North Atlantic hotspot-ridge interaction near Jan Mayen Island

At slow to ultraslow spreading rates along mid-ocean ridges, thicker lithosphere typically impedes magma generation and tectonic extension can play a more significant role in crustal production (Dick et al., 2003). The source of anomalously high magma supply thus remains unclear along ridges with ultraslow-spreading rates adjacent to Jan Mayen Island in the North Atlantic (Neumann and Schilling, 1984; Mertz et al., 1991; Haase et al., 1996; Schilling et al., 1999; Tronnes et al., 1999; Haase et al., 2003; Mertz et al., 2004; Blichert-Toft et al., 2005; Debaille et al., 2009). Here we show that Jan Mayen volcanism is likely the surface expression of a small mantle plume, which exerts significant influence on nearby mid-ocean ridge tectonics and volcanism. Progressive dilution of Jan Mayen geochemical signatures with distance from the hotspot is observed in lava samples from the immediately adjacent Mohns Ridge, and morphological indicators of enhanced magma supply are observed on both the Mohns Ridge and the nearby Kolbeinsey Ridge, which additionally locally overlies a highly heterogeneous, eclogite-bearing mantle source. These morphological and geochemical influences underscore the importance of heterogeneous mantle sources in modifying melt supply and thus the local expression of tectonic boundaries.