Colloidally separated samples from Allende residues: Noble gases, carbon and an ESCA-study

U. Ott, Johann Kronenbitter, Jose Flores, Sherwood Chang

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

A non-colloidal fraction separated by physical means from an HF HCl-resistant residue of the Allende carbonaceous meteorite exhibits a ratio of isotopically "normal" (Q-type) xenon to "anomalous" xenon (X-type) that is ~4 times larger than usually observed. Coincidentally this fraction contains carbon that is isotopically heavier by ~10%. than bulk Allende residue samples. ESCA analyses of companion colloidal separates show that the major portion of the S contained in our HF HCl-residues is elemental rather than a sulfide. They also confirm earlier observations that no elementally distinct surface coating is present, in accord with the absence of a surface-sited sulfur-bearing gas carrier, and that the oxygen content is increased after etching with nitric acid. For these separates noble gas data coupled with the ESCA data for nitrogen and the isotopic data for carbon point to the existence of heterogeneities among the noble gas-, carbon- and nitrogen-bearing phases and, thus, preservation of discrete components from the variety of source regions (or production mechanisms, or both) sampled by the Allende parent body. In sharp contrast to the success of physical and chemical methods in yielding samples in which one of the major noble gas components predominates to an extraordinary degree over the other, carbon isotopic compositions that have been inferred for the respective carrier phases in these same samples are strongly contradictory. Mass and isotope balance considerations lead us to conclude that a major fraction of the carbonaceous matter in Allende is noble-gas-poor, a result that could be confirmed by direct isolation of a sample, the carbon in which is dominated by this variety; and for that reason no simple relationship is discernable yet between observed isotopic compositions and either major noble gas component. Similar ambiguities may exist for nitrogen. The possible relationship between carbon-rich phases in ureilites and carbonaceous chondrites is considered.

Original languageEnglish
Pages (from-to)267-280
Number of pages14
JournalGeochimica et Cosmochimica Acta
Volume48
Issue number2
DOIs
Publication statusPublished - 1984

Fingerprint

Noble Gases
noble gas
Carbon
carbon
Xenon
xenon
Nitrogen
nitrogen
isotopic composition
Bearings (structural)
Meteorites
Nitric Acid
physical method
Gas bearings
etching
carbonaceous chondrite
parent body
chemical method
Sulfides
nitric acid

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Colloidally separated samples from Allende residues : Noble gases, carbon and an ESCA-study. / Ott, U.; Kronenbitter, Johann; Flores, Jose; Chang, Sherwood.

In: Geochimica et Cosmochimica Acta, Vol. 48, No. 2, 1984, p. 267-280.

Research output: Contribution to journalArticle

Ott, U. ; Kronenbitter, Johann ; Flores, Jose ; Chang, Sherwood. / Colloidally separated samples from Allende residues : Noble gases, carbon and an ESCA-study. In: Geochimica et Cosmochimica Acta. 1984 ; Vol. 48, No. 2. pp. 267-280.
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