36Ar/38Ar ratios is selected meteorites

Dating meteorites by the 40Ar/39Ar technique also allows to determine their 36Ar/38Ar ratios. The advantage of this method is that by means of the 40Ar, 39Ar and 37Ar isotopes, different mineral phases from which the main gas-volumes are delivered during the various extraction temperatures, may be distinguished. We analysed 3 Eucrites; 2 Diogenites; 1 Howardite; 1 4A-Iron meteorite with abnormal structure; 1 LL6-Amphoterite and 1 L4-Olivine-Hypersthene-Chondrite. It is generally accepted that the amounts of 36Ar and 38Ar produced by spallation are depth and also element dependent. In consequence their ratios are differing. Our measured 36Ar/38Ar ratios are in good agreement with those theoretically calculated for the moon material. For all the temperature steps of the separated Feldspar of Bjurboele, these ratios have values around 1. The same value of about 1 is obtained at the lower temperature steps for meteorites like Steinbach, St. Severin, Yamato 74013 and Johnstown, where the degassing of at least two distinct mineral phases can be observed. Values of about 0.65 are obtained for these meteorites at higher temperature steps