NE Atlantic break-up: a re-examination of the Iceland mantle plume model and the Atlantic–Arctic linkage

Abstract

Final break-up of Pangaea – opening of the NE Atlantic (NEA) and the Arctic Eurasia Basin – was associated with significant magmatism (in the NEA) and is commonly ascribed to thermal effects from a proto-Iceland plume. The plume is often assumed to be fixed with respect to the Earth’s core and to have governed NEA break-up. It is argued here that the Iceland anomaly, past and present, cannot represent a fixed plume, nor be rooted at the core–mantle boundary and that the Greenland–Faroes Ridge is inconsistent with a classic time-transgressive hotspot track. It is shown that the Iceland anomaly has probably been located at the constructive plate boundary (Mid-Atlantic Ridge and antecedents) since its inception. While recent studies allow for some ‘wandering’ of hotspots relative to the core and mantle, it is considered unlikely that such drift of a mantle plume would precisely match lithospheric drift in order to achieve constant centering on the spreading ridge. The alternative view is, therefore, supported – that the anomaly is an upper mantle response to plate break-up. The two pulses of NEA magmatism are related to separate phases of North Atlantic break-up. Early Paleocene magmatism (c. 62–58 Ma) was governed by a short-lived attempt at seeking a new rift path, intermediate in time and space between the Labrador Sea–Baffin Bay and the NEA–Eurasia Basin rifts. The voluminous Early Eocene magmatism (c. 56–53 Ma) along the NEA margins was related to final break-up of Pangaea, exploiting the collapsed Caledonian fold belt. The interpretations here are at odds with Iceland representing a classic Morgan-type plume and it is suggested that the magmatism in the NEA and the Iceland anomaly represent a ‘top-down’ effect of plate tectonics.