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An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed, and often emplaced onto continental crustal rocks. The Greek word ὄφις, ophis ( snake ) is found in the name of ophiolites, because of the superficial texture of some of them.
Ophiolites are sequences of mafic to ultramafic rock generally believed to represent ancient oceanic lithosphere.They are distributed all across the world being all of them located at present or past orogenic belts, sites of mountain building processes.
The Samail Ophiolite, also known as the Semail Ophiolite, is a large, ancient geological formation in Oman and the United Arab Emirates in the Arabian Peninsula. [2] It is one of the world's largest and best-exposed segments of oceanic crust , made of volcanic rocks and ultramafic rocks from the Earth's upper mantle that was overthrust onto the ...
Plutonic rocks are rare in this section and sheeted dyke intrusions are absent. The second group of ophiolite remnants located in the northwest and central Coast Ranges contain ultramafic rocks, gabbro, basalt, and are commonly overlain by tuffs or volcanic breccias. Sheeted dykes are only present in a few ophiolite remnants in this region.
This assemblage consists of deep-marine sedimentary rock (chert, limestone, clastic sediments), volcanic rocks (pillow lavas, volcanic glass, volcanic ash, sheeted dykes and gabbros) and peridotite (mantle rock). [6] John McPhee describes ophiolite formation by obduction as "where ocean crust slides into a trench and goes under a continent ...
The ultramafic ophiolite sequences which have been obducted onto continental crust are typically underlain by a mélange. Smaller-scale localized mélanges may also occur in shear or fault zones, where coherent rock has been disrupted and mixed by shearing forces.
Eclogite (/ ˈ ɛ k l ə dʒ aɪ t /) is a metamorphic rock containing garnet (almandine-pyrope) hosted in a matrix of sodium-rich pyroxene . Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, zoisite, dolomite, corundum and, rarely, diamond. The chemistry of primary and accessory minerals ...
Pelayo and Weins have postulated that some tsunami events have resulted from rupture through the sedimentary rock along the basal decollement of an accretionary wedge. [9] Backthrusting of the rear of the accretionary wedge, arcward over the rocks of the forearc basin, is a common aspect of accretionary tectonics.