Abstract
The preserved record of decay of now-extinct 129I into 129Xe forms the basis of the I-Xe chronometer. Comparison of the high precision I-Xe and Pb-Pb ages of chondrules and pure mineral phases separated from eight meteorites suggests the 17.5 ÷ 14.6 Ma range for the 129I half-life, assuming that the 235U and 238U half-lives are correct. The mean value of 16 Ma indicates that the 15.7 Ma half-life of 129I used here for the I-Xe age calculations is most probably correct. Since the 129I half-life value only affects the relative I-Xe ages, the few Ma relative to the Shallowater standard, the absolute I-Xe ages are almost immune to this uncertainty in the 129I half-life.
Highlights
There are four experimental values available for the 129I half-life [Table I]
Comparison of the high precision I-Xe and Pb-Pb ages of chondrules and pure mineral phases separated from eight meteorites suggests the 17.5 ÷ 14.6 Ma range for the 129I
The mean value of 16 Ma indicates that the 15.7 Ma half-life of 129I used here for the I-Xe age calculations is most probably correct
Summary
There are four experimental values available for the 129I half-life [Table I]. The recommended 129I half-life of 17 ± 1 Ma was derived from them as an unweighted average [5] and later as a weighted average, 16.1 ± 0.7 Ma [6], when experimental details for the more precise measurements [2, 3] became available. We independently evaluate the 129I half-life using the precise I-Xe ages of chondrules and different mineral phases separated from the primitive meteorites.
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