1995 Fiscal Year Final Research Report Summary
Geochemical Study on Mantle-derived Hydrocarbons.
| Project/Area Number |
05403002
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
地球化学
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| Research Institution | University of Tokyo |
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Principal Investigator |
WAKITA Hiroshi Univ.of.Tokyo, Earthquake Chem., Professor, 理学部, 教授 (40011689)
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| Co-Investigator(Kenkyū-buntansha) |
ISHIBASHI Jun-ichiro Univ.of.Tokyo, Earthquake Chem., Res.Associ, 理学部, 助手 (20212920)
NAKAI Shun'ichi Univ.of .Tokyo, Earthquake Chem., Assoc.Prof., 理学部, 助教授 (50188869)
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| Project Period (FY) |
1993 – 1995
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| Keywords | Carbon Compound / Carbon Isotope / Mantle / volcanic Gas / Natural Gas / Submarine Hydrothermal System |
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| Research Abstract |
This study aims at revealing origins, distributions and transportation mechanisms of carbon compounds in the Earth, using samples of natural gases, high temperature volcanic gases and hydrothermal vents from seafloor.
We succeeded in carbon isotopic measurement of methane of 10nM with a precision of 5 per mil with a GasChromatograph/Combustion/Mass Spectrometer system combined with a methane concentration line.
Most of natural gases from China showed a carbon isotopic distribution among hydrocarbons (C1-C5) wherein delta^<13>C becomes more negative with decreasing molecular weight of hydrocarbons, i.e.delta^<13>C1<delta^<13>C2<delta^<13>C3<delta^<13>C4, which suggests than most of natural gases formed by pyrolysys of organic matters in sediments. High temperature fumaroles collected in Satsuma-iojima contain methane formed by pyrolysys of organic matters in aquifer, which indicates difficulty to detect magma-derived methane without contamination. However, we developed a new methane extraction and concentration line for water samples and detected methane formed by an inorganic reaction in hydrothermal vent fluids collected in East Pacific Rise.
This study showed the developed concentration method combined with the GC/C/MS enabled us to investigate carbon compound in mantle. We will continue to imporve our methane concentration method and will apply the technique to other samples such as fluid inclusions in rocks.
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