setting of Hercynian accretionary orogeny, which may also cause reasonable porphyry-type polymetallic mineralization related to Late Carboniferous magmatism in the west of Barleik Fault.