Geochemical Journal, Vol. 51 (No. 6), pp. 589-594, 2017
Motoko Igisu,1* Tsuyoshi Komiya,2 Yuka Ikemoto,3 Yechuan Geng2 and Hiroki Uehara2
1Department of Subsurface Geobiology Analysis and Research, Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, Yokosuka, Kanagawa 237-0061, Japan
2Department of Earth Science and Astronomy, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
3Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198, Japan
(Received January 13, 2017; Accepted May 11, 2017)
Synchrotron radiation-based Fourier transform infrared microspectroscopy (SR micro-FTIR) was applied to ∼830 Ma prokaryotic fossils in a doubly polished thin section in order to examine the micrometer-scaled spatial distributions of organic components in the microfossils. Mapping analysis allowed us to locate aliphatic C-H bonds (∼2925 cm−1 band and ∼2850 cm−1 band) in two species of microfossils (a filament and a coccoid) with a ∼2 × 2 μm2 rectangular aperture. The distributions of the ∼2925 cm−1 band and ∼2850 cm−1 band agree with the morphology of the filament, and also seem to be partially distributed along the wall structure of the coccoid. These results suggest that the SR micro-FTIR can provide a few microscale distributions of organic/inorganic components in prokaryotic fossils in doubly polished thin sections. However, artifacts are sometimes generated when certain analytical models are used, and some caution must be exercised to avoid their generation.
Key words: SR micro-FTIR, FTIR mapping, prokaryotic fossils, thin section, aliphatic C-H bonds