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Ultramafic rocks are igneous rocks with very low silica content (less than 45%) and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). Ultramafic rocks are typical of the Earth's mantle.
Rock types include intrusive dunite and peridotite and rare volcanic komatiite and picrite. Most surface exposures of ultramafic rocks occur in ophiolite complexes where deep mantle derived rocks have been obducted into continental crust along and above subduction zones.
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