火山噴火におけるマグマ中の揮発性物質の挙動 : 斑晶中のガラス包有物の分析に基づくアプローチ

抄録

The role of volatiles in volcanic eruptions was reviewed in view of the measured concentration of volatiles in glass inclusions in phenocrysts. Since the amount of volatiles in a glass inclusion is very small (typically ranging from 10^-11 to 10^-8 mol), a special attention has to be paid to the extraction techniques and analytical methods. Advantage and disadvantage were discussed for the four extraction/analytical techniques; (1) vacuum heating methods, (2) electron-probe microanalysis, (3) ion-probe microanalysis, and (4) infrared spectrometry. The glass inclusion analyses suggest that (1) the volatile concentration in a magma of an early stage of eruption is significantly higher than that of the later stage, (2) a gas phase (H₂O, CO₂ and SO₂) accumulates in a magma chamber during its residence at a shallow depth, and (3) accumulation of data on volatiles in magmas contributes to the understanding of the effect of volcanic eruptions on the climatic changes and evolution of atmosphere.