Heavy carbon in individual oxide grains from the Murchison meteorite
- Creators
- Zinner, Ernst
- Epstein, Samuel
Abstract
The carbon isotopic composition of individual oxide grains from Murchison HF—HCl acid residue CFOc has been measured in the ion microprobe. Many grains (Mg-spinel, Cr-spinel, and Fe-oxide) contain carbon with large ^(13)C excesses ranging to 7000‰ (corresponding to ^(12)C/^(13)C= 11). In most cases the carbon is present as micron-sized subgrains. The association of silicon with the anomalous carbon points towards SiC as carrier. If this tentative identification is correct then the SiC grains most likely originated in the circumstellar atmospheres of red giants. Oxide grains in which the ^(18)O/^(16)O ratio has also been measured show variable ^(16)O excesses which are not correlated with the ^(13)C excesses. This indicates that the sources of the anomalous carbon and oxygen isotopic compositions of the oxide grains are unrelated.
Additional Information
© 1987 Elsevier Science Publishers B.V. Received March 18, 1987; revised version received May 27, 1987. We are grateful to Pat Swan and John Foote for the mounting of the oxide grains and for EDX identification. John Bradley provided electron diffraction analyses and Brigitte Wopenka laser Raman microprobe data on selected Fe-oxide grains. Jean Paul Bibring provided the carbon implantation into silicon. Robert Clayton and Toshiko Mayeda measured the oxygen isotopic composition of the terrestrial spinel standard. We thank Edward Anders, Albert Fahey and Kevin McKeegan for critical readings of the manuscript. One of us (E.Z.) enjoyed discussions with Donald Clayton and Michael Jura. We acknowledge the help of Esther Koenig and Shayla Moody with the preparation of the manuscript. This work was supported by NSF grant EAR-8415168 (E.Z.) and NASA grant NAG 9-46 (S.E).Additional details
- Eprint ID
- 39426
- DOI
- 10.1016/0012-821X(87)90001-X
- Resolver ID
- CaltechAUTHORS:20130717-154922400
- EAR-8415168
- NSF
- NAG 9-46
- NASA
- Created
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2013-07-19Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field