HR: 10:50h
AN: MR22A-03    [Abstracts]
TI: Spin Transition Zone (STZ) in the Lower Mantle
AU: * Lin, J
EM: afu@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
AU: Vanko, G
EM: vanko@rmki.kfki.hu
AF: KFKI Research Institute for Particle and Nuclear Physics, P.O. Box 49, Budapest, H-1525, Hungary
AU: Jacobsen, S D
EM: steven@earth.northwestern.edu
AF: Northwestern University, 1850 Campus Drive, Evanston, IL 60208, United States
AU: Iota, V
EM: iota1@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, United States
AU: Struzhkin, V V
EM: v.struzhkin@gl.ciw.edu
AF: Carnegie Institution of Washington, 5251 Broad Branch Rd. NW, Washington, DC, DC 20015, United States
AU: Prakapenka, V B
EM: prakapenka@cars.uchicago.edu
AF: The University of Chicago, 9700 South Cass Avenue, Chicago, IL 60439, United States
AU: Kuznetsov, A
EM: kuznetsov@cars.uchicago.edu
AF: The University of Chicago, 9700 South Cass Avenue, Chicago, IL 60439, United States
AU: Yoo, C
EM: yoo1@llnl.gov
AF: Washington State University, PO Box 642816, Pullman, WA 99164, United States
AB: Properties of the lower-mantle minerals such as ferropericlase [(Mg,Fe)O], silicate perovskite [(Mg,Fe)SiO3], and post-perovskite are affected by the electronic valence and spin states of iron, but the electronic states of iron under representative pressures and temperatures of the lower mantle have not yet been probed. Here the spin states of iron in lower-mantle ferropericlase and its crystal structure have been measured up to 95 GPa and 2000 K with x-ray emission and x-ray diffraction in a laser-heated diamond cell. Results show that an isosymmetric spin crossover of iron occurs over a wide pressure-temperature range extending from the middle part to the lower part of the lower mantle. The spin transition zone of iron in the lower-mantle phases significantly affects its implications for the geophysics, geochemistry, and geodynamics of the lower mantle. In particular, as the spin crossover of iron occurs in the lower-mantle minerals such as ferropericlase at high pressures and temperatures, their thermal compression curves, sound velocities, and transport properties will be continuously influenced by the ratio of the high-spin and low-spin states along the lower-mantle geotherm. Using recent results on the effects of the spin transitions on the density, elasticity, sound velocities, electrical conductivity, and strength of the lower-mantle phases, we will address how the electronic spin states in lower-mantle phases and their associated effects affect our understanding of the composition, geophysics, and dynamics of the lower mantle. This work was performed under the auspices of the U.S. DOE by UC\LLNL under Contract W-7405-Eng- 48.
DE: 1212 Earth's interior: composition and state (7207, 7208, 8105, 8124)
DE: 3900 MINERAL PHYSICS
DE: 3919 Equations of state
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting