Methodology for Evaluating the North Atlantic Igneous Province Reveals Multiple Hotspots at Breakup

Abstract

The North Atlantic Igneous Province (NAIP) has been the focus of numerous studies. However, a systematic integrated methodology to assess the NAIP, has so far been lacking. For this purpose, a synclinal oceanic rift approach is developed from the stratigraphic record. Mechanisms are addressed combining trace element and seismic velocity data as a proxy for excess mantle potential temperature (ΔTp), using simple mantle melting models. Unconformities play a major role in this assessment, providing evidence for a drop in ΔTp to ambient levels (≤50°C). Three phases can be delineated in the stratigraphic record: a (a) Pre‐; (b) Syn‐; and (c) Post‐breakup phase. The Syn‐breakup phase is bound at the base by the Breakup Unconformity and at the top by the Magmatic Unconformity. At breakup, magmatic crustal thickness (H) can be estimated from addition of basalt‐ and Lower Igneous Crust isopachs. These seismic estimations can be further constrained by observations on volcanic transport directions. This allows differentiation between hotspots and Volcanic Passive Margins (VPMs), where hotspots are characterized by continuous ΔTp amplitude variations, whereas VPMs only display declining or absent fluctuations post breakup. On Iceland and the Greenland‐Iceland‐Faroe Ridge, H is primary controlled by ΔTp fluctuations promoting ridge jumps and second, associated fluctuating active upwelling ratio (χ ∼ 2–4). Results suggest that there were at least three hotspots active at breakup. The West Greenland and proto‐Jan Mayen hotspots lost importance in the Oligocene, while Iceland remained and is currently the main hotspot in the North Atlantic.

Dyke swarms record the plume stage evolution of the Atla Regio superplume on Venus

“…On the other hand, if the plate is approximately stationary (as on Venus, which is currently a one-plate planet 1 ), the entire volume of plume tail magmatism would be superimposed in one location 4 . A terrestrial example is the Iceland plateau, which can be interpreted as the accumulation in one spot (fixed on a spreading ridge) from the plume tail stage following the plume head stage that produced the 62-55 Ma North Atlantic LIP 15 . Although, the volcanism of the plume tail stage is characterised by low flux, the cumulative volume can be huge.…”