GEODYNAMIC EVOLUTION OF INDIAN SHIELD DURING PROTEROZOIC - GEOCHEMICAL EVIDENCE FROM MAFIC VOLCANIC-ROCKS

Geochemical data on Proterozoic volcanic rocks of Indian shield overwhelmingly suggest that they were generated in two different tectonic settings. The mafic volcanic suites of Aravalli (Aravalli craton) and Bijawar (Bundelkhand craton) belts and those of lesser Himalayan region appear to be rift related continental type. On the other hand Delhi volcanics (Aravalli craton), Dongargarh volcanics (Bhandara craton) and Dhanjori-Jagannathpur volcanics (Singhbhum craton) exhibit the characteristic signature of subduction zone magmatism implying the destruction of oceanic lithosphere by processes akin to the of modern plate tectonics. Geochemical and geological evidences suggest the occurrence of an early Proterozoic ocean in Central India located between Dharwar-Singhbhum-Marwar protocontinent in the south and Bundelkhand protocontinent in the north. During middle Proterozoic, the oceanic lithosphere subducted towards south along the northern margin of southern protocontinent. The lack of complete calc-alkaline series in the subduction-generated volcanic suites suggests that are volcanism 210 along this margin could not acquire maturity and that the period of subduction was short lived. The collision of the two protocontinents led to the closure of ocean and induced the Satpura-Delhi orogeny at about 1500 m.y. ago. The ophiolitic seqeunce of Phulad (Delhi belt), Dalma (Singhbhum belt) and probably Tal (Bijawar belt) are the possible evidences of closure.