HR: 0800h
AN: MR11A-0910    [Abstracts]
TI: The variation of the crystal structure of magnesium silicate perovskite with chemical composition
AU: * Vanpeteghem, C B
EM: carine@vt.edu
AF: Virginia Polytechnic Institute and State University, Crystallography Laboratory Derring Hall, Blacksburg, VA 24061 United States
AU: Angel, R J
EM: rangel@vt.edu
AF: Virginia Polytechnic Institute and State University, Crystallography Laboratory Derring Hall, Blacksburg, VA 24061 United States
AU: Ross, N L
EM: nross@vt.edu
AF: Virginia Polytechnic Institute and State University, Crystallography Laboratory Derring Hall, Blacksburg, VA 24061 United States
AU: Ohtani, E
EM: ohtani@mail.tains.tohoku.ac.jp
AF: Tohoku University, Institute of Mineralogy, Petrology and Economic Geology Aza Aoba Aramaki, Aobayama, Sendai, 980-8578 Japan
AU: Litasov, K
EM: klitasov@ganko.tohoku.ac.jp
AF: Tohoku University, Institute of Mineralogy, Petrology and Economic Geology Aza Aoba Aramaki, Aobayama, Sendai, 980-8578 Japan
AB: Being the major constituent of the lower mantle, magnesium silicate perovskite MgSiO$_{3}$ has been subject to numerous past studies. More recently a lot of emphasis has been put on the physical properties and substitution mechanism of Al and Fe into the structure.While the structure of pure-MgSiO$_{3}$ and (Mg,Fe)SiO$_{3}$ have been determined, no data has been reported on the crystal structure of (Mg, Fe, Al)SiO$_{3}$ and how it varies with Al and Fe substitution. The knowledge of cell parameters, atomic positions and site occupancy of (Mg, Fe, Al)SiO$_{3}$ and how it changes with composition is of critical importance for a complete understanding of its physical properties. We have therefore carried out single-crystal X-ray structure determination at ambient pressure of two Al-Fe rich perovskites with different amounts of Al and Fe. One sample contains approximately 5 wt % of Al$_{2}$O$_{3}$ and 6 wt % of FeO and the other one has 13 wt % Al$_{2}$O$_{3}$ and 26 wt % FeO. Preliminary results show that (i) the Fe atoms tend to occupy the A-site only and (ii) that the B-site expands with total Al content of the perovskite,which indicates that the Al atoms tend to occupy the octahedral site. The implications of these first results for the evolution of the structure of (Mg, Fe, Al)SiO$_{3}$ perovskite at high pressures will be discussed.
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 3620 Crystal chemistry
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
DE: 1744 Tectonophysics
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting