On the production ratios of rare gas isotopes in stone meteorites

The abundances and isotopic compositions of argon, neon, and helium extracted from eight stone and four stony-iron meteorites were determined, and argon-potassium ages were calculated. The production ratios of cosmic-ray-produced isotopes were compared with the chemical composition of the samples. It was found that the ratios Ne21/Ar38 may be predicted with an accuracy of usually better than 20 per cent by the equation where [Si], [Al], [Mg], [Fe], and [Ca] are the concentrations of the corresponding elements. It is concluded that the cosmogenic ratios He3/Ne21, He3/Ar38, and Ne21/Ar38 in stone meteorites are determined essentially by the chemical composition of the samples only and that differences in shielding and possible diffusive losses are of minor importance.