Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Yamamoto Daiki Last modified date:2024.06.03

Assistant Professor / Department of Earth and Planetary Sciences, Graduate School of Sciences / Department of Earth and Planetary Sciences / Faculty of Sciences

1. Daiki Yamamoto, Noriyuki Kawasaki, Shogo Tachibana, Lily Ishizaki, Ryosuke Sakurai, Hisayoshi Yurimoto, An experimental simulation of oxygen isotope exchange reaction between amorphous silicate dust and carbon monoxide gas in the early Solar System, Geochimica et Cosmochimica Acta,, 374, 93-105, 2024.03, [URL], The reaction mechanism and kinetics of oxygen isotope exchange between tens of nanometer-sized amorphous silicate grains with forsterite composition (amorphous forsterite) and low-pressure carbon monoxide (CO) gas (PCO) of 0.05–1 Pa at 643–883 K were examined to investigate oxygen isotopic evolution in the protosolar disk that led to the mass-independent oxygen isotopic variation of planetary materials. Both CO gas supply- and diffusion-controlled isotope exchange reactions were observed. At 753–883 K and PCO of 0.05–1 Pa, the supply of CO gas controls the isotope exchange reaction, and its rate is 2–3 orders of magnitude smaller than that of the H2O supply-controlled isotope exchange reaction. The diffusion-controlled isotope exchange occurred at 643–703 K and PCO of 0.3 Pa, and the reaction rate of D (m2/s) = (3.1 ± 2.3) × 10−23 exp[−41.7 ± 9.6 (kJ mol−1) R−1 (1/T − 1/1200)] was obtained.

We found that the oxygen isotope exchange rates of amorphous forsterite with CO and H2O gases are larger than those of gaseous isotope exchange between CO and H2O gases at a wide range of temperatures, wherein amorphous forsterite crystallization does not precede the isotope exchange reaction of amorphous forsterite with these gases. The most sluggish isotope exchange rate between H2O and CO in the gas phase suggests that amorphous forsterite would play a role in accelerating gaseous isotopic equilibrium through the isotope exchange of amorphous forsterite with both CO and H2O. We found that the oxygen isotopic equilibrium between 0.1 μm-sized amorphous forsterite, CO, and H2O would be accomplished through the isotope exchange of amorphous forsterite at temperatures as low as ∼600–700 K in the dynamically accreting protosolar disk, which is significantly lower than expected for the case of gaseous isotope exchange (>∼800 K)..
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4. 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,, 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..
5. Yokoyama T., Nagashima K., Nakai I., ..., Yamamoto D. et al. (147人中143番目) , Samples returned from the asteroid Ryugu are similar to Ivuna-type carbonaceous meteorites, Science, DOI: 10.1126/science.abn785, 379, 6634, 2022.09, Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples of the C-type asteroid (162173) Ryugu were retrieved by the Hayabusa2 spacecraft. We measured the mineralogy and bulk chemical and isotopic compositions of Ryugu samples. The samples are mainly composed of materials similar to those of carbonaceous chondrite meteorites, particularly the CI (Ivuna-type) group. The samples consist predominantly of minerals formed in aqueous fluid on a parent planetesimal. The primary minerals were altered by fluids at a temperature of 37° ± 10°C, about 5.2+0.8−0.7 million (statistical) or 5.2+1.6−2.1 million (systematic) years after the formation of the first solids in the Solar System. After aqueous alteration, the Ryugu samples were likely never heated above ~100°C. The samples have a chemical composition that more closely resembles that of the Sun’s photosphere than other natural samples do..
6. T. Nakamura, M. Matsumoto, ..., D. Yamamoto (221人中164番) et al., Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples, Science, DOI: 10.1126/science.abn867, 379, 6634, 2022.09, Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of
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8. Kamibayashi M., Tachibana S., Yamamoto D., Kawasaki N., Yurimoto H, Effect of hydrogen gas pressure on calcium-aluminum-rich inclusion formation in the protosolar disk, The Astrophysical Journal, 10.3847/2041-8213/ac3c41, 923, 2021.10, [URL], Calcium–aluminum-rich inclusions (CAIs) are the oldest materials that formed in the protosolar disk. Igneous CAIs experienced melting and subsequent crystallization in the disk during which the evaporation of relatively volatile elements such as Mg and Si occurred. Evaporation from the melt would have played a significant role in the variation of chemical, mineralogical, and petrologic characteristics of the igneous CAIs. In this study, we investigated crystallization of CAI analog melt under disk-like low-pressure hydrogen (PH2) conditions of 0.1, 1, and 10 Pa to constrain the pressure condition of the early solar system in which type B CAIs were formed. At PH2 = 10 Pa, the samples were mantled by melilite crystals, as observed for type B1 CAIs. However, the samples heated at PH2 = 0.1 Pa exhibited random distribution of melilite, as in type B2 CAIs. At the intermediate PH2 of 1 Pa, type-B1-like structure formed when the cooling rate was 5°C hr−1, whereas the formation of type-B2-like structure required a cooling rate faster than 20°C hr−1. The compositional characteristics of melilite in type B1 and B2 CAIs could also be reproduced by experiments. The results of the present study suggest that PH2 required for type-B1-like textural and chemical characteristics is greater than 1 Pa. The hydrogen pressure estimated in this study would impose an important constraint on the physical condition of the protosolar disk where type B CAIs were formed.
9. 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,, 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..
10. Kawasaki N., Itoh S., Sakamoto N., Simon S. B., Yamamoto D. and Yurimoto H., Oxygen and Al-Mg isotopic constraints on cooling rate and age of partial melting of an Allende type B CAI, Meteoritics & Planetary Science,, 56, 6, 1224-1239, 2021.06, Coarse-grained, igneous Ca-Al-rich inclusions (CAIs) in CV chondrites formed through multiple melting events. We conducted in situ O-isotope analysis and Al-Mg systematics by secondary ion mass spectrometry of relict and overgrown minerals from a partial melting event in an Allende Type B CAI, Golfball. Golfball has a Type B CAI bulk composition and a unique structure: a fassaite-rich mantle enclosing a melilite-rich core. Many of the blocky melilite crystals in the core have irregularly shaped, Al-rich (Åk5–15) cores enclosed in strongly zoned (Åk30–70) overgrowths. Since the Al-rich melilite grains could not have formed from a melt of Golfball, they are interpreted as relict grains that survived later melting events. The O-isotopic compositions of the blocky melilite crystals plot along the carbonaceous chondrite anhydrous mineral line, ranging between Δ17O ~ −14‰ and −5‰. The Al-rich relict melilite grains and their overgrowths exhibit the same O-isotopic compositions, while the O-isotopic compositions are varied spatially among melilites. We found that the O-isotopic compositions steeply change across several melilite crystals within few tens of micrometers, indicating the O-isotopic compositions of the melt could not have been homogenized during the partial melting in that scale. According to the time scale of O self-diffusivity in the melt, the cooling rate of the partial melting event is calculated to be >6 × 104 K h−1. Al-Mg isotope data for core minerals plot on a straight line on an Al-Mg evolution diagram. A mineral isochron for Golfball gives initial 26Al/27Al of (4.42 ± 0.20) × 10–5 and initial δ26Mg* of −0.035 ± 0.050‰. The chemical and O-isotopic compositions of melilite and those initial values imply that its precursor consisted of fluffy Type A and/or fine-grained CAIs. The partial melting event for Golfball may have occurred in very short order after the precursor formation..
11. 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..
12. 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..
13. 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..