Solution mechanisms of COHN fluids in melts to upper mantle temperature, pressure, and redox conditions

We wished to advance the knowledge of speciation among volatiles during melting and crystallization in the Earth's interior; therefore, we explored the nature of carbon-, nitrogen-, and hydrogen-bearing species as determined in COHN fluids and dissolved in coexisting aluminosilicate melts. Micro-Raman characterization of fluids and melts were conducted in situ while samples were at a temperature up to 825 degrees C and pressure up to similar to 1400 MPa under redox conditions controlled with the Ti-TiO2-H2O hydrogen fugacity buffer. The fluid species are H2O, H-2, NH3, and CH4. In contrast, under oxidizing conditions, the species are H2O, N-2, and CO2.