Argon-Potassium Ages and the Isotopec Composition of Argon from Meteorites.

The potassium and the argon contents of 13 meteorites were measured by the isotopic dilution method. It is proved that the amounts of A36 and A38 found in these samples are of extra-terrestrial origin, the main source being spallation processes induced by cosmic radiation. In some chondrites an excess of A36 compared to A35 was found. Possible sources for this A36 are discussed. The 7 chondrites measured give ages between 4.4 X 1O years and 40 X 10 years. The ages of achondrites vary between 4.4 X 10 and 0 7 X 10 years