The radiometric dating of an igneous rock provides
Recent advances in the field of geochronology have led to a greater understanding of the scale and duration of geological processes.
It is currently possible to date igneous and metamorphic rocks by a variety of radiometric methods to within a million years, but establishing the depositional age of sedimentary rocks has remained exceedingly difficult.
Xenotime has the properties of an ideal U–Pb chronometer, containing elevated levels of U (generally 1000 ppm) and very low concentrations of initial common Pb.
In addition, it has an exceptional ability to remain closed to element mobility during later thermal events, and commonly yields concordant and precise dates.
Of course, Kelvin formed his estimates of the age of the Sun without the knowledge of fusion as the true energy source of the Sun.
Xenotime (YPO) is an isotopically robust chronometer, which is increasingly being recognized as a trace constituent in siliciclastic sedimentary rocks.
It may start to grow during early diagenesis, typically forming syntaxial outgrowths on detrital zircon grains.
If radiometric decay rates are not constant and rocks behave as open systems, it would be the exception, rather than the rule, for ages to agree with one another.
Here are a few examples in the recent literature of radiometric age determinations on the same rocks (using different isotopic methods The ages of the Fen Complex (A, B) are on two separate dikes within the Fen Complex.