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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