Laihunite in planetary materials: An FTIR and TEM study of oxidized synthetic and meteoritic Fe-rich olivine

• TOMIOKA Naotaka

  Department of Earth and Planetary Sciences, Graduate School of Science, Kobe University Institute for Study of the Earth's Interior, Okayama University

• MORLOK Andreas

  Department of Earth and Planetary Sciences, Graduate School of Science, Kobe University Department of Mineralogy, The Natural History Museum DPS, The Open University

• KOIKE Chiyoe

  Department of Physics, Kyoto Pharmaceutical University Department of Earth and Space Science, Graduate School of Science, Osaka University

• KÖHLER Melanie

  Institut d'Astrophysique Spatiale, Universite Paris Sud

• GRADY Monica

  Department of Mineralogy, The Natural History Museum DPS, The Open University

Abstract

In situ mid-infrared transmission measurements of matrices from carbonaceous chondrites heated up to 572 °C in air were conducted by FTIR spectroscopy. The FTIR spectra of the matrices mainly showed olivine bands. With increasing temperature, up to 477 °C, the spectra did not show significant changes. However, at 572 °C, the ~11-μm band split into a doublet, and the intensity of the ∼ 10-μm band relative to that of the ∼ 11-μm band increased significantly. In synthetic Fe-rich olivine (Fo₄₇) samples heated at 600 °C in air, their mid-infrared spectra showed changes similar to those in meteoritic samples. A TEM observation of the recovered meteoritic samples showed that most olivine grains had a stacking disorder on (001). Selected area electron diffraction patterns of the grains also exhibited extra reflections, corresponding to a similar superstructure to three-fold periodicity along c_ol known as laihunite-3M in Fe₂SiO₄. Although the synthetic Fe-rich olivine did not have any defect structures before heating, the olivine commonly had a stacking disorder on (001) after heating at 600 °C. Therefore, the changes in mid-infrared spectra of the matrices of carbonaceous chondrites were not caused by chemical reactions among their constituent minerals, but were mainly caused by oxidation of iron within the olivine structure. The mid-infrared spectra of olivine-dominating samples from this study are potential reference data for the oxidation state of olivine in in situ mid-infrared measurements on the Martian surface, in partially oxidized meteorites, on asteroidal surfaces, and in interplanetary dust particles.

Journal

• Journal of Mineralogical and Petrological Sciences

  Journal of Mineralogical and Petrological Sciences 107 (4), 157-166, 2012

  Japan Association of Mineralogical Sciences

Keywords

• Fe-rich olivine
• Laihunite
• Carbonaceous chondrites
• Infrared spectroscopy
• Transmission electron microscopy

Details

• CRID: 1390282681522852352
• NII Article ID: 10030868632
• NII Book ID: AA11460926
• DOI: 10.2465/jmps.120409
• COI: 1:CAS:528:DC%2BC38XhsFOqt77J
• ISSN: 13493825
• ISSN: 13456296
• Text Lang: en
• Data Source:
  • JaLC
  • Crossref
  • CiNii Articles
• Abstract License Flag: Disallowed