Figure 04. Siliceous Dolomites G-X Diagram.
This diagrams shows a schematic, 3D model of the Gibbs energies of the minerals calcite (Cc), quartz (Qz), magnesite (Mgs), dolomite (dol), forsterite (Fo), talc (Tlc), and tremolite (Tr) over a range of temperature. Move the temperature slider to see how the relative values of the Gibbs energies change leading to two chemical reactions. Only the Gibbs energy of Tr is shown to move, although all the Gibbs energies change with temperature. When the Gibbs energy of Tr drops below the Cc-Qz-Tlc plane, a Tr-producing ("terminal") reaction occurs that introduces Tr-bearing assemblages. When the line connecting the Gibbs energies of Tr and Dol drops below the line connecting the Gibbs energies of Cc and Tlc, Cc and Tlc react to form Tr and Dol (a "non-terminal" reaction). The chemical reactions shown can be deduced from the changes to the assemblage diagram. If the mineral formulas are substituted into these reactions, they can be balanced. Pause your mouse over a reaction to see the coefficients for the balanced reaction.
