A diapir ( //; French, from Greek diapeirein, to pierce through) is a type of intrusion in which a more mobile and ductily-deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh-Taylor instability-type structures in regions with low tectonic stress such as in the Gulf of Mexico to narrow dikes of material that move along tectonically-induced fractures in surrounding rock. The term was introduced by the Romanian geologist Ludovic Mrazek, who was the first to understand the principle of salt intrusion and plasticity. The term "diapir" may be applied to igneous structures, but it is more commonly applied to non-igneous, relatively cold materials, such as salt domes and mud diapirs.
Diapirs commonly intrude vertically upward along fractures or zones of structural weakness through denser overlying rocks because of density contrast between a less dense, lower rock mass and overlying denser rocks. The density contrast manifests as a force of buoyancy. The process is known as diapirism. The resulting structures are also referred to as piercement structures.
In the process, segments of the existing strata can be disconnected and pushed upwards. While moving higher, they retain much of their original properties such as pressure, which can be significantly different from that of the shallower strata they get pushed into. Such overpressured Floaters pose a significant risk when trying to drill through them. There is an analogy to a Galilean thermometer.
Rock types such as evaporitic salt deposits, and gas charged muds are potential sources of diapirs. Diapirs also form in the earth's mantle when a sufficient mass of hot, less dense magma assembles. Diapirism in the mantle is thought to be associated with the development of large igneous provinces and some mantle plumes.
Explosive, hot volatile rich magma or volcanic eruptions are referred to generally as diatremes. Diatremes are not usually associated with diapirs, as they are small-volume magmas which ascend by volatile plumes, not by density contrast with the surrounding mantle.
Economic importance of diapirs
Diapirs or piercement structures are structures resulting from the penetration of overlaying material. By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping petroleum and natural gas. Igneous intrusions themselves are typically too hot to allow the preservation of preexisting hydrocarbons.
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- ^ Don L Anderson (2007). "The eclogite engine: Chemical geodynamics as a Galileo thermometer". In Gillian R. Foulger, Donna M. Jurdy. Plates, plumes, and planetary processes; Volume 430 of Special Papers. American Geological Society. ISBN 0813724309. http://books.google.com/books?id=l9a7tIJBYbkC&pg=PA47.
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diapir — diapír s. n. (sil. di a ), pl. diapíre Trimis de siveco, 10.08.2004. Sursa: Dicţionar ortografic DIAPÍR s.n. (geol.) Cută anticlinală caracterizată prin prezenţa unui sâmbure de roci plastice care străbat rocile acoperitoare. [pron. di a . / cf … Dicționar Român
diapir — ● diapir nom masculin (grec diapeirein, transpercer) Structure géologique correspondant à un pli résultant de l ascension d un matériel plastique au travers de formations plus denses … Encyclopédie Universelle
Diapir — [griechisch] der, s/ e, größerer, pilz , kuppel oder blasenförmiger Gesteins oder Magmenkörper, der v. a. aufgrund geringerer Dichte als im Hangenden und/oder aufgrund großer Plastizität die überlagernden Schichten durchbrochen hat und, Klüfte … Universal-Lexikon
diapir — [dī′ə pir΄] n. Geol. a dome formation in which the rigid top layers have been split open by pressure from an underlying plastic core diapiric [dī΄ə pir′ik] adj … English World dictionary
Diapir — Une lampe à lave illustre de manière simple le principe du diapir En géologie, un diapir (du grec diapeirein, percer au travers) est une structure plus ou moins globuleuse, résultant de la remontée de roches plus légères à travers des roches plus … Wikipédia en Français
Diapir — Lavalampe Anschauungsobjekt für das Phänomen des Diapirismus Ein Diapir (von altgriechisch διαπείρειν diapeirein durchdringen) ist in der Geologie ein aufsteigender Bereich oder Körper eines Materials (z. B. Magma) mit einer geringeren Dichte als … Deutsch Wikipedia
diapir — noun Etymology: French, probably from Greek diapeirein to drive through, from dia + peirein to pierce; akin to Greek poros passage more at fare Date: 1918 an anticlinal fold in which a mobile core has broken through brittle overlying rocks •… … New Collegiate Dictionary
diapir — diapiric /duy euh pir ik/, adj. /duy euh pear /, n. Geol. a dome, or anticline, the upper regions of which have been ruptured and penetrated by material squeezed up from below. Cf. plume (def. 10), salt dome. [1915 20; < F, said to be < Gk… … Universalium
diapir — noun An intrusion of a ductile rock into an overburden … Wiktionary
Diapir — Di|a|pir 〈m.; Gen.: s, Pl.: e; Geol.〉 zumeist aus Salz bestehender Gesteinskörper, der bei Faltungen durch höhere Gesteinsschichten gepresst wurde, Salzdom, Salzhorst, Salzstock [Etym.: zu grch. diapeirein »durchbohren«] … Lexikalische Deutsches Wörterbuch