Some key thermoelastic properties of MgSiO3-perovskite (pv) have been determined at lower mantle (LM) pressures and temperatures using the quasi-harmonic approximation in conjunction with first principles phonon dispersions. The adiabatic bulk moduli (Ks) of pv and of an assemblage of 80 vol% pv and 20 vol% MgO were obtained along the thermodynamically inferred adiabat and compared with the seismic counterpart given by the preliminary reference Earth model (K-PREM) The discrepancy between calculated Ks's and K-PREM in the deep LM suggests a super-adiabatic gradient, or subtle changes of composition, or phase, or all beginning at about 1200 km. The Anderson Cruneisen parameter, delta (S) = (partial derivative lnK(S)/partial derivative ln(P))(p), was predicted to decrease rapidly with depth (from 2.7 to 1.2 across the LM) supporting the thermal origin for the lateral heterogeneities throughout most of the LM.
|Titolo:||First principles thermoelasticity of MgSiO3-perovskite: consequences for the inferred properties of the lower mantle|
|Autori:||KARKI BB; WENTZCOVITCH RM; DE GIRONCOLI S; BARONI S|
|Rivista:||GEOPHYSICAL RESEARCH LETTERS|
|Data di pubblicazione:||2001|
|Digital Object Identifier (DOI):||10.1029/2001GL012910|
|Appare nelle tipologie:||1.1 Journal article|