Crust generated above the Iceland mantle plume: From continental rift to oceanic spreading center

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Abstract
Since the North Atlantic continental breakup in the early Tertiary, the process of rifting above a mantle plume has produced large thicknesses of igneous crust. We report results of an integrated offshore‐onshore seismic study of the crust and upper mantle along a transect of the aseismic Faroe‐Iceland Ridge, between the continental fragment beneath the Faroe Islands and the present‐day spreading center in northeast Iceland. Normal‐incidence seismic data provide an image of the uppermost crust, which is complemented by a velocity model from streamer refraction analyses. These data together image four sedimentary basins, up to 400 m deep, along the crest of the ridge. The streamer refraction velocity model in turn forms the uppermost section of a full crustal velocity model derived from travel time modeling of air gun and explosive data. The compressional to shear wave velocity ratio in the crust of the Faroe‐Iceland Ridge is 1.77 ± 0.02, similar to that of eastern Iceland. The Moho beneath the Faroe‐Iceland Ridge lies at a depth of 25–30 km. Crust of 25–30 km thickness requires an upper mantle potential temperature elevated 200–250°C above normal if formed by passive adiabatic decompression melting of the mantle or a somewhat less elevated temperature if, as is likely, there is a component of active convection in the underlying mantle plume core.