# Phacolith

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Phacolith
> Markdown URL: https://mediated.wiki/source/Phacolith.md
> Source: https://en.wikipedia.org/wiki/Phacolith
> Source revision: 1352388888
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{short description|Lens-shaped igneous intrusion}}
thumb|right|Cross-sectional diagram of phacoliths (red) in older folded rocks
A '''phacolith''' is a [pluton](/source/pluton) of [igneous rock](/source/igneous_rock) parallel to the bedding plane or [foliation](/source/Foliation_(geology)) of folded [country rock](/source/Country_rock_(geology)). More specifically, it is a typically lens-shaped pluton that occupies either the crest of an [anticline](/source/anticline) or the trough of a [syncline](/source/syncline). In rare cases the body may extend as a [sill](/source/Sill_(geology)) from the crest of an anticline through the trough of an adjacent syncline, such that in [cross section](/source/cross_section_(geometry)) it has an ''S'' shape. In intensely folded terrain the hinge of folds would be areas of reduced pressure and thus potential sites for [magma](/source/magma) migration and emplacement.

The term was coined and initially defined by [Alfred Harker](/source/Alfred_Harker) in his ''The Natural History of Igneous Rocks'' in 1909.

==Examples==
* in the Franklin and Hamburg areas of [Sussex County, New Jersey](/source/Sussex_County%2C_New_Jersey), United States<ref name="BakerUSGS1970">{{cite book | title=Geology and Magnetite Deposits of the Franklin Quadrangle and Part of the Hamburg Quadrangle, New Jersey (USGS Professional Paper 638) | publisher=[USGS](/source/USGS) | last1=Baker | first1=D.R. | last2=Buddington | first2=A.F. | url=https://pubs.usgs.gov/pp/0638/report.pdf | year=1970 | page=30 | location=Washington D.C.}}</ref>
* the Omey pluton in [Ireland](/source/Ireland)<ref name="McCarthyEtAl2015">{{cite journal | url=https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/late-caledonian-transpression-and-the-structural-controls-on-pluton-construction-new-insights-from-the-omey-pluton-western-ireland/1574E9D4256A4C623BA36B4F5C66C837 | title=Late Caledonian transpression and the structural controls on pluton construction; new insights from the Omey Pluton, western Ireland | first1=William | last1=McCarthy | first2=R. John | last2=Reavy | first3=Carl T. | last3=Stevenson | first4=Michael S. | last4=Petronis | journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh | year=2015 | volume=106 | issue=1 | pages=11–28 | doi=10.1017/S1755691015000201| bibcode=2015EESTR.106...11M | s2cid=132563143 | url-access=subscription }}</ref>
* near Bayalan, [Ajmer district](/source/Ajmer_district), Rajasthan in India<ref name="Dasgupta2011">{{cite journal | title=Characteristics of pegmatoidal granite exposed near Bayalan, Ajmer district, Rajasthan | first1=N. | last1=Dasgupta | first2=T. | last2=Paljoydeep | first3=S. | last3=Ghosh | journal=Journal of Earth System Science | year=2011 | volume=120 | issue=4 | pages=617–626 | doi=10.1007/s12040-011-0100-7| bibcode=2011JESS..120..617D | doi-access=free }}</ref>
*[Corndon Hill](/source/Corndon_Hill), in [Shropshire](/source/Shropshire), England, United Kingdom<ref>{{Cite book|last=Leong|first=Goh Cheng|url=https://books.google.com/books?id=XhJ4RAAACAAJ&q=certificate+physical+and+human+geography|title=Certificate Physics And Human Geography; Indian Edition|date=1995-10-27|publisher=Oxford University Press|isbn=978-0-19-562816-6|pages=21|language=en}}</ref><ref name="EarpHains1971">{{cite book | url=https://webapps.bgs.ac.uk/Memoirs/docs/B01350.html | title=The Welsh Borderland | series=British Regional Geology | publisher=Her Majesty’s Stationery Office | first1=J.R. | last1=Earp | first2=B.A. | last2=Hains | date=1971 | edition=3rd | location=London}}</ref>

==See also==
* [Laccolith](/source/Laccolith)
*[Lopolith](/source/Lopolith)
*[Batholith](/source/Batholith)

==References==
{{Reflist}}
*Davis A. Young (2003) ''Mind Over Magma: The Story of Igneous Petrology'', page 335, Princeton University Press. {{ISBN|0-691-10279-1}}
*American Geological Institute. ''Dictionary of Geological Terms''.  New York:  Dolphin Books, 1962.

Category:Igneous rocks
Category:Igneous petrology

{{Petrology-stub}}

---
Adapted from the Wikipedia article [Phacolith](https://en.wikipedia.org/wiki/Phacolith) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Phacolith?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.