Zircon SHRIMP U-Pb dating of the Pulang porphyry copper deposit, northwestern Yunnan, China: The ore-forming time limitation and geological significance
滇西北普朗斑岩铜矿锆石离子探针U-Pb年龄: 成矿时限及地质意义

The high precision Zircon SHRIMP U-Pb dating method has been applied to measure the ages of the copper mineralized monzonite porphyry in the Pulang porphyry copper deposit, northwestern Yunnan, China, with the dated ages of 228±3Ma, 226.3±2.8Ma and 226±3Ma. The shapes of the zircon samples and the parameters of their contained uranium and thorium are in accordance with the characteristics of the typical magmatic zircon. The dated ages of zircon samples are almost identical within the range of deviation. This indicates that the magma, which formed the copper mineralized monzonite porphyry, was emplaced rapidly from its magma chamber. In the combination of the zircon SHRIMP U-Pb dating ages of the porphyry samples, and the previously published data of the Ar-Ar plateau ages of biotite samples and the Re-Os isochronism age of molybdenite sample, it is believed that the main ore-forming stage of the Pulang porphyry copper deposit occurred at 216~214Ma, and then it is inferred that the magma-hydrothermal fluid system of the Pulang porphyry copper deposit could have been lasted over 10Ma from its magma emplacement stage to the magmatic hydrothermal mineralization stage. The magmatic hydrothermal fluid, which was derived from the magma chamber and rich in ore-forming materials and volatiles, had strongly altered the Pulang porphyry complex and extracted some ore-forming material form it at the relative later stage.