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Velocity structure and composition of the lower mantle with spin crossover in ferropericlase
Author(s) -
Wu Zhongqing
Publication year - 2016
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2015jb012667
Subject(s) - mantle (geology) , composition (language) , mineralogy , thermodynamics , materials science , atmospheric temperature range , spin crossover , chemistry , condensed matter physics , geology , geophysics , crystallography , physics , linguistics , philosophy
The composition of the Earth's lower mantle (LM) is critical in understanding the Earth's interior and dynamics. Previous reports on the composition of the LM are controversial. The composition of LM, constrained here using high‐temperature and high‐pressure data of the velocities and density of minerals from first‐principles calculations, spans a large range: from pyrolite with ~ 15% ferropericlase (Fp) in weight (wt %) to perovskitic‐rich composition with ~ 10 wt % Fp. Any composition well constrained by preliminary reference Earth model (PREM) has a sufficient amount of Fp to exhibit the positive temperature dependence of V Φ (= K ρ ) at the middle LM, leading to the insensitivity of V P to temperature. The depth at which V P is insensitive to temperature variation deepens significantly with increasing temperature because the spin transition in Fp has the positive Clapeyron slope (~17 MPa/K). The Large Low Shear Velocity Provinces below Africa is estimated to be ~ 750 K higher than the ambient mantle.