A paleoproterozoic giant radiating dyke swarm in the Dharwar Craton, southern India

Abstract

Identical high precision U-Pb baddeleyite ages, together with paleomagnetic and geochemical data, on mafic dykes occurring over an area of 140,000 km², define a Paleoproterozoic giant dyke swarm at ca. 2.367 Ga in the Dharwar craton, south India, referred to here as the Dharwar giant dyke swarm. All six U-Pb ages on these dykes are identical within error and suggest emplacement of this swarm within a geologically short time span of ∼5 Myr. A systematic southward progression in the trend of dykes from N48°E to N90°E, defines a fan angle of about 40° with convergence to a focal point about 300 km west of the present-day Dharwar craton boundary, resulting in a spectacular radiating dyke swarm extending across the entire eastern Dharwar craton. The large areal extent, radiating dyke pattern and short duration imply a mantle plume origin for the Dharwar giant dyke swarm. Despite their large areal distribution, all dykes in this swarm are geochemically coherent and have similar primitive mantle-normalized trace element patterns and rare earth element characteristics. Although the NE part of the swarm is magnetically overprinted, a remanence survives that has the same direction as primary magnetizations from dykes in the southern part of the swarm.