HR: 17:15h
AN: MR14A-06    [Abstracts]
TI: In situ X-ray diffraction and X-ray emission study of magnesiowustite in Earth's lower mantle conditions: implications to the geophysics and geochemistry of the lower mantle
AU: * Lin, J
EM: j.lin@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC, DC 20015 United States
AU: Struzhkin, V V
EM: v.struzhkin@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC, DC 20015 United States
AU: Jacobsen, S
EM: s.jacobsen@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC, DC 20015 United States
AU: Hu, M Y
EM: mhu@hpcat.aps.anl.gov
AF: HPCAT, Advanced Photon Source, 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Chow, P
EM: pchow@hpcat.aps.anl.gov
AF: HPCAT, Advanced Photon Source, 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Liu, H
EM: hliu@hpcat.aps.anl.gov
AF: HPCAT, Advanced Photon Source, 9700 S. Cass Avenue, Argonne, IL 60439 United States
AU: Mao, H
EM: mao@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC, DC 20015 United States
AU: Hemley, R J
EM: hemley@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington DC, DC 20015 United States
AB: The thermodynamic behavior of iron in mantle host phases plays an important role in understanding geochemical modeling, geodynamic simulation, and seismic wave observations of the Earth's deep interior. In particular, electronic spin transitions in the iron-bearing lower mantle phases, magnesiowustite and silicate perovskite, have important geophysical and geochemical consequences such as density change, iron partitioning, change of radiative thermal conductivity, and compositional layering in the lower mantle. Recent X-ray emission spectroscopic studies at high pressures and room temperature have found such high-spin to low-spin transitions of iron in magnesiow《tite and silicate perovskite (Badro et al., 2003, 2004; Li et al., 2004), but there remains uncertainty about associated volume change. Here we use in situ X-ray diffraction and X-ray emission spectroscopic techniques to measure the density/volume change related to the electronic transition in magnesiow《tite (Mg,Fe)O with various compositions at lower mantle conditions. Our X-ray emission spectroscopic results show that the high-spin to low-spin transition of iron in magnesiow《tite occurs gradually over a wide range of pressure. We also studied ferropericlase with both techniques, and found a similar, gradual density increase over a wide range of pressure due to the electronic collapse. We will also address the temperature and compositional effect on the spin transition of iron in magnesiow《tite. These results suggest that the electronic spin transition of iron in magnesiow《tite does not contribute significantly to the geochemical and geophysical signatures in the lower mantle.
DE: 3909 Elasticity and anelasticity
DE: 3914 Electrical properties
DE: 3919 Equations of state
DE: 3924 High-pressure behavior
DE: 3954 X ray, neutron, and electron spectroscopy and diffraction
SC: Mineral and Rock Physics [MR]
MN: 2004 AGU Fall Meeting