Motivation

1
Radiative conductivity of low-spin (Mg,Fe)O in
the lower mantle
Alexander F. Goncharov, Viktor V. Struzhkin, and
Steven D. Jacobsen Geophysical Laboratory,
Carnegie Institution of Washington, 5251 Broad
Branch Road NW, Washington DC 20015, USA Present
address Department of Geological Sciences,
NorthwesternUniversity, Evanston, Illinois 60208,
USA
Motivation
Results
Heat Transport
Combined absorption data
Visual observations

• Conduction, Radiation or Convection
• Convection only occurs if the former two
• methods fail to transfer heat
• Changes in mineral conduction and radiation
• properties strongly affect mantle dynamics

0 GPa
60 GPa
Spin pairing transition at 60 GPa

• Expected change of the absorption
• spectrum at the transition (after Burns)

IR absorption increases at the spin-pairing
transition for all x.
Experiment

• DAC with Ar or Ne transmitting media

Conclusions

• UV-Visible-IR Microspectroscopy
• (grating FT IR spectrometers)

The reduced thermal conductivity in the lower
mantle may challenge existing theories on the
stability of superplumes, which appear to require
enhanced thermal conductivity to mitigate
excessive temperature gradients.

• Mg(1-x)FexO single crystals (x0.06 0.16, 0.25)

• Mechanically polished to 8-15 mm thickness
• Single-crystal x-ray diagnostics
• Mossbauer diagnostics of the ferric ion content
  (1-2)