Bulk chemistry
Major element compositions of 19 whole-rock samples the metaclastic rocks were determined using a Shimadzu SXF-1200 XRF spectrometer at Nagoya University in June 2005. The results are presented in Table 1 with CIA (Chemical Index of Alteration) values (Nesbitt and Young, 1984). Localities of analyzed samples are shown in Fig. 3.
The Shimozaisho metaclastic rocks are characterized by enrichment in Al2O3 or Fe2O3 compared to average pelite (Shaw, 1956; Fig. 5). Type 1 and type 2 rocks are richer in Al and Fe, respectively, than chloritoid-free metapelites. Maximum content of TiO2 is 2.05 wt.%. Other metaclastic rocks originating from Carboniferous protoliths also plot in the cover Al or Fe rich area in the AFM diagram (Fig. 5). Chloritoid-bearing samples have much higher CIA values than chloritoid-free samples.
Figure 5. AFM diagram for metaclastic rocks originating from Carboniferous and Permian, shelf sediments in Japan
(compiled from Onuki, 1960; Asami, 1979; Asami and Adachi, 1979; Kano, 1980; Okuyama, 1980; Hiroi, 1983; 1984; Naito, 1993; Sakashima et al., 1995; Kim and Ishiwatari, 1997).