Oxygen isotopic exchange between Ca-, Al-rich inclusion (CAI) melt and water vapor in the protosolar disk

Abstract

Oxygen isotopic exchange experiments between Ca-, Al-rich inclusion (CAI) melt and H₂¹⁸O vapor were carried out at 1390°C and P_H2O of 5×10^-2 Pa for 3 and 18 hours. Run products were mostly glass with a small amount of spinel, and showed oxygen isotopic zoning with ¹⁸O enrichment toward the sample surface, yielding the diffusion coefficients of 2.1 × 10^-7 and 4.8 × 10^-7 cm² sec^-1 for samples heated for 3 and 18 hours, respectively. The isotopic exchange efficiency between water vapor and the CAI melt at the surface was estimated to be ~0.1.