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Allan Hills 77081—an unusual stony meteorite
Authors:L Schultz  H Palme  B Spettel  HW Weber  H Wänke  M Christophe Michel-Levy  JC Lorin
Institution:Max-Planck-Institut für Chemie, D-6500 Mainz F.R.G.;Laboratoire de Minéralogie-Cristallographie, UniversitéPierre et Marie Curie, F-75230 Paris France
Abstract:Allan Hills (ALHA) 77081 is achondritic in texture while the mineral composition and the chemistry are chondritic with the exception of a few elements. An assignment to one specific group of ordinary chondrites is therefore difficult. In many respects this meteorite is similar to the unusual stone meteorite Acapulco. The REE pattern of ALHA 77081 is essentially flat and the distribution ratios of siderophile elements between metal and silicates are high compared to ordinary chondrites.Gas retention ages are 3.5±0.5 AE for U, Th-He and 4.50±0.15 AE for K-Ar. In spite of the high degree of recrystallisation the meteorite contains trapped noble gases in amounts comparable to type 4 chondrites.Cosmic ray tracks and spallogenic noble gases indicate a small preatmospheric radius of about 2–3 cm. Spallogenic nuclides produced by solar cosmic rays or stopped solar flare ions may be present.
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