Mineral Assemblage %Crn:25 %En:25 %Fo:25 %Ky:25 %Prp:25 %Qz:25 %Spr:25
Pyrope Stability Diagram with Assemblages and MAD Diagram.
The diagram on the left shows the temperature-pressure (T-P) stabilities of 7 minerals (Crn, En, Fo, Ky, Prp, Qz, Spr) in a 3-component (Mg2SiO4, SiO2, Al2O3) chemical system. Mouse over the T-P diagram on the left to see the compositions of the minerals plotted on the ternary composition diagram on the right. Tie lines connecting the compositions of minerals that can occur together at equilibrium will appear. When the mouse crosses reaction lines on the T-P diagram, the minerals in equilibrium change as indicated by a change in tie lines.
As in a 2-component system, what minerals will be in a rock at equilibrium for a 3-component system depends not only on the T and P, but also on the chemical composition of the rock. Select a T and P by clicking on the T-P diagram, then mouse over the ternary diagram to indicate a bulk composition with your mouse. The bulk composition is marked by a white dot and shown quantitatively (weight % of each of the 3 components) on the upper right. Furthermore, the equilibrium mineral assemblage for your bulk composition is shown quantitatively on the upper left and graphically with areas proportional to the numerical values determined with the ternary lever rule.
Click on the "Show MAD" button to show the Mineral Assemblage Diagram your selected mineral composition. The MAD will change if the bulk composition is changed. Or click on the ternary diagram to hold a particular bulk composition, click on the change TP button, and mouse over the T-P diagram to see the mineral assemblage changes graphically and numerically when the mouse crosses a reaction line. Notice that for some bulk compositions (the ones where the assemblages include Qz or Fo), no chemical reactions occur for the T-P conditions of the reaction diagram.