(a) Geological map (simplified from ref. 11) in the quadrilateral area (a) marked in Fig. 1a. The figure shows the locations of the samples for the major element analyses collected from the four sites of pelite (RS1) and schistose rock (RS4) from the Permian Maizuru Group, and Cretaceous rhyolite (RS2) and Cretaceous granite (RS3) in the northern part of Akaiwa city. (b) The isocon diagrams14 based on the major element composition data of the deeply weathered rocks and their host rocks. The chemical composition data are shown in Table 1. Si: SiO2, Ti: TiO2, Al: Al2O3, Fe: Fe2O3, Mn: MnO, Mg: MgO, Ca: CaO, Na: Na2O, K: K2O, P: P2O5.