Abstract
Lead isotopic composition and lead concentration were measured in four troilite samples from Canyon Diablo, two troilites from Toluca, and single troilites from Bogou, Baquedano, Gibeon, Grant and Staunton. Uranium concentrations were measured in four samples; they ranged from 2.6 to 25 ppb. Observed isotopic compositions were corrected for fractionation by the double spike technique. The lead compositions ranged from primitive compositions to modern radiogenic compositions. It is concluded that the radiogenic lead found in iron meteorites is due to terrestrial contamination. New values recommended for the primordial lead ratios are Pb 206 Pb 204 = 9.346 , Pb 207 Pb 204 = 10.218 , and Pb 208 Pb 204 = 28.96 .
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