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The Th and U abundances in chondritic meteoritesWe present new analyses of Th-232/U-238 in CI and CM meteorites. The relative abundance of these nuclides is important in estimates of the age of r-process elements. The cosmochronology based upon the Th-232/U-238 ratio (kappa) depends on the precise determinations of these two different elements in meteorites and on the production ratios. Both parameters are subject to substantial errors. Recent recalculations of this chronology have used selected values from compilations but do not adequately address the errors in terms of a reliable data base. Morgan and Lovering provided extensive neutron activation analyses for ordinary chondrites which yield an average kappa of 3.6 +/- 0.4. Their work on carbonaceous chondrites showed a wide range in kappa from 2 to 6. More recent investigations by isotopic dilution have established the following: (1) highly variable kappa from 2.7 to 11 in Allende Ca-Al-rich inclusions and a value of 3.6 in the Orgueil CI1 chondrite; (2) a range from 2.71 to 6.63 for 7 L-type chondrites and a range from 2.7 to 4.4 for 6 L, H, and LL chondrites. A further investigation of this subject matter is presented.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Chen, J. H.
(California Inst. of Tech. Pasadena, CA, United States)
Wasserburg, G. J.
(California Inst. of Tech. Pasadena, CA, United States)
Papanastassiou, D. A.
(California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1993
Publication Information
Publication: Lunar and Planetary Inst., Twenty-fourth Lunar and Planetary Science Conference. Part 1: A-F
Subject Category
Accession Number
Distribution Limits
Work of the US Gov. Public Use Permitted.

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