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

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

The Astrophysical Journal, Volume 917, Number 2


“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.”