R1: Characterization and description of minerals (Joint Session with The Gemmological Society of Japan)

[R1-09] Zn-enriched minerals in magnesio-arfvedsonite-bearing albitite from the Omi area (Japan): its diversity and geological significance

*Hiroki Oka¹, Tatsuki Tsujimori¹ (1. Tohoku Univ.)

Keywords:Albitite, 6-coordinated zinc, Sauconite, Oxygen fugacity, Omi serpentinite mélange

The difference of coordination numbers of zinc can potentially track the changing f_O2 during the fluid-mediated formation processes. In the Omi area, magnesio-arfvedsonite-bearing albitite contains trace amounts of sphalerite, Zn-rich strontio-orthojoaquinite (~8,000 µg/g Zn), and secondary sauconite (^[6]Zn-rich mineral). The sphalerite and primally Zn-rich hydrous minerals imply that an alkaline hydrothermal fluid carried SO_{2 (g)} and ZnO_(s) during the albitite formation. The sauconite indicates a f_O2 change and subsequent partial decomposition of sphalerite.