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Mg and Ca isotopic study of individual microscopic crystals from the Allende meteorite by the direct loading technique

Lee, Typhoon and Papanastassiou, D. A. and Wasserburg, G. J. (1977) Mg and Ca isotopic study of individual microscopic crystals from the Allende meteorite by the direct loading technique. Geochimica et Cosmochimica Acta, 41 (10). pp. 1473-1485. ISSN 0016-7037. http://resolver.caltech.edu/CaltechAUTHORS:20130910-134926527

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Abstract

We have developed a direct loading technique for determining the isotopic composition of Mg in chemically unseparated samples. This technique has a sensitivity and precision comparable with those of the conventional technique of analyzing pure Mg salt and eliminates contamination introduced during the chemical separation of Mg. This results in a significant reduction in sample size required for an analysis. This technique was combined with other characterization techniques of microscopic samples (e.g. optical microscopy, SEM, EPMA), and was applied to four single crystals of pure phases from an Allende inclusion ranging in size from 25 to 150 μm. Using a total sample of 4 μg, we found an anorthite crystal showing an enrichment in ^(26)Mg of 10% and were able to construct an ^(26)Al-^(26)Mg isochron which confirms our previous results obtained on macroscopic samples of the same inclusion. The isotopic composition of Ca was also measured along with Mg, on a directly loaded anorthite crystal from this inclusion, during the same mass spectrometer run and was shown to be essentially normal. Thus, the direct loading technique is applicable to Ca and will be useful in a correlative study of isotopic effects of different elements on individual microscopic samples. The extension of this technique to other elements appears feasible but will require extensive testing to control possible interferences.


Item Type:Article
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URLURL TypeDescription
http://dx.doi.org/10.1016/0016-7037(77)90252-6DOIArticle
http://www.sciencedirect.com/science/article/pii/0016703777902526PublisherArticle
Additional Information:© 1977 Published by Elsevier Ltd. Received 15 March 1977; accepted in revised form 27 June 1977. We gratefully acknowledge Dr. Jean-Paul Revel’s generosity in permitting and helping us to use the scanning electron microscope. We thank Dr A. L. Albee for ready access to the microprobe facility and Dr C. R. Lagergren of Battelle Pacific Northwest Laboratories for providing us with the design of small V-shaped filaments. Goading by Dr. F Begemann caused us to complete the description of this procedure. The calligraphy of Mr. Read Lee is appreciated. This work was supported by NSF grant PHY 76-02724 and NASA grant NGL 05-002-188.
Funders:
Funding AgencyGrant Number
NSFPHY 76-02724
NASANGL 05-002-188
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Caltech Division of Geological and Planetary Sciences2873
Record Number:CaltechAUTHORS:20130910-134926527
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20130910-134926527
Official Citation:Typhoon Lee, D.A. Papanastassiou, G.J. Wasserburg, Mg and Ca isotopic study of individual microscopic crystals from the Allende meteorite by the direct loading technique, Geochimica et Cosmochimica Acta, Volume 41, Issue 10, October 1977, Pages 1473-1479,1481-1485, ISSN 0016-7037, http://dx.doi.org/10.1016/0016-7037(77)90252-6. (http://www.sciencedirect.com/science/article/pii/0016703777902526)
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ID Code:41214
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:17 Sep 2013 23:02
Last Modified:17 Sep 2013 23:02

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