Reduced radiative conductivity of low-spin (Mg,Fe)O in the lower mantle.
Optical absorption spectra have been measured at pressures up to 80 gigapascals (GPa) for the lower-mantle oxide magnesiowüstite (Mg,Fe)O. Upon reaching the high-spin to low-spin transition of Fe2+ at about 60 GPa, we observed enhanced absorption in the mid- and near-infrared spectral range, whereas absorption in the visible-ultraviolet was reduced. The observed changes in absorption are in contrast to prediction and are attributed to d-d orbital charge transfer in the Fe2+ ion. The results indicate that low-spin (Mg,Fe)O will exhibit lower radiative thermal conductivity than high-spin (Mg,Fe)O, which needs to be considered in future geodynamic models of convection and plume stabilization in the lower mantle.
Goncharov
Alexander F
AF
Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington, DC 20015, USA. goncharov@gl.ciw.edu
Struzhkin
Viktor V
VV
Jacobsen
Steven D
SD