Isotopie-Effekt und Häufigkeiten der Edelgase in Steinmeteoriten und auf der Erde

Abstract

The rare gas content of 19 various stone meteorites has been investigated mainly for the abundance of the heavier components. Nine normal chondrites have been selected, which indicated from the A³⁶/A³⁸-ratio the presence of primordial rare gases. All of them contain primordial Kr and Xe as well as Xe¹²⁹ -excess. Their content is proportional to the A³⁶-content and increases in the sequence: normal chondrites, enstatite chondrites and carbonaceous chondrites. The relative abundances of the rare gases in the Staroe Pesjanoe and Kapoeta meteorites follow very closely the Suess-Urey abundance curve. This may indicate that their composition is very similar to that of an undifferentiated solar nebula. The isotopic variations of meteoritic and terrestrial Ne and He can be explained by isotope dependant diffusion in solids under the assumptions, that all matter contained the rare gases in solar composition previous to degassing and that Kr and A has been lost to a much smaller extent. A similar process may be responsible for the Xe-anomalies. Heating experiments confirm, that the remaining gases are in thermally resistent components. The Xe¹²⁹-problem is discussed under these aspects.