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Ophiolite assemblages in the Alps and some other collisional mountain belts are not formed during subduction, but rather represent the thinned margin of the continent that forms during rifting and continental drift.
This incipient ocean crust remains locked to the continental margin when the ocean basin closes, emplacing the incipient ocean crust into the collision zone.
Most ophiolites can be divided into one of two groups: Tethyan and Cordilleran.
Tethyan ophiolites are characteristic of those that occur in the eastern Mediterranean sea area, e.g., Troodos in Cyprus and in the Middle East such as Semail in Oman, which consist of relatively complete rock series corresponding to the classic ophiolite assemblage and which have been emplaced onto a passive continental margin more or less intact (Tethys is the name given to the ancient sea that once separated Europe and Africa).
In detail there are problems, with many ophiolites exhibiting thinner accumulations of igneous rock than are inferred for oceanic crust.
Another problem relating oceanic crust and ophiolites is that the thick gabbro layer of ophiolites calls for large magma chambers beneath mid-ocean ridges.
Consequently, some of the classic ophiolite occurrences thought of as being related to seafloor spreading (Troodos in Cyprus, Semail in Oman) were found to be "SSZ" ophiolites, formed by rapid extension of fore-arc crust during subduction initiation.
A fore-arc setting for most ophiolites also solves the otherwise-perplexing problem of how oceanic lithosphere can be emplaced on top of continental crust.
These ophiolites sit on subduction zone accretionary complexes (subduction complexes) and have no association with a passive continental margin.
Often, ore bodies such as iron-rich sulfide deposits are found above highly altered epidosites (epidote-quartz rocks) that are evidence of (the now-relict) black smokers, which continue to operate within the seafloor spreading centers of ocean ridges today..