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

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

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


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.

Original languageEnglish
Title of host publicationWater Dynamics - 5th International Workshop on Water Dynamics
Number of pages7
Publication statusPublished - 2008
Event5th International Workshop on Water Dynamics - Sendai, Japan
Duration: 2007 Sept 252007 Sept 27

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


Conference5th International Workshop on Water Dynamics


  • Degassing
  • Geochemistry
  • Hydrogen isotope
  • Hydrogen permeability
  • Noble metal
  • Volcanic eruption


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