西南日本内帯大江山地域の普甲峠変成沈積岩に産する4～4.4億年含藍晶石緑れん石角閃岩 [403-443 Ma kyanite-bearing epidote amphibolite from the Fuko Pass metacumulate in Oeyama, the Inner Zone of southwestern Japan]

Abstract

The Fuko Pass metacumulate is a tectonic block (4.5 × 1.5 km in size) within the Oeyama peridotite body in the Inner Zone of southwestern Japan. It was metamorphosed under the high-pressure and moderate-temperature condition to form a mineral assemblage hornblende+clinozoisite+kyanite+paragonite+albite+rutile. K-Ar ages were determined on hornblende separates from four epidote amphibolite samples, yielding 443-403 Ma. This suggests a Siluro-Ordovician subduction-related metamorphic event for the Fuko Pass metacumulate, which is distinct from the Late Paleozoic high-P/T type metamorphic events of the Renge metamorphic belt in the Inner Zone of southwestern Japan. The Fuko Pass metacumulate is correlated, in age, with the Early Paleozoic high-P/T type schists (445-402 Ma) of the Kurosegawa klippe in the Outer Zone.