| Daiki Yamamoto | Last modified date：2023.12.06 |
Assistant Professor /
Department of Earth and Planetary Sciences, Graduate School of Sciences
Department of Earth and Planetary Sciences
Faculty of Sciences
Department of Earth and Planetary Sciences
Faculty of Sciences
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Homepage
https://kyushu-u.elsevierpure.com/en/persons/daiki-yamamoto
Reseacher Profiling Tool Kyushu University Pure
Academic Degree
Ph. D
Country of degree conferring institution (Overseas)
Yes Bachelor Master Doctor
Field of Specialization
Cosmochemistry
ORCID(Open Researcher and Contributor ID)
0000-0001-6852-2954
Total Priod of education and research career in the foreign country
00years00months
Research
Research Interests
Membership in Academic Society
- Survivability of presolar SiC grains in the protosolar disk
keyword : presolar grains, SiC, evaporation, protosolar disk
2020.04～2023.04. - oxygen isotope exchange between CAI melt and disk gas
keyword : Oxygen isotope, isotope exchange, Ca-, Al-rich inclusion melt, protosolar disk
2018.04～2023.04. - Oxygen isotopic evolution of amorphous silicate dust in the protosolar disk
keyword : oxygen isotope, isotope exchange, reaction kinetics, protosolar disk
2018.04～2023.04.
Papers
| 1. | Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Michiru Kamibayashi, Hisayoshi Yurimoto, Oxygen isotope exchange kinetics between CAI melt and carbon monoxide gas: Implication for CAI formation in the earliest Solar System, Geochimica et Cosmochimica Acta, https://doi.org/10.1016/j.gca.2022.09.006, 336, 104-112, 2022.10, [URL], Coarse-grained igneous calcium-aluminum-rich inclusions (CAIs) are suggested to have experienced gas–melt isotope exchange of oxygen during the melting events of their precursors. Therefore, their oxygen isotope variation would preserve information about the high-temperature processes in the earliest Solar System. We experimentally determined oxygen isotope exchange kinetics between CAI analog melt and carbon monoxide (CO) gas at 1420 °C and 1460 °C under CO gas partial pressures of 0.1, 0.5, and 1 Pa to understand the role of CO gas on the oxygen isotope exchange. We observed oxygen isotope zoning profiles inside the reacted samples that formed through the oxygen isotope exchange reaction at the melt surface and oxygen diffusion in the melt. The zoning profiles were fitted using a three-dimensional spherical diffusion model with time-dependent surface concentration. The oxygen isotope exchange efficiency for colliding CO molecules is estimated to be ∼3.3 × 10–4, which is much smaller than that for H2O (0.28). The oxygen diffusion coefficient obtained in this study is similar to that obtained in the oxygen isotope exchange experiments between the CAI melt and H2O, suggesting that the diffusion species in the melt is O2–, despite the surrounding atmospheres. A comparison of the isotope exchange reaction kinetics between (1) CAI melt and CO gas, (2) CAI melt and H2O gas, and (3) CO and H2O gases shows that the reaction rate decreases in the order of (3), (2), and (1). The rapid isotope exchange of the reaction (1) indicates that the oxygen isotopic compositions of H2O and CO should have been equilibrated during the melting and crystallization processes of igneous CAIs. Both H2O and CO change the oxygen isotope compositions of molten CAI in the same direction, although reaction (2) controls the isotope exchange timescale between the CAI melt and surrounding gas. Our dataset demonstrates that type B CAIs having melilite with homogeneous oxygen isotope composition should have been heated for 2–3 days at PH2 > 100 Pa above the melilite liquidus (∼1400 °C) in the solar protoplanetary disk.. |
| 2. | Yamamoto D., Kawasaki N., Tachibana S., Kamibayashi M. and Yurimoto H, An experimental study on oxygen isotope exchange reaction between CAI melt and low-pressure water vapor under simulated Solar nebula conditions, Geochimica et Cosmochimica Acta, https://doi.org/10.1016/j.gca.2021.09.016, 314, 108-120, 2021.09, [URL], Calcium-aluminum-rich inclusions (CAIs) are known as the oldest high-temperature mineral assemblages of the Solar System. The CAIs record thermal events that occurred during the earliest epochs of the Solar System formation in the form of heterogeneous oxygen isotopic distributions between and within their constituent minerals. Here, we explored the kinetics of oxygen isotope exchange during partial melting events of CAIs by conducting oxygen isotope exchange experiments between type B CAI-like silicate melt and 18O-enriched water vapor (PH2O = 5 × 10−2 Pa) at 1420 °C. We found that the oxygen isotope exchange between CAI melt and water vapor proceeds at competing rates with surface isotope exchange and self-diffusion of oxygen in the melt under the experimental conditions. The 18O concentration profiles were well fitted with the three-dimensional spherical diffusion model with a time-dependent surface concentration. We determined the self-diffusion coefficient of oxygen to be ∼1.62 × 10−11 m2 s−1, and the oxygen isotope exchange efficiency on the melt surface was found to be ∼0.28 in colliding water molecules. These kinetic parameters suggest that oxygen isotope exchange rate between cm-sized CAI melt droplets and water vapor is dominantly controlled by the supply of water molecules to the melt surface at PH2O ∼1 Pa at temperatures above the melilite liquidus (1420–1540 °C). To form type B CAIs containing 16O-poor melilite by oxygen isotope exchange between CAI melt and disk water vapor, the CAIs should have been heated for at least a few days at PH2O > 10−2 Pa above temperatures of the melilite liquidus in the protosolar disk. The larger timescale of oxygen isotopic equilibrium between CAI melt and H2O compared to that between H2O and CO in the gas phase suggests that the bulk oxygen isotopic compositions of ambient gas at ∼1400 °C in the type B CAI-forming region is preserved in the oxygen isotopic compositions of type B CAI melilite. Based on the observed oxygen isotopic composition, we suggest that a typical type B1 CAI (TS34) from Allende was cooled at a rate of ∼0.1–0.5 K h−1 during fassaite crystallization.. |
| 3. | Yamamoto D., Tachibana S., Kawasaki N. and Yurimoto H, Survivability of presolar oxygen isotopic signature of amorphous silicate dust in the protosolar disk, Meteoritics & Planetary Science, 10.1111/maps.13365, 55, 6, 1281-1292, 2019.12, Oxygen isotope exchange experiments between tens of nanometer-sized amorphous enstatite grains and water vapor were carried out under a condition of protoplanetary disk-like low water vapor pressure in order to investigate the survivability of distinct oxygen isotope signatures of presolar silicate grains in the protosolar disk. Oxygen isotope exchange between amorphous enstatite and water vapor proceeded at 923–1003 K and 0.3 Pa of water vapor through diffusive isotope exchange in the amorphous structure. The rate of diffusive isotope exchange is given by D (m2 s–1) = (5.0 ± 0.2) × 10–21 exp[–161.3 ± 1.7 (kJ mol–1) R–1 (1/T–1/1200)]. The activation energy for the diffusive isotope exchange for amorphous enstatite is the same as that for amorphous forsterite within the analytical uncertainties, but the isotope exchange rate is ~30 times slower in amorphous enstatite because of the difference in frequency factor of the reaction. The reaction kinetics indicates that 0.1–1 μm-sized presolar amorphous silicate dust with enstatite and forsterite compositions would avoid oxygen isotope exchange with protosolar disk water vapor only if they were kept at temperatures below ~500–650 K within the lifetime of the disk gas.. |
| 4. | Yamamoto D. and Tachibana S., Water vapor pressure dependence of crystallization kinetics of amorphous forsterite, ACS Earth and Space Chemistry, 10.1021/acsearthspacechem.8b00047, 2, 778-786, 2018.02, Amorphous silicate dust grains, dominant solid components in the interstellar medium, are converted into crystalline silicate dust through thermal annealing in protoplanetary disks. Water vapor is a major reactive gas species in the protoplanetary disk, and it may affect the crystallization behavior of amorphous silicates. In this study, the water vapor pressure dependence of the crystallization kinetics of amorphous silicate with forsterite composition was investigated under controlled water vapor pressures ranging from ∼1 × 10–9 to 5 × 10–3 bar at 923–1023 K. We found that the crystallization rate depends on the water vapor pressure and becomes faster at higher water vapor pressures. We also found that the activation energy and the pre-exponential factor for crystallization rate decreases with increasing water vapor pressure. Water molecules dissolving into amorphous forsterite cut atomic bonds such as Si–O–Si and Mg–O–Mg through a hydroxyl (−OH) formation reaction. Rearrangement of structural units cut by hydroxyls occurs with a smaller energetic barrier, and thus water vapor can act as a catalyst to promote crystallization of amorphous forsterite. Based on the experimental data, we conclude that the temperature required for crystallization of amorphous forsterite within the lifetime of protoplanetary disks is ∼620–700 K irrespective of the water vapor pressure in the disk and that the observed crystalline forsterite dust in protoplanetary disks indicates the presence of dust annealed at temperatures above ∼620–700 K. Extraterrestrial materials record various thermal events in the early Solar System (e.g., chondrule formation). Considering that meteoritic evidence indicates that the H2O/H2 ratio was enhanced over the canonical ratio in the early Solar System, the thermal evolution of amorphous forsterite dust during various thermal events in the early Solar System should be discussed taking the effect of water vapor pressure into account.. |
| 5. | Yamamoto D., Kuroda M., Tachibana S., Sakamoto N. and Yurimoto H., Oxygen isotopic exchange between amorphous silicate and water vapor and its implication for oxygen isotopic evolution in the early Solar System, The Astrophysical Journal, 10.3847/1538-4357/aadcee, 865, 98, 2018.09, Meteoritic evidence suggests that oxygen isotopic exchange between 16O-rich amorphous silicate dust and 16O-poor water vapor occurred in the early solar system. In this study, we experimentally investigated the kinetics of oxygen isotopic exchange between submicron-sized amorphous forsterite grains and water vapor at protoplanetary disk-like low pressures of water vapor. The isotopic exchange reaction rate is controlled either by diffusive isotopic exchange in the amorphous structure or by the supply of water molecules from the vapor phase. The diffusive oxygen isotopic exchange occurred with a rate constant D (m2 s−1) = (1.5 ± 1.0) × 10−19 exp[−(161.5 ± 14.1 (kJ mol−1))R−1(1/T−1/1200)] at temperatures below ∼800–900 K, and the supply of water molecules from the vapor phase could determine the rate of oxygen isotopic exchange at higher temperatures in the protosolar disk. On the other hand, the oxygen isotopic exchange rate dramatically decreases if the crystallization of amorphous forsterite precedes the oxygen isotopic exchange reaction with amorphous forsterite. According to the kinetics for oxygen isotopic exchange in protoplanetary disks, original isotopic compositions of amorphous forsterite dust could be preserved only if the dust was kept at temperatures below 500–600 K in the early solar system. The 16O-poor signatures for the most pristine silicate dust observed in cometary materials implies that the cometary silicate dust experienced oxygen isotopic exchange with 16O-poor water vapor through thermal annealing at temperatures higher than 500–600 K prior to their accretion into comets in the solar system.. |
Presentations
- Japan Geoscience Union
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