Describe the four processes of magma differentiation.How does the rate of cooling impact crystal size?


the four processes of magma differentiation are starting with Fractional crystallization , Assimilation , Replenishment and Magma mixing.


Magma differentiation -

It is also called igneous differentiation , is a kind of combination term for the various processes involved in the chemical change by which magmas undergoes bulk changes during cooling , emplacement , partial melting process or eruption .

The process involved has been called the FARM process , i.e , starting with Fractional crystallization , Assimilation , Replenishment and Magma mixing.

Fractional crystallization of igneous rocks

This is the most important geochemical process that is working inside the Earth's crust and the mantle . This process of segregation and removal from the melt of the mineral precipitates , that can change the composition of the melt .

The process is complex in context as it varies by a wide variety of phenomena , that are , temperature , composition and the pressure .

Assimilation -

This process explains the mafic magmas as it get rise from the crust and the felsification of the ultramafic . The assumption involved in this process is that the hot primitive melt intrudes into a cooler and the felsic crust will melt crust and get mixed with the resulting melt , which in turns alters the composition of primitive magma .

Replenishment  -

During the process of the cooling of the melt , the results are limited so as to produce a solid body of intrusive rock , which is homogeneous in nature and which has uniform composition and mineralogy . This is due to -

The fresh magma can change the melt's composition ,and the fresh magma can destabilizes the minerals , even change in temperature can lead to rapid crystallization .

Magma mixing  -

The composition in between of two end - member magma is achived by combining two magma's and forming a single composition.

This is a common process in the volcanic magma chambers , that are a open - system chambers , and magma under goes various processs of assimilation , fractional crystallization , and partial melt extraction and are replenished . Even this process is operated deep in the crust and is one of the primary mechanism for the formation of the rocks like monzonite and andesite .

Rate of cooling impact crystal size -

Crystals are formed by the cooling of the magma ,

There are two types of cooling possible , rapid cooling and slow cooling , both can lead to different types of crystal .

If the magma is cooled quickly , i.e. , rapid cooling , the crystals will not have time to form , hence are small in size ,

And in case the magma is cooled slowly , the crystals will have ample amount to time to grow in size , and , hence will form larger crystals .

If the igneous rock has large crystals , then it indicates that the rock was formed deep inside the earth , because deep inside the earth , it is warmer .

These are called intrusive rocks, and have a phaneritic texture .

If the igneous rock has small crystals , then it is formed by rapid cooling , near the Earth's surface .  These are called extrusive rocks and have an aphanitic texture .

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