Nitrogen and hydrogen isotope compositions and solubility in silicate melts in equilibrium with reduced (N plus H)-bearing fluids at high pressure and temperature: Effects of melt structure

Solubility and solution mechanism(s) of reduced (N+H)- and H-containing N-O-H volatile components in Na2O-SiO2 composition melts in equilibrium with NH3+H-2+N-2 and H2O+H-2 fluid and H- and N-isotope concentrations ill these melts were determined experimentally at 1.5 GPa and 1400 degrees C as a function of hydrogen fugacity,fa, and melt polymerization (composition), NBO/Si (NBO/Si = 0.4-1.18). This NBO/Si-range is similar to that between dacite and olivine tholeiite melt (NBO/Si similar to 0.4-1). The f(H2) was controlled between that of the iron-wftstite + H2O [logf(H2)(IW) similar to 3.42 (bar)] and that of the magnetite-hematite + H2O [logf(H2)(MH) similar to-0.91 (bar)] buffer.