A search for nickel isotopic anomalies in iron meteorites and chondrites

We report Ni isotopic data, for ^(58,60–62)Ni, on (1) FeNi metal and sulfides in different groups of iron meteorites, (2) sulfides and a whole rock sample of the St. Séverin chondrite, and (3) chondrules from the Chainpur chondrite. We have developed improved, Multiple-Collector, Positive ion Thermal Ionization Mass Spectrometric (MC-PTIMS) techniques, with Ni+ ionization efficiency at 1‰, and chemical separation techniques for Ni which reduce mass interferences to the 1 ppm level, so that no mass interference corrections need be applied, except for ^(64)Ni (from ^(64)Zn, at the 0.1‰ level), for which we do not report results. We normalize the data to ^(62)Ni/^(58)Ni to correct for mass dependent isotope fractionation. No evidence was found for resolved radiogenic or general Ni isotope anomalies at the resolution levels of 0.2 and 0.5 εu (εu = 0.01%) for ^(60)Ni/^(58)Ni and ^(61)Ni/^(58)Ni, respectively. From the ^(56)Fe/^(58)Ni ratios and ε(^(60)Ni/^(58)Ni) values, we calculate upper limits for the initial value of (^(60)Fe/^(56)Fe)0 of (a) <2.7 × 10^−7 for Chainpur chondrules, (b) <10^−8 for the St. Séverin sulfide, and (c)