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In those cases, the inherited component (aka ‘common Pb’) needs to be quantified, which is done by normalising to non-radiogenic U) based on different isotopes of the same parent-daughter pair (i.e. This built-in redundancy provides a powerful internal quality check which makes the method arguably the most robust and reliable dating technique in the geological toolbox.The initial Pb composition can either be determined by analysing the Pb composition of a U-poor mineral (e.g., galena or feldspar) or by applying the isochron method to samples with different U and Th concentrations.We can also construct a Concordia diagram, which shows the values of Pb isotopes that would give concordant dates.The Concordia curve can be calculated by defining the following: ).Pb leakage is the most likely cause of discordant dates, since Pb will be occupying a site in the crystal that has suffered radiation damage as a result of U decay.
This treatment helps to eliminate the assumption that the phase being dated has remained closed to changes in the parent-daughter system. The dating equation used for K-Ar is: Carbon Dating Radiocarbon dating is different than the other methods of dating because it cannot be used to directly date rocks, but can only be used to date organic material produced by once living organisms. no isotope occurs in more than one series (Figure 2.2).As is the case for any isotopic system, the system needs to remain ‘closed’ in order to yield meaningful isotopic ages.This sometimes is not the case, resulting in a loss of Pb and/or U.