Granitoide

Granitoide, or granitoid, is a broad term for coarse-grained felsic intrusive igneous rocks with granitic composition. The essential mineral assemblage is quartz and alkali feldspar, with plagioclase present in variable amounts, and typically minor mafic minerals such as biotite, hornblende, or muscovite. The best-known member is granite, but granitoids also include granodiorite, tonalite, quartz monzonite, and monzogranite.

These rocks crystallize slowly underground, giving a phaneritic texture. They are characterized by high silica content and are part of the continental crust; their chemistry is generally granitic, though exact compositions vary.

They are typically grouped by dominant minerals and chemical characteristics, including granite, granodiorite, tonalite, and quartz monzonite, and they commonly show a coarse-grained, light-colored appearance.

Geological setting: Granitoids form by crystallization of silica-rich magmas in the crust, often through partial melting of existing rocks or differentiation of magma. They are common in continental crust and central to the formation of batholiths and continental crustal growth; they frequently mark past subduction-related magmatic activity in orogenic belts.

Economic and research relevance: They host mineral deposits and are widely used as dimension stone; their ages provide insights into crustal evolution, and geochronology with granitoids helps constrain tectonic histories.