Komatiites probably form in extremely hot mantle plumes. Boninite magmatism is similar to komatiite magmatism but is produced by fluid-fluxed melting above a subduction zone.

Where do you find peridotite?

Peridotite is the dominant rock of the upper part of Earth's mantle. The compositions of peridotite nodules found in certain basalts and diamond pipes (kimberlites) are of special interest, because they provide samples of Earth's mantle brought up from depths ranging from about 30 km to 200 km or more.

Where are ultramafic rocks formed?

Many surface exposures of ultramafic rocks occur in ophiolite complexes where deep mantle-derived rocks have been obducted onto continental crust along and above subduction zones.

What are komatiites rare?

Komatiites are very rare igneous rocks. They are one variety of extrusive ultramafic igneous rock (although a komatiite in Canada has been interpreted to be an intrusive sill). ... Komatiites are essentially restricted to the Archean (4.55 to 2.5 billion years ago), when Earth's heat flux was much higher.

How is spinifex texture formed?

The distinctive spinifex texture is formed by skeletal, platy, or acicular crystals of olivine, orthopyroxene, or clinopyroxene, or their pseudomorphs in ultramafic and mafic lavas or silicate-rich furnace slag. ... The complex skeletal or platy crystals may show random orientation, or may display a preferred arrangement.

Komatiite

43 related questions found

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 K₂O and other incompatible elements.

What minerals are in Komatiites?

Komatiite:

• An ultramafic, volcanic rock that is primarily composed of the minerals pyroxene and olivine.
• A very unusual and rare volcanic rock type that is not produced today. ...
• A rock type whose hotly– and wetly– debated origin sometimes galvanizes geologists to shouting matches, fist fights, and drinking contests.

How is serpentinite rock formed?

The serpentinite is formed by the hydrous alteration and low-temperature metamorphic alteration of igneous ultramafic rocks. These rocks are composed of olivine and pyroxene in different ratios to form peridotite and pyroxenite.

How is syenite formed?

Syenites are products of alkaline igneous activity, generally formed in thick continental crustal areas, or in Cordilleran subduction zones. To produce a syenite, it is necessary to melt a granitic or igneous protolith to a fairly low degree of partial melting.

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.

How ultramafic rocks are formed?

Most ultramafic metamorphic rocks are formed by alteration of peridotite or pyroxenite to serpentinite or talc–amphibole–chlorite rocks that commonly are schistose or sheared.

What is the composition of ultramafic rocks?

Ultramafic metamorphic rocks result from the metamorphism of mantle rocks and some oceanic crust and contain dominantly magnesium, silicon, and carbon dioxide, with smaller amounts of iron, calcium, and aluminum.

How are metamorphic rocks formed quizlet?

Metamorphic rocks are formed by intense heat, intense pressure, or by the action of watery hot fluids (metamorphism). Any of the rock types in the rock cycle can be metamorphosed, or changed into a metamorphic rock (metamorphic rock can be metamorphosed again).

How is basalt formed?

Basalts are formed by the rapid cooling of basaltic lava, equivalent to gabbro-norite magma, from interior of the crust and exposed at or very close to the surface of Earth. These basalt flows are quite thick and extensive, in which gas cavities are almost absent.

Where is basalt found?

It is found all over Earth, but especially under the oceans and in other areas where Earth's crust is thin. It formed in the Isle Royale-Keweenaw region because of the Midcontinent Rift. Most of Earth's surface is basalt lava, but basalt makes up only a small fraction of continents.

What environment is peridotite formed in?

It occurs in four main geologic environments: (1) interlayered with iron-, lime-, and magnesia-rich rocks in the lower parts of tabular-layered igneous complexes or masses; (2) in alpine-type mountain belts as irregular, olivine-rich masses, with or without related gabbro; (3) in volcanic pipes (funnels, more or less ...

Where is syenite located?

In Europe syenite may be found in parts of Switzerland, Germany, Norway, Portugal, in Plovdiv, Bulgaria and in Ditrău, Romania. In Africa there are syenite formations in Aswan, Egypt, and in Malawi in the Mulanje Mountain Forest Reserve. Syenite rock was used to make the Quay with Sphinxes.

Where is dolerite formed?

Formation. Dolerite cools under basaltic volcanoes, like those at mid-ocean ridges. It cools moderately quickly when magma moves up into fractures and weak zones below a volcano.

What is the chemical formula of syenite?

Nepheline syenite | Al2KNaO8Si2 - PubChem.

Why is serpentinite an important rock where plates move?

Serpentine rock, so called because the pattern of the rock surface resembles a serpent's skin, is actually a rock type originally formed from ultramafic rock. ... Ultramafic rock migrates across the ocean floor along with the crust. A process called plate tectonics drives crustal movement.

How is serpentinite formed parent rock setting and grade?

Were does serpentinite form? ... 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.

Where can I find serpentinite?

The term "serpentine" is commonly used by the general public to refer to the rock type that geologists call "serpentinite." Serpentine occurs in central and northern California -- in the Coast Ranges, the Klamath Mountains, and in the Sierra Nevada foothills.

Where is kimberlite rock found?

Generally speaking, kimberlites are found only in cratons, the oldest surviving areas of continental crust, which form the nuclei of continental landmasses and have remained virtually unchanged since their formation eons ago.

What is the origin of gabbro?

Gabbro (/ˈɡæb. roʊ/) is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. ... Gabbro is also found as plutons associated with continental volcanism.

Are ultramafic rocks rare?

Ultramafic rocks are dominated by olivine or olivine and pyroxene. Such rocks are rare on the Earth's surface, but they dominate the mantle.