We report high-precision analyses of internally-normalised Ni isotope ratios in 12 bulk iron meteorites. and E 64 Ni 58 61 , respectively, which is comparable to our sample reproducibility. We show that this 'massindependent' Ni isotope variability cannot be ascribed to interferences, inaccurate correction of instrumental or natural mass-dependent fractionation, fractionation controlled by nuclear field shift effects, nor the influence of cosmic ray spallation. These results thus document the presence of mass-independent Ni isotopic heterogeneity in bulk meteoritic samples, as previously proposed by Regelous et al. 2008 (EPSL 272, 330-338), but our new analyses are more precise and include determination of 64 Ni. Intriguingly, we find that terrestrial materials do not yield homogenous internally-normalised Ni isotope compositions, which, as pointed out by Young 2002 (GCA 66, 1095-1104, may be the expected result of using the exponential (kinetic) law and atomic masses to normalise all fractionation processes. The certified Ni isotope reference material NIST SRM 986 defines zero in this study, while appropriate ratios for the bulk silicate Earth are given by the peridotites JP-1 and DTS-2 and, relative to NIST SRM 986, yield devi-

We present new, mass-independent, Ni isotope data for a range of bulk chondritic meteorites. The data are reported as E 60 Ni 58 61 , E 62 Ni 58 61 and E 64 Ni 58 61 or the parts per ten thousand deviations from a terrestrial reference, the NIST SRM 986 standard, of the 58 Ni/ 61 Ni internally normalised 60 Ni/ 61 Ni, 62 Ni/ 61 Ni and 64 Ni/ 61 Ni ratios. The chondrites show a range of 0.15, 0.29 and 0.84 in E 60 Ni 58 61 , E 62 Ni 58 61 and E 64 Ni 58 61 relative to a typical sample precision of 0.03, 0.05 and 0.08 (2 s.e.), respectively. The carbonaceous chondrites show the largest positive

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