26Al and 10Be production in iron meteorites

D. Aylmer, V. Bonanno, G. F. Herzog, H. Weber, J. Klein, R. Middleton

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38 Scopus citations

Abstract

We have measured by accelerator mass spectrometry the 26Al contents of 20 and the 10Be contents of 14 iron meteorites. The 26Al contents are typically 30% or more lower than values obtained by counting techniques; the 10Be contents are 10-15% lower. The production rates (P) of these nuclides decrease by more than a factor of two as the 4He 21Ne ratio increases with increasing shielding from 200 to 400. For the lighter shielding conditions expected in stony meteorites we estimate P26(Fe) as 3-4 dpm/kg and P10(Fe) as 4-5 dpm/kg. The average P10 P26 activity ratio is close to 1.5. Exposure ages calculated from 21Ne 26Al ratios cannot be calibrated so as to agree with both 40K K ages and ages based on the shorter-lived nuclides 39Ar and 36Cl. If agreement with the latter is forced, then the disagreement with 40K K ages may signal a 35% increase in the cosmic-ray intensity during the last 107 a.

Original languageEnglish (US)
Pages (from-to)107-118
Number of pages12
JournalEarth and Planetary Science Letters
Volume88
Issue number1-2
DOIs
StatePublished - Apr 1988

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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