Structure of the crust and uppermost mantle of Iceland from a combined seismic and gravity study

We present a map of the depth to the base of the upper crust and the total crustal thickness across Iceland constrained by seismic refraction results, receiver function analysis and gravity modelling. Upper crustal thicknesses las defined by O.G. Flovenz, J. Geophys. 47 (1980) 211-220) lie in the range of approximately 2-11 km, with the thinnest upper crust below active and extinct central volcanoes and the thickest upper crust close to the flanks of the rift zones. The thickest crust (40-41 km) lies above the centre of the Iceland mantle plume, where active upwelling and high mantle temperatures enhance melt production. Thick crust (similar to 35 km) is also found in eastern Iceland, between the current plume centre and the Faroe-Iceland Ridge. Elsewhere, the crust thins away from the plume centre. The thinnest crust (less than or equal to 20 km) is found in the active rift in the northern part of the Northern Volcanic Zone, where melt production has been affected by a ridge jump, and in the far southwest of Iceland. The uppermost mantle below Iceland is characterised by reduced densities below the rift zones, suggesting higher mantle temperatures and the possible presence of partial melt in these regions. (C) 2000 Elsevier Science B.V. All rights reserved.