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Figure 5. Plots of SiO2 versus (A) TiO2, (B) FeOt (total iron expressed as FeO), (C) CaO, (D) aluminum saturation index (A/CNK=molar Al2O3/(CaO + Na2O + K2O), (E) Na2O + K2O, and (F) FeOt/MgO for basement rocks from the field trip area. Dashed line in A encloses field of igneous charnockites from Kilpatrick and Ellis (1992). Dashed line separating alkaline and subalkaline fields in E is from Irvine and Baragar (1971). Dashed line separating tholeiitic and calc-alkaline fields in F is from Miyashiro (1974). All data are expressed in weight percent. Symbols are the same as in figure 4. |