Retour sur le café G&E sur la thématique : ” Paleo thermal gradient distribution across an inverted hyperthinned system: example of the Mauléon fossil rift (Western Pyrenees) ” qui a eu lieu le jeudi 9 mai à 13h en salle Gottis par Nicolas Saspiturry, doctorant G&E.
Examples of fossil and present-day passive margins resulting from mantle exhumation at the ocean continent transition seem to develop under high heat flow conditions. However, the proximal-distal synrift thermal gradient along these hyper-extended margins is difficult to access.
Yet, in the objective of geothermal and petroleum explorations, it is essential to better asses the gradient distribution of these domains. The North Pyrenean Zone fossil analog, displaying HT-LP metamorphism and alkaline magmatism during the Early Cretaceous hyper-extension is of relevance to explore the synrift temperature scheme. Based on a dense outcrops and borehole samples dataset (156 samples), Raman Spectroscopy of Carbonaceous Material (RSCM) analysis was performed.
The obtained data allows us to discuss the distribution of the thermal gradient distribution across the inverted hyper-thinned Mauléon rift Basin. The paleo thermal gradients estimated in this work differ strongly according to their structural position along the Albian-Cenomanian rift domains.
Indeed, we observe a clear differentiation of the thermal anomaly along a proximal-distal margin transect as the paleo-thermal gradient increases basinward: ~29-36°C/km on the European proximal margin (Les Cassières-2 and Orthez-102 boreholes), ~37-46°C/km on the two necking zones (Bellevue-1 and Hasparren-101 wells; Mendibelza section) and 57-60°C/km on the hyper-extended domain (Ainhice-1, Uhart-Mixe-1. We also emphasized the major role of hyper-extension structural inheritance on the post-collisional proximal margins thermic evolution.