Earth's Core-Mantle Boundary: Results of Experiments at High Pressures and Temperatures

Abstract

Laboratory experiments document that liquid iron reacts chemically with silicates at high pressures (≥2.4 x 10¹⁰ Pascals) and temperatures. In particular, (Mg,Fe)SiO₃ perovskite, the most abundant mineral of Earth's lower mantle, is expected to react with liquid iron to produce metallic alloys (FeO and FeSi) and nonmetallic silicates (SiO₂ stishovite and MgSiO₃ perovskite) at the pressures of the core-mantle boundary, 14 x 10¹⁰ Pascals. The experimental observations, in conjunction with seismological data, suggest that the lowermost 200 to 300 kilometers of Earth's mantle, the D" layer, may be an extremely heterogeneous region as a result of chemical reactions between the silicate mantle and the liquid iron alloy of Earth's core. The combined thermal-chemical-electrical boundary layer resulting from such reactions offers a plausible explanation for the complex behavior of seismic waves near the core-mantle boundary and could influence Earth's magnetic field observed at the surface.