Influence of the Iceland mantle plume on oceanic crust generation in the North Atlantic

Abstract

SUMMARY When a mantle plume with elevated temperature underlies an oceanic spreading centre it affects the generation of oceanic crust by creating thicker crust. We map the variation in crustal thickness and seismic velocity along three long‐offset seismic profiles acquired over oceanic crust generated shortly after continental breakup in the North Atlantic: a 212‐km‐long flowline from the Faroes rifted continental margin across crust of 51–42 Ma age, where oceanic spreading developed close to the inferred centre of the Iceland mantle plume; a 256 km flowline extending from the Hatton rifted continental margin across crust of 52–40 Ma age, about 800 km south of the presumed centre of the mantle plume; and a 99 km strike line over oceanic crust formed at 43 Ma in the Iceland Basin off the Hatton continental margin. The crustal velocity structure along each profile is constrained by multichannel seismic reflection data, which is used primarily to map the sediments, and by densely spaced ocean‐bottom seismometers, which recorded wide‐angle reflections and refractions to offsets of more than 100 km. Over 56 000 crustal diving wave and Moho wide‐angle reflection arrivals were used in joint crustal refraction and reflection tomographic inversions. Quantitative error analysis shows that the seismic velocity of the crust is mostly constrained to within 0.1 km s−1 and the depth of the Moho to within ±250 m. We interpret the crustal thickness and velocity changes along the profiles as caused primarily by changes in the mantle temperature at the time of crustal formation. If all the oceanic crustal thickness variations are ascribed to mantle temperature changes, we infer that as mature seafloor spreading developed following continental breakup, the mantle cooled by ca. 75 °C over a 10 Myr period, although it still remained hotter than the global average of normal oceanic crust. The crust formed close to Iceland is at all times thicker than that formed further away, which we interpret as reflecting higher temperatures close to the centre of the thermal anomaly created by the mantle plume. Currently at the Reykjanes Ridge, south of Iceland, we interpret thicker than normal oceanic crust as being caused by the presence of hotter mantle, modulated by thickness variations of 1.5–2.0 km which are attributed to temporal variations in the mantle plume temperature of about 25 °C on a 3–6 Myr timescale. A 1.5 km increase in thickness of oceanic crust generated between 48 and 45 Ma on the Faroes line is similar in magnitude and duration to those occurring on the present day Reykjanes Ridge, which we suggest is due to a temperature pulse of ∼25 °C. Gravity lineations in the northern North Atlantic suggest that the oceanic crust has exhibited small thickness fluctuations of similar size throughout its history, interpreted as due to small fluctuations in the temperature of the Iceland mantle plume.

Eocene post-rift tectonostratigraphy of the Rockall Plateau, Atlantic margin of NW Britain: Linking early spreading tectonics and passive margin response

“…13) indicates a pattern that is broadly compatible with the results of seismic experiments (e.g. Barton and White, 1997;Parkin and White, 2008). The wide-angle seismic model for the iSIMM (integrated Seismic Imaging and Modelling of Margins) Hatton profile (location shown in Fig.…”

“…The wide-angle seismic model for the iSIMM (integrated Seismic Imaging and Modelling of Margins) Hatton profile (location shown in Fig. 13) indicates igneous oceanic crust decreasing in thickness from 15-16 km adjacent to the continent-ocean boundary to 10 km at a point 65 km to the NW, where there is a sharp inflection to a more gradual oceanward reduction in crustal thickness (Parkin and White, 2008;White and Smith, 2009). The gravity model contains a comparable inflection.…”

Moho and basement depth in the NE Atlantic Ocean based on seismic refraction data and receiver functions

“…1), the result of enhanced melting in the Iceland plume (White & McKenzie 1995;Staples et al 1997). Most of the NE Atlantic Ocean has shallower bathymetry and hotter mantle when compared to other oceans (Parkin & White 2008;Artemieva & Thybo 2013).…”

A review of the NE Atlantic conjugate margins based on seismic refraction data

“…The best dataset available for the margin is the iSIMM Hatton line (Fig. 3b), where the oceanic crust thins from 17 to 9 km over a distance of 70 km to remain at that thickness to the end of the line (Parkin & White 2008;White & Smith 2009). …”