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Evidence in CO3.0 Chondrules for a drift in the O Isotopic Composition of the Solar NebulaSeveral recent studies have shown that materials such as magnetite that formed in asteroids tend to have higher Delta O-17 (=delta O-17 -0.52 delta O-18) values than those recorded in unaltered chondrules. Other recent studies have shown that, in sets of chondrules from carbonaceous chondrites, Delta O-17 tends to increase as the FeO contents of the silicates increase. We report a comparison of the O isotopic composition of olivine phenocrysts in low-FeO (Fal5) type II porphyritic chondrules in the highly primitive C03.0 chondrite Yamato-81020. In agreement with a similar study of chondrules in C03.0 ALH A77307 by Jones et al., Delta O-17 tends to increase with increasing FeO. We find that Delta O-17 values are resolved (but only marginally) between the two sets of olivine phenocrysts. In two of the high-FeO chondrules, the difference between Delta O-17 of the late-formed, high-FeO phenocryst olivine and those in the low-FeO cores of relict grains is well-resolved (although one of the relicts is interpreted to be a partly melted amoeboid olivine inclusion by Yurimoto and Wasson). It appears that, during much of the chondrule-forming period, there was a small upward drift in the Delta O-17 of nebular solids and that relict cores preserve the record of a different (and earlier) nebular environment.
Document ID
20060049102
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Wasson, John T.
(California Univ. Los Angeles, CA, United States)
Rubin, Alan E.
(California Univ. Los Angeles, CA, United States)
Yurimoto, Hisayoshi
(Tokyo Inst. of Tech. Tokyo, Japan)
Date Acquired
August 23, 2013
Publication Date
May 31, 2006
Publication Information
Publication: Meteoritics and Planetary Sciences
Publisher: Meteoritical Society
Volume: 39
Issue: 9
Subject Category
Lunar And Planetary Science And Exploration
Funding Number(s)
CONTRACT_GRANT: NAG5-4766
CONTRACT_GRANT: NSF EAR-00-744076
CONTRACT_GRANT: NAG5-12967
Distribution Limits
Public
Copyright
Other

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