Accelerator mass spectrometry measurements and model calculations of iron-60 production rates in meteorites

The cosmogenic radionuclide Fe-60 (T-1/2 = 1.49 Ma) was measured in two iro n meteorites as well as in the magnetic fi actions of a stony-iron and a st ony meteorite by means of accelerator mass spectrometry (AMS). The measured Fe-60/Fe ratios range from 1.5 x 10(-14) to 6.3 x 10-14 and sh ow a significant correlation to the respective concentrations of Ni, which is the main target element. The resulting 60Fe specific activities correspo nd to production rates in meteorites in the order of I dpm/kg Ni. In additi on, model calculations of depth- and size-dependent Fe-60 production rates were performed. Although there are no experimental data for the production cross sections, our measurements are in surprisingly good agreement with th e theoretical predictions using production cross sections that were determi ned by computer model calculations.