Tracing the Boundary between UHP and HP Metamorphic Belts in the Southwestern Sulu Terrane, Eastern China: Evidence from Mineral Inclusions in Zircons from Metamorphic Rocks

摘要: The southwestern Sulu terrane, eastern China is divided into four fault-bounded lithologic units. From northwest to southeast, they are: (1) orthogneiss unit (Unit I); (2) supracrustal rock II); (3) kyanite-bearing quartzite—marble III); and (4) paragneiss—schist IV). Inclusions of index minerals in zircon separates from more than 90 samples these units were identified using laser Raman spectroscopy electron microprobe analysis. Coesite coesitebearing ultrahigh-pressure (UHP) mineral assemblages occur various amphibolite-facies metamorphic rocks Units I II. In contrast, aragonite- phengite-bearing high-pressure (HP) are preserved zircons many amphibolite-to greenschist-facies III IV. These together with previous studies yield P-T estimates peak recrystallization at 723°-852°C, P > 2.8 GPa for UHP rocks, 500°-600°C, = 1.2-2.5 HP ro...