E-catalog        

In this study, we identify a giant circumferential mafic dyke swarm associated with the 135–75 Ma High Arctic Large Igneous Province (HALIP). Previously, a HALIP giant radiating mafic dyke swarm, with portions scattered across the Canadian high Arctic islands, northern Greenland, Svalbard and Franz Josef Land, was recognized in a pre-drift plate tectonic reconstruction of the Arctic region. The radiating swarm has been interpreted to focus above a mantle plume responsible for HALIP magmatism. The newly-recognized HALIP giant circumferential swarm has a centre that is near the focus of the HALIP radiating system, and hence, is likely related to the HALIP plume. Elements of the circumferential swarm are located in each of the four regions where the radiating system is found. The circumferential swarm has a quasi-circular or slightly elliptical geometry, an outer diameter of ~1600 km and an arc of ~220°. It is one of the largest giant circumferential dyke swarms recognized on Earth, and could be linked to the outer edge of the flattening plume head. It is also the first such swarm to have been identified by means of a plate tectonic reconstruction. Although giant circumferential dyke swarms appear to be relatively rare on Earth, possible analogues are common on Venus and are also found on Mars. On Venus giant circular or elliptical tectono-magmatic features, termed coronae, are characterized by an annulus of graben or fissures and prominent topography. Some coronae include a radiating graben-fissure system. Both radiating and circumferential graben may be underlain by dykes. If so, coronae could be analogues for terrestrial giant circumferential dyke swarms such as observed in the case of the HALIP.