The solubility and solution mechanisms of reduced CAOAH volatiles in Na 2 OASiO 2 melts in equilibrium with a (H 2 + CH 4 ) fluid at the hydrogen fugacity defined by the iron-wü stite + H 2 O buffer [f H2 (IW)] have been determined as a function of pressure (1-2.5 GPa) and silicate melt polymerization (NBO/Si: nonbridging oxygen per silicon) at 1400°C. The solubility, calculated as CH 4 , increases from $0.2 wt% to $0.5 wt% in the melt NBO/Si-range $0.4 to $1.0. The solubility is not significantly pressure-dependent, probably because f H2 (IW) in the 1-2.5 GPa range does not vary greatly with pressure. Carbon isotope fractionation between methane-saturated melts and (H 2 + CH 4 ) fluid varied by $14& in the NBO/Si-range of these melts. The (C..H) and (O..H) speciation in the quenched melts was determined with Raman and 1 H MAS NMR spectroscopy. The dominant (C..H)-bearing complexes are molecular methane, CH 4 , and a complex or functional group that includes entities with C"CAH bonding. Minor abundance of complexes that include SiAOACH 3 bonding is tentatively identified in some melts. There is no spectroscopic evidence for SiAC or SiACH 3 . Raman spectra indicate silicate melt depolymerization (increasing NBO/Si). The [CH 4 /C"CAH] melt abundance ratio is positively correlated with NBO/Si, which is interpreted to suggest that the (C"CAH)-containing structural entity is bonded to the silicate melt network structure via its nonbridging oxygen. The $14& carbon isotope fractionation change between fluid and melt is because of the speciation changes of carbon in the melt.