Geochemistry, zircon U-Pb and molybdenite Re-Os dating of the Taolaituo porphyry Mo deposit in the Central Great Hinggan Range: implications for the geodynamic evolution of northeastern China

摘要

The Taolaituo porphyry-type molybdenum deposit is located in the eastern Inner Mongolia Autonomous Region in China. The mineralization occurs mainly as veins, lenses and layers within the host porphyry. To better understand the link between the mineralization and the host igneous rocks, we studied samples from the underground workings and report new SHRIMP II zircon U-Pb and Re-Os molybdenite ages, and geochemical data from both the molybdenites and the porphyry granites. Five molybdenite samples yield a Re-Os isochron weighted mean age of 133.0 +/- 0.82 Ma, whereas the porphyry granitoids samples yield crystallization ages of 133 +/- 1 Ma and 130.4 +/- 1.3 Ma. The U-Pb and Re-Os ages are similar, suggesting that the mineralization is genetically related to the Early Cretaceous porphyry emplacement. Re contents of the molybdenites range from 21.74 to 42.45 ppm, with an average of 32.69 ppm, whereas delta S-34 values vary between 3.7 parts per thousand and 4.2 parts per thousand, which is typical of mantle sulphur. The Pb-206/Pb-204, Pb-207/Pb-204 and Pb-208/Pb-204 vary in the ranges of 18.276-18.385, 15.566-15.580 and 38.321-38.382, respectively. The Taolaituo Early Cretaceous granitoids are A-type granites. These observations indicate that the molybdenites and the porphyry granites were derived from a mixed source involving young accretionary materials and enriched subcontinental lithospheric mantle. A synthesis of geochronological and geological data reveals that porphyry emplacement and Mo mineralization in the Taolaituo deposit occurred contemporaneously with the Early Cretaceous tectonothermal events associated with lithospheric thinning, which was caused by delamination and subsequent upwelling of the asthenosphere associated with intra-continental extension in northeast China. Copyright (C) 2015 John Wiley & Sons, Ltd.