A granitoid is a generic term for a diverse category of coarse-grainedigneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar.[1] Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites.[2] As only two of the three defining mineral groups (quartz, plagioclase, and alkali feldspar) need to be present for the rock to be called a granitoid, foid-bearing rocks, which predominantly contain feldspars but no quartz, are also granitoids.[2] The terms granite and granitic rock are often used interchangeably for granitoids; however, granite is just one particular type of granitoid.
Granitoids are diverse; no classification system for granitoids can give a complete and unique characterization of the origin, compositional evolution, and geodynamic environment for the genesis of a granitoid. Accordingly, multiple granitoid classification systems have been developed such as those based on: geochemistry, modal content,Шаблон:Technical inline emplacement depth, and tectonic regime.
There are several generalizations that apply to the majority of granitoids. Typically, granitoids occur where orogeny thickens continental crust either by subduction yielding a continental arc or by convergence yielding continental collisions.[3] Generally, the evolution to granitoid magmas requires a thermal disturbance to ascent though continental crust.[3] Most granitoids are generated from crustal anatexis, the partial melting of the crust; however the mantle may contribute both heat and material.[3] Granitoids can occur coeval with volcanic rocks that have equivalent chemical composition (granite–rhyolite, syenite–trachyte, granodiorite–dacite etc.) however, these extrusive rocks are often eroded so just the plutonic rocks outcrop.[3] Granitoids can form in all tectonic environments.[3]
