Typical peridotite sample (dunite, left) and large olivine crystal (right)
Composition
olivine, pyroxene
Peridotite (US: /ˈpɛrɪdoʊˌtaɪt,pəˈrɪdə-/PERR-ih-doh-tyte, pə-RID-ə-) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high proportions of magnesium-rich olivine, with appreciable iron. Peridotite is derived from Earth's mantle, either as solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle. The compositions of peridotites from these layered igneous complexes vary widely, reflecting the relative proportions of pyroxenes, chromite, plagioclase, and amphibole.
Peridotite is the dominant rock of the upper part of Earth's mantle. The compositions of peridotite nodules found in certain basalts are of special interest along with diamond pipes (kimberlite), because they provide samples of Earth's mantle brought up from depths ranging from about 30 km to 200 km or more. Some of the nodules preserve isotope ratios of osmium and other elements that record processes that occurred when Earth was formed, and so they are of special interest to paleogeologists because they provide clues to the early composition of Earth's mantle and the complexities of the processes that occurred.
The word peridotite comes from the gemstone peridot, which consists of pale green olivine.[1] Classic peridotite is bright green with some specks of black, although most hand samples tend to be darker green. Peridotitic outcrops typically range from earthy bright yellow to dark green; this is because olivine is easily weathered to iddingsite. While green and yellow are the most common colors, peridotitic rocks may exhibit a wide range of colors including blue, brown, and red.
Peridotite (US: /ˈpɛrɪdoʊˌtaɪt, pəˈrɪdə-/ PERR-ih-doh-tyte, pə-RID-ə-) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals...
Ronda peridotite is a 300-square-kilometre (120 sq mi) peridotite body in Betic Cordillera, southern Spain. List of ophiolites: Mediterranean and Peri-Arabic...
which they crystallized. The ultramafic intrusives include the dunites, peridotites and pyroxenites. Other rare varieties include troctolite which has a...
primarily of basalt and gabbro. Both continental and oceanic crust rest on peridotite of the mantle.[citation needed] Rocks may melt in response to a decrease...
and norites, from which they differ by the absence of feldspar, and to peridotites, which are distinguished from them by containing more than 40% olivine...
angle is 58° to 63°. Diopside is found in ultramafic (kimberlite and peridotite) igneous rocks, and diopside-rich augite is common in mafic rocks, such...
or percolating melts interact with surrounding peridotite, and compositions of both melts and peridotite are changed. At high mantle temperatures, solid-state...
by alternate plate collisions and rifting. The mantle-derived Eocene Peridotite Nappe is the most significant and widespread unit (labelled as "Ophiolites"...
wikidata descriptions as a fallback – An ultramafic rock, essentially a peridotite Monzogranite – Biotite granite rocks that are considered to be the final...
magma chamber. Cumulate peridotite: dunite-rich layers of minerals that settled out from a magma chamber. Tectonized peridotite: harzburgite/lherzolite-rich...
Harzburgite, an ultramafic, igneous rock, is a variety of peridotite consisting mostly of the two minerals olivine and low-calcium (Ca) pyroxene (enstatite);...
be a part of the originating mantle mineralogy. Xenoliths of dunite, peridotite and spinel lherzolite in basaltic lava flows are one example. Kimberlites...
from high degrees of partial melt. Peridotite is strongly influenced by the inclusion of moisture. Craton peridotite moisture content is unusually low...
Peridot can be found in mafic and ultramafic rocks occurring in lava and peridotite xenoliths of the mantle. The gem occurs in silica-deficient rocks such...
spinels and garnets. Plagioclase can occur in lherzolites and other peridotites that crystallize at relatively shallow depths (20 – 30 km). At greater...
Dunite is the olivine-rich endmember of the peridotite group of mantle-derived rocks. Dunite and other peridotite rocks are considered the major constituents...
Oceanic lithosphere consists mainly of mafic crust and ultramafic mantle (peridotite) and is denser than continental lithosphere. Young oceanic lithosphere...
harzburgite and lherzolite, two type of peridotite. The most dominant rock type in the upper mantle, peridotite is an igneous rock consisting mostly of...
completely solid) increase with increasing pressure in the absence of water. Peridotite at depth in the Earth's mantle may be hotter than its solidus temperature...
1884 over two years before Carvill Lewis named a similar porphyritic peridotite occurring near Kimberley, South Africa, a kimberlite. It occurs as three...
pyrope is in ultramafic rocks, typically peridotite from the Earth's mantle: these mantle-derived peridotites can be attributed both to igneous and metamorphic...
Mantle-peridotite xenolith from San Carlos Indian Reservation, Gila Co., Arizona, USA. The xenolith is dominated by green peridot olivine, together with...
Fetlar which is a remnant of the Iapetus Ocean floor made up of ultrabasic peridotite and gabbro. Much of Shetland's economy depends on the oil-bearing sediments...
plates, by several processes. One process is hydration melting of mantle peridotite followed by fractional crystallization. Water from a subducting slab rises...
Lahaye, Y.; Durali, S.; Weyer, S. (2004). "Lithium isotopic signatures of peridotite xenoliths and isotopic fractionation at high temperature between olivine...
rock (e.g. gabbro, troctolite). Spinel, (Mg,Fe)(Al,Cr)2O4, is common in peridotite in the uppermost Earth's mantle, between approximately 20 km to approximately...
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