Crustal structure of the Hatton and the conjugate east Greenland rifted volcanic continental margins, NE Atlantic

We show new crustal models of the Hatton continental margin in the NE Atlantic using wide‐angle arrivals from 89 four‐component ocean bottom seismometers deployed along a 450 km dip and a 100 km strike profile. We interpret prominent asymmetry between the Hatton and the conjugate Greenland margins as caused by asymmetry in the initial continental stretching and thinning, as ubiquitously observed on “nonvolcanic” margins elsewhere. This stretched continental terrain was intruded and flooded by voluminous igneous activity which accompanied continental breakup. The velocity structure of the Hatton flank of the rift has a narrow continent‐ocean transition (COT) only ∼40 km wide, with high velocities (6.9–7.3 km/s) in the lower crust intermediate between those of the continental Hatton Bank on one side and the oldest oceanic crust on the other. The high velocities are interpreted as due to intrusion of igneous sills which accompanied the extrusion of flood basalts at the time of continental breakup. The variation of thickness (h) and P wave velocities (v p ) of the igneous section of the COT and the adjacent oceanic crust are consistent with melt formation from a mantle plume with a temperature ∼120–130°C above normal at breakup, followed by a decrease of ∼70–80°C over the first 10 Ma of seafloor spreading. The h‐v p systematics are consistent with the dominant control on melt production being elevated mantle temperatures, with no requirement for either significant active small‐scale mantle convection under the rift or of the presence of significant volumes of volatiles or fertile mantle.