Opening of the Algerian Basin: Petrological, geochemical and geochronological constraints from the Yaddene Complex (Lesser Kabylia, Northeastern Algeria)

Abderraouf Seffari (1, 2) , Nachida Abdallah (1) , Olivier Bruguier (3) , Delphine Bosch (3) , Abdehafid Afalfiz (1) , Abdelkrim Yelles-Chaouche (2) , Abdelmalek Lekoui (4) , Aziouz Ouabadi (1)

1 USTHB - Université des Sciences et de la Technologie Houari Boumediene = University of Sciences and Technology Houari Boumediene [Alger]
2 CRAAG - Centre de Recherche en Astronomie Astrophysique et Géophysique
3 Géosciences Montpellier
4 UMSBJ - Université Mohammed Seddik Benyahia [Jijel] | University of Jijel

The Yaddene complex, located in Lesser Kabylia (northeastern Algeria), is composed of Tertiary mafic and ultramafic rocks that outcrop within syn-rift sedimentary rocks of the Algerian marginal basin, in the Maghrebide belt of North Africa. Petrographic observations show that the Yaddene complex is composed mainly of two distinct lithologies: (1) a layered quartz-bearing gabbro at the bottom, which consists mainly of plagioclase (An93), clinopyroxene (altered to actinolite) and rare interstitial quartz; and (2) layered plagioclase-bearing lherzolites composed of olivine (Fo86-88) orthopyroxene (En86–87), clinopyroxene (diopside and augite), rare plagioclase (anorthite) and amphibole of pargasitic composition. The trace element concentrations in pyroxenes and olivine of the Yadenne complex show a depletion in light rare earth elements (LREE) similar to basalts of the Mid-Ocean Ridge (N-MORB), which reflects the depletion of the mantle source. In addition, high #Cr in spinel reflects a high degree of partial melting of the mantle source. On the other hand, slight enrichment in Large Ion Lithophile Elements (Cs, Rb, Ba), weak but significant negative Nb, Ta, Zr, Hf and Ti anomalies, and positive Pb spikes are observed in both whole-rocks and minerals. These patterns are best explained by interaction between parental mantle and fluids and/or siliceous melts derived from a subducting oceanic slab. The tectonic discrimination diagrams of minerals and whole rocks indicate that the most likely geodynamic setting for emplacement of the Yaddene Complex is a back arc basin environment. In situ U-Pb dating of euhedral zircons and titanite from a quartz-bearing gabbro yields an age of 18.97 ± 0.12 Ma (2σ), which is interpreted as the crystallization age of magmatic zircons and the gabbroic magma. Zircons from a plagioclase-bearing lherzolite gave a consistent age of 19.05 ± 0.39 Ma (2σ), which is attributed to zircon growth during metamorphic/metasomatic processes coeval to gabbroic magma emplacement. The mafic/ultramafic rocks of the Yaddene complex are intercalated within fine-grained sediments of the syn-rift “Oligo-Miocene Kabyle” and the obtained early Burdigalian ages are interpreted as the early stages of an extensional regime that ultimately led to the opening of the oceanic Algerian Basin.

Mots clés: Western Mediterranean; Algerian basin; Rifting Mafic/ultramafic layered complex; Thermobarometry; U/Pb geochronology; Western Mediterranean

Domaines: Sciences de la Terre

Abderraouf Seffari, Nachida Abdallah, Olivier Bruguier, Delphine Bosch, Abdehafid Afalfiz, et al.. Opening of the Algerian Basin: Petrological, geochemical and geochronological constraints from the Yaddene Complex (Lesser Kabylia, Northeastern Algeria). Journal of African Earth Sciences, 2023, 197, pp.104783. ⟨10.1016/j.jafrearsci.2022.104783⟩. ⟨hal-03872443⟩