assimilation

geology

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June 18, 2026

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In geology, assimilation is a process where a magma incorporates and alters its surrounding wall rocks. This occurs when the hot magma melts or reacts with the rocks it comes into contact with, changing the magma's original composition.1

For example, if a magma is crystallizing certain minerals, and it tears off earlier-formed minerals from its wall rocks, these foreign minerals will react with the magma to form minerals the magma is already in equilibrium with. Conversely, if a mineral from the wall rock is at a lower temperature than the magma, it will dissolve into the magma, causing the magma to cool and crystallize. This contamination shifts the magma's composition towards that of the assimilated rock. This combined process of assimilation and fractional crystallization is known as AFC.1

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igneous rock
Assimilation
Another method of creating different daughter magmas from a parent is by having the latter react with its wall rocks. Consider a magma that is crystallizing pyroxene and labradorite. If the magma tears from its wall minerals, say, olivine and anorthite, which are formed…
Read More
Another method of creating different daughter magmas from a parent is by having the latter react with its wall rocks. Consider a magma that is crystallizing pyroxene and labradorite. If the magma tears from its wall minerals, say, olivine and anorthite, which are formed…
Read More