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 thicknesse s las defined by O.G. Flovenz, J. Geophys. 47 (1980) 211-220) lie in the ra nge of approximately 2-11 km, with the thinnest upper crust below active an d extinct central volcanoes and the thickest upper crust close to the flank s 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 temperatu res enhance melt production. Thick crust (similar to 35 km) is also found i n eastern Iceland, between the current plume centre and the Faroe-Iceland R idge. Elsewhere, the crust thins away from the plume centre. The thinnest c rust (less than or equal to 20 km) is found in the active rift in the north ern part of the Northern Volcanic Zone, where melt production has been affe cted by a ridge jump, and in the far southwest of Iceland. The uppermost ma ntle below Iceland is characterised by reduced densities below the rift zon es, suggesting higher mantle temperatures and the possible presence of part ial melt in these regions. (C) 2000 Elsevier Science B.V. All rights reserv ed.