New palaeomagnetic and rock magnetic results on Mesoproterozoic kimberlites from the Eastern Dharwar craton, southern India: Towards constraining India's position in Rodinia

Abstract

New palaeomagnetic and rock magnetic results are reported for 1.1Ga Mesoproterozoic kimberlites from the distinct fields of Wajrakarur (WKF), Narayanpet (NKF) and Raichur (RKF) occurring within the Eastern Dharwar craton, southern India. In all, 35 oriented block samples were collected from ten kimberlite pipes and our results constitute first of their kind for the kimberlites from NKF and RKF. Palaeomagnetic data reveal that characteristic remanent magnetization (ChRM) directions of the studied kimberlites show a mean declination of 39 and mean inclination of −16 (N=4, k=37.6 and α95=15.2) and yield a virtual geomagnetic pole at 44.5°N, 195.4°E (dp=8.0, dm=15.6). This new pole position is identical to the earlier reported palaeomagnetic pole that lies at 36.8°N, 212.5°E for some Wajrakarur kimberlites and other such global results at 1100Ma from Umkondo dolerites, Kalahari craton, southern Africa. The newly obtained palaeomagnetic pole also correlates well with the virtual geomagnetic pole (VGP) generated from the 1.1Ga Majhgawan kimberlite, Mahoba dyke and the Bhander–Rewa sedimentary Group in the Upper Vindhyan sequence within the Bundelkhand craton of Northern India. Our results support a Mesoproterozoic closure age of the upper sedimentary horizons for the ‘Purana’ sedimentary basins and provide evidence for accretion of the northern and southern Indian cratonic blocks prior to 1.1Ga. Our study also demonstrates that in ∼1.1Ga palaeomagnetically based Rodinia reconstructions, India occupies a lower palaeolatitudinal position, was much separated from Australia and that East Gondwana very likely did not form an assembly until the terminal Neoproterozoic.