Iron and Nickel Isotopes in IID and IVB Iron Meteorites: Evidence for Admixture of an SN II Component and Implications for the Initial Abundance of 60Fe

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David L. Cook, Bradley S. Meyer, and Maria Schönbächler

The Astrophysical Journal, Volume 917, Number 2

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“We measured Fe and Ni isotopes in 13 iron meteorites from magmatic groups IID and IVB. Resolvable deficits (≈−0.14) are observed in ε60Ni in both groups. Small deficits (≈−0.08) are also evident in ε56Fe but not in the most neutron-rich isotope of Fe (58Fe). Relative to terrestrial material, the observed εiFe values are consistent with the presence of a small excesses of material in the parent bodies of IID and IVB irons that was produced in a type II supernova. The ε60Ni and ε56Fe values are uncorrelated in both groups. This is consistent with a nucleosynthetic origin of the ε56Fe deficits, whereas the ε60Ni deficits are best explained as radiogenic in nature due to the former presence of live 60Fe (t1/2 = 2.62 Ma) in the early solar system. The 60Ni deficits correspond to 60Fe/56Fe ratios of ≈3 × 10−7 at the time of core formation on the IID and IVB parent bodies. These data, in conjunction with previously published 182Hf–182W core formation ages, are used to estimate a solar system initial 60Fe/56Fe = (6.4 ± 2.0) × 10−7 for the formation region of carbonaceous chondrites.”

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