Starting with the triangular diagram indicating the stable mineral assemblages in any divariant field in Figure 15.19 work your way clockwise around the diagram until you come back to the starting diagram and check that only one change occurs in the mineral assemblages in crossing from one divariant field to the next.

Figure 15.19

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Pressure (GPa) 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 KAI, AISI, O(OH)₂ + SiO₂ = KAISI,O, + ALSIO + H₂O (a,0 = 1) Qz 400 AIO 32 Ky, Ms' SiO₂ Kyanite Andalusite And, Kfs 500 Sil Sillimanite Andalusite Ms + Q Kfs + And And Ms + Q Kfs+ Ky Kyanite Sillimanite 2 Ms + Q Kfs + Sil 600 Temperature (°C) 700 Sil 3 800 35 30 25 20 15 10 5 0 Depth (km) (p = 2700 kg m-³)