Indian Shield: Pristine Shape, Size and Tectonic Framework

Abstract

The Precambrian terrane of Peninsular India is commonly referred to as the Indian Shield. Geological evidences suggest that the pre-existing terrane which evolved as the Indian Shield occupied a much wider area than that of Peninsular India. Known as ‘Greater India’ the pristine Indian Shield underwent repeated decimation during the Phanerozoic, which began with the Jurassic break-up of the Gondwana Land. However, relying on the information from Peninsular India, it is possible to trace out not only the history of destruction, but also the clue to divide this Precambrian crustal block into two major tectonic blocks: the initially formed Precambrian Continental core or Proto-India which formed due to amalgamation of several Protocontinents. The Proto-Indian changed into Indian Shield due to the accretion of granulite/charnockite belts, called the Suspect terranes. The six smaller Precambrian crustal blocks which together constituted the Proto-India include Dharwar, Bastar, Singhbhum, Rajmahal, Bundelkhand, and Aravalli. The Protocontinents are separated from each other by Joins marked by Lineament like the Narmada-Son, or by the Gondwana rift basins like the Godavari, Mahanadi and the Damodar Valley. Geological history of the individual Protocontinent suggests distinctive tectonic pattern, history of evolution and metallogenic traits implying independent growth of each of the Precambrian crustal blocks. Further, strictly independent growth history of the individual Protocontinents rule out operation of any global scale process in the evolution of these fundamental crustal units anal- ogous to the modern Plate Tectonics.