Figure 1.12. MORB basalt experimental phase diagram. Pressure-Temperature phase diagram for the crystallization of a Primitive MORB composition (after Thompson, 1973). Use the diagram to predict differences in the order of minerals crystallized for a Primitive MORB magma cooled at different pressures. Depths are approximate based on a uniform density of 3333 kg/m3. Use your mouse wheel and mouse to zoom and pan the map to see more detail. Press the "Recenter" button to return to the original view.