Thermoelastic properties of MgSiO(3)-perovskite: insights on the nature of the Earth's lower mantle.

We have determined by means of first principles quasiharmonic calculations the elastic constants and acoustic velocities of MgSiO3 perovskite, the most abundant mineral of the Earth's lower mantle (LM), at pertinent pressures and temperatures. Using these results, along with the effects of low concentration iron alloying and the thermoelasticity of the most important secondary LM phase, MgO, we predict the isotropic elastic moduli of likely LM aggregates. Comparison with seismic values extracted from the preliminary reference Earth model indicates that the top of the LM behaves as a typical aggregate of pyrolitic composition, likewise the upper mantle. But systematic deviations that cannot be accounted for by alterations in the geotherm alone develop toward the deep LM. This result could be viewed as evidence in support of radially inhomogeneous LM models.

[1]  Stefano de Gironcoli,et al.  First-principles determination of elastic anisotropy and wave velocities of MgO at lower mantle conditions , 1999, Science.

[2]  G. MacDonald.  Composition and petrology of the earth's mantle , 1977 .

[3]  D. Weidner,et al.  (ϖμ/ϖT)P of the lower mantle , 1996 .

[4]  Weidner,et al.  Thermal equation of state of aluminum-enriched silicate perovskite , 1999, Science.

[5]  D. L. Anderson.  The Case for Irreversible Chemical Stratification of the Mantle , 2002 .

[6]  R. Jeanloz,et al.  Aluminum in magnesium silicate perovskite: Formation, structure, and energetics of magnesium‐rich defect solid solutions , 2003 .

[7]  J. Watt,et al.  The Elastic Properties of Composite Materials , 1976 .

[8]  S. Karato,et al.  High pressure elastic anisotropy of MgSiO3 perovskite and geophysical implications , 1998 .

[9]  John P. Brodholt,et al.  Letters to Nature 934 , 2022 .

[10]  A. Ringwood.  Composition and petrology of the earth's mantle , 1975 .

[11]  A. Yeganeh-Haeri.  Synthesis and re-investigation of the elastic properties of single-crystal magnesium silicate perovskite , 1994 .

[12]  Guillaume Fiquet,et al.  Iron Partitioning in Earth's Mantle: Toward a Deep Lower Mantle Discontinuity , 2003, Science.

[13]  R. Hilst,et al.  Compositional stratification in the deep mantle , 1999, Science.

[14]  R. Cohen,et al.  Constraints on lower mantle composition from molecular dynamics simulations of MgSiO3 perovskite , 2002 .

[15]  Liebermann,et al.  Ultrasonic shear wave velocities of MgSiO3 perovskite at 8 GPa and 800 K and lower mantle composition , 1998, Science.

[16]  Stefano de Gironcoli,et al.  First principles thermoelasticity of MgSiO3‐perovskite: Consequences for the inferred properties of the lower mantle , 2001 .

[17]  J. M. Brown,et al.  Thermodynamic parameters in the Earth as determined from seismic profiles , 1981 .

[18]  G. D. Price,et al.  The composition and geotherm of the lower mantle: constraints from the elasticity of silicate perovskite , 2000 .

[19]  G. D. Price,et al.  Ab initio elasticity and thermal equation of state of MgSiO3 perovskite , 2001 .

[20]  Price,et al.  Ab initio molecular dynamics with variable cell shape: Application to MgSiO3. , 1993, Physical review letters.

[21]  S. Karato,et al.  Importance of anelasticity in the interpretation of seismic tomography , 1993 .

[22]  D. L. Anderson,et al.  Preliminary reference earth model , 1981 .

[23]  L. Stixrude,et al.  Elasticity of (Mg,Fe)SiO3‐perovskite at high pressures , 2002 .

[24]  I. Jackson.  Elasticity, composition and temperature of the Earth’s lower mantle: a reappraisal , 1998 .

[25]  T. Kondo,et al.  Thermoelastic properties of MgSiO3 perovskite determined by in situ X ray observations up to 30 GPa and 2000 K , 1996 .

[26]  Stefano de Gironcoli,et al.  High-pressure lattice dynamics and thermoelasticity of MgO , 2000 .

[27]  Stefano de Gironcoli,et al.  Phonons and related crystal properties from density-functional perturbation theory , 2000, cond-mat/0012092.