| Summary: | Allan Hills (ALHA) 77005 is a newly discovered, unique achondrite from Antarctica. Petrologic similarities with the shergottites in terms of mineralogy, oxidation state, inferred source region composition, shock metamorphic effects and shock ages suggest a genetic relationship. Volatile to involatile element ratios (e.g. K/U, Rb/U, Cs/U, Tl/U) and abundances of other trace elements support this hypothesis. ALHA 77005 may be a cumulate that crystallized from a liquid parental to those from which the shergottites crystallized; alternatively it may be a sample of the type of source peridotite from which shergottite parent liquids were derived by partial melting. Chemical similarities with terrestrial ultramafic rocks suggest that this unique meteorite provides an additional sample of the only other solar system body known to have basalt source regions chemically similar to the upper mantle of the Earth. © 1979 Elsevier B.V. Received 11 April 1979. Revised 18 June 1979. We are grateful to NSF and NASA for acquiring and making available samples of this meteorite This work was supported in part by NASA grant NSG-7413 to H Y M, NASA grant NGL 15-005-140 to MEL, and the Division of Nuclear Sciences, Office of Basic Energy Sciences, U S Department of Energy, under contract (W-7405-eng-26) with the Union Carbide Corporation.
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