Re-Os dating of molybdenite from the Kafang skarn copper (tin) deposit in the Gejiu tin polymetallic ore district and its geological significance

The Gejiu tin polymetallic ore district is a famous tin polymetallic ore producing area in Yunnan Province. The Kafang skarn copper (tin) deposit is one of important mineral deposits of the Gejiu region. Re-Os dating of five molybdenite separated from the Kafang skarn ore bodies gives an isochron age of 83.4 ± 2.1Ma and model age ranges from 82.95 ± 1.16 to 83.54 ± 1.31 Ma. This age is in good agreement with Laoka granite zircon LA-ICP-MS U-Pb age(85 ± 0.85Ma). These ages suggest that the mineralization in the Kafang skarn deposit was genetically assoicatted to the Laoka granite. The Re contents of molybdenite indicate that ore-forming materials are derived from mantle and crust. Based on the geochronological data of Dulong Sn-Zn deposit, Bainiuchang Ag super-large deposit, Dachang tin polymetallic ore field and Wangshe Cu-W deposit and analysis of tectonic evolution of Southeast of Yunnan Province, we propose that these deposits occurred at the same geodynamic framework as a result of large scale mineralization in South China