MgO-FeO Diagram

Figure 3.01. X-Y graph of MgO, FeO, and Na2O. Mass data are shown on this diagram for selected Hawaiian volcanic rocks from the PETROS Igneous Rock Database. Each of the two axes has the weight percent of one component divided by the sum of the weght percents of three componenets. Notice the inverse correllation between Wt.% MgO and Wt.% FeO. This correllation is due to fractional crystallization.