Single parent dating statistics updating uncertainties in friction angles of clean sands
Various methods have been devised to determine this initial or common Pb, but all involve making unprovable assumptions.
Zircon does incorporate initial Pb when it crystallizes. It cannot be proven that the Pb in apparently cogenetic U- or Th-free minerals is only initial Pb, and that it is identical to the initial Pb in the mineral being dated.
Zircon (Zr Si O) in particular has been the focus of thousands of geochronological studies, because of its ubiquity in felsic igneous rocks and its claimed extreme resistance to isotopic resetting (Begemann et al. However, accurate radioisotopic age determinations require that the decay constants or half-lives of the respective parent radionuclides be accurately known and constant in time.
Ideally, the uncertainty of the decay constants should be negligible compared to, or at least be commensurate with, the analytical uncertainties of the mass spectrometer measurements entering the radioisotope age calculations (Begemann et al. Clearly, based on the ongoing discussion in the conventional literature this is still not the case at present.
The uncertainties associated with direct half-life determinations are, in most cases, still at the 1% level, which is still significantly better than any radioisotope method for determining the ages of rock formations.U-Pb radioisotope dating is now the absolute dating method of first choice among geochronologists, especially using the mineral zircon.