India's Palaeoproterozoic legacy

Abstract

AbstractThe Indian lithospheric plate assembles the history of geological events covering almost the entire history of our planet. The proto-Indian continent was an integral part of the Palaeoproterozoic supercontinent Columbia. Global mantle warming beneath this supercontinent triggered rising plumes that led to rifting and the emplacement of mafic dyke swarms and large igneous provinces in many of the major cratons of Peninsular India. Continued rifting and separation of crustal blocks led to the formation of thick passive margin successions. The opening of ocean basins and their eventual closure are recorded in the travelogue of oceanic plates from mid-ocean ridge to the trench in the form of ‘ocean plate stratigraphy’ in Proterozoic belts, including the association of dismembered ophiolites, pelagic sediments and continental margin sequences that were imbricated into accretionary belts such as those in the Aravalli–Delhi domain (Western India Suture), the Central India Tectonic Zone (Central India Suture) and the eastern margin of the East Dharwar Craton (Eastern India Suture). Recent U–Pb zircon chronology from ophiolitic rocks in the eastern margin of the Dharwar Craton shows ages spanning from 1.85 to 1.33 Ga suggesting a prolonged Wilson cycle of subduction–accretion processes before the final collisional event and the extrusion of high-grade metamorphic orogens. The extruded high pressure–temperature (P–T) metamorphic belts are often associated with mafic/ultramafic units with an abyssal signature. The available geophysical information from the Indian Palaeoproterozoic belts, particularly deep seismic reflection data, provides important clues on the architecture of these orogens and the subduction polarity. Whereas the Palaeoproterozoic convergent margins in the NW and SE sectors of the Indian peninsula were characterized by the westward subduction of oceanic plates, ocean closure along the Central India Tectonic Zone probably involved a double-sided subduction. The Wilson cycle traces a continuum from Palaeoproterozoic through Mesoproterozoic to Neoproterozoic in some of these belts, with a prolonged subduction–accretion history similar to the ongoing convergent margin processes in the western Pacific region. Peninsular India thus preserves a complete record from Pacific-type accretionary tectonics along the margins of the Columbia supercontinent to Himalayan-style collisional assembly within the Neoproterozoic Rodinia supercontinent.