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Book Chapter

Phase-relation studies of mantle minerals by in situ X-ray diffraction using multianvil apparatus

By
Tomoo Katsura
Tomoo Katsura
Institute for Study of the Earth's Interior, Okayama University, Misasa, Tottori-ken 682-0193, Japan
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Published:
January 01, 2007

High-pressure and high-temperature in situ X-ray diffraction in a multianvil apparatus is the most reliable method for determination of phase boundaries of high-pressure transitions. Several basic experimental techniques are reviewed in this article. Recommendations include the equations of state for NaCl, MgO, and Au given by Brown (1999), Matsui et al. (2000), and Fei et al. (2004a), respectively, for practical use, as well as phase boundaries given by the following studies: coesite-stishovite transition in SiO2 by Zhang et al. (1995), olivine-ringwoodite transition in Fe2SiO4 by Yagi et al. (1997), and olivine-wadsleyite transition in Mg2SiO4 by Morishima et al. (1994). Although the akimotoite-perovskite transition in MgSiO3 and dissociation of ring-woodite to perovskite + periclase in Mg2SiO4 have been studied repeatedly, no reasonable agreements have been established to date. Although the wadsleyite-ringwoodite transition in Mg2SiO4 and dissociation of garnet to perovskite + corundum have also been studied, the results are still preliminary. The present state-of-the-art experimental techniques have several problems in accurately determining positions of phase boundaries, namely: (1) uncertainty of temperature distribution in a high-pressure cell, (2) an unknown pressure effect on electromotive force (EMF), (3) low equation of state reliability for pressure determination at relatively low pressures and high temperatures, (4) pressure intensification and reduction of pressure standards that are mixed with other materials to prevent grain growth, and (5) sluggish kinetics.

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Contents

GSA Special Papers

Advances in High-Pressure Mineralogy

Eiji Ohtani
Eiji Ohtani
Institute of Mineralogy, Petrology, and Economic Geology, Faculty of Science, Tohoku University, Sendai 980-8578, Japan
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Geological Society of America
Volume
421
ISBN print:
9780813724218
Publication date:
January 01, 2007

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