The Sambagawa metamorphic belt in the Mt. Ryumon district, western Kii Peninsula, consists of two giological unit, Tomobuchi unit and structurally overlying Iimori unit. Funaokayama rock, named by Hirota, 1991, exist in the northeast parts of this district. Funaokayama schists are different in metamorphic grade and mode of deformation from surrounding schists. The geological structure of the Mt. Ryumon district is charactcterized by the E-W trending Iimori syncline.
The Tomobuchi unit occupying the south parts of the Mt. Ryumon district. This unit are principally composed of pelitic and psamitic schists which are intercalated with basic and siliceous shists, but in the southeast parts of this unit, psamitic schists are predominant. Most common metamorphic minerals in pelitic schists are chlonte, but close to the boundary of the Iimori unit occuring small garnet. The Tomobuchi unit belongs to the chlorite zone, but close to the boundary of the Iimori unit belongs to low-grade garnet zone.
The Iimori unit occupying the north parts of the Mt. Ryumon district. This unit are principally composed of basic and pelitic schists which are intercalated with siliceous schists. This unit contains many ultramafic and mafic rocks. Most common metamorphc minerals in pelitic schist are chlorite and garnet, but chlonte + garnet + biotite mineral assemblage are found at Kasukami and Fujizaki. The Iimori unit belongs to the garnet zone, but partly belongs biotite zone. The biotite occurring points corresponds to biotite zone (Wang and Maekawa, 1997) predominate in this area.
The relationship between the Tomobuchi unit and Iimori unit is possibly fault because of difference to geological structure and matamorphic grade.
The Funaokayama rock are composed of basic and pelitic schists which are intercalated with siliceous schists. This schists characterized by mylonitic texture and such as ribbon quartz and mica fish.