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

Geochemical data on Proterozoic volcanic rocks of Indian shield overwh elmingly suggest that they were generated in two different tectonic se ttings. The mafic volcanic suites of Aravalli (Aravalli craton) and Bi jawar (Bundelkhand craton) belts and those of lesser Himalayan region appear to be rift related continental type. On the other hand Delhi vo lcanics (Aravalli craton), Dongargarh volcanics (Bhandara craton) and Dhanjori-Jagannathpur volcanics (Singhbhum craton) exhibit the charact eristic signature of subduction zone magmatism implying the destructio n of oceanic lithosphere by processes akin to the of modern plate tect onics. Geochemical and geological evidences suggest the occurrence of an early Proterozoic ocean in Central India located between Dharwar-Si nghbhum-Marwar protocontinent in the south and Bundelkhand protocontin ent in the north. During middle Proterozoic, the oceanic lithosphere s ubducted towards south along the northern margin of southern protocont inent. The lack of complete calc-alkaline series in the subduction-gen erated volcanic suites suggests that are volcanism 210 along this marg in could not acquire maturity and that the period of subduction was sh ort 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 bel t) and probably Tal (Bijawar belt) are the possible evidences of closu re.