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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Basalts of phases 3 and 4 have undergone moderate fractional crystallization.
This linear relationship, moreover, could indicate both degrees of partial melting and different degrees of fractional crystallization [2,16].
The process pathway of fractional crystallization of salts from the system of LiCl[O.sub.4]-NaCl-[H.sub.2]O defined in this way leads to creation of the following process/state structure shown in Figure 4.
The analysis of the process of fractional crystallization, primarily that of lithium perchlorate trihydrate, from the system of NaCL-LiCl[O.sub.4]-[H.sub.2]O, which is shown in the feasible process structure (Figure 4), was performed based on the results of the material balance simulation of the total process system.
The contrast in fractional crystallization trends between trachyte and rhyolite is highlighted by the CaO-[K.sub.2]O-[Na.sub.2]O ternary diagram (Fig.
The REE patterns of the rhyolite are characterized by a pronounced negative Eu anomaly (average Eu/[Eu.sup.*] = 0.08), consistent with low-pressure fractional crystallization of alkali and/or plagioclase feldspar.
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.g., Prestvik et al., 2001), other magma chamber processes can be important.
5-9, 11, 12) are modeled assuming that the MBG and MPG were produced by extensive low-T fractional crystallization of the same parental magma, rather than from two batch-melts that evolved separately.
There were essentially two significant questions regarding data fitting: 1) where to assign t = 0 for the fit ([[tau].sub.0]) and 2) what range of fractional crystallization to fit?
The fresh granodiorite samples define distinct variation trends for some major and trace elements where plotted against [SiO.sub.2] (Fig.5) or other differentiation indices, suggesting that the rocks underwent fractional crystallization. Large variation of Sr accompanied by relatively constant Rb/Sr (not shown) and Mg/Rb ratios with increasing [SiO.sub.2] (Fig.
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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