R5: Extraterrestrial materials

[R5-12] Oxygen isotope exchange experiments between Ca-, Al-rich inclusion (CAI) melt and carbon monoxide gas

*Daiki Yamamoto¹, Noriyuki Kawasaki², Shogo Tachibana³, Michiru Kamibayashi³, Hisayoshi Yurimoto² (1. JAXA, 2. Hokkaido Univ., 3. Univ. of Tokyo)

Keywords:CAI melt, Carbon monoxide, Oxygen isotopic exchange

O isotopic exchange experiments between CAI melt and ¹⁸O-enriched carbon monoxide gas were carried out at 1420°C and P_CO of 0.1, 0.5, and 1 Pa. All run products, composed of glass and spinel, exhibited self-diffusion of ¹⁸O with a time-variant isotopic composition at the surface, yielding the O self-diffusion coefficient of ~1.41 × 10^–11 m² s^–1 and the surface isotope exchange efficiency of ~10^–3–10^–4. The present results suggest that the rate of isotope exchange between CAI melt and gas is controlled by the rate of isotope exchange between CAI melt and H₂O gas.