Proterozoic mafic dyke swarms of Bundelkhand Craton, North India: A connection to Columbia supercontinent

The present paper addresses petrography, geochemistry and Ar-Ar geochronology of a significant number of mafic dykes from the Paleo- to Neoarchean Bundelkhand Craton in central India. The majority of the dykes are NW-SE oriented (with a few NE-SW and ENE-WSW) with tholeiitic, sub-alkaline and basalt to basaltic andesite composition. The trace element geochemistry of these dykes indicates an island arc setting during emplacement. The Ar-Ar mineral dating (plagioclase) of three representative dykes reveals an emplacement age between 1.53 and 1.46 Ga. This finding and earlier reports (2.1-1.73 Ga) point to sustained mafic magmatism throughout the Bundelkhand Craton in a preferred structural orientation between 2.1 and 1.46 Ga. Mafic magmatism was episodic and can be linked to the perpetual subduction accretion processes between the central Indian Archean continents during the development of the Columbia supercontinent. The mafic dykes were emplaced at 45 degrees to the maximum compression direction (E-W), that is, along the line of no finite longitudinal strain. This time equivalent widespread NW-SE and NE-SW trending mafic dyke system is also relatable along the adjacent continents (Singhbhum, Bastar) and thus opened up a new paradigm for the dyke's emplacement across the Indian cratons. The NW-SE and NE-SW trending Proterozoic mafic dyke swarms of central India represent conjugate shear orientation with respect to the regional N-S compression. These dykes were emplaced episodically between 2.1 and 1.46 Ga during the amalgamation of the north and south Indian micro-continents in the Columbia supercontinent assembly. image