Evidence for a Neoarchean LIP in the Singhbhum craton, eastern India: Implications to Vaalbara supercontinent.

We report eight new Pb-Pb baddeleyite ages and paleomagnetic results on a series of hitherto unknown Neoarchean NNE-SSW trending mafic dyke swarms intruding the Paleoarchean basement rocks in the Singhbhum craton, eastern India. Being the most dominant dyke swarms in the region, they occur over the entire Singhbhum craton with an areal distribution extending to about 30,000 km 2 . Of the eight dyke samples analysed across the entire dyke swarm, six were emplaced at 2762.4 ± 2.0 Ma (weighted mean of 6 dyke ages), two with similar strike directions, yielded older and younger ages of 2800.2 ± 0.7 Ma and 2752.0 ± 0.9 Ma respectively. The older 2800.2 ± 0.7 Ma dyke event appears to be coeval with several other magmatic events reported earlier from the Singhbhum craton. Emplacement of dacite tuffs within the Malaigiri basin, on the southern margin of the craton, the Budhapal and Rengali granite from the south-western and southern parts of the craton, along with the Temperkola granite activity and associated acid volcanics in the western part of the craton, and perhaps the Mayurbhanj granite (fine-grained phase) are also contemporaneous, suggesting a fairly wide spread thermal event in the region at this time. Well defined craton-wide magmatic events contemporaneous to the 2762.4 ± 2.0 Ma Singhbhum dyke activity have been reported from the Pilbara. The younger 2752.0 ± 0.9 Ma age dyke event occurring in the Singhbhum is also know from the eastern Pilbara. An older event at 2783 ± 1.2 Ma (Gaborone-Kanye-Plantation Porphyry-Derdepoort-Modipe episode) was identified in the Kaapvaal craton. Comparison of paleomagnetic data obtained on the Singhbhum Neoarchean dyke swarms with the Pilbara and Kaapvaal data, show all these continents were located at steep latitudes and could have been proximal to each other during this time. If Pilbara and Kaapvaal formed supercraton Vaalbara during the Neoarchean time, we propose Singhbhum with similar Archean geology could also have had its ancestry in the same supercraton. [ABSTRACT FROM AUTHOR]