Long-term averaged abundances of VVH cosmic ray nuclei from studies of olivines from Marjalahti meteorite

Analysis of the results of calibrating meteoritic olivine crystals with238U nuclei at the Bevalac accelerator

“…In particular, the abundance of Th-U nuclei relative to Fe nuclei was obtained equal to (1-2)x 10 -v, and 4x 10 -2 relative to Pt-Pb [15,16,19]. These values correspond reasonably well to the known Solar system abundances [20].…”

“…Such a high track density indicates that in these crystals the Th-U nuclei track density can reach 102-103 tr.cm -3 [15,16].…”

“…The detailed measurements of the track density due to Fe group nuclei performed in crystals from 16 pallasites led to the choice of the pallasites Marjalahti and Eagle Station as most suitable objects for further studies [15,16].…”

“…In spite of all the difficulties mentioned above, at the first stage of these investigations the preliminary data on the abundaneies of cosmic ray nuclei from Sn to Pt-Pb and Th-U relative to Fe group nuclei and on the energetic spectra of all the nuclei of this group (from Fe to U) were obtained [15,16,19].…”

Further Applications of Track Detectors and Some Directions for the Future

“…The observed track densities at the surface of silicate crystals adjoining the metal phase place upper limits on the SHE abundances in the distant past (~4 x 10 9 years ago) which fall short by several orders of magnitude 18,18a,18b of the stipulated concentration required to drive the ancient lunar-core dynamo. 16 Perelygin and co-workers 19,20 have examined meteoritic olivines for very long tracks produced by cosmic ray SHE. Although a very long residual track (etchable length, 365 μηι) in an annealed olivine crystal has been reported by these authors, 21 which is tentatively assigned to a SHE nucleus (Z > 110), a more rigorous calibration of the high-Z response of these crystals is needed before this claim can be regarded as confirmed (see also reference 21a).…”