Japan Geoscience Union Meeting 2014

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[U-05_30PM2] Interrelation between Life, Water, Mineral, and Atmosphere

Wed. Apr 30, 2014 4:15 PM - 5:45 PM 419 (4F)

Convener:*Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University), Yohey Suzuki(Graduate School of Science, The University of Tokyo), Fumito Shiraishi(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Takeshi Naganuma(Graduate School of Biosphere Science), Takeshi Kakegawa(Graduate School of Science, Tohoku University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University), Kentaro Nakamura(Precambrian Ecosystem Laboratory (PEL), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Chair:Yohey Suzuki(Graduate School of Science, The University of Tokyo), Takeshi Naganuma(Graduate School of Biosphere Science)

5:15 PM - 5:30 PM

[U05-P03_PG] Role of minerals for hydrogen generation in the interaction between ultramafic rocks and water

3-min talk in an oral session

*Naoki FUKUHARA1, Tsutomu SATO1, Tsubasa OTAKE1 (1.Laboratory of Environmental Geology, Hokkaido university, Graduate School of Engineering, Hokkaido U)

Hydrogen generation by high temperature serpentinization is understood as hydration of mafic and ultramafic rocks, owing to the oxidation of reduced iron present in the olivine or pyroxene. On the other hand, in the Oman Ophiolite and Lost City Hydrotherrmal Field (LCHF) in the Mid-Atlantic Ridge, hydrogen is generated via low temperature serpentinization. Moreover, previous experimental study shown generating hydrogen at low temperatures (<100 degrees C). However, since even the rate of hydrogen generation by high temperature serpentinization is slow, the mechanism of hydrogen generation by low temperature in short period is yet to be explained. Therefore, the objective of this study is to clarify the mechanism of hydrogen generation via low temperature serpentinization for a short period. Batch experiments were conducted at 30 degrees C, 60 degrees C and 90 degrees C using minerals which constitute ultramafic rocks (olivine, Magnetite, Fe-Ni alloy), and serpentinite. Samples were taken after various reaction times (3h, 6h, 12h, 24h, and 1week). Liquid samples were analyzed by ICP-AES, ion chromatography, UV-Vis, pH, and ORP. Mineral phase changes in the solid samples were characterized by TG-DTA, SEM-EDX and XRD. The concentration of hydrogen gas was determined by GC-RGD. Hydrogen generation was observed in all samples. Highest concentration of hydrogen gas was observed in the experiment using Fe-Ni alloy. In the experiment using Fe-Ni alloy, apparent surface change was not observed at the surface of Fe-Ni alloy. Therefore, hydrogen gas was generated by catalysis of Fe-Ni. The generation of hydrogen gas by this catalysis would be higher than that of generated hydrogen accomplished by the dissolution of olivine, which is the dominant mineral in the ultramafic rocks. In this study, the hydrogen generation was confirmed at a temperature of less than 90 degrees C. The hydrogen generation process is catalyzed by Fe-Ni alloys or magnetite present in secondary minerals by serpentinization.