Uranium-lead dating of Paleoproterozoic mafic dyke swarms of the south Indian shield: Implications for paleocontinental reconstructions and identifying ancient mantle plume events

A multi-technique geochronological study of Paleoproterozoic mafic dyke swarm emplacement in the south Indian shield is presented. Radiometric ages constrain the timing of emplacement of numerous mafic dykes from the Dharwar and Bastar cratons, including high precision U-Pb isotope dilution thermal ionization mass spectrometry (IDTIMS), and high spatial resolution electron microprobe (EM) chemical U-Th-total Pb age determinations.; U-Pb IDTIMS ages determined on baddeleyite and zircon from mafic dykes spanning a vast tract of the Dharwar craton define a punctuated record of mafic magmatism throughout much of the Paleoproterozoic era. Emplacement of the giant radiating Bangalore and Northern Dharwar mafic dyke swarms took place at 2.37 Ga and 2.18 Ga, respectively. Similar ages of 2.21 Ga were determined for a NW-SE trending picrite and a N-S trending sub-alkali basaltic dyke south of the Cuddapah basin. U-Pb IDTIMS ages on baddeleyite and zircon for two NW-SE trending dykes from the BD2 mafic dyke swarm, southern Bastar craton, and the Pulivendla mafic sill from the Cuddapah basin, Dharwar craton, range from 1891 to 1883 Ma, and indicate the existence of a large igneous province within the south Indian shield that is genetically associated with rifting and basin development.; For the first time, rigid time correlations are made between Paleoproterozoic mafic magmatism in southern India and the record preserved in other Archean cratons worldwide. On the basis of high precision geochronology, the emerging Paleoproterozoic record of punctuated and catastrophic mafic magmatic activity preserved in the south Indian shield bears strong resemblance to the record preserved in the Superior and Slave cratons of North America. These correlations indicate that the paleocontinents Ur and Kenorland may have broken up at the same time, and provide new evidence suggesting that these paleocontinents could have been part of a single larger Paleoaphebian continent or supercontinent called Kurnorland. This study also has implications for defining enhanced periods of global mantle plume activity at 2.2 Ga and 1.9 Ga, or alternatively, the identification of global mafic magmatism at these times in association with widespread asthenospheric upwelling not associated with mantle plumes.