Editing Gabbro (section)

==Distribution==
[[File:Zuma rock.jpg|thumb|[[Zuma Rock]], Nigeria, a massive, nearly uniform, intrusion of gabbro and [[granodiorite]].]]

Nearly all gabbros are found in plutonic bodies, and the term (as the [[International Union of Geological Sciences]] recommends) is normally restricted just to plutonic rocks, although gabbro may be found as a coarse-grained interior [[facies]] of certain thick lavas.<ref>{{cite journal |last1=Arndt |first1=N.T. |last2=Naldrett |first2=A.J. |last3=Pyke |first3=D.R. |title=Komatiitic and Iron-rich Tholeiitic Lavas of Munro Township, Northeast Ontario |journal=Journal of Petrology |date=1 May 1977 |volume=18 |issue=2 |pages=319–369 |doi=10.1093/petrology/18.2.319}}</ref><ref>{{cite book |last1=Gill |first1=Robin |title=Igneous rocks and processes: a practical guide |date=2010 |publisher=Wiley-Blackwell |location=Oxford |isbn=978-1-4443-3065-6}}</ref> Gabbro can be formed as a massive, uniform intrusion via in-situ crystallisation of [[pyroxene]] and [[plagioclase]], or as part of a [[layered intrusion]] as a [[Cumulate rock|cumulate]] formed by settling of pyroxene and plagioclase.<ref>{{Cite journal|last1=Emeleus|first1=C. H.|last2=Troll|first2=V. R.|date=August 2014|title=The Rum Igneous Centre, Scotland|journal=Mineralogical Magazine|language=en|volume=78|issue=4|pages=805–839|doi=10.1180/minmag.2014.078.4.04|bibcode=2014MinM...78..805E|issn=0026-461X|doi-access=free}}</ref> 
An alternative name for gabbros formed by crystal settling is ''pyroxene-plagioclase adcumulate''.

Gabbro is much less common than more silica-rich intrusive rocks in the [[continental crust]] of the Earth. Gabbro and gabbroids occur in some [[batholith]]s but these rocks are relatively minor components of these very large intrusions because their iron and calcium content usually makes gabbro and gabbroid magmas too dense to have the necessary buoyancy.{{sfn|Philpotts|Ague|2009|p=102}} However, gabbro is an essential part of the oceanic crust, and can be found in many [[ophiolite]] complexes as layered gabbro underling [[sheeted dike complex]]es and overlying [[ultramafic]] rock derived from the [[Earth's mantle]]. These layered gabbros may have formed from relatively small but long-lived [[magma chamber]]s underlying [[mid-ocean ridge]]s.{{sfn|Philpotts|Ague|2009|pp=370-374}}

Layered gabbros are also characteristic of [[lopolith]]s, which are large, saucer-shaped intrusions that are primarily [[Precambrian]] in age. Prominent examples of lopoliths include the [[Bushveld Complex]] of South Africa, the [[Muskox intrusion]] of the [[Northwest Territories]] of Canada, the [[Rum layered intrusion]] of Scotland, the [[Stillwater complex]] of Montana, and the layered gabbros near [[Stavanger]], Norway.{{sfn|Philpotts|Ague|2009|pp=95-99}} Gabbros are also present in [[Stock (geology)|stock]]s associated with [[Alkaline magma series|alkaline volcanism]] of [[continental rifting]].{{sfn|Philpotts|Ague|2009|p=99}}