title: Oxygen isotope exchange between refractory inclusion in Allende and solar nebula gas.
abstract: A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope composition (approximately 5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). Some of the melilite is also anomalously enriched in oxygen-16 compared with oxygen isotopes measured in other CAIs. The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI. Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula.
authors.affiliation: Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Japan. yuri@geo.titech.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Yurimoto
authors.forename: M
authors.initials: M
authors.lastname: Ito
authors.forename: H
authors.initials: H
authors.lastname: Nagasawa
mesh_terms: D003460:Crystallization; D019110:Meteoroids; D010100:Oxygen / Q000032:analysis*; D010103:Oxygen Isotopes / Q000032:analysis*; D016082:Solar System
chemical_list: D010103:Oxygen Isotopes; D010100:Oxygen