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

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Science  22 Mar 1991:
Vol. 251, Issue 5000, pp. 1438-1443
DOI: 10.1126/science.251.5000.1438


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.

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