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A new high-pressure form of KAlSi3O8 under lower mantle conditions
Geodynamics Research Center, Ehime University, Matsuyama, Japan
Geodynamics Research Center, Ehime University, Matsuyama, Japan
Geodynamics Research Center, Ehime University, Matsuyama, Japan
Geodynamics Research Center, Ehime University, Matsuyama, Japan
Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
Japan Synchrotron Research Institute, Sayo, Japan
In situ X-ray diffraction measurements have been made on KAlSi3O8 hollandite using diamond anvil cell and multianvil apparatus combined with synchrotron radiation. Both of the measurements with different techniques demonstrated that K-hollandite transforms to a new high-pressure phase (hollandite II) at ∼22 GPa upon increasing pressure at room temperature. The X-ray diffraction peaks of the new phase were reasonably indexed on the basis of a monoclinic cell with I2/m space group. Hollandite II was also confirmed to be formed at high temperatures to 1200°C and pressures to 35 GPa, which was quenched to room temperature under pressure but converted back to hollandite at about 20 GPa on release of pressure. The present result is contradictory to earlier studies based mainly on quench method, which concluded that hollandite is stable up to 95 GPa at both room temperature and high temperatures up to 2300°C.
Received 30 July 2004; accepted 10 November 2004; published 14 December 2004.
Citation: (2004), A new high-pressure form of KAlSi3O8 under lower mantle conditions, Geophys. Res. Lett., 31, L23612, doi:10.1029/2004GL021156.
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