Verification and interpretation of the I-Xe chronometer

Comparisons of I-Xe and Pb-Pb relative ages are made for phosphate and feld spar separates from 12 different meteorites. In all cases where I-Xe ages c an be measured in phosphate, I-Xe and Pb-Pb chronometers agree within exper imental uncertainty. No discordant phosphate samples are observed. With the exception of Allegan, I-Xe ages for feldspar separates generally agree wit h Pb-Pb ages for the corresponding phosphate. The general concordancy obser ved between I-Xe and Pb-Pb chronometers suggests that the I-Xe system is a reliable and interpretable chronometer when applied to single minerals syst ems. Allegan feldspar differs from the other feldspar separates, predating its phosphate by similar to 17 Ma, with an I-Xe age indistinguishable from those of Orgueil and Murchison magnetites, among the oldest observed. Copyr ight (C) 1999 Elsevier Science Ltd.