HR: 0830h
AN: U51B-0015    [PDF]
TI: Fe-Mg interdiffusion in magnesiowustite up to 35 GPa
AU: * Yamazaki, D
EM: yamazaki@sci.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan
AU: Irifune, T
EM: irifune@dpc.ehime-u.ac.jp
AF: Geodynamics Research Center, Ehime University, 2-5 Bunkyo-cho, Matsuyama, 790-8577 Japan
AB: Fe-Mg interdiffusivities in (Fe,Mg)O magnesiowustite have been measured in experiments conducted at pressures of 7-35 GPa and temperatures of 1573-1973K using a Kawai type high-pressure apparatus. The diffusion profiles were measured across the interface between MgO and (Fe$_{0.5}$,Mg$_{0.5}$)O samples by electron microprobe analysis, and the Fe-Mg interdiffusivities were determined as {\it D}$_{Fe-Mg}$={\it D}$_{0}$exp[-{\it E}$^{*}$(1+{\it PV}$^{*}$$_{Mg}$/{\it E}$^{*}$$_{Mg}$)/{\it RT}], where {\it D}$_{0}$=4.0 $\times$ 10$^{-7}$ m$^{2}$/s, {\it E}$^{*}$=(1-{\it C}$_{Mg}$){\it E}$^{*}$$_{Fe}$+{\it C}$_{Mg}${\it E}$^{*}$$_{Mg}$ (activation energy for the concentration of Mg, where {\it E}$^{*}$$_{Fe}$=113 kJ/mol and {\it E}$^{*}$$_{Mg}$=226 kJ/mol), the activation volume {\it V}$^{*}$$_{Mg}$=1.8 $\times$ 10$^{-6}$ m$^{3}$/mol. By extrapolating these results to the {\it P-T} conditions of the core-mantle boundary, we conclude that the interdiffusivity of Fe-Mg in magnesiowustite at the bottom of the lower mantle is at least one order of magnitude larger than that at the top of the lower mantle.
DE: 3902 Creep and deformation
DE: 3924 High-pressure behavior
DE: 5120 Plasticity, diffusion, and creep
DE: 8121 Dynamics, convection currents and mantle plumes
SC: U
MN: 2003 Fall Meeting