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Ion Microprobe Evidence for the Presence of Excess ^(26)Mg in an Allende Anorthite Crystal

Bradley, J. G. and Huneke, J. C. and Wasserburg, G. J. (1978) Ion Microprobe Evidence for the Presence of Excess ^(26)Mg in an Allende Anorthite Crystal. Journal of Geophysical Research B, 83 (B1). pp. 244-254. ISSN 0148-0227. doi:10.1029/JB083iB01p00244.

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An ion microprobe has been used to observe ^(26)Mg/^(24)Mg in excess of normal values in anorthite crystals from Allende refractory inclusions. In one crystal, ^(26)Mg excesses up to 40% above normal, correlated with Al/Mg, were observed, These excesses are many times larger than those observed by other techniques. The correlation with Al/Mg indicated that the excess ^(26)Mg in the Allende anorthite is uniformly distributed in the anorthite crystal. Analytical procedures and conditions were carefully controlled. Nevertheless, small but significant apparent ^(26)Mg/^(24)Mg anomalies in isotopically normal samples were observed in analyses by one ion microprobe. A repetition of the isotopic analyses using another ion probe produced normal ratios in the normal samples and confirmed large ^(26)Mg excesses in the Allende anorthite.

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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 1978 American Geophysical Union. Received January 31, 1977; revised August 15, 1977; accepted August 26, 1977. We thank A. L. Burlingame, J. H. Chen, and G. R. Tilton for providing the Allende samples to our laboratories. We thank T. Lee for selection of the actual sample grains for analysis, his encouragement, and many useful comments. All the 1976 sample analyses were done as paid service work at Applied Research Laboratories, Sunland, California. We appreciate the thoughtful and energetic work of D. Comaford as actual instrument operator during the analyses and the consideration and efforts of T. Whatley and other ARL personnel in scheduling the work and overcoming instrument problems. We appreciate the cooperation of D. Anderson, C. Meyer, and D. Phinney at the NASA Johnson Space Center in making our visit possible and productive. This work was supported by NASA grants NGL 05-002-188 and NSG 7084. Division of Geological and Planetary Sciences contribution 2866.
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NASANGL 05-002-188
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Caltech Division of Geological and Planetary Sciences 2866
Issue or Number:B1
Record Number:CaltechAUTHORS:20140115-113455649
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Official Citation:Bradley, J. G., J. C. Huneke, and G. J. Wasserburg (1978), Ion microprobe evidence for the presence of excess 26Mg in an Allende anorthite crystal, J. Geophys. Res., 83(B1), 244–254, doi:10.1029/JB083iB01p00244.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43385
Deposited By: Ruth Sustaita
Deposited On:15 Jan 2014 20:46
Last Modified:10 Nov 2021 16:36

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