Age
While the granulite facies metamorphism is dated as 2.5 Ga (billion years ago) in Nilgiris, Shevroys, Madras (Chennai) regions, the granulite facies event transforming the granitic gneisses into charnockite in the southern part of the South Indian granulite terrain is dated as 550 Ma (million years ago). Although they are certainly for the most part igneous gneisses (or orthogneisses), rocks occur along with them, such as marbles, scapolite limestones, and corundum rocks, which were probably of sedimentary origin.
Read more about this topic: Charnockite
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