From the distribution of metamorphic minerals such as prehnite, chlorite, pumpellyite and actinolite, the Sanbagawa metamorphic terrin in the cental part of Kii Peninsula can be divided into the following three zones representing a progressive mineralogical changes of regional scale:
Zone I; An assemblage of prehnite-chlorite-quartz-sodic plagioclase is most characteristic. Actinolite is not stable. Pumpellyite and epidote are commonly found.
Zone II; An assemblage of colorless actinolite-epidote (-pumpellyite)-chlorite-sodic plagioclase can be widely found. Prehnite is not stable.
Zone III; Both of pumpellyite and prehnite are not stable. Pale bluish green actinolite-epidote-chlorite-sodic plagioclase is most characteristic.
Probably, the regional metamorphism in the present district was formed under relatively lower solid pressure conditions than those prevailed in other terrains such as the Kanto Mountains of the same Sanbagawa belt of Japan.
抄録全体を表示