Trace element and isotopic fingerprints in HP-LT metamorphic rocks as a result of fluid-rock interactions (Ile de Groix, France)

► Open system behaviour during low-T seafloor hydrothermal alteration and closed system during HP event. ► Extent of greenschist facies overprint related to intensity of the pre-HP fluid-rock interaction. ► Variety of metamorphic assemblages reflect protolith compositions and pre-HP fluid overprints.