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Science 17 April 1998:
Vol. 280. no. 5362, pp. 414 - 418
DOI: 10.1126/science.280.5362.414
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Reports

Oxygen Isotopic Abundances in Calcium- Aluminum-Rich Inclusions from Ordinary Chondrites: Implications for Nebular Heterogeneity

Kevin D. McKeegan, * Laurie A. Leshin, Sara S. Russell, Glenn J. MacPherson

The oxygen isotopic compositions of two calcium-aluminum-rich inclusions (CAIs) from the unequilibrated ordinary chondrite meteorites Quinyambie and Semarkona are enriched in 16O by an amount similar to that in CAIs from carbonaceous chondrites. This may indicate that most CAIs formed in a restricted region of the solar nebula and were then unevenly distributed throughout the various chondrite accretion regions. The Semarkona CAI is isotopically homogeneous and contains highly 16O-enriched melilite, supporting the hypothesis that all CAI minerals were originally 16O-rich, but that in most carbonaceous chondrite inclusions some minerals exchanged oxygen isotopes with an external reservoir following crystallization.

K. D. McKeegan and L. A. Leshin, Department of Earth and Space Sciences, University of California Los Angeles, Los Angeles, CA 90095-1567, USA.
S. S. Russell and G. J. MacPherson, Department of Mineral Sciences, MRC NHB-119, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA.
*   To whom correspondence should be addressed. E-mail: kdm{at}ess.ucla.edu

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THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
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Stable Isotope Variations in Extraterrestrial Materials.
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