Recycled carbonates elevate the electrical conductivity of deeply subducting eclogite in the Earth’s interior

The elevated pressure and temperature conditions encountered by a subducted slab entering the deep Earth can substantially alter the chemical composition and physical properties of recycled carbonates. Carbonate-silicate reactions are believed to have a pivotal role in this process. Here we conduct high temperature and high pressure experiments on carbonated eclogite and measure the electrical conductivity in order to constrain the evolution of geophysical properties and chemical composition in the carbonate-bearing eclogitic slab. We find that the carbonate-silicate reaction elevates the conductivity of carbonated eclogite by cations (e.g., Ca, Mg, Fe) exchange between carbonates and silicate. We propose that carbonate-silicate cations exchange can alter the chemical composition of recycled carbonates, potentially impacting their stability and reducing the solidus temperature of carbonate-bearing systems. Combining thermodynamic calculations with the elevated conductivity in our experiments, we re-evaluate the contribution of recycled carbonates to the Earth mantle geophysical anomalies and obtain the potential carbonate capacity in the subducting slab.