(a) P/T-X(CO₂) mineral assemblage diagram modelled for sample 18a-26. The variance of the fields varies from two (i.e. eight phases) to five (i.e. five phases). Colours and symbols as in Fig. 8. (b) Comparison between the reconstructed protolith assemblage and that modelled at the ‘starting point’. (c) Same plot as (a), highlighting the isothermal/isobaric univariant equilibria relevant to this sample. Colours and symbols as in Fig. 8. (d) Comparison between the observed peak assemblage and that modelled at peak conditions. The black ellipses and dotted black arrows in (a) and (c) summarise the prograde and peak conditions and approximate the P–T–X(CO₂) evolution inferred for sample 18a-26 as discussed in the text.