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Published May 10, 1970 | Published
Journal Article Open

Isotopic composition of gadolinium and neutron-capture effects in some meteorites

Abstract

The isotopic composition of Gd in one chondrite, two achondrites, and the silicate inclusions of two iron meteorites has been determined. When corrected for mass discrimination, Gd in all samples except the Norton County achondrite shows the same relative isotopic abundances as terrestrial Gd. These results set an upper limit of 3×10^(15) neutrons per cm^2 on a differential integrated thermal neutron irradiation of the earth and these meteorites. Neutron-capture effects are present in Gd extracted from the Norton County achondrite. These most probably have been produced by secondary neutrons during the exceptionally long cosmic ray exposure of this large stone meteorite. The isotopic anomalies correspond to an integrated thermal neutron flux of (6.3±0.9)×10^(15) neutrons per cm^2. The percent abundances of terrestrial Gd found in our work for Gd^(160), Gd^(158), Gd^(157), Gd^(156), Gd^(155), Gd^(154), and Gd^(152) are 21.863, 24.835, 15.652, 20.466, 14.800, 2.1809, and 0.2029, respectively. Because of the higher precision, these abundances should replace the currently accepted values.

Additional Information

Copyright 1970 by the American Geophysical Union. (Received November 24, 1969; revised February 3, 1970.) We wish to thank Hannelore and Uwe Derksen for their able technical assistance and John Huneke and Günther Lugmair for useful comments on the manuscript. We are 'grateful to our colleagues who supplied meteorite samples used in this work: Norton County, Pasamonte, Forest City, and Weekeroo Station were obtained from the Nininger Meteorite Collection at the Arizona State University through the aid of C. B. Moore. Copiapo was supplied by Drs. P. Pellas, J. Orcel and F. Kraut of the Paris Natural History Museum. This work was supported by National Science Foundation grants GP 9433 and GP 9114. Division of Geological Sciences Contribution No. 1697.

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August 23, 2023
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