Fluid inclusions of garnet-pyroxene granulites from the northern Dabie mountain.

Garnet-pyroxene granulites occurring in the Northern Dabie mountain are basic granulites. There are a lot of fluid inclusions of CO2, CH4, H2S, H2O and the multiphase solidphases-bearing. The multiphases inclusions of solidphases-bearing are discovered in garnets and diopsides for the first time. The solid phases were determined as garnet, pyroxene, barite and Fe-oxide by Laser Raman Microprobe and SEM/EDS, and the gas phases as H2O, CO, CO2, H2S, H-2, CH4, C-2, H-2 and so on with homogenization temperature of 950degreesC, 975degreesC. It indicates that partial anatexis had occurred in the process of forming garnet-pyroxene granulites under reduction condition, and the melt inclusions formed which were catched by carystalling garnets and diosides. Its composition similizes to garnet and pyroxene. Among them, the early stage multiphase inclusions of garnet halite and CO2-bearing, its CO2 density: 0.65similar to0.626g/cm(3), two phase CO2 inclusions, its partial homogenization temperature: 26similar to28.2degreesC, density: 0.648similar to0.688g/cm(3) are late stage low density CO2 inclutions, the three phases H2O-CO2 fluid inclusions in quartz are lower salinity one with Th=331similar to410degreesC, melting temperature of ice point: 7.3similar to8.6degreesC, partial CO2 homogenization temperature: 25.7similar to28degreesC, density; 0.65similar to0.6988/cm(3) which may be early-middle stage inclusions catched. No high density CO, inclusions are found in whole rocks. It shows that the granulites are formed under lower density CO2 condition. The H2O-NaCl fluid inclusions in quartz with homogenization temperature: 80similar to475degreesC, density: 0.36similar to1.026g/cm(3), mainly are late stage inclusions, and a few of abundent H2O inclusions are early stage ons. By means of isochore curves, the P-T paths of garnet-pyroxene granulites are formed in a clockwise way by isothermal decompression process.