The Pulang Porphyry Copper Deposit and Associated Felsic Intrusions in Yunnan Province, Southwest China

Abstract

The Pulang porphyry copper deposit recently discovered in northwestern Yunnan province, China, is located at the south end of the Triassic Yidun island arc. To date, 15 mineralized porphyry deposits have been defined in the Pulang area and the copper resource is estimated to exceed 10 Mt. The Pulang deposit, as currently defined, is made up of five ore-bearing porphyry deposits, covering an area of approximately 9 km2. Intermediate acidic porphyritic intrusions composed of quartz-diorite, monzodiorite, quartz-monzonite, and granodiorite are widespread in the Pulang area. The alteration zones identified with the porphyry deposits include silicic, potassium silicate, quartz-sericite, and propylitic zones. The porphyry deposits have hornfels at the contact with slate, sandstone, and andesite. Re-Os ages of molybdenite, and Ar/Ar and K-Ar dating of biotite indicate that the Pulang porphyry copper deposit formed during the Indosinian tectonic episode, with the main ore formation taking place from 216 to 213 Ma (Late Triassic, Norian); however, the whole process of hydrothermal activity, including overprinting, may have extended from 235 to 182.5 Ma.