How is radioactive dating performed
There is a suspicion that the relative abundance of carbon-14 could be changing due to the thinning of the ozone layer.The amount of carbon-14 depends on the amount of radiation permeates the ozone and thus the amount could be changing. Accuracy radioactive dating is called radiometric dating. The term U–Pb dating normally implies the coupled use of both decay schemes in the 'concordia diagram' (see below).However, use of a single decay scheme (usually Pb) leads to the U–Pb isochron dating method, analogous to the rubidium–strontium dating method.
The upper intercept of the concordia and the discordia line will reflect the original age of formation, while the lower intercept will reflect the age of the event that led to open system behavior and therefore the lead loss; although there has been some disagreement regarding the meaning of the lower intercept ages.Undamaged zircon retains the lead generated by radioactive decay of uranium and thorium until very high temperatures (about 900 °C), though accumulated radiation damage within zones of very high uranium can lower this temperature substantially.Zircon is very chemically inert and resistant to mechanical weathering—a mixed blessing for geochronologists, as zones or even whole crystals can survive melting of their parent rock with their original uranium-lead age intact.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 estimates of the age of the Earth.Although zircon (Zr Si O) is most commonly used, other minerals such as monazite (see: monazite geochronology), titanite, and baddeleyite can also be used.