Tartese, RomainRuffet, GillesPoujol, MarcBoulvais, PhilippeIreland, Trevor2015-12-080954-4879http://hdl.handle.net/1885/28912Although water is ubiquitous in the continental crust, its effect on geochronometers through mineral reequilibration is rarely taken into account. Herein, we present 40Ar/39Ar analyses on muscovite and U-Pb isotopic data on zircon and monazite from a Variscan syn-tectonic granite from western France. Both the K-Ar in the muscovite and U-Pb in the monazite isotopic systems were hydrothermally reset, whereas the U-Pb radiogenic system in most of the zircons was unaffected and dates the granite emplacement age. Titanium chemical maps obtained on muscovites from various dated samples display a spectacular overprinting of their magmatic zoning resulting from increasing fluid-rock interaction. These results reiterate the need to combine geochronological data with petrological, mineralogical and geochemical studies to accurately interpret ages obtained in this type of geodynamical settings.Keywords: fluid-structure interaction; geochronology; granite; Hercynian orogeny; isotopic analysis; monazite; muscovite; overprinting; potassium-argon dating; resetting; titanium; uranium-lead dating; zircon; France201110.1111/j.1365-3121.2011.01024.x2016-02-24