Figure F52. Comparison of experimental pressures for melts equilibrated with olivine + orthopyroxene + clinopyroxene + plagioclase ± spinel, with pressures calculated using the method of Kinzler and Grove (1992, 1993). Pressures were calculated for each of four expressions using normative olivine, plagioclase, quartz, and clinopyroxene in the melt compositions. These four pressures were then averaged, as recommended by Kinzlier and Grove. The error bars on the calculated pressures show the range from maximum to minimum pressure calculated from the four expressions. As the figure shows, this method reproduces the experimental data on which it is calibrated with a precision of about ±0.2 GPa.