Eclogitic glaucophane schist occurs as a boulder (about 4 m diameter) among many other garnet glaucophane schist and epidote glaucophane schist of the late Paleozoic Renge metamorphic belt in the Yunotani valley, western Omi area. The eclogitic glaucophane schist forms a mafic layer (1.2 m wide) intercalated within pelitic schist (garnet-paragonite-phengite schist). It consists mainly of glaucophane (modal volume : 37%), garnet (21%), omphacite (19%), epidote (19%), and small amount of quartz, albite, phengite, chlorite, rutile and titanite. The eclogite facies mineral assemblage 'garnet+omphacite+glaucophane+epidote+rutile+quartz' is slightly replaced by secondary chlorite, albite, calcite and rarely actinolite, and form penetrative schistosity (S
1). The preceding epidote blueschist facies mineral inclusions 'glaucophane+epidote+titanite+quartz+albite' forming earlier schistosity (S
0) are preserved in the rotated garnet core. These petrographic features show progressive transition from the epidote blueschist facies to the eclogite facies with little retrogression. Although the relict eclogite facies minerals have been previously found in some retrogressive Renge metamorphic rocks, the Yunotani eclogitic glaucophane schist first provides evidences for the progressive P-T path leading to the eclogite facies.
View full abstract