Determination of spallogenic long-lived radionuclides in chondrites by nuclear analytical techniques

Abstract

The record of the interaction of cosmic ray particles with meteorites in space is preserved in these objects in the form of radioactive and stable nuclides. The long-lived radionuclides 10Be (t½= 1.6 × 106 years), 26Al (t½= 7.2 × 105 years) and 53Mn (t½= 3.8 × 106 years) were determined in a large number of non-Antarctic and Antarctic chondrites by means of accelerator mass spectrometry, gamma-gamma coincidence techniques and neutron activation analysis, respectively. Radiochemical separations with high decontamination factors of interfering isotopes were used. Detection limits down to 1 × 10–14 g g–1 were achieved for isotope ratio measurements. For absolute analytical techniques the detection limit could be lowered to 10–14 g g–1. The radionuclide data obtained revealed the relatively low exposure ages of the non-Antarctic H and L chondrites investigated. With the exception of the Jilin H5 chondrite the results also indicated the simple irradiation histories of these meteorites in space. The terrestrial residence times and possible genetic relationships of the Antarctic chondrites were determined; this is of interest for the elucidation of the common origin of these objects.