The Mesozoic Margin of the Maghrebian Tethys in the Rif Belt (Morocco): Evidence for Polyphase Rifting and Related Magmatic Activity

Oriol Gimeno-Vives (1) , Geoffroy Mohn (1) , Valérie Bosse (2) , Faouziya Haissen , Mohamed Najib Zaghloul , Achraf Atouabat , Dominique Frizon de Lamotte (1)

1 GEC - Laboratoire Géosciences et Environnement Cergy
2 LMV - Laboratoire Magmas et Volcans

The Rif belt (northern Morocco) is a mountain chain located at the junction between the Mediterranean and Central Atlantic Domains. Although the Rif belt underwent important Cenozoic (i.e., Alpine) shortening, remnants of the Mesozoic North African rifted margin are preserved in its external zones. This contribution aims to characterize the Mesozoic architecture and polyphase rifting history of this rifted margin. We present detailed field evidence and geochronological data from two palaeogeographic zones (Mesorif and Intrarif) preserving remnants of the former North African distal margin. The Mesorif conserves lithostratigraphic associations characterized by mafic intrusive rocks overlain by dismembered and discontinuous blocks of Lower Jurassic carbonates covered by Middle to Upper Jurassic sediments. U-Pb zircon dating of four samples from this gabbroic complex shows ages close to the Triassic-Jurassic boundary (195-200 Ma). The gabbros were emplaced within the continental crust at the end of the first Triassic rift event and exhumed shortly after during a second Middle Jurassic rift event, which presents exceptional rift-related structures. The most distal part of the margin is exposed in the Intrarif. In this unit, the Beni-Malek serpentinized peridotites exhibit ophicalcites with uppermost Jurassic limestones resting conformably on top, suggesting that exhumation of the mantle occurred at the distal part of the North African margin at this time. When integrated, these new evidences enable us to discuss the evolution of the western part of the North African rifted margin and its relations with the Moroccan Atlantic margin and Tethys system.

Mots clés: Maghrebian Tethys; Poly-phased rift; Rif

Domaines: Planète et Univers [physics]; Volcanologie

Oriol Gimeno-Vives, Geoffroy Mohn, Valérie Bosse, Faouziya Haissen, Mohamed Najib Zaghloul, et al.. The Mesozoic Margin of the Maghrebian Tethys in the Rif Belt (Morocco): Evidence for Polyphase Rifting and Related Magmatic Activity. Tectonics, 2019, 38, pp.2894-2918. ⟨10.1029/2019TC005508⟩. ⟨insu-03708952⟩