Modeling the Composition of the Earth’s Liquid Outer Core

Abstract—The paper suggests expressions, coherent with experimental data, for the calculation of the sound velocity and the temperature of a condensed medium under pressures in the Earth’s liquid outer core through parameters of the shock Hugoniot of the medium. Additives to the Earth’s liquid outer iron-nickel core were fitted so that the calculated pressure, density and sound wave velocity corresponded to geophysical values and the temperature did not exceed the admissible limits. It was established that the iron carbide Fe3C containing (4.0 ± 0.5) wt % carbon with additives of FeS2 and SiC with a total content of Si and S up to 1.5 wt % meets the required criteria as the main light additive in the upper layers of the Earth’s core. Less probable is the additive of carbon in the diamond phase up to 0.5 wt %. In the Earth’s outer core, at the boundary with the solid inner core, among the possible light additives are the iron carbide Fe3C with (3.5 ± 0.4) wt % carbon or diamond phase carbon of (4.0 ± 0.5) wt %. Additives at the bottom of the Earth’s liquid outer core, containing significant amounts of Si, S, are hardly probable. The content of H in the Earth’s liquid outer core can be significant at the minimum possible core temperatures. The content of O is insignificant.