Ultrahigh-Pressure Metamorphism and P-T-t Paths for the Eclogites from the Central Areas of Sulu Orogen, Eastern China

Eclogites from the Guanshan and Yangkou areas of Sulu orogen consist garnet, omphacite, phengite, amphibole, quartz/coesite, rutile, ilmenite. Garnet exhibits weak compositional zoning where Xgr decreases core to mantle then increases towards rim, coupled with an increase in Xpy decrease rim. Phase equilibria modelling pseudosections calculated using THERMOCALC NCKFMASHTO system for eclogites records two stages metamorphism: (I) prograde associated quick subduction (Stage-I) (II) retrograde exhumation (Stage-II). Stage-I is recorded core-mantle garnet Si content phengite a mineral assemblage Grt-Omp-Amp-Phg-Qtz-Rt ± Lws, P-T conditions are constrained at 22–26 kbar 600–615 °C Guanshan, while 24–26 595–600 Yangkou. The peak (Pmax = 33 kbar; T 685 °C) revealed by maximum minimum Grt-Omp-Phg-Coe-Rt Lws. value Pmax suggests that depth exceeds 110 km. Stage-II mantle-rim its estimated be 12–15 780–820 reflected Grt-Omp-Amp-Pl-LL-Qtz-Rt ilm, 13–14 770–790 Grt-Omp-Amp-Pl-LL-Qtz-Rt. metamorphism study overall consistent regional metamorphic events, ultra-high-pressure eclogite facies, through high pressure amphibole ages 245, 227 195 Ma, respectively.