Dyke swarms as indicators of major extensional events in the 1.9–1.2 Ga Columbia supercontinent

The six large fanning dyke swarms mapped here using aeromagnetic data span two periods in the evolution of the Columbia supercontinent: (i) 1.9–1.7 Ga during and immediately following maximum packing of Columbia; and (ii) 1.3–1.2 Ga during the period of final Columbia break-up. The dyke swarms define the locus of hotspot generated magmatism associated with dyke intrusion and their current relationship to continental margins and or intracratonic rifts can be used to identify the tectonic setting associated with each swarm. Three swarms were associated with failed or aborted rifts and indicate multiple hotspots were active during the break-up of Columbia. Three dyke swarms were related to successful rifting and ocean opening. These swarms provide a constraint on palaeo-continental block positions that are not accounted for in the current reconstructions of Columbia.