| 研究実績の概要 |
In FY2023, the rock samples from Merapi were successfully delivered to Japan, thin sections of the rocks were created and petrographically and geochemically analyzed, the rocks were powdered and analyzed for their bulk compositions, experimental powders were created and sealed into experimental capsules, and six high-temperature and pressure experiments have been performed at different pressure and temperature conditions. The experimental products were mounted in epoxy, ground, and polished, and the glass and mineral phases were analyzed for their major element compositions using an EPMA.
All of the experiments contain newly grown amphibole phenocrysts and their compositions vary as a function of the oxygen fugacity, temperature, and pressures of the experimental runs. These findings have significance for the magmatic system at Merapi and for the mechanisms potentially controlling chemical zonation of amphibole phenocrysts at other volcanoes globally. Specifically, the experimental results indicate that the amphiboles observed in the products of the 2010 eruption experienced polybaric (deeper and shallower) fractional crystallization to form amphibole phenocrysts with the observed zonation patterns. These results provide better constraints on the pre-eruptive magma dynamics leading up to the 2010 event. Additionally, there is a framework for interpreting the chemical zonation of amphibole phenocrysts at other volcanoes and how fluctuations in oxygen fugacity, pressure, and temperature can influence the equilibrium amphibole chemistry.
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| 今後の研究の推進方策 |
For the remainder of FY2024, we plan to continue with the experimental work by performing both buffered and unbuffered experiments at similar pressure and temperature conditions. The phases of the experimental capsules will be analyzed on an EPMA and potentially a LA-ICP-MS. These results will allow us to better constrain the amphibole stability field of the products of the 2010 eruption of Merapi Volcano and how the pressure, temperature, and oxygen fugacity impact the composition of the equilibrium amphibole. Additional work will be completed with the natural samples including whole-rock analyses and phase proportion determination. Additional effort will be dedicated to analyzing the data gathered, determining the appropriate method of presenting the results, and drafting figures and text for presentation at conferences and ultimately for publication.
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| 次年度使用額が生じた理由 |
The fellow took parental leave for 6 months in FY2023. Thus, the project has been pushed back 6 months.
In FY2024, we will purchase consumables for experiments and analysis as planned, and the fellow will attend an international conference (AGU in USA) that he was unable to attend in FY2023.
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