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

Abstract

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