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High-temperature fractional crystallization of relatively water-poor granite magmas may produce single-alkali-feldspar granite, and lower-temperature crystallization of relatively water-rich magma may produce two-feldspar granite. [13] During the process of fractional crystallization, melts become enriched in incompatible elements. [14]
The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...
More typically, they are mixes of melt and crystals, and sometimes also of gas bubbles. [15] Melt, crystals, and bubbles usually have different densities, and so they can separate as magmas evolve. [89] As magma cools, minerals typically crystallize from the melt at different temperatures. This resembles the original melting process in reverse.
A parental melt is a magma composition from which the observed range of magma chemistries has been derived by the processes of igneous differentiation. It need not be a primitive melt. For instance, a series of basalt lava flows is assumed to be related to one another.
At the bottom of the magma reservoir, a cumulate rock forms. Cumulate rocks are the typical product of precipitation of solid crystals from a fractionating magma chamber. These accumulations typically occur on the floor of the magma chamber, although they are possible on the roofs if anorthite plagioclase is able to float free of a denser mafic ...
Alkaline magmas tend to show high titanium oxide (TiO 2) content, typically in excess of 3% by weight. Other incompatible elements, such as phosphorus and light rare earth elements, are also elevated. This is attributed to a very low degree of partial melting of the source rock, with only 5% or less of the source rock going into the magma melt. [3]
During cooling, crystals will form from the melt. Thus, the crystal/melt ratio increases, generating a magma, a crystal-mush, and finally a cumulate rock. A crystal mush is magma that contains a significant amount of crystals (up to 50% of the volume) suspended in the liquid phase (melt). [1]
Previous research using seismology found that a large reservoir of magma sat beneath the caldera. However, the recent study, using a method known as magnetotellurics that tracks the electric ...