GeoClassroom Physical Geology Historical Geology Structure Lab Mineralogy Petrology

Fractionation Mechanisms

Fractionation mechanisms relate the final composition observed in an igneous suite to the original, primary composition of the source material which yields the end product.

For fractionation an Evolutionary link is implied, yet no specific process is suggested.


  • Formation of a variety of substances from an initially homogeneous, single parent material. Any mechanism which accomplishes this is a fractionation or differentiation mechanism.

Every fractionation mechanism involves the migration or transport of atoms of a particular element relative to other elements, resulting in different bulk compositions formed from a single starting product.

The composition of the source material producing the magma may effect the type and degree of fractionation the magma undegoes.

The obvious manifestation of fractionation is the variation observed in the chemical composition for a single volcanic flow or pluton.

We will look at three fractionation processes:

  1. Liquid Immiscibility
  2. Hybridization and Assimilation
  3. Fractional Crystallization

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