Recondite interstellar carbon components in the allende meteorite revealed by preparative precombustion

Journal Article · Wed Jan 31 23:00:00 EST 1990 · Geochimica et Cosmochimica Acta; (USA)

DOI:https://doi.org/10.1016/0016-7037(90)90333-G· OSTI ID:7188865

Ash, R D; Grady, M M; Wright, I P; Pillinger, C T ^[1]; Arden, J W ^[2]

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1. Open Univ., Milton Keynes (England)
2. Univ. of Oxford (England)

Prolonged combustion at low temperatures (390-450{degree}C and 450-510{degree}C) removes large quantities of isotopically normal carbon from an acid (HF/HCl) residue of the Allende meteorite to reveal two isotopically heavy carbon components. One of them, called C{sub {aleph}} (carbon aleph) because of its possible relationship to C{sub {alpha}} of the host of Ne-E(L), has {delta}{sup 13}C of +345{per thousand} and a combustion temperature of 700-750{degree}C. It is believed that the presence of C{sub {aleph}} is masked in the bulk acid residue because of a tailing effect in the combustion of less stable forms of carbon. The second heavy carbon component burns over the temperature regime 900-1000{degree}C and has a {delta}{sup 13}C of > 527{per thousand}. This component called C{sub {kappa}} (carbon kappa) is distinguishable from the well known types of heavy carbon called C{sub {beta}} and C{sub {epsilon}}, the hosts of s-Xe and NeE(H), respectively, and now recognized as forms of SiC. C{sub {kappa}}, however, could also be a form of very poorly crystalline SiC; it appears to be released from the Allende acid residue because the precombustion slowly degrades a secondary hot mineral, which is possibly a variety of spinel. Likewise, a component of light carbon, possibly C{sub {theta}}, poorly crystalline graphite, is also liberated by the precombustion reaction after between 52 and 108 h of treatment. The discovery of C{sub {aleph}}, C{sub {kappa}}, and C{sub {theta}}, together with C{sub {lambda}}, a component very rich in {sup 12}C confirms that primitive meteorites are a prolific source of interstellar grains. Preparative precombustion demonstrates that the legacy to be found in Allende is far more complicated than at first envisaged from the noble gas record of this meteorite.

• OSTI ID: 7188865
• Journal Information: Geochimica et Cosmochimica Acta; (USA), Journal Name: Geochimica et Cosmochimica Acta; (USA) Vol. 54:2; ISSN GCACA; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
640106 -- Astrophysics & Cosmology-- Cosmology
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACIDIFICATION
ALKALINE EARTH METAL COMPOUNDS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CARBON
CARBON COMPOUNDS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
ELEMENTS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METEORITES
MINERALS
NONMETALS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PYROLYSIS PRODUCTS
PYROLYTIC CARBON
SPINELS