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Published September 1982 | public
Journal Article

Chemical composition of HAL, an isotopically-unusual Allende inclusion

Abstract

Thirty-seven major, minor and trace elements were determined by INAA and RNAA in samples of hibonite, black rim and portions of friable rim from an unusual Allende inclusion, HAL. The peculiar isotopic, mineralogical and textural properties of HAL are accompanied by very unusual trace element abundances. The most striking feature of the chemistry is the virtual absence of Ce from an inclusion otherwise highly enriched in REE compared to Cl chondrites. HAL is also depleted in Sr, Ba, U, V, Ru, Os and Ir, relative to other refractory elements. Of the lithophile elements determined which are normally considered to be refractory in a gas of solar composition, Sr, Ba, Ce, U and V are the most volatile in oxidizing gases. The distribution of REE between hibonite and rims seems to have been established when hibonite and other refractory minerals were removed at slightly different temperatures from a hot, oxidizing gas in which they previously coexisted as separate grains. On the basis of HAL's chemical and isotopic composition, possible locations for the chemical and mass dependent isotopic fractionation are in ejecta from the low temperature helium-burning zone of a supernova and in the locally oxidizing environment generated by evaporation of interstellar grains of near-chondritic chemical composition.

Additional Information

© 1982 Pergamon Press Ltd. Received July 17, 1981; accepted in revised form May 6, 1982. We thank J. M. Lattimer for the use of unpublished data and for performing new calculations on Cl chondritic gases, J. M. Allen for the use of unpublished electron microprobe analyses of HAL and B. Mason and H. Palme for the use of unpublished analyses of volatile elements in coarse-grained inclusions. We are grateful for valuable discussions with J. M. Allen, R. N. Clayton, I. Kawabe and G. J. MacPherson. We thank W. V. Boynton and H. Palme for their thorough reviews of this paper. This work was supported by funds from the National Aeronautics and Space Administration through grants NGR 14-001-249 (L.G.) and NGL 05-002-188 (G.J.W.), the Alfred P. Sloan Research Foundation (L.C.) and the Enrico Fermi institute and Robert R. McCormick Trust (T.L.). Parts of this paper were written by L.G. while on leave at the Hebrew University of Jerusalem where he was supported by funds from the Lady Davis Fellowship Trust and funds from Mr. Lester M. Finkelstein.

Additional details

Created:
August 19, 2023
Modified:
October 19, 2023