Multistage metamorphism of the Onodani eclogites in the Sambagawa metamorphic belt, Besshi district, central Shikoku, Japan

抄録

Garnets of the eclogites from the Onodani area in the Besshi district, central Shikoku consist of resorbed spessartine core and overgrowing almandine-rich rim. The spessartine-rich core shows a sector zoning, and it includes such minerals as clinopyroxene, almandine-rich garnet, sodic-calcic amphibole, epidote, albite and quartz. Peak P-T associated with the epidote-blueschist to eclogite facies conditions. The almandine-rich rims of the garnets include clinopyroxene, sodic-calcic amphibole, epidote and quartz. The matrix minerals consisting of garnet, omphacite, epidote, phengite, amphibole, albite and quartz, also representing the peak metamorphic mineral assemblage of the eclogite facies. Omphacites in the matrix are partly or completely altered into omphacite/sodic-augite+hornblende+albite symplectites. And oligoclase and pargasitic amphiboles are in some omphacite/sodic-augite+hornblende symplectite.