Zircon geochronology of deformed alkaline rocks along the Eastern Ghats Belt margin: India–Antarctica connection and the Enderbia continent
Abstract Linear chains of Deformed Alkaline Rocks and Carbonatites (DARCs) mark sutures where continents had rifted apart and later amalgamated. Since DARCs are products of two well-defined components of Wilson cycle, i.e., continental rifting and subsequent collision, geochronological constraints from DARCs along the Singhbhum/Bastar Craton-Eastern Ghats Belt contact in eastern India is used to unravel the history of continental breakup and amalgamation in the Indo-Antarctic Enderbia continent. Proto India and East Antarctica were involved in several episodes of collision and breakup during the assembly of past supercontinents. The Napier Complex of East Antarctica collided with the Dharwar Craton and Ongole Domain at 1.60 Ga forming the central-eastern Indian shield. Zircon U-Pb ages from DARCs at the craton-Eastern Ghats Belt margin show that the alkaline complexes (Kamakhyanagar: 1350 ± 14 Ma; Rairakhol: 1379 ± 6 Ma; Koraput: 1387 ± 34 Ma; Kunavaram: 1360 ± 5 Ma; Jojuru: 1352 ± 6 Ma) were emplaced between 1320 Ma and 1370 Ma. The alkaline magmatism marks an episode of rifting in the Indo-Antarctic continental fragment, correlatable with the breakup of the Columbia supercontinent. The Khariar alkaline complex was emplaced at 1478 ± 5 Ma during an earlier phase of crustal extension coeval with the formation of the Mesoproterozoic Chattisgarh rift basin. Metamorphic zircons from the alkaline rocks furnish age populations at 953–930 Ma, 808–795 Ma, and 661–563 Ma. The 953–930 Ma ages are correlated with oceanic closure between Ruker Terrane of East Antarctica and India during Rodinia assembly. The resultant collision of the Ruker Terrane with India-Napier Complex composite produced the Grenville-age Eastern Ghats Province-Rayner Complex orogen. The 808–795 Ma ages record disintegration of Rodinia when India broke away from East Antarctica. In the early Paleozoic, India redocked with East Antarctica and Australia during Gondwanaland assembly. The 661–563 Ma zircon ages date the resulting collisions during Pan-African orogenesis. The assembly of the Eastern Ghats Province and the Rayner Complex with the Bastar-Singhbhum Craton occurred in the early Neoproterozoic during the final stages of Rodinia assembly, supporting the existence of Enderbia continent comprising crustal units from India and East Antarctica.