How do you identify komatiite?
Komatiites often show pillow lava structure, autobrecciated upper margins consistent with underwater eruption forming a rigid upper skin to the lava flows. Proximal volcanic facies are thinner and interleaved with sulfidic sediments, black shales, cherts and tholeiitic basalts.
Why is komatiite important?
In addition to the information they provide about the tectonics and the thermal evolution of Archean Earth, komatiites are economically important because they host locally significant magmatic Ni-sulfide (Ni-Cu-PGE) mineralization.
Is komatiite extrusive or intrusive?
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). They are named after the Komati River in South Africa, the type locality. Komatiite is an exceedingly rare type of lava.
Where are komatiites found?
Komatiites are fairly rare rocks, but they are found throughout the world in places such as Canada and South Africa. Most komatiites were formed billions of years ago in the Archean (approximately 2.5 to 3.8 billion years ago).
Is komatiite fine grained?
The course-grained version of an ultramafic rock is peridotite, and the fine-grained version is komatiite. It makes sense to use different names because rocks of different grain sizes form in different ways and in different geological settings.
How are Boninites formed?
Most boninite magma is formed by second stage melting in forearcs via hydration of previously depleted mantle within the mantle wedge above a subducted slab, causing further melting of the already depleted peridotite.
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.
Is Komatiite fine grained?
Is Komatiite magnetic?
(1990) point out, gold occurs in a wide variety of host rocks. All the deposits studied here are hosted by strongly magnetic volcanic and sedimentary rocks such as komatiites, tholeiites and BIF.
What kind of rock is a komatiite made of?
[4] According to the simple definition, a komatiite is an ultramafic volcanic rock (a lava or volcanoclastic rock containing more than 18% MgO) [ Arndt and Nisbet, 1982 ].
Where are komatiites most likely to be found?
Since most komatiites are only found in Archean regions, they are thought to be evidence for Earth being hotter than when it was initially formed. The youngest komatiite was recently discovered on the island of Gorgona, Colom. …a magnesium-rich lava called a komatiite (named for the Komati River in South Africa).
Why was the crystallization of komatiite not efficient?
Slow cooling of stagnant lava in the tube allowed crystallization, forming the ortho- and mesocumulate textural zones. Preserved orthocumulate and mesocumulate textures indicate that crystal settling was not efficient, most likely because of the low density contrast between olivine crystals and the melt.
Where does komatiite fractionate from in the flow?
Komatiite tends to fractionate from high-magnesium compositions in the flow bases where olivine cumulates dominate, to lower magnesium compositions higher up in the flow.
