Gabbro Dry
Gabbro Wet
Gabbro Both
Peridotite Dry
Peridotite Wet
Peridotite Both

P increases up
P increases down

Figure 2.09. Dry and Wet Melting for Gabbro and for Peridotite. Beginning of melting curves (solidus) and completely melted curves (liquidus) for dry and wet gabbro and for dry and wet peridotite based on experimental studies of natural rock samples. Wet melting experiments are performed in the presence of excess water under pressure (P=PH2O). Notice that both gabbro and peridotite melt at much lower temperatures in the presence of excess water than the melting of dry samples. Melting conditions for gabbro should be a good guide for basalt melting conditions, but without the complicating issues of glass, oxidation, and hydration. Use the radio buttons to select which melting curves are shown and whether pressure increases upward or downward in the graph.

The diagrams drafted for this figure are based on laboratory melting experimental at pressure reported in or summarized by Lambert and Wyllie (1972) for gabbro, and by Grove and others (2006) for peridotite.