Mélanges and ophiolites during the Pan-African orogeny: the case of the Bou-Azzer ophiolite suite (Morocco)
Published:January 01, 2008
Romain Bousquet, Rachid El Mamoun, Omar Saddiqi, Bruno Goffé, Andreas Möller, Atman Madi, 2008. "Mélanges and ophiolites during the Pan-African orogeny: the case of the Bou-Azzer ophiolite suite (Morocco)", The Boundaries of the West African Craton, Nasser Ennih, Jean-Paul Liégeois
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Since the discovery of ophiolite sequences, the Bou-Azzer inlier has been considered a key area for understanding the evolution of the northern margin of the West African craton during the Pan-African orogeny. For about 20 years, it had been commonly accepted that the Bou-Azzer inlier represents an accretionary mélange accreted onto the West African craton under blueschist metamorphic conditions, similar to the Franciscan Complex and the Sanbagawa facies series. This would imply that a low geothermal gradient was prevalent during the subduction of the Pan-African oceanic plate, and that the ocean was subducted with a high convergence rate. A...
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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.