Chemistry of Igneous Rocks

The chemical composition of an igneous rock is also an important parameter of its classification. The chemical composition of a rock may be expressed by the types of minerals present and their relative abundances or in the rock color. Rocks may also be analyzed chemically using quantitative chemical analysis techniques to determine the relative proportions of chemical elements present. These chemical abundances can be used directly to classify igneous rocks. The chemical composition of the mother magma and to a lesser extent that of the country rock (i.e., host rock) largely controls the types of minerals which may be formed. 

Non-alkaline igneous rocks n(NajO)+n(KjO) n(AljOj) n(NajO)+n(KjO) l/6(SiOJ 

Clarke, F.W. and Washington, H.S. The Composition of the Earth s Crust U.S. Geol. Survey, Profess. Paper 127 117 p. (1924). 

Hypovolcanic igneous rocks Perlplutonic igneous rocks 

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