What is the origin of peridotite?
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.
Where is peridotite found?
Layered intrusions with cumulate peridotite are typically associated with sulfide or chromite ores. Sulfides associated with peridotites form nickel ores and platinoid metals. Most of the platinum used in the world today is mined from the Bushveld Igneous Complex in South Africa and the Great Dyke of Zimbabwe.
What type of magma is formed by peridotite?
Basaltic magma forms when peridotite is partially melted. Basalt and peridotite differ in composition because rocks are mixtures of minerals, but each mineral has its own melting temperature. Some minerals start melting earlier and form basaltic magma which migrates upward because of lower density.
What layer of the Earth is mainly made up of peridotite?
Earth’s mantle is thought to be composed mainly of peridotite. Some of the occurrences of peridotite on Earth’s surface are thought to be rocks from the mantle that have been brought up from depth by deep-source magmas. Ophiolites and pipes are two structures that have brought mantle peridotite to the surface.
What type of igneous rock is peridotite?
Intrusive
Peridotite
| Type | Igneous Rock |
|---|---|
| Texture | Phaneritic (Coarse-grained) |
| Origin | Intrusive/Plutonic |
| Chemical Composition | Ultramafic |
| Color | Medium Green |
How are Pyroxenites formed?
Pyroxenites can be formed as cumulates in ultramafic intrusions by accumulation of pyroxene crystals at the base of the magma chamber. Here they are generally associated with gabbro and anorthite cumulate layers and are typically high up in the intrusion.
Is peridotite found in oceanic crust?
It is found on land as part of oceanic crust sequences called ophiolites which have been thrust in or on to a continental mass, or as localised intrusions.
What kind of magma is made the partial melting of mantle peridotite?
mafic/basaltic magmas
In general, melting of a mantle source (garnet peridotite) results in mafic/basaltic magmas. Melting of crustal sources yields more siliceous magmas. In general more siliceous magmas form by low degrees of partial melting.
Is the mantle made of peridotite?
Summary. The mantle is composed of solid peridotite. Conduction from the core heats the lower mantle.
What is characteristic of peridotite?
Peridotite is a very dense, coarse-grained, olivine-rich, ultra- mafic intrusive rock. It is noted for its low silica content, and contains very little or no feldspar ( orthoclase, plagioclase). It is a common component of oceanic lithosphere, and is derived from the upper mantle.
Where is Dunite formed?
Dunite is rarely found within continental rocks, but where it is found, it typically occurs at the base of ophiolite sequences where slabs of mantle rock from a subduction zone have been thrust onto continental crust by obduction during continental or island arc collisions (orogeny).
How is biotite formed?
Biotite in the majority of cases forms when clay-rich sedimentary rocks are buried deep enough for the clay minerals to metamorphose to it. Biotite also forms in impure metamorphosed carbonate rocks and in metabasic rocks.
What are found at the oceanic crust?
Oceanic crust is about 6 km (4 miles) thick. It is composed of several layers, not including the overlying sediment. The topmost layer, about 500 metres (1,650 feet) thick, includes lavas made of basalt (that is, rock material consisting largely of plagioclase [feldspar] and pyroxene).
Where does magma come from?
Magma originates in the lower part of the Earth’s crust and in the upper portion of the mantle. Most of the mantle and crust are solid, so the presence of magma is crucial to understanding the geology and morphology of the mantle.
What is peridotite igneous rock?
peridotite, a coarse-grained, dark-coloured, heavy, intrusive igneous rock that contains at least 10 percent olivine, other iron- and magnesia-rich minerals (generally pyroxenes), and not more than 10 percent feldspar.
How do we know peridotite makes up the mantle?
They know this because of seismic waves, meteorites, and the heat that comes from inside the planet. Mantle rock is mostly peridotite, which is rich in iron and magnesium (Figure below). Peridotite is rare at Earth’s surface. The rock of the mantle is mostly peridotite.
Is Peridot igneous sedimentary or metamorphic?
Peridot crystals form in magma from the upper mantle and are brought to the surface by tectonic or volcanic activity where they are found in extrusive igneous rocks.
Is dunite and peridotite?
How are dunite formed?
Dunite occurs in layered, gabbroic igneous complexes (see gabbro). It probably forms from the accumulation of dense, early crystallizing grains of olivine that sink to the bottom of low silica magma. Intrusions of dunite form sills or dikes. Some dunite has been altered to form serpentine.
Where is biotite found on Earth?
Biotite occurs in the lava of Mount Vesuvius, at Monzoni, and many other European locations. In the United States, it is found in the pegmatites of New England, Virginia and North Carolina, as well as in the granite of Pikes Peak, Colorado. Biotite was named in honor of the French physicist Jean Baptiste Biot.