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

摘要

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 similar to 2.80 Ga to similar to 1.76 Ga, and include the similar to 2.80 Ga NE-SW trending Keshargaria swarm, similar to 2.75-2.76 Ga NNE-SSW to NE-SW trending Ghatgaon swarm, the similar to 2.26 Ga NE-SW to ENE-WSW trending Kaptipada swarm (based on a new U-Pb ID-TIMS age 2256 +/- 6 Ma), the similar to 1.77 Ga WNW-ESE trending Pipilia swarm, the earlyPaleoproterozoic 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 similar to 2.26 Ga Kaptipada and 1.77 Ga Pipilia, are closely matched with the similar to 2.26-2.25 Ga Ippaguda-Dhiburahalli and similar to 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 PipiliaPebbair 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 SinghbhumBastar-Dharwar reconstruction has age matches in the Vestfold Hills of Antarctica (similar to 2.24 Ga dykes), the Kaapvaal craton (the similar to 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 h