­A Giant Circumferential Dyke Swarm Associated with the High Arctic Large Igneous Province (HALIP) – a Possible Analogue for Coronae on Venus

English Abstract:

Giant sub-circular tectono-magmatic features called coronae are common on Venus. They may be associated with mantle plumes or diapirs, are typically hundreds of kilometres in diameter, and usually have a raised annulus with an associated circumferential graben-fissure system that may be underlain by dykes. On Earth, corona analogues appear to be rare, perhaps because erosion has removed the distinctive topographic features. However the dyke swarms should persist. An excellent example of a giant circumferential swarm has been reported recently at Lake Victoria in Africa and there are several other tentative examples. We identify a giant circumferential swarm associated with the 125-80 Ma High Arctic Large Igneous Province (HALIP) and its previously documented giant radiating swarm. The circumferential dykes are roughly perpendicular to the radiating dykes. However, the centre of the circumferential swarm appears to be slightly offset (~200 km) from the focus of the radiating swarm, a feature of some venusian coronae. The circumferential swarm has a diameter of ~1200-1600 km. It is most clearly visible in reconstructions of North Greenland, Svalbard and Franz Josef Land, where segments of the swarm fall along an arc of ~100⁰. An extension of the swarm into the Canadian Arctic islands is likely, but more speculative, because of uncertainties in undoing deformation associated with the Eurekan orogeny on Ellesmere and Axel Heiberg islands and the presence of dykes of other discordant trends. The age ranges of the circumferential and radiating swarms are uncertain, although many radiating dykes are associated with the early part of the HALIP event and a single dyke associated with the North Greenland portion of the circumferential swarm has previously been dated at 82±1 Ma (Ar-Ar), near the end of the event. Identifying giant circumferential swarms on Earth is important for understanding the evolution of large igneous provinces and interpreting coronae on Venus.