These minerals often produce lower precision ages than igneous and metamorphic minerals traditionally used for age dating, but are more common in the geologic record.
and most refined of the radiometric dating schemes.
Finally, ages can also be determined from the U-Pb system by analysis of Pb isotope ratios alone. Clair Cameron Patterson, an American geochemist who pioneered studies of uranium-lead radiometric dating methods, is famous for having used it to obtain one of the earliest accurate estimates of the age of the Earth.It can be used to date rocks that formed from about 1 million years to over 4.5 billion years ago with routine precisions in the 0.1–1 percent range.Pb) leads to multiple dating techniques within the overall U–Pb system.), though it can be used on other minerals such as monazite, titanite, and baddeleyite.
Therefore we can assume that the entire lead content of the zircon is radiogenic.
Primordial lead is thought to have been formed by stellar nuclear reactions, released to space by supernovae explosions, and incorporated within the dust cloud that constituted the primordial solar system; the troilite (iron sulfide) phase of iron meteorites contains lead that approximates the primordial composition.