S3: Mineralogy, Petrology and Economic Geology of Northeast Asia (Special Session)

[S3P-03] Cristobalite inclusion in garnet in pelitic gneiss from the Hanhohiyn Mountains, northwestern Mongolia.

*Tatsuro Adachi¹, Yasuhito Osanai¹, Nobuhiko Nakano¹, Kundyz Syeryekkhaan¹, Sereenen Jargalan², Masaaki Owada³, M. Satish-Kumar⁴ (1. Kyushu Uni. , 2. Mongol. Uni. Sci. Tech., 3. Yamaguchi Uni., 4. Niigata Uni.)

Keywords:

cristobalite,pelitic gneiss,Hanhohiyn Mountains,Mongolia

Cristobalite inclusions were found in garnet in garnet-sillimanite-biotite gneiss from the Hanhohiyn Mountains, northwestern part of Mongolia. Cristobalite is preserved in the core portion of garnet and is as a prograde mineral assemblage. Fine-grained cristobalite inclusions are found with chlorite, pyrophyllite and quartz in garnet. Cristobalite occurring with minerals stable under low-temperature condition suggests that garnet should grow at a faster rate than transition from cristobalite to quartz.