{{Short description|Category of coarse-grained igneous rocks}} thumb|Granite rock hand-sized sample
A '''granitoid''' is a broad term referring to a diverse group of coarse-grained igneous rocks that are widely distributed across the globe, covering a significant portion of the Earth's exposed surface and constituting a large part of the continental crust.<ref>{{Cite journal |last=Tomás |first=R. |last2=Cano |first2=M. |last3=Pulgarín |first3=L. F. |last4=Brotóns |first4=V. |last5=Benavente |first5=D. |last6=Miranda |first6=T. |last7=Vasconcelos |first7=G. |date=2021-11-01 |title=Thermal effect of high temperatures on the physical and mechanical properties of a granite used in UNESCO World Heritage sites in north Portugal |url=https://linkinghub.elsevier.com/retrieve/pii/S2352710221006811 |journal=Journal of Building Engineering |volume=43 |article-number=102823 |doi=10.1016/j.jobe.2021.102823 |issn=2352-7102|hdl=10045/115630 |hdl-access=free }}</ref> These rocks are primarily composed of quartz, plagioclase, and alkali feldspar.<ref>{{cite web | url=https://mrdata.usgs.gov/catalog/science.php?thcode=4&term=4.4 | title=USGS: Mineral Resources On-Line Spatial Data: Granitoid }}</ref> Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites.<ref name="Streckeisen-1974">{{cite journal |last=Streckeisen |first=A. |year=1974 |title=Classification and Nomenclature of Plutonic Rocks: Recommendations of the IUGS Subcommission on the Systematics of Igneous Rocks |journal=Geologische Rundschau |volume=63 |issue=2 |pages=773–86 |bibcode=1974GeoRu..63..773S |doi=10.1007/BF01820841 |s2cid=130569261 |language=de}}</ref> 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.<ref name="Streckeisen-1974" />
== Nomenclature and classification ==
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 composition, emplacement depth, and tectonic regime.
== Generalizations == thumb|Illustration of continental collision as a result of convergence 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.<ref name="Winter-2014">{{cite book | last=Winter | first=John D. | title=Principles of igneous and metamorphic petrology | publication-place=Harlow | date=2014 | isbn=978-1-292-02153-9 | oclc=890442947 | page = 402}}.</ref> Generally, the evolution to granitoid magmas requires a thermal disturbance to ascent though continental crust.<ref name="Winter-2014" /> Most granitoids are generated from crustal anatexis, the partial melting of the crust; however the mantle may contribute both heat and material.<ref name="Winter-2014" /> 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.<ref name="Winter-2014" /> Granitoids can form in all tectonic environments.<ref name="Winter-2014" />
There are numerous exceptions to these generalizations.<ref name="Clarke-1992">Clarke, D. B. (1992) Granitoid Rocks, Chapman & Hall, London.</ref><ref name="Winter-2014" /> For example, granitoids can form in anorogenic environments, a granitoid source rock can be from the mantle (for example, at intraplate hotspots) and the melting mechanism can be radiogenic crustal heat.<ref name="Clarke-1992" /><ref>Pitcher, W. S. 1982. Granite type and tectonic environment. ''In'' Hsu, K. J. (ed.) ''Mountain Building Processes'', 19–40. London: Academic Press.</ref><ref>{{cite journal | last=Barbarin | first=Bernard | title=Granitoids: Main petrogenetic classifications in relation to origin and tectonic setting | journal=Geological Journal | publisher=Wiley | volume=25 | issue=3–4 | year=1990 | issn=0072-1050 | doi=10.1002/gj.3350250306 | pages=227–238| doi-access=free | bibcode=1990GeolJ..25..227B }}</ref>
==References== {{reflist}}
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Category:Granitic rocks