Figure F53. Estimated conditions for equilibration of MORB glass compositions from 14° to 16°N along the Mid-Atlantic Ridge with olivine + orthopyroxene + clinopyroxene + plagioclase ± spinel. Equilibration pressures were calculated as described in the caption for Figure F52. Equilibration temperatures were calculated using each of the four pressure estimates for each glass composition, and then averaged. For both pressure and temperature (P-T), the error bars for each individual composition show the range from maximum to minimum calculated pressure and temperature. Error bars for the average P-T estimate for primitive glasses, with molar Mg# > 0.6, are for 2 standard deviations from the mean pressure and temperature. The standard error of the mean for the average pressure-temperature estimate for primitive glasses is about 90 times smaller than the standard deviation.