Carbon Speciation and Solubility in Silicate Melts

To improve our understanding of the Earth’s global carbon cycle, it is critical to characterize the distribution and storage mechanisms of carbon in silicate melts. Presently, the carbon budget of the deep Earth is not well constrained and is highly model‐dependent. In silicate melts of the uppermost mantle, carbon exists predomi­ nantly as molecular carbon dioxide and carbonate, whereas at greater depths, carbon forms complex polymer­ ized species. The concentration and speciation of carbon in silicate melts is intimately linked to the melt’s composition and affects its physical and dynamic properties. Here we review the results of experiments and calculations on the solubility and speciation of carbon in silicate melts as a function of pressure, temperature, composition, polymerization, water concentration, and oxygen fugacity.