Cosmogenic nuclides in differentiated antarctic meteorites: measurements and model calculations

The cosmogenic radionuclides 10Be, 26Al and 53Mn and stable He-, Ne- and Ar-isotopes were measured in differentiated meteorites from Antarctica using accelerator mass spectrometry, γ-γ-coincidence techniques, radiochemical neutron activation analysis and conventional mass spectrometry. No depth effects were seen in meteorites from which several samples were analyzed. In most of the meteorites 10Be and 26Al were in saturation at time of fall, but the 26Al concentrations are partially lowered by substantial terrestrial ages. For 10Be some extremely low concentrations were found which cannot be explained by the decay during terrestrial residence. The experimental data are discussed together with rare gas measurements in the context of model calculations of the depth- and size-dependent production of cosmogenic nuclides in differentiated stony meteorites. Based on the model calculations minimal exposure ages, 21Ne53Mn and shielding corrected 21Ne exposure ages were calculated. A detailed discussion of the production rates and of possible pairing of meteorites is given.