As is observed in the Aridagawa riverbanks, sandstones and mudstones originated from the Shimanto and Chichibu Belts are widely distributed. Coarse-grained sandstone and conglomerate are also found, which are not observed in the Aridagawa river. Various sorts of schist of the Sanbagawa Belt (psammitic schist, pelitic schist, siliceous schist and greenschist), and greenstones of the Mikabu Belt are also common. In addition, granitoids of the Ryoke Belt and tuffs of the Kumano Volcanics are found, which are not observed in the Aridagawa river.

Pelitic Schist
A schist of mudstone protolith. Recrystallisation under differential stress formed a planer structure by preferred orientation of muscovite (in a direction of upper-right to lower-left in this photo). Quartz is broken and recrystallised as finer-grained crystals during deformation. On the other hand, plagioclase remains as a large crystal because it is more rigid than quartz. Like this plagioclase, a mineral grain occurring as a large crystal in finer-grained matrix in a metamorphic rock is called porphyroblast.

Welded Tuff
Tuff is a rock formed by deposition of volcanic ash. If ash is still at high temperature when it was deposited, it melts at some extent during compaction. Tuffs of such an origin are called as welded tuff. Some of quartz phenocrysts have an embayment texture (indicated as red arrows). These quartz grains were originally crystallised as high-temperature type quartz (ß-quartz), and transformed into low-temperature type quartz (a-quartz). The embayment texture was formed by volume reduction related to transformation from ß-quartz to a-quartz during cooling.

Quartz is overwhelmingly dominant, followed by albite (Ca-free plagioclase), muscovite, K-feldspar, plagioclase (except for albite), biotite and chlorite. Feldspars and micas are derived from granitoids and associated metamorphic rocks of the Ryoke bekt, and albite and chlorite are from the Sanbagawa metamorphic belt.

Heavy Minerals

The most dominant epidote and the following hornblende, micas and chlorite occupy a major proportion of the heavy minerals. Epidote and chlorite are derived from the Sambagawa belt, and micas and hornblend are derived from the Ryoke belt.
Rare but important minerals are spinels and Ca-garnet. These minerals are considered to be derived from ultramafic rocks and carbonates, which are minor components of the Shimanto belt.

To be analyzed