Seamounts and Oceanic Igneous Features in the Northeast Atlantic: A Link Between Plate Motions and Mantle Dynamics

Abstract:

Volcanism in the NE Atlantic region is dominated by the presence of anomalous mantle –presently manifested through recent volcanism in Iceland. Besides active and extinct volcanoes on Iceland and on the Jan Mayen island, and older volcanic activity on the shallow submarine Greenland-Faroe Ridge, seamount-like oceanic igneous features (abbreviated SOIF) in the NE Atlantic cluster on three distinct types of oceanic crust. Seamounts on 54 to 50 Ma crust are formed on smooth oceanic basement, which resulted from high spreading rates and magmatic productivity enhanced by higher than usual mantle plume activity. Late Eocene to Early Miocene SOIF clusters are located close to newly formed tectonic features on rough oceanic crust situated south and northeast of Iceland, reflecting an unstable tectonic regime prone to local re-adjustments of mid-ocean ridge and fracture zone segments accompanied by extra igneous activity. We conclude that Iceland plume episodic activity combined with regional changes in relative plate motion led to local mid-ocean ridge re-adjustments, which enhanced the likelihood of seamount formation.

Furthermore, we attempt to correlate the distribution of younger submarine volcanic features with a new tomographic model that image in greater detail than before the upper mantle of NE Atlantic. We observe that high negative S-wave velocity anomaly present under Iceland, is continuing under the Kolbeynsei Ridge, south of the Jan Mayen Fracture Zone (JMFZ), where recent high submarine volcanic activity has been reported from the Eggvin Bank region. Another striking observation is that the “hottest” mantle anomalies in the Greenland Sea, are not centered on the Mohn’s mid-ocean ridge, but in the SW Greenland Sea, north of the JMFZ. That region hosts one of the biggest seamount in the NE Atlantic – the Vesteris seamount whose latest eruption was in Quaternary. An asymmetric SOIF distribution along the Mohn’s ridge, with more seamounts located on its western flank, seems to correlate well with the upper mantle pattern. We postulate that recent volcanism in the NE Atlantic away from the Iceland plume reflects the shallower distribution of plume material within smaller plume heads and/or the ascending sub-horizontal flow of the asthenosphere under a thin lithosphere.