XAFS study of Zr in Cretaceous–Tertiary boundary clays from Stevns Klint

• TOBASE Tsubasa

  Graduate School of Science and Technology, Kumamoto University

• YOSHIASA Akira

  Graduate School of Science and Technology, Kumamoto University

• WANG Ling

  Graduate School of Science and Technology, Kumamoto University

• HIRATOKO Tatsuya

  Graduate School of Science and Technology, Kumamoto University

• HONGU Hidetomo

  Graduate School of Science and Technology, Kumamoto University

• OKUBE Maki

  Materials and Structures Laboratory, Tokyo Institute of Technology

• SUGIYAMA Kazumasa

  Institute for Materials Research, Tohoku University

Abstract

The local structure of K–T boundary clays was studied by Zr K–edge X–ray absorption fine structure (XAFS) in order to provide quantitative data on Zr–O bonding distance, coordination number and oxidation state. The Zr XANES spectra in K–T boundary clays are similar to those from rhyolitic volcanic glass samples (obsidian and pitch stone) and tektite. Since tektite was formed at meteorite impact, those observations suggest that the thermal quenching history at meteorite impact is kept preserved as the local structure of Zr in K–T clays. The Zr–O distance in K–T boundary clays is 2.164 Å (4) and the average coordination number is 6.3. The threshold energy on Zr XANES spectra from the K–T clays is lower than those found on natural glasses, and total effective charge of zirconium ion (formally 4+) estimated from the shift of the spectrum is 3.8+ – 3.9+. The partial reduction of zirconium ion in K–T clays is ascribed to its formation environment, high temperature under reductive environment. Preservation of the partial reduction state also indicates quick quench of K–T clays at their formation, and this observation give as a clue to distinguish sedimentary rocks deposited at periods of so–called extinction events by investigating Zr local structure.

Journal

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 110 (2), 88-91, 2015

  Japan Association of Mineralogical Sciences

Keywords

• Local structure of Zr
• K–T boundary clays
• EXAFS
• XANES

Details

• CRID: 1390282681522119168
• NII Article ID: 130005067165
• DOI: 10.2465/jmps.141022a
• ISSN: 13493825
• ISSN: 13456296
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed