peralkalic

from The Century Dictionary.

• In petrography, in the quantitative classification of igneous rocks (see rock), extremely alkalic: said of salic minerals, or of magmas in which they preponderate, when the ratio of the salic K₂O and Na₂O to salic CaO is greater than 7:1. It is applied to femic minerals, or to magmas in which they preponderate, when the ratio of the femic K₂O and Na₂O to femic CaO, MgO, and FeO is greater than 7:1.