Obduction


Obduction

Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks at a convergent plate boundary. It can occur during an orogeny, or mountain-building episode.

Obduction occurs where a fragment of continental crust is caught in a subduction zone with resulting overthrusting of oceanic mafic and ultramafic rocks from the mantle onto the continental crust. Obduction often occurs where a small 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.

The characteristic rocks of obducted oceanic crust are the ophiolites; consisting of basalt, gabbro, peridotite, dunite, and eclogite. There are many examples of oceanic crustal rocks and deeper mantle rocks that have been obducted and exposed at the surface worldwide. New Caledonia is one example of recent obduction. The Klamath Mountains of northern California contain several obducted oceanic slabs. Obducted fragments also are found in Oman, Cyprus, Newfoundland, New Zealand, the Alps of Europe, and the Appalachians of eastern North America.

Most obductions appear to have initiated at back-arc basins above subduction zones[citation needed]. These basins occur where the edge of the continent collapses seawards, and extension in the back-arc basin enhances volcanism and crustal accretion. While the continental crust is being subducted, the upper lithosphere is exposed, and ophiolitic volcanism accretes metamorphic rock series. As orogeny succeeds subduction, the ophiolites and their metamorphic basement end up atop mountain ranges.

See also


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  • Obduction — Ob*duc tion, n. [L. obductio.] The act of drawing or laying over, as a covering. [Obs.] [1913 Webster] …   The Collaborative International Dictionary of English

  • Obduction — (v. lat.), die gesetzmäßige Untersuchung eines Körperzustandes, od. auch sonst eines Stoffes, dessen Ausmittelung die Grundlage einer rechtlichen Entscheidung ist, von beglaubigten Sachverständigen u. nach gesetzlichen Formen bewirkt; kommt bes.… …   Pierer's Universal-Lexikon

  • Obduction — Obduction, lat. deutsch, im weitern Sinne gerichtlich medicin. Untersuchung, im engern die gerichtlich medicin. Untersuchung eines Leichnams. Zur formellen Legalität einer O. gehören: daß dieselbe auf Befehl einer obrigkeitlichen Behörde von… …   Herders Conversations-Lexikon

  • obduction — ● obduction nom féminin (latin obductio, onis, action de couvrir) Phénomène géodynamique par lequel des portions de croûte océanique (ophiolites), ayant échappé à la subduction, sont charriées sur la marge continentale ou l arc insulaire …   Encyclopédie Universelle

  • Obduction — L obduction est le chevauchement d une croûte continentale par une croûte océanique. Elle entraîne la formation de complexes ophiolitiques (exemples : Oman, massif du Chenaillet et Mont Viso dans les Alpes, etc.) Conditions nécessaires au… …   Wikipédia en Français

  • Obduction — Ich beantrage sofortige Obduction, denn es ist reine Verleumdung, sagte der Mann zum Richter, als dieser ihm vorhielt, seine Frau habe ihn angeklagt, sie mit Arsenik vergiften zu wollen …   Deutsches Sprichwörter-Lexikon

  • obduction — noun ( s) Etymology: Latin obduction , obductio, from obductus (past participle of obducere to obduce) + ion , io ion : an act or instance of drawing or laying something (as a covering) over …   Useful english dictionary

  • obduction — ob·duc·tion (ob dukґshən) [L. obductio] a medicolegal autopsy …   Medical dictionary

  • obduction — n. concealment, covering up (Archaic) …   English contemporary dictionary

  • CHAÎNES DE MONTAGNES (typologie) — À la surface de la Terre, les zones de relief élevé qui forment ce que l’on appelle des « chaînes de montagnes» constituent un trait morphologique de première importance, comparable à celui des dorsales qui sillonnent le fond des océans. Les… …   Encyclopédie Universelle