Abstracts for Annual Meeting of the Mineralogical Society of Japan
2005 Annual Meeting of the Mineralogical Society of Japan
Session ID : K3-09
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Cation order and hydrogen bonding of high-pressure phases in the Al2O3-SiO2-H2O system
*Xianyu XueMasami KanzakiHiroyuki FukuiEiji ItoTakafumi Hashimoto
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Topaz-OH (Al2SiO4(OH)2), phase egg (AlSiO3OH) and delta-AlOOH are hydrous phases in the Al2O3-SiO2-H2O system that have been found to be stable at successively higher pressures up to those of the lower mantle, and thus may be important in the siliceous sediments of subducting slab. Although the crystal structures of these phases have been determined by X-ray diffraction, this technique is insensitive to H positions and Al-Si disorder. We have applied 1H, 29Si and 27Al NMR and micro-Raman spectroscopy to gain additional insights. Our study revealed that the octahedral Al-Si distribution in phase egg is partially disordered, which is expected to have a significant effect on its physical and thermodynamic properties and stability field. In addition, these data also suggest the presence of some structural disorder in topaz-OH. Finally, our data support that hydrogen bonding is strong in phase egg and delta-AlOOH, but weak in topaz-OH.

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© 2005 Japan Association of Mineralogical Sciences
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