What type of rock is komatiite?
Komatiites are ultramafic volcanic rocks. An ultramafic rock is a rock that has very low silicon (SiO2), sodium (NaO), and potassium (K2O) and very high and iron (FeO) and magnesium (MgO) content, generally greater than 18 weight percent MgO*.
Is komatiite an igneous rock?
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.
Is komatiite a basalt?
The komatiite-basaltic sequence is composed of a 150-m-thick lower basaltic unit overlain by a 600-m-thick komatiitic unit, which is capped by 200 m of basalts in the upper part of the sequence (Fig.
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.
What minerals are found in komatiite?
Komatiite (/koʊˈmɑːtiaɪt/) is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% MgO. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content.
What is the texture of komatiite?
Many komatiite flows have spinifex textures consisting of arrays of numerous subparallel olivine blades that extend 10’s of cm to m’s from the flow tops. The habit of the strongly anisotropic crystals is suggestive of fast cooling near the flow margin, yet the crystals form deep within the flows.
Who discovered komatiite?
Komatiites were first identified by Richard and Morris Viljoen in 1969, in the Archean greenstone belt in the Barberton Mountain land of South Africa as a distinctive and “new” class of magnesium-rich (20-30 wt % MgO) volcanic rocks.
What color is komatiite?
This should discriminate some picrites without the corresponding texture to be classified as komatiites. Colour Black, grey, locally grey-green. Structure Pillow-like, porphyric, spinifex. Texture Porphyric – spinifex.
How do you identify komatiite?
Komatiite can be classified according to the following geochemical criteria;
- SiO2; typically 40–45%
- MgO greater than 18%
- Low K2O (<0.5%)
- Low CaO and Na2O (<2% combined)
- Low Ba, Cs, Rb (incompatible element) enrichment; ΣLILE <1,000 ppm.
- High Ni (>400 ppm), Cr (>800 ppm), Co (>150 ppm)