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Mineralogy and petrography of HAL, an isotopically-unusual Allende inclusionResults of a detailed mineralogical and textural study of the HAL (Hibonite ALlende) inclusion of the Allende meteorite, which has been found to exhibit no Mg-26 excesses despite very high Al-27/Mg-24 ratios and large fractionation effects with small nuclear effects in its Ca, are reported. The inclusion is found to consist of three up to 1-mm diameter hibonite crystals partially surrounded by a black rim resembling a devitrified glass and containing an anisotropic Al-Fe oxide, which is in turn surrounded by a 2-mm thick friable rim sequence consisting of five layers distinguishable by mineral composition. From the available evidence, it is concluded that each of the layers of the friable rim formed by the accretion of an assemblage of condensate grains rather than by the complete reaction of a HAL precursor with a nebular gas, thus explaining its unusual isotopic characteristics and supporting the conclusion that the solar nebular contained isotopically-distinct reservoirs.
Document ID
19800050021
Document Type
Reprint (Version printed in journal)
Authors
Allen, J. M.
(Chicago Univ. Chicago, IL, United States)
Grossman, L.
(Chicago Univ. Chicago, IL, United States)
Lee, T.
(Chicago, University Chicago, Ill., United States)
Wasserburg, G. J.
(California Institute of Technology Pasadena, Calif., United States)
Date Acquired
August 10, 2013
Publication Date
May 1, 1980
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 44
Subject Category
Lunar And Planetary Exploration
Funding Number(s)
CONTRACT_GRANT: NSF PHY-76-83685
CONTRACT_GRANT: NGL-05-002-188
CONTRACT_GRANT: NGR-14-001-249
Distribution Limits
Public
Copyright
Other
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