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Characterization of Thermal Transport in One-dimensional Solid Materials
Published on: January 26, 2014
Radiative conductivity in the Earth's lower mantle
Alexander F Goncharov1, Benjamin D Haugen, Viktor V Struzhkin
1Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA. goncharov@gl.ciw.edu
Nature
|November 14, 2008
Summary
Ferric iron (Fe3+) in lower mantle silicate perovskite significantly impacts thermal conductivity. This finding suggests a lower radiative conductivity than previously estimated, affecting mantle evolution and plume dynamics.
Area of Science:
- Geophysics
- Mineral Physics
- High-Pressure Science
Background:
- Iron oxidation states influence Earth's biogeochemical cycles and mantle properties.
- Iron in lower mantle minerals like silicate perovskite and ferropericlase affects thermal conductivity and core heat flux.
- The impact of iron oxidation states on transport properties in the deep Earth remains poorly understood.
Purpose of the Study:
- To investigate the role of iron oxidation states on the radiative thermal conductivity of lower mantle minerals.
- To determine how ferric iron (Fe3+) concentration affects optical absorption and radiative conductivity in silicate perovskite.
- To provide new insights into the thermal state and evolution of Earth's lower mantle.
Main Methods:
- Measured optical absorption spectra of silicate perovskite and ferropericlase at high pressures (up to 133 GPa) and temperatures (up to 800 K).
- Analyzed spectral data to identify contributions from different iron species (Fe2+, Fe3+) and charge transfer mechanisms.
- Calculated pressure-dependent radiative thermal conductivity (k(rad)) based on experimental optical absorption data.
Main Results:
- Optical absorption in silicate perovskite is primarily driven by O-Fe(3+) charge transfer and Fe(3+)-Fe(2+) intervalence transitions.
- Fe(3+) concentration directly controls the radiative component of thermal conductivity in silicate perovskite.
- Radiative conductivity (k(rad)) was estimated to be 2-5 times lower than previously inferred, with minimal temperature dependence in ferropericlase up to 60 GPa.
Conclusions:
- The concentration of ferric iron (Fe3+) is a critical factor controlling radiative thermal conductivity in Earth's lower mantle silicate perovskite.
- Lower-than-expected radiative conductivity has significant implications for mantle dynamics, including the generation and stability of thermo-chemical plumes.
- This research refines our understanding of heat transfer in the deep Earth and its influence on planetary evolution.
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