Thermal regime in the earth's core and lower mantle

Abstract

Current views favour the presence of sulphur in the core, giving a composition of Fe + FeS. It is argued that the core composition is close to the eutectic and that this eutectic composition is Fe 2S. The consequences for the thermal regime in the core are examined in terms of the most likely properties of the Fe 2S eutectic. This leads to much lower temperatures than would be expected for an iron or FeSi core. Consideration of the thermal regime in the mantle and the probable thermal properties of lower-mantle assemblages leads to a similar low temperature for the core-mantle boundary. These temperatures require a temperature gradient near the adiabatic in the mantle, implying a convective thermal history.