研究課題/領域番号 |
20K14586
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研究種目 |
若手研究
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配分区分 | 基金 |
審査区分 |
小区分17040:固体地球科学関連
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研究機関 | 国立研究開発法人海洋研究開発機構 |
研究代表者 |
McIntosh Iona 国立研究開発法人海洋研究開発機構, 海域地震火山部門(火山・地球内部研究センター), 研究員 (70780899)
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研究期間 (年度) |
2020-04-01 – 2024-03-31
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研究課題ステータス |
交付 (2022年度)
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配分額 *注記 |
4,160千円 (直接経費: 3,200千円、間接経費: 960千円)
2022年度: 1,820千円 (直接経費: 1,400千円、間接経費: 420千円)
2021年度: 1,560千円 (直接経費: 1,200千円、間接経費: 360千円)
2020年度: 780千円 (直接経費: 600千円、間接経費: 180千円)
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キーワード | FTIR / H2O / submarine eruption / Izu-Oshima / volatiles / paleointensity / Quaternary / Volatiles / Submarine eruptions |
研究開始時の研究の概要 |
To assess future hazards of island arc volcanoes, we need to know when, why and how past eruptions occurred. However, the timing and processes of their submarine eruptions, and how these relate to their better studied subaerial eruptions, are poorly known. Focusing on Izu-Oshima’s submarine ridge eruptions, I will develop and apply a new method to date these late Quaternary eruptions for the first time. With this new time context I will constrain the temporal evolution of magmatic and eruptive processes that drive both submarine and subaerial basaltic eruptions and control their hazards.
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研究実績の概要 |
New samples of submarine basaltic lavas from past ridge eruptions of Izu-Oshima were prepared for volatile analysis by FTIR. These include new pieces from the original rock collection as well as new samples collected by a recent cruise in the area. Samples have been prepared as wafers, as individual glass shards, and as melt inclusions. There is still some difficulty with low volatile concentrations giving large analytical uncertainties for thin samples. This large analytical uncertainty prevents these data being used for estimating eruption age from the change in sea level (eruption pressure) since the time of eruption. FTIR analysis is therefore continuing, with the aim of preparing suitably glassy samples of sufficient thickness for smaller analytical uncertainties. Meanwhile, magnetic paleointensity of a subset of samples has been analysed by collaborator Usui. By combining the magnetic paleointensity and geochemistry data for these samples, it is possible to constrain their eruption ages (without volatile data and sea level estimation, for now). The data suggest relatively young eruption ages, consistent with their stratigraphic relation to onland eruptions of known age. A manuscript on this topic has been submitted and is currently under revision.
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現在までの達成度 (区分) |
現在までの達成度 (区分)
4: 遅れている
理由
Small crystals within the matrix glass continue to be a problem for volatile analysis, even in newly selected samples. Sample preparation is time consuming, and unfortunately has a high degree of analytical failure (uncertainties on measured concentrations are too large for the planned application of the data for estimating eruption age from sea level change). Installation and set up of the new FTIR took longer than planned, which further delayed analyses, particularly because I was a participant in a 2-month research cruise soon after the FTIR had been installed and therefore could not perform labwork.
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今後の研究の推進方策 |
FTIR analyses of matrix glasses will continue on the newly selected samples, and may yet produce suitable data for estimating eruption age from sea level. Although these analyses will continue, there will be an increased focus on analyses that will support the other objectives of the project i.e. melt inclusion analyses (for estimating magma chamber depths and sample cooling rates after eruption) and rock porosity analysis (for investigating bubble characteristics and eruption styles of submarine basaltic ridge eruptions). Equipment for porosity analyses (sensitive mass balance, etc) have been purchased and are ready for use.
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