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Fractional crystallization is the removal and segregation from a melt of mineral precipitates; except in special cases, removal of the crystals changes the composition of the magma. [2] In essence, fractional crystallization is the removal of early formed crystals from an originally homogeneous magma (for example, by gravity settling) so that ...
Flow banding is the result of a process of fractional crystallization which occurs by convection, if the crystals which are caught in the flow-banded margins are removed from the melt. The friction and viscosity of the magma causes phenocrysts and xenoliths within the magma or lava to slow down near the interface and become trapped in a viscous ...
Bowen's reaction series is important for understanding the idealised sequence of fractional crystallisation of a magma. [89] Magma composition can be determined by processes other than partial melting and fractional crystallization. For instance, magmas commonly interact with rocks they intrude, both by melting those rocks and by reacting with ...
Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the feldspar in the rock consisting of plagioclase. This places andesite in the basalt /andesite field of ...
Within the field of geology, Bowen's reaction series is the work of the Canadian petrologist Norman L. Bowen, [1] who summarized, based on experiments and observations of natural rocks, the sequence of crystallization of common silicate minerals from typical basaltic magma undergoing fractional crystallization (i.e. crystallization wherein early-formed crystals are removed from the magma by ...
Magmatism along strike-slip faults is the process of rock melting, magma ascent and emplacement, associated with the tectonics and geometry of various strike-slip settings, most commonly occurring along transform boundaries at mid-ocean ridge spreading centres [1] and at strike-slip systems parallel to oblique subduction zones. [2]
Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition because different minerals crystallize from the melt. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the ...
Whilst the dominant process of layering is fractional crystallisation, layering can also result in a magma body through assimilation of the wall rocks. This will tend to increase the silica content of the melt, which will eventually prompt a mineral to reach the liquidus for that magma composition.