Precise Pb–Pb Baddeleyite Ages of 1765 Ma for a Singhbhum 'Newer Dolerite' Dyke Swarm

The Singhbhum craton in eastern India hosts a number of mafic dyke swarms popularly called 'newer dolerites'. Previous attempts to obtain emplacement ages of these rocks were limited to a few poor-precision K-Ar whole-rock and Rb-Sr isochron ages. Here, two prominent dykes from the WNW-ESE trending swarm in the south central region of the craton were dated using Pb-Pb baddeleyite thermal extraction-thermal ionization mass spectrometer method. These dykes yielded identical baddeleyite Pb-Pb ages of 1766.2 ± 1.1 Ma (SKJ-10) and 1764.5 ± 0.9 Ma (SKJ-15) respectively, which are interpreted as the time of emplacement of the WNW-ESE trending 'newer dolerite' dyke swarm. The predominantly parallel dyke trend in this swarm for over 100 km along strike indicates these dyke fractures were formed due to horizontal compressive stresses in a region that may have been associated with a palaeo compressional system.

Coeval ∼1770 Ma magmatism in the Singhbhum craton and in China, Australia, Brazil and Uruguay confirms this event was globally widely dispersed. The timing of this event also coincides with orogenic activity in majority of continents that may have formed during the assembly of supercontinent Columbia.