P-T-a(H2O) Conditions in the Thermal Aureole

Abstract

In this chapter estimates are made of the pressure of emplacement of the Ballachulish Igneous Complex and the range of maximum temperatures in the surrounding thermal aureole. Using these P-T estimates, quantitative estimates of a(H2O) are made for pelites at different grades in the aureole. Activity of H2O is shown to vary between pelites above and below the onset of partial melting, and between graphitic and non-graphitic pelites at the same grade.