LiDAR offshore structural mapping and U/Pb zircon/monazite dating of Variscan strain in the Leon metamorphic domain, NW Brittany
|Author(s)||Le Gall Bernard1, Authemayou Christine1, Ehrhold Axel2, 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|
|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.|