MASS FRACTIONATION OF NICKEL ISOTOPES IN METALLIC COSMIC SPHERES

The isotopic abundances of stable Ni isotopes were measured by inducti vely coupled plasma mass spectrometry (ICP/MS) in seven cosmic, metall ic (Type I) spheres collected from the deep sea. Mass-dependent enrich ments of the heavier isotopes range from 0.5-2.8% / AMU, values larger than those reported previously for Ni in any solid, extraterrestrial sample. This mass fractionation most likely reflects the high-temperat ure vaporization and loss from some spheres of over 90% of the Ni init ially present.