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Search for extinct natural radioactivity of Pb205 via thallium-isotope anomalies in chondrites and lunar soil.Thallium and Pb204 contents were determined by stable-isotope-dilution analysis in 16 chondrites, one achondrite, and Apollo 11 and 12 lunar fines. Meteoritic thallium contents vary over a large range, 0.02 to 100 ppb, corresponding to the fact that thallium is a highly fractionated volatile element. Lunar thallium contents are less than 5 ppb. The Tl205/Tl203 ratio was determined in most of the samples, with precision ranging from 0.03% to several percent depending mainly on the amount of thallium present. No variations from the terrestrial ratio were observed. The chondritic isochron slope for Pb205 (13.8-m.y. half-life) is less than or equal to 0.00009 (99% confidence level), corresponding to an interval of at least 60 m.y. and possibly exceeding 120 m.y. between the termination of s-process nucleosynthesis and the lead-thallium fractionations.
Document ID
19730029307
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Huey, J. M.
Kohman, T. P.
(Carnegie-Mellon University Pittsburgh, Pa., United States)
Date Acquired
August 7, 2013
Publication Date
November 1, 1972
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 16
Subject Category
Space Sciences
Accession Number
73A14109
Funding Number(s)
CONTRACT_GRANT: NAS9-8073
CONTRACT_GRANT: AT(30-1)-844
CONTRACT_GRANT: AT(11-1)-3236
Distribution Limits
Public
Copyright
Other

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