Abstract
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.
Original language | English (US) |
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Article number | 5428 |
Journal | Nature communications |
Volume | 5 |
DOIs | |
State | Published - Nov 11 2014 |
Funding
We thank Maddury Somayazulu, Takashi Yoshino, Reinhard Boehler and Amol Kar-andikar for their experimental assistance. Suggestions from Takashi Nakagawa improved the manuscript. Jay Bass and Satoshi Okumura are gratefully acknowledged for their valuable comments. This work was supported by Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT)/The Japan Society for the Promotion of Science (JSPS) Kakenhi grant numbers 22684028, 24654170 and 25247087, and a Grant for Program Research from Frontier Research Institute for Interdisciplinary Sciences, Tohoku University (to M.M.), and by the National Science Foundation (NSF) EAR-1015239, NSF EAR/IF-1128867 and Army Research Office (to A.F.G.). Mössbauer experiments were performed under the approval of SPring-8 (2011A3501).
ASJC Scopus subject areas
- General Chemistry
- General Biochemistry, Genetics and Molecular Biology
- General Physics and Astronomy