ophiolites

An Ophiolite is a section of the Earth's oceanic crust and the underlying upper mantle that has been uplifted or emplaced to be exposed within continental crustal rocks. Ophio is Greek for "snake", lite means "stone".The term ophiolite was originally used by Alexandre Brongniart (1813) for an assemblage of green rocks (serpentine, diabase) in the Alps; Steinmann (1927) later modified its use to include serpentine, pillow lava, and chert ("Steinmann's trinity"), again based on occurrences in the Alps. The term was little used in other areas until the late 1950's to early 1960's, with the recognition that this assemblage provided an analog for oceanic crust and the process of seafloor spreading. This recognition was tied to two events: (1) the observation of magnetic anomaly stripes on the seafloor, parallel to oceanic ridge systems, interpreted by Vine and Matthews (1963) to represent the formation of new crust at the oceanic ridge and its subsequent spreading away from that ridge, and (2) the observation of a sheeted dike complex within the Troodos ophiolite (Cyprus) by Gass and co-workers, which must have formed by 100% intrusion of new magma, since no older wall rocks are preserved within the complex (Gass 1968). Moores and Vine (1971) concluded that the sheeted dike complex at Troodos could only form by a process similar to the sea-floor spreading proposed by Vine and Matthews (1963). Thus, it became widely accepted that ophiolites represent oceanic crust that had been emplaced on land.
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