[S-IT15] Mass and energy transport properties and processes in the crust and the mantle

[SIT15-07] Reactions and transport of iron in the mantle during Earth's first four billion years

*Jie Li¹ (1.University of Michigan Ann Arbor)

Keywords:magma ocean, redox reaction, metal-silicate reaction, geodynamo, habitable planet, Earth differentiation

Earth’s oxidized atmosphere and long-lasting magnetic field likely enabled its evolution into an inhabited world. Recent studies suggest that iron disproportionation in early magma ocean may have played a crucial role in producing an oxidized atmosphere in the Hadean eon (e.g., Hirschmann 2023 Earth and Planetary Science Letters). The process involves segregation of iron metal (Fe) from the mantle and transport of ferric iron (Fe³⁺) to the shallow part of the mantle. Meanwhile, precipitation of light elements such as magnesium, silicon, and oxygen from the core has been proposed as a potential mechanism to power the geodynamo through the Archean and Proterozoic eons. The process involves exsolution of iron oxide (FeO) from the core and mixing it back into the mantle through a “conveyor belt”– like mechanism (Mittal et al. 2020 Earth and Planetary Science Letters). Noting that the mantle would be enriched in ferric iron before taking back FeO from the core, here I present a model that connects the two planet-scale chemical differentiation processes. The model incorporates experimental and theoretical constraints on iron disproportionation reactions in dense silicate melt and metal-silicate reactions at extreme pressure and temperature conditions. I will compare the predicted abundance and speciation of iron in the mantle over time with geological records and discuss the implications for the formation of habitable worlds.