Petrography, mineralogy, and Mg isotope composition of VICTA : A vigarano CaAl4O7-bearing type A inclusion
- Author
- Long, J. V. P.
- Published
- JAN 1, 1993.
- Physical Description
- 1 electronic document
- Additional Creators
- Morse, A. and Greenwood, R. C.
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Free-to-read Unrestricted online access - Summary
- Thermodynamic calculations predict that Ca-dialuminate (CaAl4O7) condenses from a cooling gas of solar composition after hibonite and before melilite. Although Ca-dialuminate has now been recorded from Ca Al-rich inclusions (CAI's) in at least 9 meteorites, compared to hibonite it is a relatively rare phase. As pointed out by Michel-Levy et al., the absence of Ca-dialuminate from most hibonite-bearing inclusions poses a serious problem for the condensation model of CAI formation. Here we describe an inclusion which contains abundant CA-dialuminate partially altered to a hercynite-rich (FeAl2O4) assemblage. The evidence from VICTA indicates that compared to all other phases in type A inclusions, Ca-dialuminate is the most susceptible to secondary alteration; a feature which may explain its restricted occurrence. Unaltered Ca-dialuminate and melilite in VICTA display excess Mg-26 indicative of in situ decay of Al-26.
- Other Subject(s)
- Collection
- NASA Technical Reports Server (NTRS) Collection.
- Note
- Document ID: 19940011730.
Accession ID: 94N16203.
Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M; p 573-574. - Terms of Use and Reproduction
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