Analysis of the Pb isotope composition

"Common lead" is lead in a sample with a zero or negligible content of uranium, so that the proportion of radiogenic lead added to the original composition is very small. Thus in low-U materials (minerals or total rocks), variations in the isotope composition (207Pb/204Pb and 206Pb/204Pb) can by ascribed to the different rate of decay of parent isotopes (235U and 238U) in the source of the materials and these ratios may be used to estimate the age of formation without knowing the need to measure the concentration of U.

The Common Lead method has been used, mainly in the field of geosciences, for determining the model ages in galenas and cerussite, as well as an isotopic tracer in feldspars. In some cases, in very old rocks (> 1000 Ma) it has been used to estimate the age by the isochron method.

Over the last decade, there has been a considerable development of common lead analysis, as it can be extremely important in environmental studies as a useful tracer for contamination processes.