Age of the Pulang porphyry copper deposit in NW Yunnan and its geological significance

The Pulang porphyry copper has its peculiarity in China's porphyry deposits. It is of great significance for both basic geological research and evaluation of mineral resources in the Zhongdian island-arc zone. However, no precise chronological data are available about the porphyry copper deposit. By molybdenite Re-Os dating and single-grain K-Ar dating, it was for the first time determined that the age of mineralization of biotite-quartz monzonite-porphyry in the Pulang porphyry copper ranges from 235.4±2.4 to 221.5±2.0 Ma, while the molybdenite Re-Os age of the quartz-molybdenite stage is ～213±3.8 Ma. The two ages are close to each other, which suggests that mineralization of the Pulang porphyry copper deposit occurred in the Indosinian. The K-feldspar K-Ar dating of the main orebodies reveals that the hydrothermal activity related to porphyry copper continued to ～182.5±1.8 Ma, suggesting that the lifespan of the hydrothermal system lasted at least 40 Ma. This long-active hydrothermal system may be one of the necessary conditions for producing large high-grade porphyry copper deposits.