Stability of Perovskite (MgSiO3) in the Earth's Mantle
Available thermodynamic data and seismic models favor perovskite (MgSiO3) as the stable phase in the mantle. MgSiO3 was heated at temperatures from 1900 to 3200 kelvin with a Nd-YAG laser in diamond-anvil cells to study the phase relations at pressures from 45 to 100 gigapascals. The quenched products were studied with synchrotron x-ray radiation. The results show that MgSiO3 broke down to a mixture of MgO (periclase) and SiO2 (stishovite or an unquenchable polymorph) at pressures from 58 to 85 gigapascals. These results imply that perovskite may not be stable in the lower mantle and that it might be necessary to reconsider the compositional and density models of the mantle.
S. K. Saxena, L. S. Dubrovinsky, P. Lazor, Y. Cerenius, P. Haggkvist, Theoretical Geochemistry, Institute of Earth Sciences, Uppsala University, S-752 36 Uppsala, Sweden. M. Hanfland, European Synchrotron Radiation Facility, Boite Postale 220, Avenue des Martyrs, 38043 Grenoble Cedex, France. J. Hu, Center for High Pressure Research, Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC, USA.
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Saxena
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Dubrovinsky
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Haggkvist
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Hanfland
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