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Geology / petrology: Classification of Granitoids Essay Example

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Geology / petrology: Classification of Granitoids

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Geology / petrology: Classification of Granitoids. Granitoid is formed when magma or molten rock is pressed between other rocks in the earth’s crust. It when cooled gets crystallized in the deep underground and low cooling process makes large crystals to form. Granitoids generally form large intrusion in the core of mountain ranges and they are generally are surrounded by metamorphic rocks. These rocks are formed due to pressure or heat. Granitoid is the most abundant form igneous rock found on earth’s surface. These are classified by visual inspection and according to the source of origin. Granitoid is called by petrologic what might be for normal people granite because of their mineral composition. Magma or molten rock is that become granites.

As per (Murphy,2007.21-34 ) “Magmas with intermediate compositions can also be produced by mixing at depth of mafic and felsic end-member compositions”.S- type granitoids are derived from sedimentary rocks in a phenomenon called anatexis or ultrametamorphis.S – type has a reddish brown color when it comes to appearance. They also have intense pleochroic haloes. The S- type granitoids have the characteristics of beingXenolithe type or minerals not absorbed fully during anatexis.The S – type granitoids have low sodium content and have a MOL ration of greater than 1. S- type also has various isotope composition. Their mineralogy is different from other types and they have high AI but no hornblende. They have biotite, muscovite, cordierite, and garnet. In the source rock, there is high Rb. The initial S r ration is > 0. S- type granitoids are predominant in quartz-rich adamellites and granodiorites. S- type is mostly early in the intrusive.87Sr/86Sr, due to the enrichment of Rb relative to Sr in the pelitic rock. S-type also contains xenolith type minerals which are partially absorbed by the anatexis.In this type, restite milky quartz inclusion is common.One of the examples of S- type granite are Sikait leucogranite and Azna granitoid.However SIAM classification of S – type granitoids can be confusing about the granite setting. Geology / petrology: Classification of Granitoids.

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