The Cambrian volcano-sedimentary formations of the westernmost High Atlas (Morocco): their place in the geodynamic evolution of the West African Palaeo-Gondwana northern margin
Published:January 01, 2008
A. Pouclet, H. Ouazzani, A. Fekkak, 2008. "The Cambrian volcano-sedimentary formations of the westernmost High Atlas (Morocco): their place in the geodynamic evolution of the West African Palaeo-Gondwana northern margin", The Boundaries of the West African Craton, Nasser Ennih, Jean-Paul Liégeois
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In the westernmost part of the High Atlas, two Palaeozoic formations, rich in mafic volcanic rocks, are distinguished. They belong to different structural blocks created during the Variscan orogeny. New U–Pb dating yields an Early Cambrian age. The basaltic lavas have the composition of continental tholeiites and the magmatic signature of an initial rifting tectonic setting. They are related to the western Moroccan Cambrian rift. Their geodynamical context could be a passive margin initiated from an active rift that aborted in the Middle Cambrian.
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The Boundaries of the West African Craton
The boundaries of rigid cratons can be affected by subsequent orogenic events, leading to ‘metacratonic’ characteristics not often properly recognized and still poorly understood. Major lithospheric thickening is absent and early events such as ophiolites are preserved; however, metacratonic boundaries are affected by major shear zones, abundant magmatism and mineralizations, and local high-pressure metamorphism.
West Africa, marked by the large Eburnian (c. 2 Ga) West African craton, the absence of Mesoproterozoic events, the major Pan-African (0.9–0.55 Ga) mobile belts that generated the Peri-Gondawanan terranes, and the weaker but enlightening Variscan and Alpine orogenies, is an excellent place for tackling this promising concept of metacratonization.
The papers in this book consider most of the West African craton boundaries, from the reworking of the Palaeoproterozoic terranes, through the Pan-African encircling terranes, the late Neoproterozoic-early Palaeozoic extension period and the Peri-Gondwanan terranes, the Variscan imprint to the current situation.