LiDAR offshore structural mapping and U/Pb zircon/monazite dating of Variscan strain in the Leon metamorphic domain, NW Brittany

Type Article
Date 2014-09
Language English
Author(s) Le Gall Bernard1, Authemayou Christine1, Ehrhold AxelORCID2, Paquette Jean-Louis3, 4, Bussien Denise1, Chazot Gilles1, Aouizerat Arthur1, Pastol Yves5
Affiliation(s) 1 : Inst Univ Europeen Mer, UMR CNRS6538, Domaines Ocean, F-29280 Plouzane, France.
2 : IFREMER, Ctr Brest, Unite Rech GM, Lab Environm Sedimentaires, F-29280 Plouzane, France.
3 : CNRS, UMR6524, Lab Magmas & Volcans, F-63038 Clermont Ferrand, France.
4 : Univ Clermont Ferrand, F-63038 Clermont Ferrand, France.
5 : Serv Hydrog & Oceanog Marine, F-29228 Brest, France.
Source Tectonophysics (0040-1951) (Elsevier Science Bv), 2014-09 , Vol. 630 , P. 236-250
DOI 10.1016/j.tecto.2014.05.026
WOS© Times Cited 17
Note Supplementary table : Zircon and monazite U–Th–Pb dataset obtained by in situ laser ablation ICP-MS. http://www.sciencedirect.com/science/MiamiMultiMediaURL/1-s2.0-S0040195114002996/1-s2.0-S0040195114002996-mmc1.xls/271882/FULL/S0040195114002996/f22c02e3472470ee6dac2dab65508a45/mmc1.xls
Keyword(s) Armorican massif, Leon metamorphic domain, Offshore structural mapping, LiDAR records, Dextral ductile shearing, U/Pb zircon/monazite dating
Abstract An exceptional structural picture of the immerged Variscan basement, offshore the Leon metamorphic domain, is supplied by high-resolution LiDAR and echosounder data recorded in the Molene archipelago, western Brittany (France). Various types of fabrics are identified and, from in situ rock sample analyses further combined with field structural data, are interpreted on a lineament trajectory map as the trace of magmatic and tectonic structures. Our onshore/offshore study leads us to propose a two-phase kinematic model that emphasizes the role of a strike-slip duplex in an EW-trending relay zone linking the North Armorican and Pierres Noires ductile shear zones (NASZ, PNSZ). Dextral shearing occurred within a transtensional setting, synchronously with magmatic intrusions (St-Renan granite and an offshore gabbro-diorite complex) dated at 314-320 Ma by new U-Th/Pb ages. It post-dated an early regional foliation related to top-to-the-NE ductile transpresional shearing. Our study emphasizes the key role of strike-slip tectonics in the NW part of the Armorica Variscan belt.
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Le Gall Bernard, Authemayou Christine, Ehrhold Axel, Paquette Jean-Louis, Bussien Denise, Chazot Gilles, Aouizerat Arthur, Pastol Yves (2014). LiDAR offshore structural mapping and U/Pb zircon/monazite dating of Variscan strain in the Leon metamorphic domain, NW Brittany. Tectonophysics, 630, 236-250. Publisher's official version : https://doi.org/10.1016/j.tecto.2014.05.026 , Open Access version : https://archimer.ifremer.fr/doc/00194/30490/