Über die Isotopenzusammensetzung und über den Sitz der leichten Uredelgase in Steinmeteoriten

Abstract

Using newly developed techniques for the separate measurements of rare gases in different mineral components of stone meteorites, comprehensive investigations were carried out on meteorites containing primordial rare gases. For the bronzite chondrites Breitscheid and Pantar, we could prove that all main mineral components contain light primordial gases, probably this is also true for the carbonaceous chondrite Murray and for the achondrite Kapoeta. The light primordial gases are highly concentrated in the outmost layers of the single mineral grains. The ratios for 4He/3He and 20Ne/22Ne vary for different meteorites and also for different mineral components within a single meteorite. Both ratios shows a correlation with the diffusion coefficients of the minerals involved; the lighter isotope being always more depleted in those minerals with the higher diffusion losses. According to the observed diffusion losses, the original primordial Helium content of Pantar comes out to be at least about two orders of magnitude higher than at present. For the true and original elemental and isotopic ratios we obtained values of 13.8 and 14.0 for 20Ne/22Ne, 2200 for 4He/3He and 800 for 4He/20Ne. These ratios have been altered considerably on account of gas losses by diffusion.