Paleomagnetism and geochronology of the Malani Igneous Suite, Northwest India: Implications for the configuration of Rodinia and the assembly of Gondwana

New paleomagnetic and geochronologic data from the Malani Igneous Suite (MIS) in Rajasthan, northwest India, improve the paleogeographic reconstruction of the Indian subcontinent between dispersal of the Mesoproterozoic supercontinent Rodinia and late Neoproterozoic assembly of Gondwana. The MIS comprises voluminous phases of felsic and volumetrically insignificant mafic volcanism followed by granitic plutonism. Large (up to 5 m wide) felsic and mafic dikes represent the terminal phase of magmatism. A zircon U-Pb age on a rhyolitic tuff constrains the initial volcanism in the MIS to 771 +/- 5 Ma. A paleomagnetic direction obtained from four mafic dikes has a declination = 358.8 degrees and inclination = 63.5 degrees (with kappa = 91.2 and alpha(95) = 9.7). It overlaps with previously reported results from felsic MIS rocks. This direction includes a fine-grained mafic dikelet that showed a reversed direction with declination = 195.3 degrees and inclination = -59.7 degrees (kappa = 234.8 and alpha(95) = 8.1 degrees) and also records an overprint of normal polarity from the larger dikes. The VGP obtained from this study on mafic dikes is combined with previous studies of the Malani suite to obtain a mean paleomagnetic pole of 67.8 degrees N, 72.5 degrees E (A95 = 8.8 degrees). Supported by a tentative baked contact test, we argue that this pole is primary, and permits improved reconstruction of the Indian subcontinent for 771-750 Ma. Data from the MIS and equivalent data from the Seychelles at 750 +/- 3 Ma are compared with paleomagnetic data from the 755 +/- 3 Ma Mundine Well dikes in Australia to indicate a latitudinal separation of nearly 25 degrees between the Indian and Australian plates. These suggest that East Gondwana was not amalgamated at ca. 750 Ma and therefore these two cratonic blocks were assembled later into the Gondwana supercontinent, during the ca. 550 Ma Kuunga Orogeny. (C) 2008 Elsevier B.V. All rights reserved.