著者

下司 信夫 嶋野 岳人 長井 雅史 中田 節也

出版者

特定非営利活動法人 日本火山学会

雑誌

火山 (ISSN:04534360)

巻号頁・発行日

vol.47, no.5, pp.419-434, 2002

参考文献数

36

被引用文献数

6

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Erupted magma of the 2000 eruption of the Miyakejima volcano changed from basaltic andesite to basalt during the caldera formation, from aphyric basaltic andesite with SiO₂=54 wt.% to plagioclase-phyric basalt with SiO₂=51.5 wt.%. Whole-rock compositions of the basaltic andesite of the June and July eruptions are plotted on the extension of the temporal variation of the previous eruptive materials, suggesting that the andesitic magma erupted in June and July eruptions were driven from the magma system worked for the last 500 years. Petrological character of the basalt in the eruptive materials of August, by contrast, is different from the previous lavas of the Miyakejima volcano. This shows that a new basaltic magma ascended to the shallow magma system after the caldera collapse. Identical ratio of the incompatible elements among the eruptive materials of the 2000 eruption and the recent eruptions suggests that they were driven from a common parental magma.