Carbon Storage in Earth's Deep Interior Implied by Carbonate‐Silicate‐Iron Melt Miscibility

Abstract Carbonate melts have been proposed to exist in the lower mantle, but their interaction with other mantle melt compositions is poorly understood. To understand miscibility carbonate‐silicate‐metal system, we simulate endmember, binary, and ternary mixtures study how Gibbs free energies of mixing evolve pressure. We find that carbonate‐metal carbonate‐silicate gaps close increasing pressure, while silicate‐metal are immiscible at all lower‐mantle pressures. Extending this analysis core‐mantle boundary, suggest three miscible fields near endmember carbonate, silicate, iron compositions. Analysis densities these indicates some carbonate‐rich silicate‐rich gravitationally stable boundary could be candidate explain ultra‐low velocity zones. Additionally, evaluate speciation an example composition various pressures throughout identify reduced carbon species would expected form melt. Our reveals a majority Earth's transported core during differentiation much may stored deep interior today.