Isochemical phase diagrams computed for compositions corresponding to garnet micaschists from the Najac unit: (a) sample NJC11 used to determine the prograde P-T path; (b) sample NJC12a used to determine the peak P-T conditions and the retrograde path. Garnet in/out and chlorite in/out curves are indicated in bold to better localize the retrogression in greenschist facies conditions.