High-pressure radiative conductivity of dense silicate glasses with potential implications for dark magmas.
The possible presence of dense magmas at Earth's core-mantle boundary is expected to substantially affect the dynamics and thermal evolution of Earth's interior. However, the thermal transport properties of silicate melts under relevant high-pressure conditions are poorly understood. Here we report in situ high-pressure optical absorption and synchrotron Mössbauer spectroscopic measurements of iron-enriched dense silicate glasses, as laboratory analogues for dense magmas, up to pressures of 85 GPa. Our results reveal a significant increase in absorption coefficients, by almost one order of magnitude with increasing pressure to ~50 GPa, most likely owing to gradual changes in electronic structure. This suggests that the radiative thermal conductivity of dense silicate melts may decrease with pressure and so may be significantly smaller than previously expected under core-mantle boundary conditions. Such dark magmas heterogeneously distributed in the lower mantle would result in significant lateral heterogeneity of heat flux through the core-mantle boundary.
Department of Earth and Planetary Materials Science, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
Motohiko
M
Murakami
Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.
Alexander F
AF
Goncharov
Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan.
Naohisa
N
Hirao
Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan.
Ryo
R
Masuda
Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan.
Takaya
T
Mitsui
Department of Geoscience, University of Nevada, Las Vegas, Nevada 89154, USA.
Sylvia-Monique
SM
Thomas
Department of Earth and Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA.
Craig R
CR
Bina