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Igneous differentiation. In geology, igneous differentiation, or magmatic differentiation, is an umbrella term for the various processes by which magmas undergo bulk chemical change during the partial melting process, cooling, emplacement, or eruption. The sequence of (usually increasingly silicic) magmas produced by igneous differentiation is ...
There is considerable evidence for magma mixing just before many eruptions, including magnesium-rich olivine crystals in freshly erupted silicic lava that show no reaction rim. This is possible only if the lava erupted immediately after mixing since olivine rapidly reacts with silicic magma to form a rim of pyroxene. [13]
When this basaltic material mixes with the evolved rhyolitic magma, the composition is returned to andesite, its intermediate phase. [27] Evidence of magma mixing is provided by the presence of phenocrysts in some andesites that are not in chemical equilibrium with the melt in which they are found. [14]
Magma (sometimes colloquially but incorrectly referred to as lava) is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. [3] Besides molten rock, magma may also contain suspended crystals and gas bubbles.
Evidence for this theory is the existence of pumice consisting of light and dark material, the dark material being of much hotter origin. Such material reportedly is less than five per cent of the content of the Krakatoa ignimbrite, and some investigators have rejected this as a prime cause of the 27 August explosions.
Magma mixing is another aspect of granite formation that must be taken into account when observing granites. Magma mixing occurs when magmas of a different composition intrude a larger magma body. In some cases, the melts are immiscible and stay separated to form pillow like collections of denser mafic magmas on the bottom of less dense felsic ...
Diffusion chronometry is a geological technique that examines the chemical zoning within phenocrysts to estimate the duration of events in a magmatic system (e.g. magma mixing, magma decompression, magma degassing, etc.) and their associated eruptions. In simple terms, the phenocryst acts as a “crystal clock” to determine how long a ...
The Moon’s south pole was once covered in an ocean of liquid molten rock, according to scientists. The findings back up a theory that magma formed the Moon's surface around 4.5 billion years ago.