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.
What type is dunite?
Dunite (/ˈduːˌnaɪt, ˈdʌnˌaɪt/) (also known as olivinite, not to be confused with the mineral olivenite) is
an igneous, plutonic rock, of ultramafic composition
, with coarse-grained or phaneritic texture. … Dunite is the olivine-rich end-member of the peridotite group of mantle-derived rocks.
How is dunite formed?
Cumulative dunite is
formed by fractionation of olivine from a mafic melt
. Replacive dunite is a product of the reaction between a pyroxene-bearing host rock and an olivine-saturated magma, which dissolves orthopyroxene in the host peridotite and sometimes crystallizes olivine.
How is serpentinite rock formed?
In the Franciscan Complex, it formed when
ocean water carried down with subducting ocean crust was heated and moved through upper mantle and basal ocean crust rocks
, hydrating their magnesium- and iron-rich minerals, like olive and pyroxene, to form magnesium-rich serpentine minerals.
What is so special about dunite?
Dunite is
an ultramafic plutonic rock that is composed almost exclusively of olivine
. “Ultramafic” means that mafic minerals form more than 90% on the rocks composition. … Peridotite that contains more than 90% olivine have a special name, they are called dunite (named in 1864 after Dun mountain in New Zealand).
How are komatiites formed?
Komatiites are considered to have been formed by
high degrees of partial melting
, usually greater than 50%, and hence have high MgO with low K
2
O and other incompatible elements.
What is Dunite used for?
Peridotite Uses
As
a source of valuable ores and minerals
, including chromite, platinum, nickel and precious garnet; diamonds are obtained from mica-rich peridotite (kimberlite) in South Africa.
Is dunite plutonic?
Dunite is an
igneous plutonic rock
of ultramafic composition with coarse-grained granular or phaneritic texture and often massive or layered.
Are dunite and peridotite the same?
Peridotite is a very dense, coarse-grained, olivine-rich, ultra- mafic intrusive rock. … Mineral content – generally olivine with lesser pyroxene ( augite) (dunite is dominantly olivine), always contains some metallic minerals, e.g. chromite, magnetite.
Is dunite a volcanic?
Dunite (otherwise called olivinite, not to be mistaken for the mineral olivenite) is
a volcanic, plutonic shake, of ultramafic arrangement
, with coarse-grained or phaneritic surface.
Where is eclogite found?
Eclogite is a rare and important rock because it is formed only by conditions typically found in
the mantle or the lowermost part of thickened crust
.
What type of rock is diorite?
| Type Igneous Rock | Texture Phaneritic (Coarse-grained) | Origin Intrusive/Plutonic | Chemical Composition Intermediate | Color Approximately half dark, half white minerals |
|---|
What type of rock is chalk?
Chalk,
a sedimentary rock
, is a soft form of limestone that is not well cemented and thus is often powdery and brittle.
What is the hardness of Dunite?
The hardness of Dunite is
3.5-4
whereas its compressive strength is 107.55 N/mm
2
.
Where is dolerite formed?
It usually occurs as small intrusions called ‘dykes’ or ‘sills’ which are sheet-like and cut through the surrounding rocks. Like gabbro, dolerite forms from
magma that is rich in iron and magnesium
, and poor in silica (quartz).
Does Obsidian exist?
obsidian, igneous rock occurring as a
natural glass formed by the rapid cooling of viscous lava from volcanoes
. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite. Obsidian has a glassy lustre and is slightly harder than window glass.
