Ophiolite

An ophiolite is a sequence of oceanic crust and upper mantle rocks emplaced on land, usually during tectonic collision. Its rock layers preserve fragments of oceanic lithosphere.

Oceanic crust: The basaltic outer layer of Earth beneath most ocean basins. Ophiolites preserve pieces of this seafloor layer on land.
Obduction: The tectonic emplacement of oceanic lithosphere over continental or island-arc crust. This process brings oceanic rocks onto land to form many ophiolites.
Semail Ophiolite: A large, well-preserved ophiolite exposed in the mountains of Oman and the United Arab Emirates. Its extensive exposures preserve a detailed section of oceanic crust and mantle.
Gustav Steinmann: A German geologist who studied the association of serpentine, diabase, and pillow lava in the Alps. His observations helped define the classic rock association later called the Steinmann trinity.
Chromite: A chromium-bearing oxide mineral that is the principal ore of chromium. Some ophiolite mantle rocks host economically significant chromite deposits.
Upper mantle: The mantle region extending from the base of the crust to about 660 kilometers depth. Ophiolites can include mantle rocks that once lay beneath oceanic crust.
Subduction: The descent of one tectonic plate beneath another into Earth's mantle. Ophiolite emplacement commonly occurs near convergent margins where subduction operates.
Troodos Ophiolite: An ophiolite complex exposed in the Troodos Mountains of Cyprus. Its rocks preserve evidence for seafloor hydrothermal activity and ancient oceanic crust.
Steinmann trinity: The association of serpentine, diabase, and pillow lava recognized in some Alpine ophiolites. It was an early field-based description of rocks now interpreted as oceanic lithosphere.
Hydrothermal circulation: The movement of heated water through permeable rocks, driven by heat and chemical gradients. Ophiolite alteration records ancient seawater circulation through oceanic crust.

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