Ophiolite

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Related to Ophiolites: Benioff Zone, Turbidites

ophiolite

[′äf·ē·ə‚līt]
(petrology)
A distinctive assemblage of mafic plus ultramafic rocks, generally considered to be fragments of oceanic lithosphere that have been tectonically emplaced onto continental margins and island arcs.

Ophiolite

 

a group of ultrabasic and basic intrusive (dunites, peridotites, pyroxenites, various gabbros, tonalites), effusive (primarily basalts and their tuffs), and sedimentary (pelagic oceanic deposits) rocks that are found together.

The concept of ophiolite was introduced by the Swiss scientist G. Steinmann in 1905. Ophiolites are usually associated with the manifestation of magmatism in the early stages of the formation of geosynclinal systems.

During the 1960’s and 1970’s, in connection with intensive study of the oceans, the problem of ophiolites attracted a great deal of attention. Scientists began viewing ophiolites in folded regions as relics of oceanic crust tectonically moved to the margins of the continents. Moreover, serpentinized ultrabasites are viewed as part of the mantle; gabbroids, as the “basalt layer”; and the effusive sedimentary series, as an analogue of the “first” and “second” layers of the present-day oceanic crust. A partial disruption of this sequence of rocks results from the tectonic factors that cause the development of a specific geological formation, a serpentinite rock, in which all members of the ophiolite group, as well as other rocks, are chaotically intermixed and “cemented together” by serpentinites.

Ophiolites are a common component of the earth’s linear folded regions. They are widespread in geosynclinal systems, forming within them protrusions (rock masses tectonically intruded in the solid state into the deposits covering them) or nappes thrust over the miogeosynclinal or platform sediments that overlie the continental crust. The study of ophiolites is important in discovering deposits of chromium, nickel, platinum, gold, mercury, and other ores genetically related to ophiolites, and for studying the historical development of the earth’s crust.

REFERENCES

Peive, A. V. “Okeanicheskaia kora geologicheskogo proshlogo.” Geotektonika, 1969, no. 4.
Hess, H. H. “History of Ocean Basins.” In Buddington Volume. New York, 1962.

A. L. KNIPPER

References in periodicals archive ?
At the time, ophiolites offered a way to investigate how ocean crust forms, Dick said--but they were fossilized and extracted out of their original contexts, and, as such, provided limited value for revealing whatever dynamic processes are going on at the Moho.
Again the patchy Qahlah and/or shallow marine Simsima Formation overlie ophiolites and the Simsima Formation is again extremely fossiliferous.
This piece of the Hajar Mountain, between Oman and UAE, is the biggest exposed ophiolite complex in the world.
The Noorabad ophiolite is part of the High Zagros situated between the Zagros Folded Belt and SanandajSirjan Zone (Fig.
1984: Magmatismes du Mesozoique a F Actuei en Amerique Centrale: L'example de Costa Rica, des Ophiolites aux Andesites.
The Upper Cretaceous sequence includes (from base to top): Semail ophiolites (serpentine andserpentinized predotite), the oldest exposed rocks in Al-Ain area, Qahlah Formation (red and yellow Unfossiliferous clast-supported conglomerates of serpentized predotite, derived from the Semail ophiolites, Simsima Formation (marine bioclastics limestones with rudists, corals and echinids, it is disconformably overlies the Qahlah Formation (Hamdan and Anan, 1993).
Magmatismes du Mesoique a l'Actuel en Amerique Centrale L'exemple du Costa Rica, des ophiolites aux andesites, These doctorat d'Etat, Universite de Paris VI, 318 pp.
Dr Martin Flower from University of Illinois gave presentation on 'Plate Collision End-games: A Possible Role for Collision-Induced Mantle Extrusion' and said his current work focuses on ophiolites in the complex NW India-Asia syntaxis where a collage of accreted micro-continents is associated with a complex sequence of neo-Tethyan basin closure, in many cases post-dating those associated with the 'hard' of India.