Assimilation is the process whereby solid or fluid foreign material is incorporated into magma. The term implies no specific mechanism and the process depends on many factors, including temperature, cooling rate of the magma, gas pressure, and the composition of the material being assimilated. The result is a contaminated magma and, on cooling, rocks that are referred to as being contaminated. Wholesale assimilation requires the magma to be superheated, which is rarely the case for a fractionating magma. Hybridization can be synonymous with contamination but most commonly it refers either to mixing of two magmas or to one magma digesting earlier-formed magmatic material.
Reactions involved in the assimilation of sedimentary material by basic magma are given by Bowen (1928): magma crystallizing early-formed high-temperature members of the continuous and discontinuous reaction series incorporate the lower-temperature phases in the sedimentary material into the liquid fraction....
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