Opaque Lowermost Mantle
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...
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ftzenodo:oai:zenodo.org:3716258 2024-09-15T18:07:27+00:00 Opaque Lowermost Mantle Lobanov, Sergey S. Soubiran, Francois Holtgrewe, Nicholas Badro, James Lin, Jung-Fu Goncharov, Alexander F. 2020-03-19 https://doi.org/10.5281/zenodo.3716258 unknown Zenodo https://doi.org/10.5281/zenodo.3716257 https://doi.org/10.5281/zenodo.3716258 oai:zenodo.org:3716258 info:eu-repo/semantics/openAccess Creative Commons Attribution 4.0 International https://creativecommons.org/licenses/by/4.0/legalcode info:eu-repo/semantics/preprint 2020 ftzenodo https://doi.org/10.5281/zenodo.371625810.5281/zenodo.3716257 2024-07-26T11:17:18Z 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, bridgmanite in the lowermost mantle is moderately transparent while ferropericlase is highly opaque. Our measurements suggest a very low (< 1 W/m/K) and largely temperature-independent radiative conductivity in the lowermost mantle, at odds with previous studies. This implies that the radiative mechanism has not contributed significantly to cooling the Earth’s core throughout the geologic time and points to a present-day CMB heat flow of 9-11 TW. Opaque ferropericlase is electrically conducting and mediates strong core-mantle electromagnetic coupling, explaining the intradecadal oscillations in the length of day, low secular geomagnetic variations in Central Pacific, and the preferred paths of geomagnetic pole reversals. Report Geomagnetic Pole Zenodo |
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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, bridgmanite in the lowermost mantle is moderately transparent while ferropericlase is highly opaque. Our measurements suggest a very low (< 1 W/m/K) and largely temperature-independent radiative conductivity in the lowermost mantle, at odds with previous studies. This implies that the radiative mechanism has not contributed significantly to cooling the Earth’s core throughout the geologic time and points to a present-day CMB heat flow of 9-11 TW. Opaque ferropericlase is electrically conducting and mediates strong core-mantle electromagnetic coupling, explaining the intradecadal oscillations in the length of day, low secular geomagnetic variations in Central Pacific, and the preferred paths of geomagnetic pole reversals. |
format |
Report |
author |
Lobanov, Sergey S. Soubiran, Francois Holtgrewe, Nicholas Badro, James Lin, Jung-Fu Goncharov, Alexander F. |
spellingShingle |
Lobanov, Sergey S. Soubiran, Francois Holtgrewe, Nicholas Badro, James Lin, Jung-Fu Goncharov, Alexander F. Opaque Lowermost Mantle |
author_facet |
Lobanov, Sergey S. Soubiran, Francois Holtgrewe, Nicholas Badro, James Lin, Jung-Fu Goncharov, Alexander F. |
author_sort |
Lobanov, Sergey S. |
title |
Opaque Lowermost Mantle |
title_short |
Opaque Lowermost Mantle |
title_full |
Opaque Lowermost Mantle |
title_fullStr |
Opaque Lowermost Mantle |
title_full_unstemmed |
Opaque Lowermost Mantle |
title_sort |
opaque lowermost mantle |
publisher |
Zenodo |
publishDate |
2020 |
url |
https://doi.org/10.5281/zenodo.3716258 |
genre |
Geomagnetic Pole |
genre_facet |
Geomagnetic Pole |
op_relation |
https://doi.org/10.5281/zenodo.3716257 https://doi.org/10.5281/zenodo.3716258 oai:zenodo.org:3716258 |
op_rights |
info:eu-repo/semantics/openAccess Creative Commons Attribution 4.0 International https://creativecommons.org/licenses/by/4.0/legalcode |
op_doi |
https://doi.org/10.5281/zenodo.371625810.5281/zenodo.3716257 |
_version_ |
1810444825525223424 |