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Editor's Highlight
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GEOPHYSICAL RESEARCH LETTERS,
VOL. 33,
L12S01,
doi:10.1029/2006GL025691,
2006
Unsolved problems in the lowermost mantle
Kei Hirose
Department of Earth and Planetary Sciences, Tokyo Institute of Technology, Tokyo, Japan
Shun-ichiro Karato
Department of Geology and Geophysics, Yale University, New Haven, Connecticut, USA
Vernon F. Cormier
Physics Department, University of Connecticut, Storrs, Connecticut, USA
John P. Brodholt
Department of Earth Sciences, University College London, London, UK
David A. Yuen
Department of Geology and Geophysics and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota,
USA
Abstract
Many characteristics of D″ layer may be attributed to the recently discovered MgSiO3 post-perovskite phase without chemical heterogeneities. They include a sharp discontinuity at the top of D″, regional variation
in seismic anisotropy, and a steep Clapeyron slope. However, some features remain unexplained. The seismically inferred velocity
jump is too large in comparison to first principles calculations, and the sharpness of the discontinuity may require a chemical
boundary. Chemical heterogeneity may play an important role in addition to the phase transformation from perovskite to post-perovskite.
Phase transformation and chemical heterogeneity and the attendant changes in physical properties, such as rheology and thermal
conductivity, are likely to play competing roles in defining the dynamical stability of the D″ layer. Revealing the relative
roles between phase transition and chemical anomalies is an outstanding challenge in the study of the role of D″ in thermal-chemical
evolution of the Earth.
Received 6
January
2006;
accepted 24
February
2006;
published 31
March
2006.
Index Terms: 1212 Geodesy and Gravity: Earth's interior: composition and state (7207, 7208, 8105, 8124); 1213 Geodesy and Gravity: Earth's interior: dynamics (1507, 7207, 7208, 8115, 8120); 3924 Mineral Physics: High-pressure behavior; 7208 Seismology: Mantle (1212, 1213, 8124); 8121 Tectonophysics: Dynamics: convection currents, and mantle plumes.
Subscriber Access to Full Article (Nonsubscribers may purchase for $9.00, Includes print PDF, file size: 83614 bytes)
Citation: Hirose, K., S. Karato, V. F. Cormier, J. P. Brodholt, and D. A. Yuen
(2006),
Unsolved problems in the lowermost mantle,
Geophys. Res. Lett.,
33,
L12S01,
doi:10.1029/2006GL025691.
Copyright 2006 by the American Geophysical Union.
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