| 研究課題/領域番号 |
17K05712
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| 研究機関 | 明治大学 |
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研究代表者 |
Snyder Glen 明治大学, 研究・知財戦略機構, 特任教授 (90751777)
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| 研究分担者 |
鈴木 庸平 東京大学, 大学院理学系研究科(理学部), 准教授 (00359168)
松本 良 明治大学, 研究・知財戦略機構, 特任教授 (40011762)
佐野 有司 東京大学, 大気海洋研究所, 教授 (50162524)
戸丸 仁 千葉大学, 大学院理学研究院, 准教授 (80588244)
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| 研究期間 (年度) |
2017-04-01 – 2020-03-31
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| キーワード | gas hydrate / microdolomite / Sea of Japan / authigenesis / stable isotope / microbial / noble gas / seawater |
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| 研究実績の概要 |
During the first year of the grant, we were able to carry out the following analyses: 1. SEM imaging of external texture of microdolomite aggregates (Gas Hydrate Research Lab,Meiji Univ.). 2. XRD determination of mineral composition of microdolomite (Gas Hydrate Research Lab, Meiji Univ.). 3. Stable isotope determination of microdolomite (Gas Hydrate Research Lab, Meiji Univ.). 4. Determination of the composition of gas inclusions in dolomite (Sano Noble Gas Lab, Univ. Tokyo AORI) 5. High resolution digital imagery of dolomite and inclusions (Univ. Tokyo, AORI) 6. Elemental mapping of microdolomite (Univ. Tokyo, AORI) 7. Stable isotope composition of gas hydrate water from samples where dolomite was recovered (Univ. Tokyo, Kano Stable Isotope Lab) as well as dissolved inorganic carbon (Chiba Univ. Tomaru Lab). 8. Preliminary DNA staining techniques to confirm microbial matter inside of the microdolomite (Univ. Tokyo, Suzuki Geomicrobiology Lab).
Major findings thus far: Microdolomite aggregates change in external texture, becoming smoother with depth. Seawater is trapped inside of the inclusions and has been modified by internal growth of dolomite. Strontium is enriched in the residual fluids inside the dolomite. Microbial matter is preserved within the dolomite.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
Most of the initial proposed research has been carried out. Difficulties included finding samples appropriate for analyzing the internal gas voids for gas composition, although we did have 4 which were large enough.
An effort is being made to find dolomites from other sites aside from Umitaka Spur in the sea of japan. These include the Hidaka Trough, offshore Hokkaido where we did shallow piston coring last summer. Unfortunately, the shallow cores did not enough dolomite inside of the gas hydrate to analyze.
Despite these challenges, the initial work on analyzing microbial matter inside of grains from one core was quite promising and similar work should be carried out on the other samples.
EPMA elemental mapping of polished dolomite grains revealed accumulations of Na, Cl, and Sr within the grains, while the grains themselves contain Ca and Mg (as expected with dolomite), but same also have banded regions high in Fe.
Growth habit was also revealed by SEM imagery, digital imagery of polished grains, and EPMA elemental mapping. In addition to single grains, interconnected paired grains, and even interconnected chains of grains surrounding organic matter exist. What remains to be determined is the mechanism that gave rise to these unusual morphologies.
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| 今後の研究の推進方策 |
Upcoming research this year includes: Biomarker analyses of the oils associated with dolomite inclusions in gas hydrate. These should tell us if the source of the hydrate is from depth or from locally generated methane associated with organic matter in the sediment (Bowden Lab, Univ. Aberdeen, Scotland).
A major focus this year will be genomic analysis of the organic matter inside of the microdolomite: Extractions of genetic material inside of the dolomite to see what types of microbes lived inside of the gas hydrate and became trapped inside of the dolomite, as well as if there are still viable microbial communities inside the dolomite.
Along with compiling the results from these analyses, we will be developing models regarding how the dolomite grains formed and what they tell us about gas hydrate accumulation in marine sediments.
In addition, an effort will be made to recover and analyze similar dolomite from shallow gas hydrate samples from the western margin of the Sea of Japan (offshore Primoria, Russia) as well as archived pressure cores of deep drilling samples which recovered gas hydrate from the Gulf of Mexico. If obtainable, similar analyses as those planned for the Sea of Japan Umitaka Spur samples will be carried out.
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| 次年度使用額が生じた理由 |
Costs were less than expected because some of the analyses have not been carried out yet, in particular, the microbial RNA and genomic analysis. This will be carried out by Suzuki Yohey at the University of Tokyo this year. We also anticipate having a small workshop with Stephen Bowden from the University of Aberdeen to discuss results before publishing this fiscal year and will use some of the funding for that. In addition, the University of Texas in Austin has agreed to provide me with Gulf of Mexico gas hydrate stored in pressure cores there, and to correct samples along with Dr. Steve Phillips who works there. So, some funding will be used to collect more microdolomite at that institution. Other costs incurred this year publication costs for scientific journals.
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| 備考 |
Stephen Phillips (Univ. of Aberdeen) will analyze oils from the gas hydrate for biomarkers. Dr. Steve Phillips (Univ. of Texas in Austin) is in charge of gas hydrate pressure cores (JIP2),
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