When tracing the origin of the eruption, Kolbeinsey Ridge and the relevant convection rolls are actually the most relevant cause. The Arctic rolls are the upper most of the system, in direct contact with the tectonic plate at around 120 km depth. This could even be tested with petrological relationship between the Kolbeinsey Ridge and the primitive form of magma finding its way up to the surface at Reykjanes. Here is a drawing showing the upper most roll and its relationship with Reykjanes, with the upwelling division line passing the west coast of the Reykjanes Peninsula.
Red line is for upwelling, blue for downwelling. The convection roll is of course a part of a comprehensive system of rolls, extending mathematically to the pole itself. The convection roll shaping the Reykjanes Ridge is actually subducted by this Arctic roll and its eastern counterpart at the latitudes of Reykjanes. Therefore, tensional direction ruling dike formation should be induced by the Kolbeinsey roll, not the Reykjanes roll. At 64°N, the two rolls have exactly the same alignment, but the difference can be recognized at the latitude of the eruption at the southern half of Reykjanes Peninsula (slightly south of 64°N), where the direction is close to N44°E.