Al-rich metapelites traditionally play important roles in determination of the metamorphic zones (e.g. Eskola 1915; Thompson, 1957) because of their temperature-sensitive Al-rich minerals such as chloritoid. However, the source of the Al-rich content is still a matter of debate. Some authors have demonstrated that the Al-rich metapelite originated from paleosoil (e.g. Liou and Chen, 1978; Sharma, 1979; Barrientos and Selverstone, 1987). Others have suggested that the protolith of Al-rich pelites consists of soil-derived detritus (e.g. Iwao, 1978; Kawamura et al., 1985; Franceschelli et al., 1998). More advanced understanding of the chemical reactions in weathering has produced a vast body of paleoclimatic literature based on paleosoil chemistry (e.g. Nesbitt and Young, 1982; Retallack, 2001). In this study, we attempt to evaluate the soil-derived materials in metaclastic rocks by applying an analysis of metamorphic reactions to provenance analysis in order to understand weathering and metamorphic processes for Al-rich pelites.

Some metaclastic rocks originating from Carboniferous rocks in Japan yield index minerals such as staurolite, chloritoid and aluminosilicate minerals (e.g. Seki, 1955; Asami, 1979; Hiroi, 1983; Okuyama-Kusunose, 1994; Sakashima et al., 1999), which imply Al-rich bulk compositions. To understand age constraint of characteristic bulk composition, we described the petrographical and geochemical features of the metaclastic rocks of the Shimozaisho Group in the Itoshiro area, Gifu Prefecture, Japan. We then evaluate the Al-enrichment process and the degree of weathering of the source rocks, provenance of the protolith and tectonic background causing the detrital supply.