Evolution of multi-stage ore-forming fluid and mineralization: Evidence form fluid inclusions in Yulong porphyry copper deposit, East Tibet
藏东玉龙斑岩铜矿床多期流体演化与成矿的流体包裹体证据

Petrographic observation,microthermometry,Laser Raman Microprobe Analysis (LRM) and Scanning Electron Microscope/Energy Dispersion Spectrum(SEM/EDS) was performed to fluid inclusion in phenocryst quartz and molybdenite-quartz vein.Different kinds of inclusions was observed including melt inclusions,two phase aqueous fluid inclusions and multi-phase fluid inclusions with daughter minerals.Most of fluid inclusions in phenocryst quartz formed in K-silicate and quartz-sericite stage.Little melt inclusion survived later alteration.The ore-forming fluid related to K-silicate and quartz-sericite alteration is characterized by K- rich,high temperature and high salinity with meaning of magmatic origin.Argillic alteration is attributed to a Ca-rich,low-temperature fluid.From porphyry mineralization to hypergene mineralization,Ore-forming fluid evolved form NaCl-KCl-H_2O-CO_2(CH_4) to CaCl_2- H_2O-CO_2 system.The authors think that there are some origin affinity between early high temperature,K-rich fluid and later low temperature Ca-rich fluid.K-silicate,quartz sericite and argillic alteration occurred in different evolution stage.Unmixing of fluid caused by falling of pressure and temperature is the dominated factor for mineralization.