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Title: Iron-rich perovskite in the Earth;s lower mantle

The equations of state of perovskite with (Mg{sub 0.75},Fe{sub 0.25})SiO{sub 3} and MgSiO{sub 3} compositions have been investigated by synchrotron X-ray diffraction up to 130 GPa at 300 K in diamond anvil cells. Here we show that the addition of 25% Fe in MgSiO{sub 3} perovskite increases its density and bulk sound velocity (V{phi}) by 4-6% and 6-7%, respectively, at lower-mantle pressures. Based on concurrent synchrotron X-ray emission and Moessbauer spectroscopic studies of the samples, the increase in V{phi} and density can be explained by the occurrence of the low-spin Fe3+ and the extremely high-quadrupole component of Fe{sup 2+}. Combining these experimental results with thermodynamic modeling, our results indicate that iron-rich perovskite can produce an increase in density and a value of V{phi} that is compatible with seismic observations of reduced shear-wave velocity in regions interpreted as dense, stiff piles in the lower mantle. Therefore, the existence of the Fe-rich perovskite in the lower mantle may help elucidate the cause of the lower-mantle large low-shear-velocity provinces (LLSVPs) where enhanced density and V{phi} are seismically observed to anti-correlate with the reduced shear wave velocity.
Authors:
; ; ; ; ; ; ;  [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [2]
  1. (NIU)
  2. (
Publication Date:
OSTI Identifier:
1027657
Resource Type:
Journal Article
Resource Relation:
Journal Name: Earth Planet. Sci. Lett.; Journal Volume: 309; Journal Issue: (3-4) ; 09, 2011
Research Org:
Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
Sponsoring Org:
FOREIGNNSFDOE - BASIC ENERGY SCIENCES
Country of Publication:
United States
Language:
ENGLISH
Subject:
58 GEOSCIENCES; DIAMONDS; EQUATIONS OF STATE; PEROVSKITE; SHEAR; SIMULATION; SYNCHROTRONS; THERMODYNAMICS; VELOCITY; X-RAY DIFFRACTION