Structures and Magmatism Associated With a Failed Triple Junction in Traill Ø, East Greenland

Abstract The Late Eocene–Oligocene post‐breakup magmatism of the North Atlantic Igneous Province (NAIP) in East Greenland, is represented by sub‐volcanic intrusions associated with a NE‐SW oriented magmatic lineament, the Werner Bjerge Rift. This onshore magmatism extends for more than 100 km from eastern Traill Ø to Werner Bjerge. In the same region, strike‐slip post‐breakup faulting is documented along N‐S trending faults extending more than 300 km from Traill Ø up to the north, along the Loch Fyne Fault Zone. Offshore East Greenland, the NW‐SE trending East Jan Mayen Fracture Zone, has represented the northern boundary of the Jan Mayen Micro Continent in the Eocene–Oligocene, and extended westward, toward Traill Ø. The Werner Bjerge Rift, the Loch Fyne Fault Zone and the East Jan Mayen Fracture Zone were active during the Late Eocene–Oligocene and intersected in eastern Traill Ø with a 120° angle, resembling a triple junction. This study presents the onshore deformation and magmatism associated with a failed triple junction that was active between 40 and 25 Ma, highlighting the importance of inherited structures in response to stress variations and plate tectonics modifications. The tectonic trends of the Fault‐Fault‐Ridge Traill Ø triple junction are inherited structures from the Caledonian Orogeny and from multi‐stage rifting episodes that characterized the East Greenland basin system since the Late Carboniferous. New age and geochemistry of the magmatism in the Werner Bjerge Rift, combined with structural analyses of fault systems suggest that the Traill Ø triple junction was generated by plate tectonics configuration and not by a mantle plume.