187Re–187Os systematics in meteorites and cosmochemical consequences

• DOI: 10.1038/302130a0
• Publication Date: 2004-11-17T22:45:59Z
• Authors: Jean-Marc Luck; Claude J. Allègre
• Keywords: Osmium; Microprobe

A new technique based on isotope dilution1 has allowed the reappraisal of 187Re–187Os isotopic tracers2,3. Rhenium and osmium were chemically separated and their isotopic compositions determined by ion-microprobe mass spectrometry. Such an approach led to the absolute dating of meteorites1 and allowed us to estimate the evolution of the Os isotopic composition in the Earth's mantle4. Having improved the analytical procedure and recalibrated our osmium spike, we found that the value we had used previously1 was too high by a few percent. We therefore include here our eight previous results on iron meteorites and on St Severin, corrected for this change in spike calibration. Our data now include 11 analyses on irons, and the iron phases of 10 chondrites and of one mesosiderite. From these data we propose a revised and more precise value for the rhenium decay constant, together with a new estimate for the age of the Galaxy.