Meteoric fluid‐rock interaction in Variscan shear zones

Camille Dusséaux (1) , Aude Gébelin (1) , Philippe Boulvais (2) , Véronique Gardien (3) , Stephen Grimes (1) , Andreas Mulch (4)

1 SoGEES - School of Geography, Earth and Environmental Sciences [Plymouth]
2 GR - Géosciences Rennes
3 LGL-TPE - Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement
4 SBiK-F - Senckenberg Biodiversity and Climate Research Centre

Variscan shear zones in the Armorican Massif represent sites of strong fluid‐rock interaction. The hydrogen isotope composition of muscovite (δDMs) from syntectonic leucogranite allows to determine the source of fluids that infiltrated the footwall of three detachment zones and the South Armorican Shear Zone. Using temperatures of hydrogen isotope exchange estimated from microstructural data, we calculate the hydrogen isotope ratios of water (δDwater) present within the shear zones during high‐temperature deformation. A ~40‰ difference in δDwater values from deep to shallow crustal level reveals a mixing relationship between deep crustal fluids with higher δD values that range from −34 to −33‰, and meteoric fluids with δD values as low as −74‰ in the upper part of detachment footwalls.

Domains: Geochemistry

Camille Dusséaux, Aude Gébelin, Philippe Boulvais, Véronique Gardien, Stephen Grimes, et al.. Meteoric fluid‐rock interaction in Variscan shear zones. Terra Nova, 2019, 31 (4), pp.366-372. ⟨10.1111/ter.12392⟩. ⟨insu-02270566⟩