Study on the metallogenesis during the early stage of continental collision in southern Gangdese, Tibet

Many porphyry Cu-Mo and Cu-Pb-Zn polymetal deposits have been found in the southern Gangdese belt, forming a porphyry copper ore belt and a polymetal ore belt, respectively. Previous geochronologic results indicate that most deposits in the southern Gangdese belt were formed after 30Ma and in post-collisional extension evnironment. In this paper, we analyze zircon U-Pb age of igneous rocks closely associate with the Jialong skarn Fe deposit and the Sadang Au-Ag deposit, respectively, and molybdenite Re-Os age of the Duodigou skarn Mo deposit in the southern Gangdese. The Jialong biotite monzonite granite closely associated with skarn Fe deposit has zircon LA-ICP-MS U-Pb age of 61.1±0.4Ma with MSWD=0.94. The Sadang andesite closely associated with Au-Ag mineralization has zircon LA-ICP-MS U-Pb age of 62.6±0.5Ma with MSWD=1.51. The molybdenite Re-Os model ages of the Duodigou skan Mo deposit varies from 64.3±0.8Ma to 69.2±3.3Ma, with an average weight age of 66.7±6.4Ma, MSWD=8.1. Our new results suggest that the three deposits own their origin to the magmatic events triggered by early Indus-Eurasia collision. Our results, together with former work, reveal that the southern Gangdese has undergone large-scale mineralization associated with the strong magmatic activities during the early Indus-Eurasia collision. It is, therefore, suggested that the southern Gangdese could be an important target area for mineralization related to early Indus-Eurasia collision.