Reinvestigating the Dufek Intrusion, through joint gravity and magnetic models

The Dufek layered mafic intrusion represents the only exposed, deep-seated, part of the Ferrar Large Igneous Province, which extends >3500 km across Antarctica and into parts of Tasmania and New Zealand. The Dufek Intrusion is in a key position at the boundary between the Jurassic Weddell Sea Rift System and the East Antarctic Craton. It may have been a conduit for some of the Ferrar magmas, or a deep-seated equivalent to the shallower sills seen in other sectors of Antarctica. Although a significant intrusion, equivalent at least to the Stillwater complex in the USA, its true scale and geometry, along with the relative timing of emplacement is disputed. We present new 3D models of gravity and magnetic data which constrain the geometry of the intrusion, show how separate lobes of the intrusion are linked and identify a possible extension of the intrusion to the east. We also discuss the implications for how the intrusion may have been emplaced. • New compilations of gravity and magnetic data used to model Dufek Intrusion. • Dufek intrusion formed of ∼24,000 km 3 magma in two lobes with common structure. • New linear intrusive magmatic structure identified adjacent to main intrusion. • Stratification interpreted to be due to multiple phases of magma emplacement.