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an ion microprobe study of cais from co3 meteoritesWhen attempting to interpret the history of Ca, Al-rich inclusions (CAIs) it is often difficult to distinguish between primary features inherited from the nebula and those produced during secondary processing on the parent body. We have undertaken a systematic study of CAIs from 10 CO chondrites, believed to represent a metamorphic sequence with the goal of distinguishing primary and secondary features. ALHA 77307 (3.0), Colony (3.0), Kainsaz (3.1), Felix (3.2), ALH 82101 (3.3), Ornans (3.3), Lance (3.4), ALHA 77003 (3.5), Warrenton (3.6), and Isna (3.7) were examined by Scanning Electron Microscopy (SEM) and optical microscopy. We have identified 141 CAIs within these samples, and studied in detail the petrology of 34 inclusions. The primary phases in the lower petrologic types are spinel, melilite, and hibonite. Perovskite, FeS, ilmenite, anorthite, kirschsteinite, and metallic Fe are present as minor phases. Melilite becomes less abundant in higher petrologic types and was not detected in chondrites of type 3.5 and above, confirming previous reports that this mineral easily breaks down during heating. Iron, an element that would not be expected to condense at high temperatures, has a lower abundance in spinel from low-petrologic-type meteorites than those of higher grade, and CaTiO3 is replaced by FeTiO3 in meteorites of higher petrologic type. The abundance of CAIs is similar in each meteorite. Eight inclusions have been analyzed by ion probe. The results are summarized. The results obtained to date show that CAIs in CO meteorites, like those from other meteorite classes, contain Mg* and that Mg in some inclusions has been redistributed.
Document ID
19950042229
Document Type
Reprint (Version printed in journal)
Authors
Russell, S. S.
(California Institute of Technology, Pasadena, CA US, United States)
Greenwood, R. C.
(Natural History Museum London, UK, United States)
Fahey, A. J.
(California Institute of Technology, Pasadena, CA US, United States)
Huss, G. R.
(California Institute of Technology, Pasadena, CA US, United States)
Wasserburg, G. J.
(California Institute of Technology, Pasadena, CA US, United States)
Date Acquired
August 16, 2013
Publication Date
July 1, 1994
Publication Information
Publication: Meteoritics
Volume: 29
Issue: 4
ISSN: 0026-1114
Subject Category
LUNAR AND PLANETARY EXPLORATION
Funding Number(s)
CONTRACT_GRANT: NAGW-3040
Distribution Limits
Public
Copyright
Other

Related Records

IDRelationTitle19950042052Analytic PrimaryMeteoritical Society Annual Meeting, 57th, Prague, Czech Republic, July 25-29, 1994