A recent article by Afifé El Korh and co-authors from Nancy (France) has been published in Lithos (doi: 10.1016/j.lithos.2020.105876)
This study investigates Fe, Ge and O isotope fractionation during high-temperature to low-temperature hydrothermal alteration in a series of ultrabasic and basic rocks from the Variscan Limousin ophiolite (French Massif Central). While O isotopic compositions are typical of high-temperature hydrothermally altered rocks, different behaviour of Fe and Ge isotopes can be observed in ultrabasic and basic rocks. In serpentinites, oxidising conditions during hydrothermal alteration of peridotite protoliths have enhanced Fe isotope fractionation to a larger extent than Ge isotopes. By contrast, Fe isotope compositions of amphibolite-facies metagabbros reflect the signature of the basic protoliths. Ge isotope fractionation has prevailed over Fe isotope fractionation in basic rocks that have conserved a MORB-like Fe reduced state during hydrothermal alteration. Hence, the coupling of non-traditional (Fe, Ge) and traditional (O) isotopic systems allows efficient tracing of magmatic vs. hydrothermal processes in ophiolite-derived rocks.