Measurement of the melting curve of Mg0.9Fe0.1SiO3at lower mantle conditions and its geophysical implications

An experimental determination of the melting of Mg0.9Fe0.1SiO3 under lower mantle conditions is presented. Samples were compressed and laser heated (Nd-YAG) in a Mao-Bell-type diamond cell. The temperature fields generated in the sample are measured using a simple tomographic technique and spectroradiometer. Mg0.9Fe0.1SiO3 in the perovskite structure melts at 3000 ± 300 K independently of pressure over the range of 22–65 GPa. The melting curve of Mg0.9Fe0.1SiO3 represents an experimental upper bound upon the geotherm from 700 to 1500 km. This melting curve corresponds to a homologous temperature of 0.70 or 0.85 for one- or two-layer mantle convection, respectively. This is consistent with either one- or two-layer mantle convection and a lower mantle of constant viscosity (based upon homologous temperature arguments).