Concentration of Uranium and Lead and the Isotopic Composition of Lead in Meteoritic Material

Abstract

The cosmic abundance of lead and uranium have been determined by studying the lead and uranium contents of meteoritic materials. Lead is found to be present to 8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}3}$ atom/10 000 atoms of silicon, and uranium to 1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ atom/10 000 atom of silicon. The new value for lead removes the hump in the cosmic abundance curve in the 206-208 mass region. The relative primordial abundances of lead isotopes of mass 204, 206, 207, and 208 are found to be 1:9.4:10.3:29.2, respectively.