Simultaneous resetting of the muscovite K-Ar and monazite U-Pb geochronometers: a story of fluids

Romain Tartese (1) , Gilles Ruffet (1) , Marc Poujol (1) , Philippe Boulvais (1) , Trevor R. Ireland (2)

1 Terre, Temps, Traçage
2 RSES - Research School of Earth Sciences [Canberra]

Although 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.

Domains: Earth Sciences

Romain Tartese, Gilles Ruffet, Marc Poujol, Philippe Boulvais, Trevor R. Ireland. Simultaneous resetting of the muscovite K-Ar and monazite U-Pb geochronometers: a story of fluids. Terra Nova, 2011, 23 (6), pp.390-398. ⟨10.1111/j.1365-3121.2011.01024.x⟩. ⟨insu-00643497⟩