Noble gases in the grain-size fractions of presolar diamond from the Boriskino CM2 meteorite

摘要: Presolar diamond recovered from the Boriskino CM2 meteorite was separated into size fractions by sedimentation in an ultracentrifuge. The average grain sizes of ranged ~1.4 to ~5.3 nm. Noble gases were measured each fraction and bulk sample course stepped pyrolysis up 700 subsequent oxidation between 600 900. following main results obtained: (a) fine diamond are strongly different coarse ones elemental composition P3 component noble gases, which is most likely related element fractionation during implantation grains; (b)in presolar a single meteorite, wide range Xe-P3/Xe-HL ratio detected for first time, 0.130.06 3.95 0.37 fraction, suggestive different energies ions HL noble gas components their grains; (c) calculated upper limit 136Xe/132Xe isotopically anomalous xenon (0.71 0.04) fraction identical value 0.7 determined Hass Lewis (1994) Xe-LH ther- mally metamorphosed meteorites. Such coincidence suggests that Xe-HL formed as individual com- ponent before its grains result mixing products r- p-processes nucleosynthesis supernova explosion with normal gases. latter significantly the component, at least respect 36Ar/132Xe.