In situ high-temperature visible microspectroscopy for volcanic materials |
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Authors: | Yamanoi Yuta Nakashima Satoru |
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Affiliation: | Interactive Research Center of Science and the Department of Earth and Planetary Sciences, Graduate School of Science and Engineering, Tokyo Institute of Technology, O-okayama 2-12-1, Meguro-ku, Tokyo 152-8551, Japan. yuta@ess.sci.osaka-u.ac.jp |
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Abstract: | In situ high-temperature visible microspectroscopy has been developed in order to study color change kinetics of volcanic materials. Olivine thin sections put on a synthetic alumina plate are heated on a heating stage at 600-800 degrees C under a visible microspectroscope. Changes in visible absorption spectra are monitored every 60 s for 5 hours. The obtained high-temperature visible spectra showed a gradual increase with time in absorbance in the shorter wavelength region (400-600 nm). The 430 nm absorbance (ligand field transition of Fe3+ increased more with time at higher temperatures. Assuming diffusional transport in plane sheets, apparent diffusion coefficients were determined at temperatures of 600-800 degrees C. The activation energy for this diffusion in olivine is 208 +/- 17 kJ/mol. This activation energy value is similar to those for the metal vacancy diffusion in olivine. This newly developed in situ high-temperature visible microspectroscopy can provide kinetic measurements of visible spectral change of materials at high temperatures such as volcanic materials. |
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