The Isotopic Constitution of Lead and the Measurement of Geological Time. III

Abstract

A mass spectrographic measurement of the relative abundances of the isotopes in eight samples of radiogenic lead and thirteen samples of common lead has been made. As five of the radiogenic lead samples originated from minerals containing both uranium and thorium, three independent determinations of the age could be made. One of the samples was the oldest so far studied and appears to have an age close to two billion years. The common lead samples were found to have large variations in the relative abundances of the same sort as were reported in a previous investigation of twelve other samples.