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The relative isotopic abundance of K^(40) in terrestrial and meteoritic samples

Burnett, D. S. and Lippolt, H. J. and Wasserburg, G. J. (1966) The relative isotopic abundance of K^(40) in terrestrial and meteoritic samples. Journal of Geophysical Research, 71 (4). pp. 1249-1269. ISSN 0148-0227. doi:10.1029/JZ071i004p01249.

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Fowler, Greenstein, and Hoyle have proposed that the inner solar system was heavily irradiated during its formation. A consequence of this proposal is that sizable differences in meteoritic and terrestrial K^(41)/K^(40) ratios are possible if the fraction of material which was irradiated was different in the two cases. The isotopic composition of potassium was measured by mass spectrometry for nine stone meteorites, silicate from the Vaca Muerta mesosiderite and the Weekeroo Station iron meteorite, and four terrestrial samples. The measured K^(41)/K^(40) ratios were corrected by normalizing the measured K^(39)/K^(41) ratio to the Nier value of 13.47. This normalization procedure approximately cancels out any variations in the isotopic abundance except those due to nuclear processes. Measurements on enriched standards showed that any variations greater than 1% would certainly have been detected, and variations greater than ½% would probably have been detected with replicate analyses. Within these limits, no variations in the K^(40) abundance between the terrestrial and meteoritic samples could be found which could be ascribed to particle irradiation in the early history of the solar system. Small K^(40) enrichments were observed in Norton County, Weekeroo Station, and Vaca Muerta; however, these appear to have been produced during cosmic-ray irradiation by the Ca^(40)(n, p) reaction. The present results set relatively strong limitations on possible mechanisms for the formation of the earth and the meteorites if the idea of a large-scale irradiation in the early history of the solar system is to be retained. Independent of the model of Fowler et al., limits have been placed on any differential uniform irradiation. The implications of the present work on the K-Ar ages of stone and iron meteorites are discussed. The possibility that iron meteorites are considerably older than the solar system as a whole appears unlikely.

Item Type:Article
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Burnett, D. S.0000-0001-9521-8675
Wasserburg, G. J.0000-0002-7957-8029
Alternate Title:The relative isotopic abundance of K40 in terrestrial and meteoritic samples
Additional Information:Copyright 1966 by the American Geophysical Union. (Manuscript received October 15, 1965.) We wish to thank Professor R. E. Folinsbee, Professor C. Frondel, Walter Nichiporuk, and Professor L. T. Silver for meteorite samples used in this work. We wish to acknowledge especially the cooperation of Professor C. B. Moore and the Nininger Meteorite Collection in obtaining and discussing meteorite samples. We are grateful to Professors W. A. Fowler and L. T. Silver for valuable discussions. This work was supported in part by the Office of Naval Research [Nonr-220(47)], the National Aeronautics and Space Administration [NGR-05-002-028], the U.S. Atomic Energy Commission [AT(04-3)-427], and the National Science Foundation.
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Office of Naval Research (ONR)Nonr-220(47)
Atomic Energy CommissionAT(04-3)-427
Issue or Number:4
Record Number:CaltechAUTHORS:20141107-164204989
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Official Citation:Burnett, D. S., H. J. Lippolt, and G. J. Wasserburg (1966), The relative isotopic abundance of K40 in terrestrial and meteoritic samples, J. Geophys. Res., 71(4), 1249–1269, doi:10.1029/JZ071i004p01249.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:51472
Deposited By: George Porter
Deposited On:10 Nov 2014 16:19
Last Modified:10 Nov 2021 19:11

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