Uranium, thorium and REE partitioning into sulfide liquids: Implications for reduced S-rich bodies

For sulfide-silicate partitioning at 1.5 GPa and 1400 °C we obtain DNd/DSm of about 1.4 and DTh ∼ 0.1DU. With increasing temperature the differences between these geochemically similar element pairs decreases such that, at 2100 °C DNd/DSm is 1.0 and DTh/DU is about 0.3. We used these results, together with DU and DSm to model addition of a putative Mercury-like component (with FeS core) to early Earth. We find that the 1400° results could lead to a significant (∼11 ppm) 142Nd anomaly in silicate Earth and add >8 ppb U to the core, but lead to an unreasonably high Th/U of silicate Earth (4.54). Based on the 2100 °C results the 142Nd anomaly would be 0 but addition of the sulfur-rich body could add up to 10 ppb of U to the core, generating, when the accompanying 21 ppb Th is also considered, ∼3 TW of the energy required for the geodynamo. In this case, the Th/U ratio of silicate Earth would approximate 4.3, within the range of some estimates.