A search for ^(70)Zn anomalies in meteorites

Abstract

No ^(70)Zn 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 ^(70)Zn was averaged out by mixing in the solar nebula before planetary accretion in the solar system. Because neutron-rich nuclides ^(70)Zn and ^(60)Fe are produced by similar nucleosynthetic processes in core-collapse supernovae, the homogeneity of ^(70)Zn 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 ^(70)Zn/^(64)Zn ratio measured here implies that the ^(60)Fe/^(56)Fe 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.

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