Primordial noble gases in separated meteoritic minerals, II

Gregory F. Herzog, Edward Anders

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15 Scopus citations

Abstract

Eight silicate samples from the Orgueil carbonaceous chrondrite were analyzed for He, Ne, Ar, and Xe by a stepwise heating technique. Six of the samples, including two etched with NaOH, were density fractions covering the following ranges: < 2.35, 2.35-2.45, 2.45-2.48, and > 2.48 g/cm3. Two others were grain-size fractions, separated according to their ability to form a colloid at pH 11.5. All fractions are grossly deficient in cosmogenic neon, having retained only 8-33% of their normal complement. Retentivity increases with density. All fractions give low 20Ne/22Ne ratios above 950°C, suggestive of D.C. Black's exotic "Neon-E" component of 20Ne/22Ne ≤ 3.4. The lowest ratios were found in the low-density and especially the non-colloidal fractions. This suggests that the host phase of Ne-E is a clay mineral of lower iron content and coarser grain size than the main silicates of Orgueil. The main fraction, ρ = 2.35-2.45 g/cm3, is inhospitable to Xe; it contains less Xe and releases it more readily at low temperatures (30-35% in 1 hour at 550°C) than do any of the other fractions.

Original languageEnglish (US)
Pages (from-to)173-181
Number of pages9
JournalEarth and Planetary Science Letters
Volume24
Issue number2
DOIs
StatePublished - Dec 1974
Externally publishedYes

All Science Journal Classification (ASJC) codes

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

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