On neutron-induced and other noble gases in Allende inclusions

Noble gases have been measured in one bulk sample, six light inclusions, and one black xenolith from four specimens of the carbonaceous chondrite Allende which cover a range in their 60Co content of about a factor of ten. The release pattern obtained upon heating the samples at different temperature steps shows: 1.) The parent nuclides of radiogenic 4He are finely dispersed throughout the inclusions in host minerals with grain sizes smaller than the typical range of α-particles within them; 2.) Neon from the inclusions contains a component deficient in sup(20,21)Ne which is most conspicuous at low temperatures. The apparent excess 22Nesup(*) is attributed to spallation reactions on sodium although the reasons for excluding NeE are weak; 3.) 36Ar/ 38Ar ratios up to 90 are observed at release temperatures around 8000C. For inclusions from the same specimens the excess 36Arsup(*) is proportional to the chlorine content, for different specimens the chlorine-normalized amounts of 36Arsup(*) tend to correlate with 60Co; 4.) sup(80,82)Kr are found enriched about 80 fold,the ratio of the excess amounts 80Krsup(*)/82Krsup(*) is 2.68 +- 0.06; 5.) Xenon is dominated by 129Xe, the overabundances are accompanied by much smaller excesses of 128Xe. The results are discussed. (author)