A sequence of rocks characterized by ultramafic rocks at the base and (in ascending order) gabbro, sheeted dikes, pillow lavas, and deep-sea sediments. The typical sequence of rocks constituting the oceanic crust. We see ophiolites when they have been abducted onto the edge of continental crust.
A group of mafic and ultramafic igneous rocks derived by metamorphism, whose origin is associated with an early phase of the development of a geosyncline.
(o'-phi-o-lite) A stratigraphic section consisting of a suite of mafic and ultramafic igneous rocks and associated marine sediments and their metamorphic equivalents representing the oceanic crust and upper part of the mantle formed either at a oceanic spreading ridge or in a back arc basin behind a island arc. A complete section consists of a basal peridotite representing the upper layer of oceanic mantle, layered ultramafic and mafic igneous rocks ranging in composition from peridotite through gabbro, a dike complex consisting of steeply inclined basic feeder dikes, basaltic lavas and pillow lavas (formed by submarine eruption of basaltic lavas), capped by a layer of chalcedony and other marine sediments. This sequence of rocks is typically extensively altered to serpentine and other secondary minerals, and strongly tectonically deformed.
A slice of oceanic crust that has been thrust onto continental crust.
Forms during subduction. Sequence of rock that represents a part of the oceanic crust (and in some cases upper mantle) that has been forced up onto a continental landmass during subduction (i.e. instead of being subducted with the rest of the oceanic plate, the ophiolite section becomes stuck on the continental landmass).
a group of basic to ultrabasic igneous rocks and deep sea sediments (cherts) thought to represent oceanic lithosphere (principally crustal) material, which is tectonically emplaced onto an island arc or continental margin.
An assemblage of mafic (ferro-magnesium mineral-rich rock type) and ultramafic igneous rocks, including their metamorphic equivalents (like serpentinite) formed from later metamorphism of the mafic and ultramafic rocks. The origin of this assemblage is associated with the early development of a geosyncline (a large downwarped basin or trough in the Earth's crust into which large amounts of sediment and volcanics accumulate).
a sequence of rocks that are believed to be a section of oceanic crust with the underlying mantle rock
association of basic ( basalt, dolerite, gabbro) and ultrabasic rocks ( peridotite) deriving from obduction of oceanic crust.
any of a group of mafic and ultramafic igneous rocks, ranging from basalt to peridotite and including those rich in serpentine. [AHDOS
