Layering of garnet grains observed in the pelitic schists of the Sambagawa metamorphic belt, central Shikoku

Abstract

EPMA analysis on a thin section of a pelitic schist sample from the Sambagawa metamorphic belt in central Shikoku revealed that two groups of garnet grains with different chemical composition are layered within a hand sample. The difference in size and chemical composition observed in garnet is consistent with that caused by the variation of bulk rock (i.e., chlorite) chemistry, based on the prediction by the forward model. It suggests that rocks with slightly different bulk rock chemistry were sandwiched after the peak of the metamorphism, simultaneously forming the mineral foliation.