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Peridotite, a type of ultramafic rock. Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usually composed of greater than 90% mafic minerals (dark colored, high magnesium and iron content).
Lherzolite – an ultramafic and ultrabasic rock that is composed of olivine and pyroxene – An ultramafic rock, essentially a peridotite Monzodiorite – igneous rock Pages displaying wikidata descriptions as a fallback An intrusive igneous rock intermediate in composition between diorite and monzonite
Such rocks typically contain less than 45% silica. Ultramafic rocks are further classified by their relative proportions of olivine, orthopyroxene, clinopyroxene, and hornblende, which are the most abundant families of mafic minerals in most ultramafic rocks. Peridotite is then defined as coarse-grained ultramafic rock in which olivine makes up ...
Blue Ridge Ophiolite is an ultramafic series of pods found in the Blue Ridge Mountains of the Appalachian mountain chain. [1] The pods formed before the Taconic orogeny. [1] Throughout the middle and late Ordovician period, the rocks were affected by regional metamorphism leading to resulting in altered mineralogy for some pods. [2]
The change of rock composition most responsible for the creation of magma is the addition of water. Water lowers the solidus temperature of rocks at a given pressure. For example, at a depth of about 100 kilometers, peridotite begins to melt near 800 °C in the presence of excess water, but near 1,500 °C in the absence of water. [ 69 ]
Pages in category "Ultramafic rocks" The following 15 pages are in this category, out of 15 total. This list may not reflect recent changes. ...
The width of the intrusions vary from 3 to 12 km (7.5 mi). The Great Dyke is unusual in that most ultramafic layered intrusions display near horizontal sill or sheet forms. The well-layered lower units of ultramafic rocks comprising the Great Dyke are locally overlain by erosional remnants of gabbroic rock. These mark the centres of the four ...
As indicated by the name, the ophiolite is defined by the presence of ultramafic rocks in the California Coast Ranges. Pillow lavas and oceanic basalts are among the most common rocks found within the formation.