Heat flow and deep temperatures in the Southeast Basin of France: Implications for local rheological contrasts | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Heat flow and deep temperatures in the Southeast Basin of France: Implications for local rheological contrasts

Type de publication:

Journal Article

Source:

Bulletin De La Societe Geologique De France, Volume 181, Ticket 6, p.531-546 (2010)

ISBN:

0037-9409

Numéro d'accès:

ISI:000287683400005

URL:

http://bsgf.geoscienceworld.org/content/181/6/531.abstract.html.fr

Mots-clés:

UMR 7154 ; Géosciences marines

Résumé:

<p>Triassic salt at 5-10 km depth may drive some of the recent tectonic features in southeastern France. We estimate the likely temperature range of the salt using two different approaches. The first of these, based on the extrapolation of deep temperatures obtained in oil exploration wells, predicts temperatures at a depth of 8 km to be in the range of 230-300 degrees C. However, this prediction could be biased by a lack of deep measurements and problems related to lateral heat transfer caused by thermal conductivity contrasts. The second approach can overcome these problems by modelling the actual heat transfer for appropriate basin geometry, including temperature-dependent thermal properties, and a mantle heat flow of 35 mW.m(-2). This latter value enables us to reproduce available temperature measurements and surface heat flow data. Here we evaluate the stationary temperature field along two sections constrained by seismic profiles, one at a local scale across the Vistrenque graben and the other at a more regional scale across the Southeast Basin. Our findings suggest that the temperatures in the deepest parts of the evaporitic layer (11 km depth) can reach up to 398 degrees C, but can be as low as 150 degrees C on the edge of the basin at the top of the salty layer. This temperature difference leads to important changes in salt viscosity. Results indicate that at a depth of 8 km, lateral viscosity contrasts within the evaporitic layer may reach 40. Such rheological contrasts might favour and amplify local subsidence, as seems to have been the case near the two Palaeogene half-grabens of Vistrenque and Valence, where deep hot zones are identified.</p>

Notes:

Guillou-Frottier, Laurent Lucazeau, Francis Garibaldi, Cynthia Bonte, Damien Coueffe, Renaud