Local structure of Zr in K-T boundary clays probed by XAFS

Abstract

The local structure of K-T boundary clays was studied by Zr K-edge XAFS in order to provide quantitative data on bonding distance and coordination numbers. The zirconium XANES spectra in K-T boundary clays are similar to rhyolitic volcanic glasses (obsidian and pitch stone) and tektite. It suggested that local structures of Zr in K-T clays remain the thermal quenching history at meteorite impact. The Zr-O distance in K-T boundary clays is 2.164 Å and the coordination number is 6.3. The data suggested that Zr local structure in K-T boundary clays are formed relatively under the condition of higher temperature and lower oxidation state than volcanic glasses and total electric charge of Zr ions is less than 4 and estimated as 3.8.