A search for 70Zn anomalies in meteorites

Abstract

No ⁷⁰Zn isotopic anomalies have been detected in primitive meteorites to a level of precision of less than 40 parts per million (2σ). Any pre-existing nucleosynthetic anomaly on ⁷⁰Zn was averaged out by mixing in the solar nebula before planetary accretion in the solar system. Because neutron-rich nuclides ⁷⁰Zn and ⁶⁰Fe are produced by similar nucleosynthetic processes in core-collapse supernovae, the homogeneity of ⁷⁰Zn in meteorites limits the possible heterogeneity of extinct ⁶⁰Fe radioactivity in the early solar system. Assuming that Fe and Zn have not been decoupled during incorporation into the solar system, the homogeneity of the ⁷⁰Zn/⁶⁴Zn ratio measured here implies that the ⁶⁰Fe/⁵⁶Fe ratio was homogenized to less than 15% dispersion before the formation of planetary bodies. The lack (Zn, Ni, Fe) or presence (Ti, Cr) of neutron-rich isotopic anomalies in the iron mass region may be controlled by the volatility of presolar carriers in the nebula. © 2009. The American Astronomical Society.