Measurement of the melting curve of Mg_0.9Fe_0.1SiO₃ at lower mantle conditions and its geophysical implications

Abstract

An experimental determination of the melting of Mg 0.9 Fe 0.1 SiO 3 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. Mg 0.9 Fe 0.1 SiO 3 in the perovskite structure melts at 3000 ± 300 K independently of pressure over the range of 22–65 GPa. The melting curve of Mg 0.9 Fe 0.1 SiO 3 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).