Abstract: Fluids trapped inside fluid inclusions in quartz from the multiphase Starav monzogranite in Etive, Argyll, were extracted under vacuum and quantitative data for H₂O and CO₂ were obtained manometrically. Na and K were determined on an aqueous leach from the decrepitated grains. A bivariate diagram of H₂O/CO₂ versus Na/K discriminates between magma pulses and mirrors the whole-rock trace-element chemistry. This work shows that compositional variations of fluids in quartz from a weakly mineralised granitoid intrusion are sensitive indicators of its magmatic history and identify subtle changes in its mineralogical composition.