Abstract
Located in the Internal domain of the Rif belt, the Beni Bousera massif is characterized by astack of peridotites and crustal metamorphic units. The massif is intruded by granitic dykes and affected byseveral normal ductile shear zones. Structural, petrological and40Ar–39Ar dating analyses performed onthese two elements highlight that (1) the granitic dykes are emplaced within major N70°to N140°trendingnormal faults and shear zones, resulted from an NNE-SSW extension (2) the Aaraben fault in its NE part ischaracterized by N70°to N150°trending ductile normal shear zones, resulted from a nearly N-S extensionand (3) the age of this extensional event is comprised between 22 and 20 Ma. Available paleomagnetic dataallow a restoration of the initial orientation of extension, which was nearly E-W contemporary with theAlboran Basin opening in back-arc context, during the Early Miocene. At the onset of the extension, theperidotites were somehow lying upon a partially melted continental crust, and exhumed during this event bythe Aaraben Normal Shear Zone. Afterward, the Alboran Domain suffered several compressional events.