Discovery of eclogitic glaucophane schist from the Omi area, Renge metamorphic belt, the Inner Zone of south western Japan

Abstract

Eclogitic glaucophane schist has been discovered as a boulder (about 4m diameter) from the Yunotani valley in the western Omi area of the late Paleozoic Renge metamorphic belt (Fig.1). The eclogitic glaucophane schist (Fig.2) occurs as a mafic layer (1.2m wide) intercalated within pelitic schist (garnetparagonite-phengite schist), and is characterized by the mineral assemblage garnet (modal volume: 21%)+omphacite (19%)+ glaucophane (37%)+epidote (19%)+rutile+phengite+albite+quartz (Fig.3). This is the first finding of the late Paleozoic eclogite facies metabasite, which is almost devoid of retrogression and preserving textural evolution (Fig.4) and mineral zoning (Fig.5) during progressive metamorphism. This rock provides an evidence for the eclogite facies metamorphism in the late Paleozoic Western-Pacific margin. More detailed description will appear in Tsujimori et al. (in press).