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Demonstration of ^(26)Mg excess in Allende and evidence for ^(26)Al

Lee, Typhoon and Papanastassiou, D. A. and Wasserburg, G. J. (1976) Demonstration of ^(26)Mg excess in Allende and evidence for ^(26)Al. Geophysical Research Letters, 3 (1). pp. 41-44. ISSN 0094-8276. doi:10.1029/GL003i001p00041.

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We report the discovery of a large anomaly in the isotopic composition of Mg in a Ca-Al rich chondrule from the Allende meteorite. This anomaly is manifest independently of instrumental fractionation and is due to an enrichment of about 1.3 percent in ^(26)Mg while the abundances of ^(25)Mg and ^(24)Mg are terrestrial in value. There is a strong correlation in this chondrule between the ^(26)Mg excess and the Al/Mg ratio so that the most plausible cause of the anomaly is the in situ decay of now extinct ^(26)Al (τ_½ = 0.72 × 10^6 yr). Mineral phases extracted from a Ca-Al-rich aggregate have distinct Al/Mg but show identical, small Mg anomalies which are apparent after correction for fractionation (δ^(26)Mg = 0.3%). These data indicate that this aggregate was isotopically homogenized in a high Al/Mg environment after the decay of ^(26)Al had occurred or that some of the Mg anomalies are due to effects other than in situ decay of ^(26)Al.

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Wasserburg, G. J.0000-0002-7957-8029
Alternate Title:Demonstration of 26Mg excess in Allende and evidence for 26Al
Additional Information:© 1976 American Geophysical Union. Received October 6, 1975; accepted December 4, 1975. The first two paragraphs of this paper were omitted from the January 1976 issue due to an oversight by the AGU Office. We thank A.L. Burlingame. W. Compston and C'.M. Gray for their generosity in providing us with critical samples. A.L. Albee provided advice on some mineralogical aspects of the work. Discussion of nucleosynthesis With W.A. Fowler was instructive. We benefited greatly from incisive reviews by A.G.W. Cameron and R.N. Clayton. This work was supported by NSF MPS 71-02670 A05 and by NASA NGL 05-002-188. A summary of this work was presented at the 1975 winter meeting of the American Physical Society. [Lee et. al., 1975). This is contribution 2693, Division of Geological and Planetary Sciences. Correction [to “Demonstration of ^(26)Mg excess in Allende and evidence for ^(26)Al”]. Geophysical Research Letters, 3: 109–112. doi: 10.1029/GL003i002p00109
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NSFMPS 71-02670 A05
NASANGL 05-002-188
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Caltech Division of Geological and Planetary Sciences2693
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Deposited By: Ruth Sustaita
Deposited On:16 Dec 2013 22:08
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