Thermobarometry Example with Non-ideal Solution Models. Enter the compositions of biotite (Bt), garnet (Grt), and plagioclase (Pl) to see the equilibrium temperature and pressure described by Grt-Bt thermometer (red-brown line) and the GASP barometer (blue line) with compositional corrections using the solution models of Hodges and Spear (1982). The mineral compositions should be entered in mole units, as the models use mole fractions in the calculation. Click on the "Coordinate" buttons and mouseover the intersection of the two colored lines to see the T and P calculated with this thermobarometry model. Other reference reactions can be shown by clicking on the appropriate check boxes.
