A recalibration of the chlorite—biotite—muscovite geobarometer

Massonne (1981) reported experiments on the composition of muscovite in the assemblage phlogopite-muscovite-K-feldspar-quart. The experimental data have been used to recalculate the equilibrium conditions for the chlorite-muscovite-biotite-quartz assemblage which has been proposed as a new geobarometer by Powell and Evans (1983).The recalculated equilibrium shows much steeperdp/dT slopes than those calculated by Powell and Evans (1983). Nevertheless, with the necessary precautions it is suggested that the barometer may provide the critical user with valuable pressure estimates.