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The Atakor massif is a part of the Hoggar volcanic province, which was emplaced on top of a basement swell initiated during the Cretaceous. There have been three main episodes of volcanic activity since the Miocene, separated by long periods of quiescence. The lava flows and domes were emitted along lithosphere-scale fault zones. With its famous scenery, the Atakor massif is one of the largest (2150 km2) volcanic districts of the province. Mafic volcanic rocks are abundant in the center of the massif, but become scarce to the south, where only few scarps are observed. Phonolites occur only in the Assekrem area, whereas trachytes occur everywhere, with a marked enrichment in quartz to the south and the southeast (Tahifet area), where rhyolites are also exposed. Two magmatic groups have been identified based on field and petrological observations. The mafic group has a basanite-phonotephrite association, forming uplifted plateaus, scoria cones, and valley-filling lava flows. The presence of mantle-derived amphibole ± biotite megacrysts and peridotite mantle xenoliths together with the nonprimary chemical compositions of the magmatic rocks suggest that magmatic differentiation may have occurred within the upper mantle. The felsic group is composed of two diverging trends, a silica-saturated benmoreite-trachyte-rhyolite trend and a silica-undersaturated trachyte-phonolite trend. The primary magmas are considered to have been produced as a consequence of lithospheric mantle delamination along linear megashear zones inducing low degrees of decompression partial melting at variable depths (110–40 km) in the upwelling asthenosphere. The discrete volcanic episodes correspond to periods of reactivation of the major fault zones in response to discrete Neogene extensional tectonic events associated with Alpine orogenesis in the Western Mediterranean region induced by Africa-Eurasia collision.

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