Isotope geochemistry of the Limousin ophiolite-derived rocks

Non-traditional stable isotope geochemistry in ophiolites is a powerful tool for the understanding of geochemical processes during hydrothermal alteration (or hydrothermal metamorphism) in ancient oceanic lithosphere. Ge and Fe isotopes can fractionate during low-temperature (T) hydrothermal processes (< 350°C), but also under high-T hydrothermal or magmatic conditions. While O isotope fractionation is mainly controlled by T and fluid flow during hydrothermal alteration on (sub-)seafloor, Ge and Fe isotope fractionation during hydrothermal processes strongly depends on the chemistry of fluids (composition, speciation, ligand composition, …) and redox conditions of the environment. For this reason, multi-isotope studies (Fe, Ge, O) are expected to trace hydrothermal vs. magmatic processes in ancient oceanic lithosphere.

This study investigates non-traditional Ge and Fe isotopes and traditional O isotopes in a series of serpentinites (deriving from peridotites and troctolites) and amphibolite-facies metagabbros from the Limousin (Variscan belt, French Massif Central). The results will further our understanding of the processes and modes of isotope fractionation during hydrothermal metamorphism in ophiolite-derived rocks.

Microphotograph of a serpentinite from Le Cluzeau (Limousin, French Massif Central) in cross-polarised light; © A. El Korh

Duration: since 2018

Funded by: University of Fribourg, TelluS-SYSTER program [Institut National des Sciences de l’Univers (INSU)]

Collaborators: PD Dr. Afifé El Korh, Dr. Béatrice Luais (CRPG-Nancy, France), Dr. Marie-Christine Boiron (GeoRessources, University of Lorraine, Nancy, France)



PD Dr. Afifé El Korh
Earth Sciences
Department of Geosciences
University of Fribourg
Chemin du Musée 6

1700 Fribourg
 +41 26 300 89 45