The nuclear track record of core samples from the H5 chondrite Jilin

Abstract— Based on 43 documented drill core samples of the H5 chondrite Jilin, the depth profile of track densities was investigated. The study of olivine and pyroxene crystals extracted from the two drill cores A and B of the main fragment no. 1 yields a track background for the Jilin interior of 150 ± 90 cm^?2. To estimate the contribution of different track origins, the U microdistribution of sample sections and single grain sections was mapped by neutron-induced ²³⁵U-fission using high-purity quartz glass detectors. The average U content of 0.59 ± 0.22 ppb for pyroxenes and 0.12 ± 0.06 ppb for olivines is consistent with the observed fission track background in these minerals. There are no indications of spontaneous fission of ²⁴⁴Pu, secondary mobilisation of U in the bulk sample, or substantial track annealing. As deduced from the calculated fission track density, the track contribution from galactic cosmic rays is negligible in the core samples investigated.