Thermoelasticity of Al3+- and Fe3+-bearing bridgemanite

Thursday, 18 December 2014
Gaurav Shukla and Renata M Wentzcovitch, University of Minnesota Twin Cities, Minneapolis, MN, United States
We present quasi-harmonic LDA+U calculations of thermoelastic properties of Fe3+- and Al3+-bearing bridgemanite (MgSiO3), the main phase of the Earth’s lower mantle, at relevant P,T conditions and compositions. Four charge-coupled substitutions, namely, Al3+-Al3+, Fe3+-Fe3+, Fe3+-Al3+, and Al3+-Fe3+have been studied. Aggregate elastic moduli and sound velocities are compared with available experimental measurements. In the case of the Fe3+-Fe3+ substitution, the effect of pressure induced high-spin (HS) to low-spin (LS) crossover in the B-site iron has been investigated in great detail. Using these results, we analyze the possible influence of Al and Fe on lower mantle velocity heterogeneities.