富士火山1707年(宝永4年)噴出物の層序にそった組成変化
1986 年 31 巻 4 号 p. 253-264
詳細
1986 年 31 巻 4 号 p. 253-264
Chemical analysis for major and minor elements were performed on the pumice and scoria samples from the 17 fall units of the 1707 fallout tephra of Fuji volcano. Analytical results showed that there exsisted three magmas different in chemical composition, implying that a layered magma reservoir with downward increasing basicity may have been formed prior to the eruption or a magma mixing might occur during the eruptive activity. The trude density of the pyroclastics also varied along with the variation of the chemical composition. The crystalline phases in ejecta were observed to be more abundant in the later ejecta than in the earlier. The variation in porosity of the ejecta observed along the stratigraphic column togather with the content of lithic fragments in the respective fall unit may discriminate the pyroclastics ejected from the two earlier formed craters from the ejecta from the later formed crater.
