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In 11 iron meteorites the isotopic abundances of potassium have been measured. For some meteorites we obtained mass spectra of essentially cosmogenic potassium. For example, we obtained from Aroos  39 K 42.0%,  40 K 18.9%,  41 K 39.1%. In other meteorites (e. g. Lombard  39 K 88.0%,  40 K 2.1%,  41 K 9.9%) the primordial potassium predominates. From the isotopic abundances, the radiation ages of the iron meteorites were calculated from two different approaches: in the first case under the assumption that the potassium isotopes were produced in the same proportion in all meteorites; in the second case it was assumed that the energy spectrum of the radiation and hence the production ratios of the potassium isotopes differed from meteorite to meteorite. The He/Ne-ratios in the meteorites were taken to be characteristic of the nature of the energy spectrum. Since the relationship between the He/Neratio and the production ratios for the potassium isotopes is not yet well known the calculated radiation ages are probably only approximately correct. They vary between 1400 · 10 6  years (Clark County) and 200 · 10 6  years (Lombard).

Massenspektrometrische Isotopenhäufigkeitsmessungen an Kalium aus Eisenmeteoriten und das Problem der Bestimmung der 41 K- 40 K-Strahlungsalter