Hydrous Ca-Al silicates in pelitic schists from the chlorite zone of the Sanbagawa metamorphic belt, central Shikoku

Abstract

We report mode of occurrence and chemical composition of the hydrous Ca-Al silicates in pelitic schists from chlorite zone of the Sanbagawa metamorphic belt, central Shikoku, and discuss on their phase relationship. The most ubiquitous mineral among the hydrous Ca-Al silicates is epidote. Pumpellyite and lawsonite were found only sporadically. Coexistence of the three hydrous Ca-Al silicates were observed from only one sample. Upper metamorphic grade limits of the presence of pumpellyite and lawsonite are close to the disappearance of pumpellyite in hematite-free basic schists. We discuss on the appearance and disappearance of pumpellyite and lawsonite in chlorite zone by applying mixed volatile equilibria in the excess of graphite, calcite, quartz and albite.