R8: Metamorphic rocks and tectonics

[R8P-01] Different growth timings of host garnet and inclusion osumilite in a garnet-sillimanite gneiss from Rundvågshetta, the Lützow-Holm Complex, East Antarctica

[Presentation award entry]

*Kota Suzuki¹, Tetsuo Kawakami¹ (1. Kyoto Univ.)

Keywords:ultrahigh-temperature metamorphism, osumilite, prograde metamorphism, partial melting, nanogranitoid

We re-examined growth timings of host garnet and inclusion osumilite in a Grt-Sil gneiss from Rundvågshetta. A previous study interpreted that garnet and osumilite were formed simultaneously during post-peak isothermal decompression. However, this study revealed that osumilite is always anhedral and included in nanogranitoids. This mode of occurrence suggests that osumilite is a daughter mineral crystallized within melt inclusion after the entrapment into host garnet. Therefore, this Grt-Sil gneiss might not reached the stability field of Grt+Osm (>960 ^oC).