Precambrian mafic dyke swarms in the Singhbhum craton (eastern India) and their links with dyke swarms of the eastern Dharwar craton (southern India)

Abstract

Based on trend, cross-cutting relationships and U-Pb dating, Precambrian mafic dykes in the Singhbhum craton, earlier collectively identified as ‘Newer Dolerite Swarm’, have been separated into seven distinct swarms, which are thought to be the plumbing systems for Large Igneous Provinces (LIPs). These Singhbhum swarms range in age from ∼2.80 Ga to ∼1.76 Ga, and include the ∼2.80 Ga NE-SW trending Keshargaria swarm, ∼2.75–2.76 Ga NNE-SSW to NE-SW trending Ghatgaon swarm, the ∼2.26 Ga NE-SW to ENE-WSW trending Kaptipada swarm (based on a new U-Pb ID-TIMS age 2256 ± 6 Ma), the ∼1.77 Ga WNW-ESE trending Pipilia swarm, the early-Paleoproterozoic E-W to ENE-WSW trending Keonjhar swarm, the middle-Paleoproterozoic NW-SE to NNW-SSE trending Bhagamunda swarm, and the late-Paleoproterozoic N-S to NNE-SSW trending Barigaon swarm. Two of the Singhbhum swarms, the ∼2.26 Ga Kaptipada and ∼1.77 Ga Pipilia, are closely matched with the ∼2.26–2.25 Ga Ippaguda-Dhiburahalli and ∼1.79 Ga Pebbair swarms, respectively, of the eastern Dharwar craton. The correlations suggest that the Singhbhum and Dharwar cratons were close enough at these times to share two reconstructed LIPs, a 2.26–2.25 Ga Kaptipada– Ippaguda-Dhiburahalli LIP and a 1.79–1.77 Ga Pipilia-Pebbair LIP, and if so, both swarms must be present in the intervening Bastar craton (candidates are proposed). Also, the 2.76–2.75 Ga Ghatgaon swarm of the Singhbhum craton can be provisionally correlated with ∼2.7 Ga Keshkal swarm of the Bastar craton. The 2.26–2.25 Ga Kaptipada–Ippaguda-Dhiburahalli LIP of the Singhbhum-Bastar-Dharwar reconstruction has age matches in the Vestfold Hills of Antarctica (∼2.24 Ga dykes), the Kaapvaal craton (the ∼2.25–2.23 Ga Hekpoort lavas) and perhaps the Zimbabwe craton (2.26 Ga Chimbadzi troctolite intrusions). The 1.76–1.79 Ga Pipilia-Pebbair LIP of the Singhbhum-Bastar-Dharwar reconstruction has age matches in the North China, Australian Shield, Amazonian, Rio de Plata and Sarmatia cratons. The relevance of these matches for reconstructions will require future testing using paleomagnetic studies. While there are ∼2.7–2.8 Ga LIP-type greenstone belts in many crustal blocks, there are no precise matches with the 2.76–2.75 Ga Ghatgaon swarm of the Singhbhum craton. However, the 2.80 Ga Keshargaria swarm can be potentially linked with units in the Pilbara and Yilgarn cratons.