Alkali amphiobole-bearing schist in the Sambagawa metamorphic terrane, central Kii peninsula.

Alkali amphibole-bearing schist is found in the Sambagawa metamorphic terrane, central Kii Peninsula where the zone of the glaucophane schist facies has never been recognized. Alkali amphibole is rimmed or included by actinolite and coexists with epidote, chlorite, albite and quartz, occasionally associated with stilpnomelane, muscovite, sphene and calcite. Microprobe analyses of the alkali amphiboles reveal that they fall into the two compositional fields of glaucophane and crossite to magnesioriebeckite. The petrological evidence shows that the metamorphic grade in the study area has attained to the glaucophane schist facies; actinolite enclosing the alkali amphibole is regarded as being formed during a later probably low-pressure phase of the metamorphism.