Figure 5.20. Sample Thompson AFM Assemblage Diagram - Muscovite Projection.

Equilibrium mineral assemblages projected from muscovite (Ms), quartz (Qz), and water (H2O) onto the 3-component A=(Al2O3-3K2O), F=(FeO), M=(MgO) composition diagram. The minerals biotite (Bt), garnet (Grt), staurolite (St), and chlorite (Chl) are solid solutions and their compositions are show as black lines or areas. Kyanite (Ky) has a fixed composition that plots at the A point. 2-mineral (red tie lines) and 3-mineral (green triangles) assemblages are shown. Because of the projection from Ms, biotite (Bt) compositions plot at negative values of A. Ms, Qz, and water are present in all assemblages at equilibrium.

The diagram was calculated from the thermodynamic model dataset SPaC (version 4/2000) developed originally by Spear and Cheney (1989). AFM topologies were calculated by Frank Spear following the procedures of Spear (1999).