Metamorphic processes of the Kuga group and the low-grade part of Ryoke belt in the Iwakuni area, southwest Japan

Abstract

The Iwakuni area, western part of Yamaguchi prefecture is dominated by the unmetamorphosed Kuga group in north and the low-grade part of Ryoke belt in south. The Kuga group conformably overlays the Ryoke belt without any structural gaps. According to the degree of graphitization, the metamorphic grade progressively increases from the Kuga group to the Ryoke belt regardless of any deformational features. The Kuga group was formed as the accretionary complex followed by undergoing the low-pressure type of the Ryoke metamorphism. Therefore, the main deformational events occurred to be prior to the Ryoke metamorphism.