A PALEO-MESOPROTEROZOIC DRIFT HISTORY OF THE INDIAN SUBCONTINENT; CONSTRAINTS FROM WIDESPREAD RADIATING MAFIC DYKE SWARMS

The Indian subcontinent is central to many Precambrian paleogeographic reconstructions including the supercontinents of Columbia and Rodinia. Geologic features such as orogenic belts, Large Igneous Provinces (LIPs), and patterns of mafic dyke swarms are often used in creating these types of reconstructions. Radiating dyke swarms that accompany LIPs can be used to locate potential plume centers as well as determine the breakup timing of different cratonic nuclei. Within the Dharwar craton, and to the south and west of the Cuddapah Basin, mafic dyke swarms intrude the older Archean granites and gneisses. It has been suggested that the largest of these magmatic events are fragments of ancient LIPs (Ernst 2007). The mafic dykes are oriented in a variety of directions ranging from E-W, WNW-NW, NE-ENE, and N-S. Recent paleomagnetic and geochronologic work on the Dharwar and Bastar cratons indicates several periods of dyke emplacement during the Paleo-Mesoproterozoic. Halls et al. (2007) identified a 2.37 Ga swarm of E-W trending dykes within the Dharwar craton. French and Heaman (2010) used precise U-Pb dating and determined the emplacement ages for some of the dykes to be 2369-2365 Ma, 2221-2209 Ma, and 2181-2177 Ma. Meert et al. (2011) presented preliminary paleomagnetic results from 1.88 Ga dykes intruding the Bastar craton that were correlated with Dharwar volcanics, lending support to Ernst and Srivastava’s (2008) hypothesis of a widespread LIP at 1.9 Ga within the Indian subcontinent. We targeted dyke swarms located near Hassan, Tiptur and Kunigal (west of Bangalore) along with numerous dykes in the Tirupati-Chitoor region (E-NE of Bangalore). Here we present new results from the Dharwar mafic dykes and compare our results with the most recent paleomagnetic and geochronologic work. Proposed mantle plume centers for several events are evaluated and different cratonic relationships are considered through the reconstruction of the radiating dyke swarms. The classic Columbia model based on geologic arguments will be evaluated in light of the new paleomagnetic data, and an updated Apparent Polar Wander Path (APWP) for the Indian subcontinent will be presented for the Paleo-Mesoproterozoic.