Composition Isotopique du plomb total de Roches: Méthodologie Lead Isotopic Composition in Whole Rocks: Methodology

Abstract

AbstractThe different stages of the lead isotopic analysis and the determination of the Pb and U concentration in whole rocks are treated. We examine successively.the dissolution of the sample;the chemical separation of Pb and U on ion exchange resin columns.the isotopic analysis of Pb by mass spectrometry with a precision better than one per mil per atomic mass unit;the determination of Pb and U contents by isotopic dilution mass spectrometry at ±1% (on samples with 1.5 to 0.1 μg of Pb and 0.8 to 0.05 μg of U);the contamination problem for the whole chemical procedure with blank values less than 3 ng of Pb;the accuracy and reproducibility of the results at the 0.1% level (by analysis of the Pb standard NBS 981 and by repeated analysis of the same sample).