研究課題/領域番号 |
20K14586
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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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キーワード | FTIR / H2O / submarine eruption |
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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次年度使用額が生じた理由 |
Costs will be focused on travel expenses related to ongoing analyses (for example, for SIMS analysis at an institute in Shikoku) and conference travel and participation. In particular, the increased costs of international travel and the weak exchange rate will make the cost of attending important international conferences such as AGU much more expensive than when the budget for this grant was originally devised. However, such conference attendance is necessary for promoting dissemination of research results. Other costs will be related to manuscript publication fees.
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