Editing Granitoid

{{Short description|Category of coarse-grained igneous rocks}}
[[File:Granite.jpg|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 |pages=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 [[tonalite]]s to alkali-rich [[syenite]]s and from quartz-poor [[monzonite]]s to quartz-rich [[quartzolite]]s.<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, [[feldspathoid|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]], [[QAPF_diagram|modal composition]], emplacement depth, and [[Tectonics|tectonic regime]].

== Generalizations ==
[[File:Continental-continental convergence en.svg|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 [[Tectonic Plate|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 [[magma]]s requires a thermal disturbance to ascent though continental crust.<ref name="Winter-2014" />&nbsp; Most granitoids are generated from [[Magma differentiation|crustal anatexis]], the partial melting of the crust;&nbsp; however the mantle may contribute both heat and material.<ref name="Winter-2014" />&nbsp; Granitoids can occur coeval with [[volcanic rock]]s that have equivalent chemical composition (granite–[[rhyolite]], syenite–[[trachyte]], [[granodiorite]]–[[dacite]] etc.) however, these extrusive rocks are often [[Erosion|eroded]] so just the [[plutonic rock]]s outcrop.<ref name="Winter-2014" />&nbsp; 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&nbsp; & Hall, London.</ref><ref name="Winter-2014" />&nbsp; For example, granitoids can form in [[Anorogenic magmatism|anorogenic&nbsp;environments]], a granitoid source rock can be from the mantle (for example, at intraplate [[Hotspot (geology)|hotspot]]s) and the melting mechanism can be [[Radiogenic nuclide#Radiogenic heating|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==
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[[Category:Granitic rocks| ]]


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