Abstract
Specimens collected from light greenish gray colored alteration zones found at the outcrops and boring cores in the Umanosedanigawa River landslide area (Iyomishima city, Ehime Prefecture) near MTL were microscopically investigated to elucidate theinitial mechanism of landslide occurrence. The light greenish gray colored alteration zones are generally observed in Sanbagawapelitic schist. It is inferred that the alteration zones were formed by the hydrothermal alteration during rhyolitic intrusive activities.A lot of green fine-grained quartz was characteristically recognized in the light greenish gray colored alteration zones. Smectitewas crystallized in interstices developed as network pattern in green fine-grained quartz. It was confirmed that slaking-likedestruction was occurred in green fine-grained quartz by swelling of smectite. It is considered from these results that the expandingof smectite formed in green fine-grained quartz serves as a trigger of landslides in the investigated area.
