Figure 6.04. H2O-NaCl-KCl Phase Diagram at 100°C. The brine field is larger at 100°C than at 20°C. Use the button in the text to switch between the two temperatures. More salt, particularly sylvite, can be dissolved in brine at higher temperatures.
Figure 6.01 shows the H2O-NaCl-KCl phase diagram at 20°C. As discussed in the Binary Saturation Diagrams chapter, more salt can be dissolved in water at higher temperature. Figure 6.04 shows the H2O-NaCl-KCl phase diagram at 100°C. Click and toggle here: to compare the 20°C and 100°C versions. The halite and especially the sylvite saturation (liquidus) curves shift to higher salinity at higher temperatures.
As the temperature changes, the liquidus (saturation) curves for minerals in magmas change their composition, just as the saturation curves for sylvite and halite change their compositions with temperature. If a range of temperatures is considered, the liquidus curves become a liquidus surface in three dimensions.
Figure 6.05. CaMgSi2O6-MgSiO4-CaAl2Si2O8 Liquidus Diagram. Click on the diagram and move the slider to switch from the 2D contour diagram of the liquidus surface to a 3D model.
Figure 6.05 shows the diopside (Di), forsterite (Fo), and anorthite (An) liquidus surfaces as a temperature-contoured projection onto a CaMgSi2O6-MgSiO4-CaAl2Si2O8 ternary diagram. Each temperature contour gives the location of the liquidus curve at a particular temperature. Most geologists will get a sense of the shape of this diagram because of the similarity of the diagram with topographic maps. If you click on the diagram, a large version will open with a slider that can be used to show a persective view of the 3D graph. Move the slider on the larger version of Figure 6.05 to switch from the 2D contour diagram of the liquidus surface to a 3D model with the Di liquidus surface (yellow), the Fo liquidus surface (green), and the An liquidus surface (blue). Two-dimensional Di-An vs. T and An-Fo vs. T diagrams are shown as side cross sections of the 3D diagram.
