Figure 1

Comparing the volume of the vapour bubble to the corresponding (a) MI volume and (b) mass of CO₂ in the bubble for all samples in this study. Inset in (a) refers to the area indicated by the grey dashed box. Coloured lines indicate volume ratio between the bubble and the MI; typically, the bubble comprises between 0.2 and 10 vol %. Volumetric proportions larger than this suggest the bubble is secondary, or pre-existing, and likely formed due to MI leakage, and/or rupturing of the host crystal. On both graphs, Mount Cayley and Garibaldi Lake data refer to values before re-heating. The mass of CO₂ in the bubble was calculated using the Raman spectra, and assuming that CO₂ is the only phase present in the bubble. Overall, the linear correlation suggests that every vapour bubble in this study is primary, was nucleated within the MI, and contains CO₂ gas that was exsolved from the glass. One Mount Meager MI has a lower ratio of bubble to MI volume (MMA200; 1.2 vol%) due to a large MI volume, but a bubble size that is globally consistent. Error bars are 2σ and, in most samples, correspond to the size of the data marker.