Mg2SiO4-CaAl2Si2O8-SiO2 Diagram. Ternary phase diagram for melting the system Mg2SiO4-CaAl2Si2O8-SiO2 at 0.1 MPa, and also at 1.0 GPa when you press the "Change Pressure" button. The 0.1 MPa diagram is based on data from Irvine (1975). The 1.0 GPa diagram is based on data from Sen and Presnell (1984). The 2.0 GPa diagram is based on data from Liu and Presnell (1990). Temperature is in degrees Celcius and composition is in weight pecent.
The chemical composition of spinel (MgAl2O4) does not plot on this diagram. Nevertheless, some magmas with compositions that plot on this diagram will crystallize spinel when cooled. An interactive version of the ternary Mg2SiO4-CaAl2Si2O8-SiO2 diagram with the spinel field removed for simplicty can be found here.