Cosmogenic argon and neon in stone meteorites

The abundance and isotopic composition of argon and neon in six chondrites and an achondrite were measured. The results of previous investigations are confirmed, namely Ar/K ages from 1.3 to 4.6 billion years and exposure ages from 4 to 24 million years. It is shown that the differences of the ratios Ar/sup 3//sup 6//Ar/sup 3//sup 8/ are due mainly to small amounts of trapped primordial or atmospheric argon. Using the corrected Ar/sup 3//sup 8/ abundances, a value of 9.0 with a total spread of plus or minus 20 per cent is found for the corrected Ne/sup 2//sup 1//Ar/sup 3//sup 8/ ratios. The possibility of diffusive losses of cosmogenic rare gases is discussed. (auth)