Fractional Crystallization


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fractional crystallization

[¦frak·shən·əl ‚krist·əl·ə′zā·shən]
(petrology)
Separation of a cooling magma into multiple minerals as the different minerals cool and congeal at progressively lower temperatures. Also known as crystallization differentiation; fractionation.

Fractional Crystallization

 

a means of separating and purifying substances by converting them into a solid state during crystallization from a solution or melt. Crystallization can occur as a result of cooling, introduction of impurities that lower the solubility, or isothermal evaporation of the solvent. The effectiveness of the separation depends on the ratio of the quantities of the separable components, on their solubility, and on the conditions of the fractional crystallization. If substances being separated are present in comparable quantities, each component solidifies independently. If one of the components is present in trace quantities, it may coprecipitate rather than forming an independent solid phase with the macrocomponents. Fractional crystallization is a multiphase process that is used for the separation of substances with nearly identical chemical properties—for example, compounds of niobium and tantalum and of radium and barium.

REFERENCE

Bresler, S. E. Radioaktivnye elementy, 3rd ed. Moscow, 1957.
References in periodicals archive ?
The process pathway of fractional crystallization of salts from the system of LiCl[O.
The analysis of the process of fractional crystallization, primarily that of lithium perchlorate trihydrate, from the system of NaCL-LiCl[O.
The contrast in fractional crystallization trends between trachyte and rhyolite is highlighted by the CaO-[K.
08), consistent with low-pressure fractional crystallization of alkali and/or plagioclase feldspar.
Samarium-Nd and Rb-Sr isotopic studies can be used to distinguish between felsic magmas derived from fractional crystallization of a more mafic parent (which would have similar values) and those derived from the melting of ancient crust.
Phase equilibria predict that intermediate and felsic rocks can originate by fractional crystallization of a more basic parent because the early fractionation of olivine, clinopyroxene and plagioclase drives the liquid toward more silicic compositions (Fig.
Although fractional crystallization is seen as the dominant process yielding highly evolved rocks (e.
On the basis of field relations, petrography, petrochemistry, and trace element modeling, the MBG and MPG are interpreted to be linked through extreme fractional crystallization and supracrustal contamination; fluid fractionation may have played a role in formation of the late MPG.
Fractional crystallization, however, not only reduces the abundance of compatible elements, but also increases the concentrations of incompatible elements (e.
2] (sample 27) by fractional crystallization of plagioclase and biotite in the proportion of 2.
This limited primary compositional variation can be mostly explained by closed-system fractional crystallization of plagioclase and biotite.
A correlation between decreasing [epsilon]-Nd ([approximately equal to] -2 to 5) and increased fractionation within the suite is best explained by mid-crustal (current exposed emplacement depth) assimilation and fractional crystallization processes.

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