| Project/Area Number |
11308020
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Environmental dynamic analysis
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| Research Institution | HOKKAIDO UNIVERSITY (2000-2001)
The University of Tokyo (1999) |
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Principal Investigator |
GAMO Toshitaka Hokkaido Univ., Grad. School of Sci., Prof., 大学院・理学研究科, 教授 (70143550)
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| Co-Investigator(Kenkyū-buntansha) |
MATSUMOTO Ryo Univ. Tokyo, Grad. School of Sci., Prof., 大学院・理学系研究科, 教授 (40011762)
TSUNOGAI Urumu Hokkaido Univ., Grad. School of Sci., Assoc., Prof., 大学院・理学研究科, 助教授 (50313367)
OKADA Hisatake Hokkaido Univ., Grad. School of Sci., Prof., 大学院・理学研究科, 教授 (80111334)
ISHIBASHI Junichiro Kyushu Univ., Grad. School of Sci., Assoc. Prof., 大学院・理学研究院, 助教授 (20212920)
YOSHIDA Naohiro Tokyo Inst. Tech., Grad. School of Sci., Engineer., Prof., 大学院・総合理工学研究科, 教授 (60174942)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Submarine hydrothermal activity / Submarine cold seepage / Methane / Carbon isotope ratio / Microbiological activity / Plate boundaries / Gas hydrate / Continuous flow mass spectrometry |
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| Research Abstract |
This study aimed at elucidating the behavior of methane in the oceanic environment, especially in oceanic waters and pore fluids in sedimentary layers. Concentration and stable carbon isotope ratios (^<13>C/^<12>C) of methane were precisely measured by using an isotope-ratio-monitoring gas chromatography/mass spectrometry system newly constructed in this study. Submarine hydrothermally active areas at spreading centers and arc volcanoes (Central Indian Ridge, Gulf of Aden, Mariana Trough, Okinawa Trough, Suiyo Seamount etc.) and cold seepage areas at plate subduction zones (Nankai Trough, Eastern Japan Sea etc.) were investigated in detail using research vessels and submersibles, in order to take fluid samples for methane analysis from these areas. The carbon isotope ratio of methane has enabled us to distinguish the following three different types of methane: magmatic methane, methane from thermocatalytic decomposition of organic matter, and biogenic methane. In addition, oxidative decomposition of methane was recognized in pore fluids as well as in seawater, by detecting the enrichment of ^<13>C of methane to occur during microbiological processes. Gas hydrate below seafloor was also discussed as an important source of methane from the sediment to seawater.
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