抄録
Limestone is accompanied with widely distributed Ryoke metamorphic rocks in islands of the Seto Inland Sea. Ko-Oge Island is situated in this zone and mainly composed of pelitic hornfels and crystalline schist rarely interbedded with dark color and massive Al-Fe rich sediments, so called emery.
Emery from Ko-Oge Island is charactarized by high TiO2 contents and by relict of primary texture such as pisolitic one. Emery can be divided, according to the mineral assemblage and texture of rocks: 1. zone of emery, 2. metasomatic zone of emery, 3. metasomatic zone of emery with limestone, and 4. metamorphic zone of another emery. The main constituent minerals of Zone1 are corundum, hercynite, ilmenite, and plagioclase, which occur as granoblastic aggregates. Perovskite, grossular, and vesuvianite occur in Zone 3. It was concluded that emery of Zone 3 is formed by Ca metasomatism in later stage of the prograde and retrogrede stages of metamorphism.
Original rock of emery is probably sediment such as laterite, rich in the TiO2, Al2O3, and Fe oxide. The rock is composed of gibbsite, Fe-hydrooxide, anatase, kaolinite, and calcite.
