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A prominent component of the 130-80 Ma High Arctic Large Igneous Province (...
A prominent component of the 130-80 Ma High Arctic Large Igneous Province (HALIP) is a giant radiating dyke swarm, elements of which are found in the Canadian Arctic islands, north Greenland, Svalbard and Franz Josef Land. Its overall radial pattern is only clear in a pre-drift plate tectonic reconstruction of the Arctic region. The swarm has been interpreted to focus above a mantle plume responsible for HALIP magmatism. It spans an arc of ~220° and extends up to 1000 km from the focus. In this study, we identify a HALIP giant circumferential dyke swarm whose centre is near, but slightly offset from the focus of the HALIP radiating system. Elements of the circumferential swarm are found in each of the four regions where the radiating system has been recognized. The circumferential swarm has a slightly elliptical geometry, a maximum outer diameter of ~1800 km and an arc of ~190°. It is one of the largest giant circumferential dyke swarm recognized on Earth and the first such swarm to have been identified by means of a plate tectonic reconstruction. Giant circumferential dyke swarms appear to be relatively rare on Earth. However, 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 grabens or fissures and prominent topography. Some coronae are linked to a radiating graben-fissure system. Both radiating and circumferential grabens 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.
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