Question

Why is Sial named as granitoid?

Answer 1

When molten magma cools down inside the surface of the earth, it becomes solid and forms intrusive igneous rocks. Example- Granite. and when molten magma cools down on the surface of the earth it forms extrusive igneous rocks. As the intrusive igneous rocks takes a lot more time to cool down (because of the heat present inside the earth) in comparision to the extrusive igneous rocks, the grains present in intrusive rocks gets accumulated and forms larger grains and extrusive igneous rocks cools down faster so the grains present in them don't get easily accumulated...

Answer 2

A granitoid or granitic rock is a variety of coarse grained plutonic rock — granite or similar — which mineralogically is composed predominantly of feldspar and quartz mica . Examples of granitoid rocks include granite, quartz monzonite, quartz diorite, syenite, granodiorite, tonalite and trondhjemite. Many are created by continental volcanic arc subduction or the collision of sialic masses. Volcanic rocks are common with granitoids and typically have the same origins. However, they are normally worn away after years of erosion.

Many granitoid rocks are located in areas that have experienced crustal thickening during orogenies but others, known as anorogenic granitoids, are unrelated to convergent boundaries or subduction zones;these anorogenic granitoids may represent the deep sources for rift volcanism exposed where erosion has removed the volcanic rocks and other evidence of rifting. These A-type granitoids may have been produced by hotspots or mantle plumes.

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