Fluid-Rock Interaction in UHP Phengite-Kyanite-Epidote Eclogite from the Sulu Orogen, Eastern China

Combined petrographic, minerochemical, fluid inclusion, and stable isotope studies have been carried out on phengite-kyanite-epidote (Phe-Ky-Ep) eclogites from Hushan and Qinglongshan (Donghai area, UHP Sulu orogen, China) to unravel their metamorphic evolution and fluid-rock interaction. A complex metamorphic evolution, from coesite-eclogite (P = 3.5-4.0 GPa and T = 840 ± 50°C) to greenschist facies conditions (P ≈ 0.2 GPa and T ≈ 350°C), through quartz-eclogite and HT amphibolite-facies conditions, was recognized. The associated fluids are aqueous and show a progressive change in salinity and composition, reflecting different metamorphic stages. Stable isotope data confirm that, prior to subduction, the Sulu eclogite protolith experienced a meteorichydrothermal alteration, and indicate that during metamorphic evolution the rocks recrystallized without pervasive fluid infiltration.