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Unsolved problems in the lowermost mantle
Author(s) -
Hirose Kei,
Karato Shunichiro,
Cormier Ver F.,
Brodholt John P.,
Yuen David A.
Publication year - 2006
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2006gl025691
Subject(s) - discontinuity (linguistics) , post perovskite , geology , anisotropy , geophysics , mantle (geology) , perovskite (structure) , thermal conductivity , silicate perovskite , jump , phase (matter) , petrology , thermodynamics , physics , chemistry , mathematical analysis , mathematics , quantum mechanics , crystallography
Many characteristics of D″ layer may be attributed to the recently discovered MgSiO 3 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.