HR: 0800h
AN: T41A-0376    [Abstracts]
TI: Heat-Flow at the edges of continental lithosphere and implications for the evolution of extensional margins
AU: * Goutorbe, B
EM: goutorbe@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75252, France
AU: Lucazeau, F
EM: lucazeau@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75252, France
AU: Perry, C
EM: perry@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75252, France
AU: Bonneville, A
EM: bonneville@ipgp.jussieu.fr
AF: Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, 75252, France
AB: Heat-Flow variations across continental rifted margins are difficult to obtain for methodological reasons: direct measurements are not possible below a certain water depth and values derived from oil exploration are often biased by perturbations on temperature records and unreliable conductivity estimates. We have developed recently a methodology that provides better estimates of thermal conductivity in oil exploration wells, based on neural networks linking this physical property to geophysical well logs. The method has been applied systematically on a large number of wells on Atlantic and Australian margins, providing almost 1,000 new heat- flow estimates. In all cases, the mantle heat-flow below the margins is comparable to that of oceanic domain, and in some cases higher. These conclusions arise from old margins (>50 Ma), but measurements on young margins (e.g. Red Sea, Aden) show unexpected high values. This is interpreted as a consequence of temperature differences at depth between continental and oceanic lithospheres. Several 2D numerical experiments show that such anomalies are likely to develop with variable amplitude and pattern depending on the temperature regime of the continental lithosphere, rheology of the mantle and geometry of the interface. It seems that such anomalies can appear rapidly after the break-up of continents and maintain permanently. This changes significantly the subsidence evolution and the relations with the pre-existing thermal regime of the continent.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8159 Rheology: crust and lithosphere (8031)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting