Isotopic Fractionation of Zn During Impact on Earth

Abstract : The isotope fractionation of Zn in lunar soils [1] is surprisingly large (up to 3 per mil per amu). These fractionations have been attributed to vaporization due to impact by micrometeorites onto the surface of the moon. Recently, Albarede et al. [2] extended the study of isotopic fractionation of Zn to shocked rocks from a terrestrial impact site, Meteor Crater. They observed a negative correlation between isotope compositions and shock grade in 7 samples of Coconino sandstone and concluded that, even on Earth, vaporization at high temperature due to impact is capable to fractionate the isotopic compositions of rather heavy elements to a measurable extent. Here, we investigate the degree of isotopic fractionation of Zn in rocks from two terrestrial impact craters: (1) impactites from the Lonar crater, India, and (2) the impact melt rocks from the Bosumtwi crater (Ghana), as well as the related Ivory Coast tektites (IVC)