Figure 8. P-XCO2 projection at constant T = 650°C, in the system Al2O3-FeO-MgO-Na2O, after projection through SiO2 and CaO. A. Univariant reactions (thick solid lines) and invariant points (solid circles). B. Enlarged portion of diagram in A shows the phase relationships and stability conditions of the assemblage clinopyroxene + grossular-rich garnet + amphibole + anorthite + quartz + calcite (shaded field) and of the breakdown reaction of clinopyroxene to produce amphibole in the presence of anorthite-rich plagioclase (shaded arrow). Thick solid lines represent univariant reactions, long dashed lines contour the anorthite content in plagioclase, thin solid lines contour the grossular content in garnet, and dotted lines represent the conditions of clinopyroxene reacting to amphibole for different anorthite contents in plagioclase. Minerals on the right side of the reactions are stable at high-pressure conditions. Mineral abbreviations are after Kretz (1983).

Figure 8. P-X_CO2projection at constant T = 650°C, in the system Al₂O₃-FeO-MgO-Na₂O, after projection through SiO₂and CaO. A. Univariant reactions (thick solid lines) and invariant points (solid circles). B. Enlarged portion of diagram in A shows the phase relationships and stability conditions of the assemblage clinopyroxene + grossular-rich garnet + amphibole + anorthite + quartz + calcite (shaded field) and of the breakdown reaction of clinopyroxene to produce amphibole in the presence of anorthite-rich plagioclase (shaded arrow). Thick solid lines represent univariant reactions, long dashed lines contour the anorthite content in plagioclase, thin solid lines contour the grossular content in garnet, and dotted lines represent the conditions of clinopyroxene reacting to amphibole for different anorthite contents in plagioclase. Minerals on the right side of the reactions are stable at high-pressure conditions. Mineral abbreviations are after Kretz (1983).