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Extreme thinning of the continental crust and mantle exhumation at passive margins. Constraints from the Pyrenean analog

Abstract : We present an overview of the Mid-Cretaceous hyper-extended rift system exposed in the northern part of the Pyrenean mountain range. Its inversion during the Pyrenean orogeny allows for precious observations of the deep-seated processes occurring at the foot of distal margins. Some peculiar aspects characterizing the pre-Alpine hyper-extended domain are examined throughout the 400 km long suture that is fossilized in the North Pyrenean Zone (NPZ). The high temperature/low pressure (HT/LP) thermal imprint of the extensional event is studied thanks to a dataset of more than hundred peak temperature measurements by Raman spectroscopy of the carbonaceous material (RSCM). The pre- and syn-rift metasediments are characterized by an intense, synmetamorphic ductile deformation. Focusing on several key-localities of the NPZ, we examine the emplacement conditions of the peridotites in response to this extreme crustal thinning. Geological evidences such as the occurrence of peridotite bodies directly underlying metamorphic pre-rift sediments indicate an early attenuation of the rifted continental crust. Moreover, syn-rift, Albian-Cenomanian flysch sequences were deposited synchronously with the syn-metamorphic ductile deformation of the pre-rift sequences. All along the Internal Metamorphic Zone (IMZ), the base of the flysch deposits also recorded the HT tectonic event. Such a synchronicity between geological events, which are generally separated in time, is not common in mountain belts. We examine how tectonics, metamorphism and sedimentation may be active in a single basin during extension. We propose an original mechanism for the evolution of the basins involving continuous basal extraction of the pre-rift metamorphic sediments. This early HT deformation event relates to the « phase anté-Cénomanienne » described by Pyrenean geologists since 1930.
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Conference papers
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https://hal-insu.archives-ouvertes.fr/insu-01080795
Contributor : Isabelle Dubigeon <>
Submitted on : Thursday, November 6, 2014 - 11:39:34 AM
Last modification on : Tuesday, September 22, 2020 - 3:57:45 AM

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  • HAL Id : insu-01080795, version 1

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Camille Clerc, Yves Lagabrielle, Abdeltif Lahfid, Alain Vauchez, Pierre Labaume, et al.. Extreme thinning of the continental crust and mantle exhumation at passive margins. Constraints from the Pyrenean analog. 24 ème Réunion des sciences de la Terre 2014, Oct 2014, Pau, France. pp.227. ⟨insu-01080795⟩

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