Opaque Lowermost Mantle
Sergey S. Lobanov, Fran\c{c}ois Soubiran, Nicholas Holtgrewe, James, Badro, Jung-Fu Lin, Alexander F. Goncharov

TL;DR
This study investigates the opacity and conductivity of key mantle minerals at core-mantle boundary conditions, revealing low radiative heat transfer and strong electromagnetic coupling implications for Earth's core dynamics.
Contribution
It provides the first measurements of mineral opacity at CMB conditions, challenging previous assumptions about radiative heat transfer in the lowermost mantle.
Findings
Ferropericlase is highly opaque and electrically conductive.
Bridgmanite remains moderately transparent at CMB conditions.
Radiative conductivity in the lowermost mantle is very low and temperature-independent.
Abstract
Earth/s lowermost mantle displays complex geological structures that likely result from heterogeneous thermal and electromagnetic interaction with the core. Geophysical models of the core-mantle boundary (CMB) region rely on the thermal and electrical conductivities of appropriate geomaterials which, however, have never been probed at representative pressure and temperature (P-T) conditions. Here we report on the opacity of single crystalline bridgmanite and ferropericlase, which is linked to both their radiative and electrical conductivity, measured in dynamically- and statically-heated diamond anvil cells as well as computed from first-principles at CMB conditions. Our results show that light absorption in the visible spectral range is enhanced upon heating in both minerals but the rate of change in opacity with temperature is a factor of six higher in ferropericlase. As a result,…
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Taxonomy
TopicsHigh-pressure geophysics and materials · Geomagnetism and Paleomagnetism Studies · Earthquake Detection and Analysis
