Figure 11
From: Carbon and Nitrogen Speciation in N-poor C-O-H-N Fluids at 6.3 GPa and 1100–1400 °C
Schematic of the upper mantle volatile cycle and main carbon and nitrogen species of C-O-H-N fluids in depleted and enriched domains38, 39. Black arrows show paths and estimates of the relative magnitudes of carbon, nitrogen and hydrogen fluxes and blue arrow is mantle upwelling. Right panel: potential mantle fO2 as a function of depth. The Fe0-FeO and Fe3+/Fe2+ (equilibria involving the exchange of Fe3+ and Fe2+ between silicate minerals) curves are according to refs 1 and 56. Oxygen fugacity of CW (maximum H2O content in C-O-H fluids), EMOD/G (equilibria enstatite + magnesite = olivine + graphite/diamond) and MORB (mid-ocean ridge basalts) are according to refs 1 and 24. ‘Redox melting’ process at depths of 120–150 km is according to refs 1 and 24.
