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Search for isotopic anomalies in oldhamite (CaS) from unequilibrated (E3) enstatite chondritesThe Ca isotopic compositions of 32 oldhamite (CaS) grains from the Qingzhen (EH3), MAC88136 (EL3), and Indarch (EH4) enstatite chondrites were determined by ion microprobe mass spectrometry. Also measured were the S isotopic compositions of eight oldhamite, two niningerite (MgS), and seven troilite (FeS) grains. The S isotopic compositions of all minerals are normal, but oldhamite grains of the first two meteorites exhibit apparent small Ca-48 excesses and deficits that are correlated with isotopic mass fractionation as determined from the Ca-40-Ca-44 pair. The interpretation of these results is complicated by the fact that none of the established mass fractionation laws can account for the data in the Norton County oldhamite standard. The method of analysis is carefully scrutinized for experimental artifacts. Neither interferences nor any known mass frationation effect can satisfactorily explain the observed small deviations from normal isotopic composition. If these are truly isotopic anomalies, they are much smaller than those observed in hibonite. The nucleosynthetic origin of Ca isotopes is discussed.
Document ID
19950031759
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Lundberg, Laura L.
(Washington Univ. St. Louis, MO, United States)
Zinner, Ernst
(Washington Univ. St. Louis, MO, United States)
Crozaz, Ghislaine
(Washington Univ. St. Louis, MO, United States)
Date Acquired
August 16, 2013
Publication Date
May 1, 1994
Publication Information
Publication: Meteoritics
Volume: 29
Issue: 3
ISSN: 0026-1114
Subject Category
Lunar And Planetary Exploration
Accession Number
95A63358
Funding Number(s)
CONTRACT_GRANT: NSF EAR-90-17587
Distribution Limits
Public
Copyright
Other

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