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Geochemical and Sm-Nd Isotopic Data of the Tachdamt and Bleida Formations (Bou-Azzer, Anti-Atlas, Morocco): Evidence for Two Sep-arate LIPs on the NW Margin of the West African Craton During the Early Neoproterozoic

Marieme Jabbour1,  Moha Ikenne1, Brian Cousens2, Hafida El Bilali2, Richard Ernst2, Mustapha Souhassou3, Ali El-Masoudy4, Ismail Bouskri5, Abdelilah BenHammou5, Amine Bajddi5

  • Affiliations:  1Laboratory of Applied Geology and Geo-Environment (LAGAGE) Department of Geology, Ibn Zohr University. B.P 8106, Dakhla city, 80 000 Agadir, Morocco;  2 Ottawa-Carleton Geoscience Centre, Department of Earth Sciences, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada; 3Polydisciplinary Faculty of Taroudant, Ibn Zohr University, Agadir, Morocco;  4Moulay Ismail University Faculty of Science and Technology Errachidia.  5MANAGEM Group, Twin Center, Tour A, BP 5199, Casablanca. Morocco. 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 71

  • Programme No: 6.2.7

  • Theme 6 > Session 2

Abstract

This study presents new geochemical and Sm-Nd isotopic data from the mafic rocks of the Tachdamt and Bleida formations in the Bou Azzer inlier, Anti-Atlas, Morocco. These formations, once considered a single sequence, have been redefined by U/Pb zircon dating into two distinct units: the Bleida Formation (770--700 Ma) and the Tachdamt Formation (c. 883 Ma). Our aim is to assess the origin and geodynamic significance of these rocks based on updated geochronology. The Tachdamt Formation, characterized by flood basalts, marks the onset of Tonian rifting along the northern edge of the West African Craton. In contrast, the Bleida Formation is interpreted as an arc-related terrane along the Anti-Atlas margin. Both formations contain mafic rocks, mainly basalts, and dolerites, showing tholeiitic signatures typical of passive margins. Light rare earth element (LREE) patterns suggest an E-MORB-type mantle source, with some samples showing enrichments in heavy rare earth and large ion lithophile elements, possibly indicating a distinct magmatic episode. Neodymium isotopes reveal positive εNd(t) values, indicating a juvenile magma source. Depleted Mantle model ages for the Bleida Formation are grouped into three ranges: 2080, 1600, and 1244 Ma, while the Tachdamt Formation ranges from 1990 to 1710 Ma. The εNd(t) vs. SiO2 plot suggests minimal crustal contamination. This study reveals two separate magmatic events in the area, but geochemical and isotopic similarities point to a common mantle source, shedding light on the region's complex Neoproterozoic magmatism.