HR: 1340h
AN: MR23B-0054    [Abstracts]
TI: Physics and chemistry of ferromagnesian silicate post perovskite
AU: * Mao, W L
EM: wmao@uchicago.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Ave, Chicago, IL 60637 United States
AU: * Mao, W L
EM: wmao@uchicago.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Mao, H
EM: h.mao@gl.ciw.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Ave, Chicago, IL 60637 United States
AU: Mao, H
EM: h.mao@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Mao, H
EM: h.mao@gl.ciw.edu
AF: , Carnegie Institution of Washington, HPCAT, Advanced Photon Source 9700 South Cass Ave., Argonne, IL 60439 United States
AU: Hu, M
EM: mhu@hpcat..aps.anl.gov
AF: , Carnegie Institution of Washington, HPCAT, Advanced Photon Source 9700 South Cass Ave., Argonne, IL 60439 United States
AU: Chow, P
EM: pchow@hpcat.aps.anl.gov
AF: , Carnegie Institution of Washington, HPCAT, Advanced Photon Source 9700 South Cass Ave., Argonne, IL 60439 United States
AU: Meng, Y
EM: ymeng@hpcat.aps.anl.gov
AF: , Carnegie Institution of Washington, HPCAT, Advanced Photon Source 9700 South Cass Ave., Argonne, IL 60439 United States
AU: Shen, G
EM: shen@cars.uchicago.edu
AF: , Carnegie Institution of Washington, HPCAT, Advanced Photon Source 9700 South Cass Ave., Argonne, IL 60439 United States
AU: Shen, G
EM: shen@cars.uchicago.edu
AF: University of Chicago, GSECARS 5640 S. Ellis Ave., Chicago, IL 60637 United States
AU: Prakapenka, V B
EM: prakapenka@cars.uchicago.edu
AF: University of Chicago, GSECARS 5640 S. Ellis Ave., Chicago, IL 60637 United States
AU: Shu, J
EM: j.shu@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Campbell, A J
EM: ajc@geol.umd.edu
AF: University of Maryland, Department of Geology, College Park, MD 20742 United States
AU: Fei, Y
EM: y.fei@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AU: Heinz, D L
EM: heinz@geosci.uchicago.edu
AF: University of Chicago, Department of the Geophysical Sciences 5734 S. Ellis Ave, Chicago, IL 60637 United States
AU: Hemley, R J
EM: r.hemley@gl.ciw.edu
AF: Carnegie Institution of Washington, Geophysical Laboratory 5251 Broad Branch Road, NW, Washington, DC 20015 United States
AB: Pressure effects on the physics and chemistry of the post-perovskite (ppv) phase in the FeO-MgO-SiO₂ system have been studied with synchrotron x-ray diffraction and x-ray emission spectroscopy. Synthetic and natural starting materials of orthopyroxene and olivine compositions were compressed up to 150 GPa and heated to 2000 K with a double-sided laser system. The formation of ferromagnesian silicate post perovskite were monitored with in-situ x-ray diffraction and after temperature quench. Addition of Fe stabilizes the ppv and shifts the perovskite-ppv transition to lower pressures. Fe K-beta emission peak shape indicates that Fe in ppv is in a magnetic, spin-paired (low-spin), electronic state. The low spin state reduces the free energy of formation of the iron-rich post-perovskite, reduces the partial molar volume of Fe, reduces the seismic velocity, reduces infrared absorption, and increases radiative heat transfer. It enables the mantle silicate to uptake Fe from the metallic core to form a dense, Fe-rich silicate layer. The layer, too heavy to rise during mantle upwelling, will be left behind, providing a possible explanation for ultra-low velocity zones.
DE: 1212 Earth's interior: composition and state (7207, 7208, 8105, 8124)
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005