ABSTRACT
Most prograde metamorphic reactions involve devolatilisation. The main volatile components produced are H2O and CO2, although the relative proportions of these varies considerably from one rock to the next. Once produced, volatiles tend to migrate upwards through the crust, the mechanism and rate of flow being largely a function of temperature, fluid pressure (P f) gradients, and bulk rock permeability (e.g. Fyfe et al, 1978; Ferry, 1980; Etheridge et al., 1983; Wood & Walther, 1986; Yardley, 1986; Thompson, 1987).
