Tectonic implications from Re–Os dating of Mesozoic molybdenum deposits in the East Qinling–Dabie orogenic belt

Abstract

The East Qinling–Dabie molybdenum belt is part of a larger East–West trending metallogenic belt in eastern China. Most of the molybdenum deposits occur as porphyry or porphyry–skarn type, but there are also some vein type deposits. Following systematic Re–Os dating of molybdenite from 13 deposits and comparisons with two previously dated deposits, we have recognized that the molybdenum mineralization in the East Qinling–Dabie belt was developed during hydrothermal activity linked to magmatism and the emplacement of granitoid stocks. Three pulses of granitoid magmatism and Mo mineralization are recognized corresponding to significant tectonic events in the East Qinling–Dabie belt. Vein type deposits dated at 233–221 Ma were formed in detachment fractures, indicating localized extension within the collisional setting of the North China and Yangtze Cratons. I-type and transitional I- and S-type granites and related mineralization dated at 148–138 Ma may have formed part of a continental magmatic arc, with widespread magmatism and back-arc extension caused by subduction of the Izanagi or Paleopacific plate beneath the Eurasian continent in a WNW–ESE direction in the Late Jurassic–Early Cretaceous. Both S-type and transitional S- and I-type granite-associated porphyry molybdenum deposits dated at 131–112 Ma are part of an extensive mineralization event throughout East China that can be ascribed to regional large-scale lithospheric thinning, delamination and thermal erosion.