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Geological Society, London, Special Publications; 2008; v. 297; p. 329-343;
DOI: 10.1144/SP297.16
© 2008 Geological Society of London

The late Neoproterozoic-early Palaeozoic extension along the West African craton and the Peri-Gondwanan terranes

The magmatic evolution at the Moroccan outboard of the West African craton between the Late Neoproterozoic and the Early Palaeozoic

H. Ezzouhairi1, M. L. Ribeiro2, N. Ait Ayad1, M. E. Moreira3, A. Charif1, J. M. F. Ramos3, D. P. S. de Oliveira2,4 & C. Coke5

1 Université Chouaïb Doukkali, Faculté des Sciences, Department de Géologie, BP. 20, 24 000, El Jadida, Morocco (e-mail: ezzouhairi_hassan{at}yahoo.fr)
2 INETI—Área de Geociências, Estrada da Portela, Zambujal, 2721-866 Alfragide, Portugal
3 Laboratoire de INETI, R. da Amieira, Ap. 89, 4465, S, Mamede de Infesta Codex, Portugal
4 CREMINER, Centro de Recursos Minerais, Mineral. e Cristalografia, Ed. C6, piso 3, 1749-016, Lisbon, Portugal
5 Universidade de Tras-Os-Montes e Alto Deuro, Apartada 1013, 5001-911 Vila Real codex, Portugal

The Late Neoproterozoic Ouarzazate Group crops out on the north margin of the West African craton (WAC). In this group an important post-collisional magmatism is characterized by a great diversity in plutonic and volcanic rock types of the high-K calc-alkaline series. This series evolved mainly by crystal fractionation and by an important crustal contamination from an anomalous mantle source. The Early Cambrian magmatism began at the same time on both sides of the Anti-Atlas Major Fault, the southwestern side (Kerdous region) and northeastern side (Ouarzazate-Agdz region), interbedded in the Early Cambrian Basal Series and spread later to the Western High Atlas of the Morocco northern WAC outboard areas. This magmatism changes from a continental tholeiitic series (HPT and LPT) at the beginning to an alkaline series at the top (Adoudou and ‘Lie de vin’ formations). Fractional crystallization and pelagic or crustal contamination were the most important processes in the magma differentiation. The geochemical inversion from calc-alkaline to tholeiitic magmatism between the Late Neoproterozoic and the Early Cambrian is documented, as is the major extension of the tholeiitic activity on both sides of the South Atlas Fault. This geochemical variation indicates a transition of the tectonic regime from compressive to extensional. The late local Jbel Boho alkaline magmatism indicates the sink of the source and the mitigation or closure of the extensional cycle at this time.





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J. J. Alvaro, M. Macouin, H. Ezzouhairi, A. Charif, N. A. Ayad, M. L. Ribeiro, and M. Ader
Late Neoproterozoic carbonate productivity in a rifting context: the Adoudou Formation and its associated bimodal volcanism onlapping the western Saghro inlier, Morocco
Geological Society, London, Special Publications, 2008; 297: 285 - 302.
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