Temperature dependence of elastic moduli of β-(Mg, Fe )₂SiO₄

The elastic moduli of polycrystalline wadsleyite, β(Mg_0.91Fe_0.09)₂SiO₄, were measured up to 470 K by means of the resonant sphere technique. The adiabatic bulk (K_S) and shear (μ) moduli were found to be 165.72(6) and 105.43(2) GPa at room temperature. The average slopes (dKs/dT and dμ/dT) in the range were determined to be the -0.0175(3) and -0.0159(1) GPa/K. We estimated that the P-, S-wave velocity and density jumps for the α- to β-phase transformation at the 410-km depth condition were 9.5, 11.2 and 5.4%, respectively. These results suggest that the olivine component at the depth should be 52 and 42 volume % for P- and S-waves.