Ophiolite
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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.
Ordovician ophiolite in Gros Morne National Park, Newfoundland
Chromitic serpentinite, Bay of Islands Ophiolite, Lewis Hills, Newfoundland
Chromitite ore with chromite (black) & talc and/or antigorite (whitish). Shetland Ophiolite Complex, ~425-500 Ma. Shetland Islands, North Sea, UK
A simplified structure of an ophiolite suite: axial magma chamber pelagic sediments pillow basalts sheeted basaltic dykes intrusive, layered gabbro dunite/peridotite cumulates
Ultramafic rock
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Ultramafic rocks are igneous and meta-igneous rocks with a very low silica content, generally >18% MgO, high FeO, low potassium, and are usually composed of greater than 90% mafic minerals. Earth's ma
Peridotite, a type of ultramafic rock
Melilitite from Hohenstoffeln (Hegau)