HR: 10:50h
AN: T32A-03    [Abstracts]
TI: How warm are passive continental margins? A 3D case study from the Norwegian margin
AU: * Scheck-Wenderoth, M
EM: leni@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam in der Helmholtz Gemeinschaft, Telegrafenberg, Potsdam, 14473, Germany
AU: Maystrenko, Y
AF: GeoForschungsZentrum Potsdam in der Helmholtz Gemeinschaft, Telegrafenberg, Potsdam, 14473, Germany
AB: Though being of increasing economic relevance, the heat flow regime at passive continental margins is debated. This is due to different hypotheses on the thermal structure below continents and oceans which, in turn, is related to the difference in thickness of the lithosphere and in thermal properties between both areas. Accordingly, the lithosphere-scale thermal field from the continent over the margin to the ocean is poorly understood. Here we show how far detailed knowledge of the crustal part of the system provides constraints for the thermal field of the lithosphere. We calculate the 3D conductive thermal field for a detailed structural model of the Norwegian passive margin and evaluate the lithospheric configuration consistent with two independent observables: temperature and gravity. We find that the thickness of a 55 Ma year old oceanic lithosphere controls to a large degree the conductive thermal field of the entire margin and needs to be less than 70 km. Our results support thickness estimates from seismology and disagree with predictions derived from cooling models assuming an equilibrium thickness of the oceanic lithosphere of 125 km. We obtain higher upper mantle temperatures and heat flows beneath the ocean than beneath the continent that can explain the reduced p-wave velocities and the smaller densities derived for the oceanic lithospheric mantle compared to the continent. The lateral temperature variation across the margin is ~100°K at 5 km depth and increases to ~400°K at 50 km depth. Thus, knowing the lithosphere configuration appears to be essential to correctly assess the present temperature conditions at passive margins and the related impact on the maturity of organic matter for petroleum exploration.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8130 Heat generation and transport
DE: 8169 Sedimentary basin processes
SC: Tectonophysics [T]
MN: 2007 Fall Meeting