Chemistry of rock-forming minerals in epidote amphibolites and eclogites in the Tonaru epidote-amphibolite mass in the Sambagawa metamorphic belt, Besshi district, central Shikoku, southwest Japan

Abstract

The Tonaru epidote amphibolite mass is one of several tectonic blocks occurring in the Sambagawa metamorphic belt，central Shikoku，Japan．It consists mainly of various types of epidote-amphibolites with diverse lithology，and minor eclogites surviving after amphibolitization．There are two types of amphibolite：T-I and T-II type amphibolites．T-I type amphibolite is composed of clinopyroxene-amphibolite and serpentinite，and T-II type amphibolite is composed of epidote-amphibolite and eclogite．
EPMA analyses of the constituent minerals in the Tonaru mass show that garnets in T-II type amphibolite are of almandine-rich type，and that omphacites in T-II eclogites have maximum Jd contents of 45 mol.%．Amphiboles from the epidote amphibolites in both T-I and T-II type amphibolites are classified mostly as Ca-amphiboles．Amphibole inclusions in the garnets in T-II eclogites are Na- and Na-Ca amphiboles，whereas symplectitic amphiboles in the matrix
of the eclogites are Ca-amphiboles．White micas in T-II type amphibolites include both paragonite and phengite．