Editing Obduction (section)

{{Short description|Overthrusting of oceanic lithosphere onto continental lithosphere at a convergent plate boundary}}
{{distinguish|Abduction (disambiguation){{!}}Abduction}}
{{about|the geological process|the video game|Obduction (video game)|the medical procedure|autopsy}}
'''Obduction''' is a geological process whereby denser [[oceanic crust]] (and even upper [[mantle (geology)|mantle]]) is scraped off a descending ocean [[Plate tectonics|plate]] at a [[Convergent boundary|convergent plate boundary]] and [[thrust fault|thrust]] on top of an adjacent plate.<ref>{{Cite web|title=Obduction|url=https://www.dictionary.com/browse/obduction}}</ref><ref>{{Cite web|title=Plate Tectonics > Glossary > M – R|url=https://www.geolsoc.org.uk/Plate-Tectonics/Glossary/M-R}}</ref> When oceanic and continental plates converge, normally the denser oceanic crust sinks under the [[continental crust]] in the process of [[subduction]].<ref>{{Cite journal|title=Geodynamic models of continental subduction and obduction of overriding plate forearc oceanic lithosphere on top of continental crust|year=2015|doi=10.1002/2015TC003884|url=https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015TC003884|url-status=dead|last1=Edwards|first1=Sarah J.|last2=Schellart|first2=Wouter P.|last3=Duarte|first3=Joao C.|journal=Tectonics|volume=34|issue=7|pages=1494–1515|bibcode=2015Tecto..34.1494E|s2cid=129467525|access-date=2021-09-28|archive-date=2021-09-28|archive-url=https://web.archive.org/web/20210928074859/https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015TC003884|doi-access=free}}</ref> Obduction, which is less common, normally occurs in plate collisions at [[orogenic belts]] (some of the material from the subducting oceanic plate is emplaced onto the continental plate)<ref name="Dewey, J. F. 1975">Dewey, J. F., 1975. The role of ophiolite obduction in the evolution of the Appalachian/Caledonian orogenic belt. In: N. Bogdanov (editor), Ophiolites in the Earth’s Crust. Acad. Sci. U.S.S.R. (in press)</ref> or [[back-arc basins]] (regions where the edge of a continent is pulled away from the rest of the continent due to the stress of plate collision).<ref>{{cite journal |last1= Scliffke|first1= Nicholas|last2= van Hunen|first2= Jeroen|last3= Gueydan|first3= Frédéric|last4= Magni|first4= Valentina|last5= Allen|first5= Mark B.|date= 2021-08-12|title= Curved orogenic belts, back-arc basins, and obduction as consequences of collision at irregular continental margins|journal= Geology|volume= 49|issue= 12|pages= 1436–1440|doi= 10.1130/G48919.1|bibcode= 2021Geo....49.1436S|s2cid= 238718200|doi-access= free}}</ref>

Obduction of oceanic [[lithosphere]] produces a characteristic set of rock types called an [[ophiolite]]. This assemblage consists of deep-marine sedimentary rock ([[chert]], [[limestone]], [[Clastic rock|clastic]] sediments), volcanic rocks ([[pillow lava]]s, [[volcanic glass]], [[volcanic ash]], [[sheeted dyke complex|sheeted dykes]] and [[gabbro]]s) and [[peridotite]] (mantle rock).<ref name="Robinson et al. 2008">{{cite journal|last1=Robinson|first1=Paul T.|last2=Malpas|first2=John|last3=Dilek|first3=Yildirim|last4=Zhou|first4=Mei-fu|title=The significance of sheeted dike complexes in ophiolites|journal=GSA Today|date=2008|volume=18|issue=11|pages=4–10|doi=10.1130/GSATG22A.1|bibcode=2008GSAT...18k...4R |url=http://www.geosociety.org/gsatoday/archive/18/11/pdf/i1052-5173-18-11-4.pdf|doi-access=free}}</ref> John McPhee describes ophiolite formation by obduction as "where ocean crust slides into a trench and goes under a continent, [and] a part of the crust—i.e., an ophiolite—is shaved off the top and ends up on the lip of the continent."<ref>{{cite book |last= McPhee|first= John|date= 1998|title= Annals of the Former World|location= New York|publisher= Farmer, Strauss, and Giroux|page= 505}}</ref>

Obduction can occur where a fragment of continental [[crust (geology)|crust]] is caught in a subduction zone with resulting overthrusting of oceanic [[mafic]] and [[Ultramafic rock|ultramafic]] rocks from the mantle onto the continental crust. Obduction often occurs where a small [[Plate tectonics|tectonic plate]] is caught between two larger plates, with the crust (both [[island arc]] and oceanic) welding onto an adjacent [[continent]] as a new [[terrane]]. When two continental plates collide, obduction of the oceanic crust between them is often a part of the resulting [[orogeny]].{{Citation needed|date=August 2012}}