Petrological Studies on the Ryoke Metamorphic Rocks in the Toyone-mura Area, Aichi Prefecture, Japan

Abstract

The Ryôke metamorphic rocks in the Toyone-mura area, Aichi Prefecture are described in regard to their mode of occurrence, petrography, chemistry and mineralogy. Physical conditions of the Ryôke regional metamorphism are discussed from the viewpoints of mineralogical equilibria and the nature of the constituent minerals. The metamorphic terrain of this area can be divided into three progressive zones based on the mineralogical variations in the pelitic rocks. The metamorphic rocks are characterized by the mineral association of cordierite-K-feldspar, and the metamorphic reactions of andalusitesillimanite transition and muscovite breakdown in pelitic ones. The Ryôke regional metamorphism can be regarded as the result of the general upheaval of iso-geotherm intimately connected with the vast granitic intrusions. The geological situation of the Ryôke zone is refered its special character to the metamorphism which had occurred in the ascending part of the Honshû geosyncline during or continued from the time preceeding to the metamorphism.