Abstract
The contents and isotopic composition of He, Ne and Ar in 81 stony meteorites have been determined. The 3He exposure ages, and the radiogenic 4He and K-Ar ages confirm the conclusions of previous publications. The exposure ages of diogenites are clustered around 20 × 10 6 yr. The H-chondrites Benoni, Cee Vee, Grassland, Heredia, Hessle and Menow, the L-chondrite Bishunpur and the carbonaceous chondrites Alais and Essebi contain He and Ne as primordial components. A dark inclusion in the amphoterite Krähenberg has an extremely high K-content of 12000 ppm. The contents of 84Kr and 132Xe and the 129Xe: 132Xe ratio have also been determined in 92 stony meteorites. Not only the 84Kr and 132Xe contents but also the content of the 129Xe-excess are proportional to the primordial 36Ar content over a larger range. The primordial 36Ar contents are related to the petrological classes of Van Schmus and Wood. The 129Xe: 132Xe ratios of all ordinary chondrites lie between 1 and 3 and all enstatite chondrites have ratios between 3 and 7. If one assumes the I- 129Xe relation from the work by Reynolds and co-workers to be valid, one has to conclude that all ordinary chondrites had initially about the same Xe:I ratio and that most of them lost a large fraction of their primordial rare gases after the 129I decay while the high temperature fraction retained all of the 129Xe. This imposes quite narrow constraints on the model on I- 129Xe dating.
Published Version
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