Magma process of the Younger granites (Kibe pluton) in the Yanai district of the Ryoke belt, Southwest Japan

Abstract

The Cretaceous granitic rocks in the Yanai district, the eastern part of Yamaguchi Prefecture, are divided into three groups: Older Ryoke granites, Younger Ryoke granites and Sanyo granites. The Kibe pluton belongs to Younger Ryoke granites. The pluton consists mainly of biotite-granite including euhedral K-feldspar as phenocrysts. Field occurrence, peterography and geochemical studies reveal that lithological variation of the Kibe pluton can be explained by assimilation and fractionation model.