R7: Petrology, Mineralogy and Economic geology (Joint Session with Society of Resource Geology)

[R7P-01] Petrography of syenite from Hakata Island, Geiyo Islands, Ehime Prefecture, Japan.

[Presentation award entry]

*Toko FUKUI¹, Satoshi SAITO¹ (1. Graduate School of Science and Engineering, Ehime University )

Keywords:Syenite, Hakata Island, metasomatic alteration

In this study, we describe field occurrences, petrographic characteristics and whole-rock chemical compositions of syenite in Hakata Island, Geiyo Islands, Ehime Prefecture, Japan. Gradual lithological variation is observed at the boundary of the syenite and surrounding granites. Aggregates of fine-grained clinopyroxene and garnet are observed. The syenite have higher Na₂O contents compared to granites in the island. These observations are suggestive of syenite formation through metasomatic reactions by Na-rich hydrothermal fluids.