P–T grid with reactions relevant for model chromitite (red, eq. 1) and other rocks (grey) in the MASH system. Phase relations with cummingtonite, gedrite, staurolite, sapphirine and anhydrous cordierite, which pertain to the high-SiO2, high-Al2O3 field of the composition space at >ca. 700°C, have been omitted for clarity. The terminal reaction of chlorite is from Jenkins (1981). The triangular phase diagram (inset) is for P–T conditions above the maximum stabilities of chlorite and anthophyllite. A model mixture of spinel and olivine with 0.8 and 0.2 mole fractions, respectively, is represented in this diagram (red dot). General phase diagrams for fields I and II (below) and III (above; eq. 1) are presented in Fig. 3. The metamorphic effects of isobaric cooling of oceanic lithosphere after magmatic accretion (point a) and orogenic heating (b) and cooling (c) upon punctuated or pervasive fluid infiltration are discussed in the text.
