Mg₂SiO₄-CaAl₂Si₂O₈-SiO₂ Diagram. Ternary phase diagram for melting the system Mg₂SiO₄-CaAl₂Si₂O₈-SiO₂ at 0.1 MPa pressure based on data from Irvine (1974). Temperature is in degrees Celcius and composition is in weight pecent. Melting temperatures of the three minerals forsterite (Fo), anorthite (An), and cristobalite are shown, along with temperatures of three binary eutectic points and one peritectic point. Cotectic curves and one reaction curve are shown. The liquidus (saturation) surfaces for each mineral are shown by temperature contours. The spinel field (non-ternary) and high silica two-liquid field have been removed to simplify the diagram for petrologists in training. To see the Mg₂SiO₄-CaAl₂Si₂O₈-SiO₂ diagram with spinel shown click here. The saturation surfaces have been smoothed somewhat and adjusted to simplify coding the phase percentages animation.

Drag the temperature slider on the right to show isothermal sections through the diagram. Once the slider is selected, you may use up and down arrow buttons to have more control over the speed of temperature change. Click on the "Coordinates" button to see the compositions of points in the diagram as the mouse is moved over the diagram. Click on the "Show Phases" button to see the equilibrium phase assemblages of points in the diagram as the mouse is moved over the diagram. With the "Show Phases" button clicked, click on the diagram to select and hold a particular bulk composition. Then to see how the phase assemblage changes for the selected bulk composition (shown by a white circle), click on the "Change T" button and use the temperature slider. To cancel the selected bulk composition, click on the "Animate" button. Return to Previous View