We combine new and published 40Ar/39Ar age determinations from incremental heating experiments on whole rocks and mineral separates to assess the timing, duration and distribution of volcanic activity during construction of the North Atlantic Igneous Province. We use these ages together with volume estimates of erupted magmas and their cumulates to calculate melt production rates for the early Tertiary flood basalts of East Greenland and the Faeroes Islands. The lavas lie at opposite ends of the Greenland-Iceland-Faeroes Ridge, the postulated Iceland hotspot track, and record volcanic activity leading up to, during and following continental breakup between Greenland and Europe.
Dominantly basaltic (but also alkalic and picritic) magmas were erupted from beneath thick continental lithosphere simultaneously, at 61 Ma, from Baffin Island, to the western and eastern margins of Greenland, to the Faeroe Islands and the western British Isles, a roughly circular area 2000 km in diameter. Volcanic activity was increasingly intermittent by 57-56 Ma, but at 56.1 ± 0.5 Ma the average melt production rate increased by more than an order of magnitude over previous levels (from < 200 to > 3000 km3/km of rift/my), coinciding with continental rifting and shallow decompressional melting of the mantle that fed subaerial volcanic activity along most of the eastern margin of Greenland and its complement on the northwestern European margin. Offshore, abnormally thick oceanic crust was produced along the line of plate separation. The upper part of this crust comprises seismically imaged, seaward-dipping, subaerially erupted lavas.
By 50 Ma, eruption rates had diminished drastically and volcanic activity had narrowed to a much restricted portion of the East Greenland margin, at the western end of the Greenland-Iceland ridge, that subsequently connected in an age-progressive trend to present hotspot activity in southeastern Iceland. The startup mantle plume head and tail model, with moderate excess temperature (ΔT ~ 100 °C) and active upwelling, best explains the time, space and compositional aspects of volcanism in this province. © 2007 Elsevier B.V. All rights reserved