Presentation Information
[O06-P24]The occurrence of accretionary lapillis from Okuta Tuff bed in the Iwadono hills
*Kento Watanabe1, Kai Tonegawa1, Genki Akazawa1 (1. Saitama Prefectural Kumagaya High School)
Keywords:
Okuta tuff,accretionary lapilli,occurrence
We surveyed features and minerals of the bed which include accretionary lapillis of Okuta Tuff bed and the two beds which exist above it in the border between Iwadono area in Higashimatsuyama city and Ishizaka area in Hatoyama town, Saitama prefecture. Consequently, the diameter of accretionary lapillis is about 7.7 mm on average. Speaking of density, there are about 13.8 accretionary lapillis in 10 cm square. Examining the bed which includes accretionary lapillis of Okuta Tuff bed and the two beds which exist above it by panning, we found out that they include quartz and feldspar in a large proportion, a ten percent biotite and a few amphibole. Therefore, magma is consistently rhyolitic after eruption which made accretionary lapillis.