Fig. 19

Phase boundaries of reactions R19, R20, R31 and R32 involving addition of Na⁺ and removal of Ca²⁺ at the X_CO2 defined by R28, lowest X_Ca2+ defined by R4 (melilite-anorthite equilibrium – top left panel of Fig. 20). The activity of aqueous SiO₂ in reactions R31 and R32 is set at the upper limit of X_SiO2 defined by R27. The “condensed steam” field designates an aqueous solution formed by in situ condensation of steam as opposed to the “external” aqueous solution, which comes to a CAI from outside (matrix?) as a liquid