Uranium-lead dating
type of radiometric dating / From Wikipedia, the free encyclopedia
Uranium-lead is one of the oldest[1] and most refined of the radiometric dating schemes.
It can be used over an age range of about 1 million years to over 4.5 billion years. Precision is in the 0.1-1 percent range.[2]
The method relies on two separate decay chains, the uranium series from 238U to 206Pb, with a half-life of 4.47 billion years and the actinium series from 235U to 207Pb, with a half-life of 704 million years.[3]
The existence of two 'parallel' uranium-lead decay routes allows several dating techniques within the overall U-Pb system.
The term 'U-Pb dating' normally implies the coupled use of both decay schemes. However, use of a single decay scheme (usually 238U to 206Pb) leads to the U-Pb isochron dating method, analogous to the rubidium-strontium dating method.
Finally, ages can also be determined from the U-Pb system by analysis of Pb isotope ratios alone. This is termed the lead-lead dating method. 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.