Scandium 45 in meteoritic irons

概要

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This report presents the results of determinations of cosmogenic ^<45>Sc and light noble gases in iron meteorites. Sc and REE were simultaneously determined using radiochemical neutron activation method. This method is sensitive enough for detection of as little as lower than 10^<-13>gSc/g, compared to the level of cosmic ray effects in irons which are usually in the range of 10^<-9>-10^<-12>gSc/g. The lowest concentration found in irons was 2×10^<-12>gSc/g in the Campo del Cielo and similar contents were observed in the Gibeon, DRP-78008 (and Brenham-metal). Even at these low levels, Sc seems mostly attributable to cosmic ray production. The Sc content in irons is best compared with cosmogenic ^4He. The ratio of Sc to ^4He, approximately 1×10^<-12>gSc/1×10^<-8>cc ^4He, or an average atomic ratio of 1 : 19±3,was observed independent of shielding. Technical aspects of metal phase separation from ordinary chondrites were studied. In one Peace River metal sample, 0.9 ppbSc was found. This number corresponds to 0.01% of the stone phase in the metal. This level of contamination seems still higher than the cosmogenic level of 0.2 ppbSc expected in the metal phase of this meteorite.
国立極地研究所の論文