Over the last decades, many experimental studies have focused on the effect of CO2 on phase equilibria and melting behavior of synthetic eclogite and peridotite rocks as function of pressure and temperature. These studies have been of fundamental importance to understanding the origin of carbonated magmas varying in composition from carbonatitic to kimberlitic. The occurrence of diamonds in natural rocks is a further evidence of the presence of (reduced) carbon in the Earth’s interior. The oxygenation of the Earth’s interior (i.e. its redox state) through time has strongly influenced the speciation of carbon from the mantle to mantle-derived magmas and, in turn, to the released volcanic gases to the atmosphere. This paper explains how the knowledge of the oxygen fugacity recorded by mantle rocks and determined through the use of appropriate oxy-thermobarometers allows modeling the speciation of carbon in the mantle, its mobilization in the asthenospheric mantle by redox partial melting, and its sequestration and storage during subduction by redox freezing processes. The effect of a gradual increase of the mantle fo2 on the mobilization of C is here discussed along with the main variables affecting its transport by subduction down to the mantle.
Scientific editing by Maria Luce Frezzotti