Métagabbros amphiboliques et mise en place crustale des lherzolites des Pyrénées (France)

Slices of ultramafic rocks from the subcontinental Pyrenean mantle, emplaced in the north Pyrenean zone, mainly consist of layered lherzolites and anhydrous pyroxenites. In the lherzolite massifs of the Ariege, the layering is cross-cut by dykes of amphibole-pyroxenites and hornblendites, interpreted as mineral segregates of Cretaceous alkaline magmas under mantle conditions. In the central and western Pyrenees, the lherzolites contain dykes of amphibole metagabbros. Petrological and geochronological characteristics of these rocks show that they crystallized from alkaline liquids, possibly linked to the Cretaceous magmatism. These metagabbros therefore represent a stage in the emplacement of the ultramafic bodies within the crust.