Presentation Information
[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
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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).
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).