Below the earths' crust the great depths and lot of pressure is responsible for the development of granite. There are several theories about its origin and each one of them is slightly different from another.

When I was reading about the history of granite worktops I came across one interesting journal that is presented by R.A. Kanen who disclosed some insightful details about the origin of granite stone. As we all know that granite is produced from hot molten lava but what we do not know is this molten lava is known as "granitic magma" that specifically responsible for the birth of granite rock.

The granite rock that we extract from its quarries was basically buried inside the inner layer of earth's crust but due to erosion of plutonic granite that is available in the form of sheets and sills expose that buried granite and makes our extraction process easy.
According to R.A. Kanen two most interesting theories were appeared that strongly justifies the origin of granite rock. One is called "Magmatic Theory" and other is "Granitization theory"

1.    Magmatic theory
As per magmatic theory granite is the outcome of crystal fractionation process that happens on magma. In this theory researchers discovered that development of granite took place due to Bowen Reaction Series in which tholeiitic basalt compound goes under crystal fractionation process and the end product of this reaction was granite.
Granite is found near volcanic region because the structure of granite was firmly placed and synchronised due to volcanic eruption. This scenario was observed in year 1974 and initially that granite was just an alkali granite rock.
There were criticism as well on this theory like how large portion of country rock displaced just to make a vacancy for batholith? However there were many explanations for this like massive explosion, deliberate removal of country rock, dissolution of country rock due to volcanic eruption and many others.

2.    Granitization theory
Granitization process took place in its original place that is without any displacement or removal of any rock. According to this theory ultra metamorphism took place on earth that resulted into granite formation.

This ultra metamorphism process is also known as "Anatexis". Under this mechanism the pre-existing rocks melt down due to volcanic magma and resulted into formation of granite rock. According to this theory granite is the outcome of two intermingled but distinguishable components called neosome and pleosome.

This phenomenon takes place in several phases that finally resulted into formation of granite stone.