Granitic Rocks

Abstract

Granites are coarse-grained crystalline rocks of igneous aspect composed of quartz, feldspar, and micas or ferromagnesian minerals such as hornblende. In this chapter we shall include under the heading of granitic rocks such related varieties as quartz monzonite, granodiorite, quartz diorite, and monzonite — all of which are mineralogically similar to granites. These granitic rocks collectively make up the large batholiths of the world, and many of the smaller stocks, laccoliths, dikes, and sills. They are by far the most abundant plutonic igneous rocks in the continental crust. If the scope of the definition were widened to encompass gneissic rocks of similar mineral composition, which may have had granites as parents, many of the rocks of the Precambrian Shield areas would also be included.