Precise Re-Os dating of molybdenite from the east Qinling molybdenum belt in central China and its geodynamic implications

Located in central China on the southern margin of the North China craton, the East Qinling molybdenum belt is one of the important large molybdenum belts in China. This study provides reliable Re-Os isotopic dating results for the metallogenetic epoch of four deposits by inductively coupled plasma mass spectrometry (ICP-MS), with analytical errors of Re and Os between 0.11–0.4% (2sigma). The results show that the Re-Os model ages are 141.8±2.1 Ma for the Nannihu deposit, 145.4±2.0 to 144.5±2.2 Ma (averaging 145.0±2.2 Ma) for the Sandaozhuang deposit, 145.8±2.1 to 143.8±2.1 Ma (averaging 144.8±2.1 Ma) for the Shangfanggou deposit, and 133.1±1.9 to 131.6±2.0 Ma (averaging 132.4±2.0 Ma) for the Leimengou deposit. According to these ages, combined with the results of previous work in the molybdenum belt, it is suggested that the age of the molybdenite deposits in the East Qinling molybdenum belt is mainly ∼140 Ma. These deposits are the product of transformation from the N-S to the nearly E-W tectonic regime in eastern China. Except for the Huanglongpu Mo deposit, which originated at ∼220 Ma, the deposits appears to have geodynamically formed in the extensional stage of the post-collisional orogeny between the North China craton and the Yangtze craton.