{{Short description|Igneous rock}} {{Infobox rock |name = Troctolite |alternative_name = |type = Mafic |type_link = Mafic_Rock |image = Troctolite76535.jpg |image_size = |alt = |caption = Troctolite 76535 from the Apollo 17 landing site |coordinates = |composition = olivine, calcic plagioclase, minor pyroxene |composition_secondary = }} '''Troctolite''' {{IPAc-en|ˈ|t|r|ɒ|k|t|ə|l|aɪ|t}} (from Greek τρώκτης 'trout' and λίθος 'stone') is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene. It is an olivine-rich anorthosite, or a pyroxene-depleted relative of gabbro. However, unlike gabbro, no troctolite corresponds in composition to a partial melt of peridotite. Thus, troctolite is necessarily a cumulate of crystals that have fractionated from melt.<ref>{{Cite journal|last1=Emeleus|first1=C. H.|last2=Troll|first2=V. R.|date=2014-08-01|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|issn=0026-461X|doi-access=free|bibcode=2014MinM...78..805E }}</ref>
Troctolite is found in some layered intrusions such as in the Archean Windimurra intrusion of Western Australia, the Voisey's Bay nickel-copper-cobalt magmatic sulfide deposit of northern Labrador,<ref>[http://gac.esd.mun.ca/gac_2001/seven/sub_program.asp?sess=98&form=10&abs_no=237 Sulphide segregation in the Mushuau Intrusion of northern Labrador as recorded by nickel-in-olivine magmatic stratigraphy] {{Webarchive|url=https://web.archive.org/web/20171023230922/http://gac.esd.mun.ca/gac_2001/seven/sub_program.asp?sess=98&form=10&abs_no=237 |date=2017-10-23 }} abstract, BRADLEY, L.A. and SYLVESTER, P.J., Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NF, A1B 3X5</ref> the Stillwater igneous complex of Montana, the Duluth Complex of the North American Midcontinent Rift,<ref name="PacesMiller1993">{{cite journal|last1=Paces|first1=James B.|last2=Miller|first2=James D.|title=Precise U-Pb ages of Duluth Complex and related mafic intrusions, northeastern Minnesota: Geochronological insights to physical, petrogenetic, paleomagnetic, and tectonomagmatic processes associated with the 1.1 Ga Midcontinent Rift System|journal=Journal of Geophysical Research: Solid Earth|volume=98|issue=B8|year=1993|pages=13997–14013|issn=0148-0227|doi=10.1029/93JB01159|bibcode=1993JGR....9813997P }}</ref> and the Tertiary Rhum layered intrusion of the island of Rùm, Scotland.<ref>https://www.turnstone.ca/rhumal.htm Troctolite (allivalite): Isle of Rhum, northwestern Scotland</ref> Troctolite is also found, for example, in the Merensky Reef of the Bushveld Igneous Complex, South Africa and in the Lizard complex in Cornwall.<ref>[http://www.projects.ex.ac.uk/geomincentre/06The%20Lizard.pdf The Lizard]</ref>
==References== {{Commons category|Troctolite}} {{Reflist}} * Blatt, Harvey and Robert J. Tracy, 1996, ''Petrology: Igneous, Sedimentary and Metamorphic,'' 2nd ed., p. 72, Freeman, {{ISBN|0-7167-2438-3}} {{Rock type}}
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Category:Igneous rocks Category:Mafic rocks