Where can I find komatiite?
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).
What is komatiite rock?
Komatiite (/koʊˈmɑːtiaɪt/) is a type of ultramafic mantle-derived volcanic rock defined as having crystallised from a lava of at least 18 wt% MgO. Lower temperature mantle melts such as basalt and picrite have essentially replaced komatiites as an eruptive lava on the Earth’s surface.
Why are Komatiites rare on Earth’s surface today?
Komatiites are very rare igneous rocks. Komatiite is an exceedingly rare type of lava. No volcano on Earth erupts this material today. Komatiites are essentially restricted to the Archean (4.55 to 2.5 billion years ago), when Earth’s heat flux was much higher.
What is the cooling rate of komatiite?
Donaldson (1982) estimated that cooling rates in the A3 layer of a typical 5–10 m thick komatiite flow were <1 C/h. In contrast, to reproduce the dendritic mor- phology of platy spinifex olivine crystals in normal dynamic cooling laboratory experiments requires cooling rates >50 C/h (Donaldson, 1982).
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. Many ultramafic rocks found on the surface in fact were brought up from the mantle by rising bodies of magma that erupted on the surface.
Where does Komatiite come from?
Komatiite, a magnesium-rich, high-temperature volcanic rock derived from very hot mantle (part of the Earth between the crust and the core), was extruded in abundance during the early Precambrian when the heat flow of the Earth was higher than it is today. Blueschist, which contains…
Why is it impossible to find quartz and olivine in the same rock?
In yet other cases there is a true chemical incompatibility. It is because of this that quartz is never found with olivine, corundum, sodalite or lazurite. These minerals are just not chemically stable together. The reason is that corundum forms only in a low silica environment, but quartz only in a high silica one.
Why is it so rare to find beach sand that contain olivine?
Olivine is actually very rare in sand because it is highly susceptible to weathering. There is little hope of finding olivine grains in continental sand. If there are bright green grains, it is most likely epidote.