These new rocks rapidly accumulated more Pb isotopes due to the concurrent accelerated radioactive decay of U and Th in them during the Flood.Thus, without being able to unequivocally distinguish the daughter Pb atoms produced by in situ U and Th decay from the initial Pb atoms in a mineral or rock, it is impossible to determine their absolute U-Pb ages.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.The stunning improvements in the performance of mass spectrometers during the past four or so decades, starting with the landmark paper by Wasserburg et al.(1969), have not been accompanied by any comparable improvement in the accuracy of the decay constants (Begemann et al.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.
Then catastrophic plate tectonics during the Flood stirred the mantle and via partial melting added new rocks to the crust.
U decay in those rocks added daughter Pb isotopes to the common or initial Pb isotopes in them, inherited from the rock’s sources.
So the Pb isotope ratios measured in these rocks today must be interpreted before their U-Pb ages can be calculated.
U-Pb radioisotope dating is now the absolute dating method of first choice among geochronologists, especially using the mineral zircon.
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.