However, problems remain in the interpretation of the measured Pb isotopic ratios to transform them into ages.
Among them is the presence of non-radiogenic Pb of unknown composition, often referred to as common or initial Pb.
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.
All the unprovable assumptions ultimately depend on an assumed deep time history.
Its rejection is recognized as fatal to the earth’s claimed age of billions of years.
A variety of analytical instruments have also now been developed using different micro-sampling techniques coupled with mass spectrometers, thus enabling wide usage of U-Pb radioisotope dating.
These new rocks rapidly accumulated more Pb isotopes due to the concurrent accelerated radioactive decay of U and Th in them during the Flood.