An example from Newfoundland. Isotopic results from late orogenic and post-orogenic, granitoid plutons. The yellow dots show where plutons were derived from the mantle (i.e. very deep). The black dots show where plutons were formed by melting of crustal (deep) and supra-crustal (shallow) rockss.

Under favourable circumstances, the age of the deep crust may be determined. All this is particularly important in regions of complex geology where the upper and lower parts of the crust may have evolved independently and been structurally juxtaposed. Many other isotope systems and other geochronologic methods (e.g. "fission track" dating) provide critical chronological data.
Important economic applications of geochronology and radiogenic isotopes relate to the determination of the emplacement times of ore deposits and determination of the sources of their chemical components.