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JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 111,
B09203,
doi:10.1029/2005JB004052,
2006
Single-crystal elasticity and sound velocities of (Mg0.94Fe0.06)O ferropericlase to 20 GPa
Jennifer M. Jackson
Department of Geology, University of Illinois, Urbana, Illinois, USA
Stanislav V. Sinogeikin
Department of Geology, University of Illinois, Urbana, Illinois, USA
Steven D. Jacobsen
Geophysical Laboratory, Carnegie Institution of Washington, Washington, D. C., USA
Hans J. Reichmann
GeoForschungsZentrum, Potsdam, Germany
Stephen J. Mackwell
Lunar and Planetary Institute, Houston, Texas, USA
Jay D. Bass
Department of Geology, University of Illinois, Urbana, Illinois, USA
Abstract
The single-crystal elastic properties of high-spin (Mg0.94Fe0.06)O ferropericlase were measured by Brillouin spectroscopy on a sample compressed to 20 GPa with diamond anvil cells using
methanol-ethanol-water as a pressure-transmitting medium. At room pressure, the adiabatic bulk (K
0S) and shear (μ0S) moduli are K
0S = 163 ± 3 GPa and μ0S = 121 ± 2 GPa, in excellent agreement with ultrasonic results from the same bulk sample (Jacobsen et al., 2002). A fit to
all our high-pressure Brillouin data using a third-order finite-strain equation of state yields the following pressure derivatives
of the adiabatic bulk and shear moduli: K′0S = 3.9 ± 0.2 and μ′0S = 2.1 ± 0.1. Within the uncertainties, we find that K
0S and K′0S of (Mg0.94Fe0.06)O are unchanged from MgO. However, μ0S and μ′0S of (Mg0.94Fe0.06)O are reduced by 8% and 11%, respectively. The aggregate compressional (V
P) and shear (V
S) wave velocities are reduced by 4% and 6%, respectively, as compared to MgO. The pressure dependence of the single-crystal
elastic moduli and aggregate sound velocities is linear within the investigated pressure range. The elastic anisotropy of
(Mg0.94Fe0.06)O is about 10% greater than that of MgO at ambient conditions. At the highest pressure obtained here, the elastic anisotropy
of (Mg0.94Fe0.06)O is close to zero. On the basis of our measurements and earlier ultrasonic measurements, we find that the pressure derivatives
of shear moduli obtained at room pressure for low iron concentrations (<20 mol% FeO) of high-spin ferropericlase are inconsistent
with those inferred from the lower mantle PREM model.
Received 15
September
2005;
accepted 6
March
2006;
published 7
September
2006.
Keywords: ferropericlase;
elasticity;
high-pressure.
Index Terms: 3909 Mineral Physics: Elasticity and anelasticity; 3919 Mineral Physics: Equations of state; 3924 Mineral Physics: High-pressure behavior; 3934 Mineral Physics: Optical, infrared, and Raman spectroscopy.
Read Full Article (file size: 450941 bytes) Cited by
Citation: Jackson, J. M., S. V. Sinogeikin, S. D. Jacobsen, H. J. Reichmann, S. J. Mackwell, and J. D. Bass
(2006),
Single-crystal elasticity and sound velocities of (Mg0.94Fe0.06)O ferropericlase to 20 GPa,
J. Geophys. Res.,
111,
B09203,
doi:10.1029/2005JB004052.
Copyright 2006 by the American Geophysical Union.
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