An Antarctic iron meteorite contains preterrestrial impact-produced diamond and lonsdaleite

Details An Antarctic iron meteorite contains preterrestrial impact-produced diamond and lonsdaleite An Antarctic iron meteorite contains preterrestrial impact-produced diamond and lonsdaleite

Jun 1981

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1981natur.291..396c&link_type=abstract

Nature, vol. 291, June 4, 1981, p. 396-398.

Computer Science

18

Antarctic Regions, Iron Meteorites, Metallography, Meteoritic Composition, Meteoritic Diamonds, Abundance, Atmospheric Entry, Carbonaceous Meteorites, Microstructure, Shock Loads, Meteorites, Antarctic Meteorites, Iron Meteorites, X-Ray Diffraction, Allan Hills Meteorites, Alha77283, Diamond, Lonsdaleite, Graphite, Data, Photomicrographs, Characteristics, Canyon Diablo Meteorite, Comparisons, Mineralogy, Formation, Metallography, Samples, Meteorite

Scientific paper

The discovery of diamond and lonsdaleite inclusions in an iron meteorite recovered from Allan Hills, Antarctica, which are attributed to preterrestrial impact is reported. ALHA 77283, a 10.5-kg carbon-rich octahedrite of chemical group IA similar in composition and structure to the Canyon Diablo meteorite, was found to contain troilite-graphite-schreibersite-cohenite inclusions containing unusually hard protrusions identified as carbonado-type diamond-lonsdaleite nodules. Metallographic examination of polished sections of the meteorite revealed a well developed heat-altered zone over most of the sample edge, which indicates that the meteorite was ablatively decelerated upon atmospheric entry and landed softly. Metallographic changes indicative of shock loading as well as the presence of the diamond and lonsdaleite were thus concluded to have been produced before atmospheric entry, but after Widmanstaetten pattern formation, most likely at the time of parent body break-up or subsequent collisions in space.

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