Crustal Evolution and Metallogeny-Evidence from the Indian Shield: A Review

A survey of the important metalliferous deposits of India has been attempted in the light of developing ideas about crustal evolution and metallogeny. Mantle dominated volcanic regime of the Archaean is indicated to be characterized by simple ores of gold, chromium, nickel and copper. A marked change is apparent at the end of the Archaean with the emergence of large areas of land and oxygenated atmosphere and hydrosphere. Near surface processes begin to play the dominant role. Proterozoic is thus marked by the first appearance of uranium-gold-bearing conglomerate, spectacular development of banded iron formations and sediment-hosted Pb-Zn-Cu deposits. High temperature albitization phenomena connected with younger plutons has led to concentration of beryllium, tantalum, niobium, zirconium and tin in granite pegmatites. A special type of barium-rich volcanism has given rise to a unique type of barite deposit within the Proterozoic Cuddapah Basin. Tensional tectonic regime of the Proterozoic has given place to plate tectonic regimes in the Phanerozoic, thereby enabling further recycling of crustal material and concentration of metals. The full metal potential of the Himalayan folded mountain belt is yet to be ascertained. Alluvium and palaeo-channels of major rivers, off-shore extensions of beach placers, and metals on the sea bed are promising fields where exploration effort has to be concentrated in the coming years.