Abstract:

The Pulang copper deposit is a superlarge porphyry type polymetallic deposit in northwestern Yunnan Province. It occurs in an Indosinian quartz diorite-quartz monzonite porphyry-granodiorite porphyry complex and previous study showed it was formed during the Indo-Chinese period. Comprehensive studies on petrology, microthermometry as well as carbon-hydrogen-oxygen isotope of fluid inclusions showed that there are such three types of fluid inclusions as halite-bearing three-phase, aqueous two-phase as well as vapor-rich in quartz from chalcopyrite±pyrite-quartz veins, the ore-forming fluids are of medium to high temperature, high salinity NaCl-H₂O type hydrothermal solutions and mainly derived from the Indonisian magmatism; whereas three types of fluid inclusions, including halite-bearing three-phase, aqueous two-phase as well as CO₂-bearing three-phase respectively are observed in quartz from molybdenite±chalcopyrite-quartz veins, the ore-forming fluids are of medium to high temperature, high salinity NaCl-CO₂-H₂O type hydrothermal solutions and might come from later magmatism. Only aqueous two-phase fluid inclusions are found in calcite from the latest chalcopyrite±molybdenite-calcite veins and the ore-forming fluids are of low to medium temperature, low salinity NaCl-H₂O type hydrothermal solutions, a later evolution product of the former NaCl-CO₂-H₂O type hydrothermal solutions is presumed. In combination with the regional metallogenic background that Mo and Cu mineralization in the Yanshanian period are widely spread in the area, so the conclusion can be drawn that in the Pulang copper deposit Mo and Cu mineralization of the Yanshanian period might also co-exist.

Key words: Pulang copper deposit, ore-forming fluid characteristics, ore genesis, isotopes, Yunnan Province