Japan Geoscience Union Meeting 2019

Presentation information

[J] Poster

S (Solid Earth Sciences ) » S-VC Volcanology

[S-VC39] Hydrothermal systems of volcanoes

Mon. May 27, 2019 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall8, Makuhari Messe)

convener:Yasuhiro Fujimitsu(Department of Earth Resources Engineering, Faculty of Engineering, Kyushu University), Wataru Kanda(Volcanic Fluid Research Center, School of Science, Tokyo Institute of Technology), Takeshi Ohba(Department of chemistry, School of Science, Tokia University)

[SVC39-P03] Determination on the stable isotopic compositions of H2O in a volcanic plume

*Masanori Ito1, Urumu Tsunogai1, Koji U Takahashi2, Fumiko Nakagawa1 (1.Nagoya University, Graduate School of Environmental Studies, 2.Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology)

Keywords:Volcanic gases, Stable isotopic compositions, Cavity Ring-Down Sectroscopy

The fumarolic H2O occupied more than 80% of volatiles ejected from volcanic fumaroles (volcanic gases). The origin of fumarolic H2O is either magma (magmatic water) or groundwater (meteoric water). Because of the significant differences in the isotopic ratios (δD and δ18O) of H2O between magmatic water and meteoric water, we can differentiate the origins of fumarolic H2O (magmatic water or meteoric water), if we can determine the isotopic ratios of fumarolic H2O from those in volcanic plumes during a volcanic eruption. This is extremely useful for us to differentiate the mechanism of each volcanic eruption, magmatic eruption or phreatic eruption.
In this study, we determined the isotopic ratios of H2O in a volcanic plume that had been ejected from accessible fumaroles to confirm whether the isotopic ratios (δD and δ18O) estimated from plume H2O is consistent with those of fumarolic H2O or not.
The samples were taken in Hakone volcano from 2014 to 2018. We collected around 20 volcanic plume samples into pre-evacuated glass bottle (ca. 1000 ml) during each sampling, while changing the distances from the fumarole. Besides, we also collected the fumarolic H2O through condensation using a cold trap.
The isotopic ratios (δD and δ18O) of plume H2O showed strong linear correlation (R2 = 0.9 or more) with the reciprocal of H2O concentration. The isotopic ratios (δD and δ18O) estimated as the intercept of the linear correlation found in the plume H2O was consistent with fumarolic H2O. We concluded that we can estimate the stable isotopic ratios of fumarolic H2O remotely using those in plume H2O.
This study was supported by MEXT Scientific Research Program grants “Integrated Program for Next Generation Volcano Research and Human Resource Development”.