Geophysical insights and early spreading history in the vicinity of the Jan Mayen Fracture Zone, Norwegian–Greenland Sea

Abstract

Using a new high-resolution aeromagnetic survey (JAS-05) that was acquired along the trend of the Jan Mayen Fracture Zone (JMFZ), west of the Vøring volcanic margin, we investigated the geodynamic framework of the early spreading evolution of the Norwegian–Greenland Sea. The tectonic structure, main faults and magnetic chrons have been reinterpreted based on new magnetic gridded data and integrated with bathymetry, gravity and seismic data. The new interpretation reveals more details about the early spreading history of the Norwegian–Greenland Sea in the vicinity of the JMFZ. Although anomalous melt production (seaward-dipping reflectors, underplating) associated with the breakup of the Mid-Norwegian margin has been described in many studies, we present data that suggest that significant magmatism continued episodically during the opening of the Norwegian–Greenland Sea along the trend of the JMFZ. The Vøring Spur (VS), an anomalous oceanic high, lying north of the eastern segment of the JMFZ exhibits a contrasting Bouguer gravity low and a complex magnetic signature. The gravity signature of the VS can be modelled and explained as an abnormal thick oceanic crust, which locally can reach up to 15 km. We propose that the thick oceanic crust (overcrusting) was syn-rift and formed during Mid- to Late Eocene. A plate reconstruction at Eocene time suggests that the VS could be part of a triple junction initiated during the breakup between the Vøring Marginal High and the Greenland part of the Traill–Vøring igneous complex, now located offshore East Greenland. Mantle upwelling beneath the early spreading ridge and/or local stress reorganisation could have induced transtension and lithospheric thinning along the JMFZ and magmatic activity would have increased locally along this ‘leaky transform’. We suggest that the Early Tertiary tectono-magmatic processes that operated in the Norwegian–Greenland Sea are similar to the processes involved in the modern triple junction evolution of the Azores Plateau region.