Purely physical separation of a small fraction of the Allende meteorite that is highly enriched in noble gases

Abstract

Fine material that floats during freeze-thaw disaggregation of the Allende meteorite is greatly enriched in noble gases compared to the bulk meteorite. Not only the elemental concentrations, but also most isotopic ratios of the noble gases in this fraction, strongly suggest that this material is very similar to the gas-rich carbonaceous residue isolated from the bulk meteorite by chemical treatment. The only significant difference in noble gas signature between our separated fraction and the chemical residues is that the 129Xe/132Xe ratio in the former is significantly lower than that in the latter, which suggests readsorption of 129Xe released from the dissolved minerals during the chemical treatment. This is the first time that a gas-rich residue of a meteorite has been separated by a purely physical method alone. We also show that noble gases in phase Q and presolar diamond may be separable physically, although both are closely associated.