Grt-Bt Thermometer. Temperatures of metamorphosed shales using the compositions of garnet (Grt) and biotite (Bt) based on the experiments of Ferry and Spear (1978) and using equation 15-44 of Spear (1993) are shown with a rust-colored line. Move the sliders to change the KD values or the Grt and Bt compositions, or enter XMg (= Mg/(Mg+Fe) in moles) values into the boxes. Notice that pressure has little effect on the temperature for a given KD (the rust-colored line is nearly vertical).
Other reference reactions can be shown by clicking on the appropriate check boxes. Reactions for metamorphosed shale subsystems from the thermodynamic model dataset SPaC (version 4/2000) developed originally by Spear and Cheney (1989) may be shown by checking the boxes KASH, KFASH, KMASH, and KFMASH.
