Figure 5.21. Sample Thompson AFM Assemblage Diagram - K-feldspar Projection.

Equilibrium mineral assemblages projected from K-feldspar (Kfs), quartz (Qz), and water (H2O) onto the 3-component A=(Al2O3-K2O), F=(FeO), M=(MgO) composition diagram. The minerals biotite (Bt) and cordierite (Crd) are solid solutions and their compositions are show as black lines or areas. Andalusite (And) has a fixed composition that plots at the A point. 2-mineral (red tie lines) and 3-mineral (green triangles) assemblages are shown. Kfs, 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).