Petrological characteristics and volatile content of magma from the 2000 eruption of Miyakejima Volcano, Japan

• Published in: Bulletin of volcanology 2005-03, Vol.67 (3), p.268-280
• Main Authors: SAITO, Genji, UTO, Kozo, KAZAHAYA, Kohei, SHINOHARA, Hiroshi, KAWANABE, Yoshihisa, SATOH, Hisao
• Format: Article
• Language: English
• Subjects: Bubbles; Crystalline rocks; Degassing; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Explosions; Igneous and metamorphic rocks petrology, volcanic processes, magmas; Magma; Natural hazards: prediction, damages, etc; Volcanic eruptions; Volcanic gases; Volcanoes; Volcanology
• ISSN: 0258-8900; 1432-0819
• DOI: 10.1007/s00445-004-0409-z

Issue Title: The 2000 eruption of Miyakeijma volcano, Japan Among the series of eruptions at Miyakejima volcano in 2000, the largest summit explosion occurred on 18 August 2000. During this explosion, vesiculated bombs and lapilli having cauliflower-like shapes were ejected as essential products. Petrological observation and chemical analyses of the essential ejecta and melt inclusions were carried out in order to investigate magma ascent and eruption processes. SEM images indicate that the essential bombs and lapilli have similar textures, which have many tiny bubbles, crystal-rich and glass-poor groundmass and microphenocrysts of plagioclase, augite and olivine. Black ash particles, which compose 40% of the air-fall ash from the explosion, also have similar textures to the essential bombs. Whole-rock analyses show that the chemical composition of all essential ejecta is basaltic (SiO^sub 2^=51-52 wt%). Chemical analyses of melt inclusions in plagioclase and olivine phenocrysts indicate that melt in the magma had 0.9-1.9 wt% H^sub 2^O,