Paleomagnetic and geochronological studies of the mafic dyke swarms of Bundelkhand craton, central India: Implications for the tectonic evolution and paleogeographic reconstructions

The paleogeographic position of India within the Paleoproterozoic Columbia and Mesoproterozoic Rodinia supercontinents is shrouded in uncertainty due to the paucity of high quality paleomagnetic data with strong age control. New paleomagnetic and geochronological data from the Precambrian mafic dykes intruding granitoids and supracrustals of the Archean Bundelkhand craton (BC) in northern Peninsular India is significant in constraining the position of India at 2.0 and 1.1 Ga. The dykes are ubiquitous within the craton and have variable orientations (NW-SE, NE-SW, ENE-WSW and E-W). Three distinct episodes of dyke intrusion are inferred from the paleomagnetic analysis of these dykes. The older NW-SE trending dykes yield a mean paleomagnetic direction with a declination = 155.3 degrees and an inclination = -7.8 degrees (kappa = 21; alpha(95) = 9.6 degrees). The overall paleomagnetic pole calculated from these 12 dykes falls at 58.5 degrees N and 312.5 degrees E (dp/dm = 6.6 degrees/7.9 degrees). The overall mean direction calculated from four ENE-WSW Mahoba dykes has a declination = 24.7 degrees and inclination =-37.9 degrees (kappa = 36; alpha(95) = 15.5 degrees). The virtual geomagnetic pole (VGP) for these four dykes falls at 38.7 S and 49.5 E (dp/dm = 9.5 degrees/16.3 degrees). A third, and distinctly steeper, paleomagnetic direction was obtained from two of the NE-SW trending dykes with a declination = 189.3 degrees and inclination = 64.5 degrees. U-Pb geochronology generated in this study yields a U-Pb Concordia age of 1979 +/- 8 Ma for the NW-SE trending dykes and a mean Pb-207/Pb-206 age of 1113 +/- 7 Ma for the Mahoba suite of ENE-WSW trending dykes, confirming at least two dyke emplacement events within the BC. We present global paleogeographic maps for India at 1.1 and 2.0 Ga using these paleomagnetic poles. These new paleomagnetic results from the similar to 2.0 Ga NW-SE trending Bundelkhand dykes and the paleomagnetic data from the BastariCuddapah suggest that the North and South Indian blocks of the Peninsular India were in close proximity by at least 2.5 Ga. The paleomagnetic and geochronological data from the Mahoba dyke is significant in that it helps constrain the age of the Upper Vindhyan strata. The pole coincides in time and space with the Majhgawan kimberlite (1073 Ma) and the Bhander-Rewa poles from the Upper Vindhyan strata. The most parsimonious explanation for this coincidence is that the age of the Upper Vindhyan sedimentary sequence is > 1000 Ma. (C) 2011 Elsevier B.V. All rights reserved.