radioactive ages of micas from granitic rocks by Rb‐Sr and K‐A methods
1958; American Geophysical Union; Volume: 39; Issue: 6 Linguagem: Inglês
10.1029/tr039i006p01124
ISSN2379-6723
AutoresL. T. Aldrich, G. W. Wetherill, Gheorghe-Alexandru David, G. R. Tilton,
Tópico(s)Radioactive contamination and transfer
ResumoAnalytical data and ages are given for K‐A, Rb‐Sr, U‐Pb and Th‐Pb ages from a number of locations. Comparisons of the ages obtained indicate (a) that K‐A and Rb‐Sr ages of mica usually agree when modern laboratory determined values of the decay constants of K 40 and Rb 87 are used; (b) that the K‐A and Rb‐Sr ages of micas agree with the U‐Pb ages of cogenetic uraninite, zircon, and monazite when the U‐Pb ages are concordant; (c) that when the U‐Pb ages of these uranium minerals are discordant, the mica ages agree best with the Pb 207 ‐Pb 206 age; (d) that the pattern of K‐A and Rb‐Sr ages of micas can be most simply explained by postulating the loss of variable but small amounts of argon from the mineral.
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