It is also known as crustal assimilation. “Assimilation of rocks with magma” occurs when magma rises up towards the earth’s surface. The rising magma can engulf fragments of the country rocks through which it passes. If these fragments are digested by the magma, the process is called “assimilation”. If they are not digested, they remain entrapped within the mass of crystallized magma. Such entrapped fragments are called “xenoliths”.
As assimilation involves remixing of rocks in magma, it may be regarded as the reverse of differentiation. Assimilation also produces variation in the composition of igneous rocks. Igneous rocks containing partly digested xenoliths are called “hybrid rocks”. In hybrid rocks, mutual reactions take place between “xenolith” and invading magma. As a result, the acid magma is basified and the basic xenoliths are acidified.
Because magmas usually have a limited amount of superheat, their capacity to digest xenoliths is not much. They can assimilate xenoliths only up to 10% of their own mass. Thus the process of assimilation is not of much importance in causing variation in igneous rocks.
- Introduction to rocks
- Igneous Rocks and their types
- Chemical Composition of Igneous Rocks
- Occurrence of Igneous Rocks
- The Texture of Igneous Rocks
- Structures of Igneous Rocks
- Different Forms of Igneous Bodies/Material
- Mechanics of Intrusion
- Formation of Igneous Rocks
- Origin of Igneous Rocks
- Magmatic Differentiation