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Nor can the measured Pb isotope ratios be used to somehow decide what proportions of them are the initial Pb without recourse to unprovable assumptions about the mineral or rock’s history or their interpreted U-Th-Pb ages within an assumed deep time history.
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.
The decay of Pb, respectively, forms the basis for one of the oldest methods of geochronology (Dickin 2005; Faure and Mensing 2005).
While the earliest studies focused on uraninite (an uncommon mineral in igneous rocks), there has been intensive and continuous effort over the past five decades in U-Pb dating of more-commonly occurring trace minerals.
However, even uncertainties of only 1% in the half-lives lead to very significant discrepancies in the derived radioisotope ages.
The recognition of an urgent need to improve the situation is not new (for example, Min et al. It continues to be mentioned, at one time or another, by every group active in geo- or cosmochronology (Boehnke and Harrison 2014; Schmitz 2012).