Application of hydrogen isotope geochemistry to volcanology: Recent perspective on eruption dynamics

M. Nakamura, Y. Kasai, N. Sato, S. Yoshimura

研究成果: Conference contribution

抄録

Degassing of magma is central to understand the dynamics of volcanic eruption. Hydrogen isotopic composition of volcanic rocks reflects degassing processes. The natural obsidian samples in some eruptions typically show a gently and then rapidly decreasing δD trends with decreasing water content; this led to the two-stage degassing model, with closed-system volatile exsolution (batch fractionation of hydrogen isotope) during the explosive phase followed by open-system degassing (Rayleigh fractionation) to produce the low δD value of the dome and flow lavas[1,2]. However, the relationship between pattern of degassing (and fractionation) and mode of eruption is controversial[3]. Based on the CO2/H2O ratio of the obsidians, Rust et al.[4] suggested that the analyzed samples with relatively constant δD value and high water content were buffered (re-equilibrated) with vapor of relatively constant isotopic composition, assuming that silicic magma along conduit wall is fragmented and highly permeable. However, the timing and mechanism of the shift to open system degassing (Rayleigh fractionation) has not been clarified. To further constrain the eruption dynamics, experimental study on the hydrogen isotope fractionation during degassing would be helpful, although common noble metals used as sample capsules, including Au, are permeable to hydrogen at magmatic temperature, and even to water molecule in the prolonged run, probably due to the change of grain boundary properties such as thermal grooving.

本文言語English
ホスト出版物のタイトルWater Dynamics - 5th International Workshop on Water Dynamics
ページ93-99
ページ数7
DOI
出版ステータスPublished - 2008 3月 17
イベント5th International Workshop on Water Dynamics - Sendai, Japan
継続期間: 2007 9月 252007 9月 27

出版物シリーズ

名前AIP Conference Proceedings
987
ISSN(印刷版)0094-243X
ISSN(電子版)1551-7616

Other

Other5th International Workshop on Water Dynamics
国/地域Japan
CitySendai
Period07/9/2507/9/27

ASJC Scopus subject areas

  • 物理学および天文学(全般)

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