The South-Western Branch of the Variscan Belt: Evidence from Morocco

Michard, André; Soulaı̈mani, Abderrahmane; Hoepffner, Christian; Ouanaimi, Hassan; Baïdder, Lahssen; Rjimati, Ech-Cherki; Saddiqi, Omar

doi:10.1016/j.tecto.2010.05.021

Cited by 242 publications

(236 citation statements)

References 80 publications

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“…The Paleozoic evolution of the Anti-Atlas domain as described in the literature was characterized by a strong subsidence and deposition of thick clastic sedimentary sequences between the Cambrian and the Carboniferous (Helg et al 2004;Burkhard et al 2006;Soulaimani and Burkhard 2008;Michard et al 2010;Soulaimani et al 2014). The subsidence was first controlled by crustal extension that started in the Late Proterozoic and lasted until the Early Cambrian.…”

Section: Paleozoic Evolutionmentioning

confidence: 96%

“…In the Carboniferous-Early Permian, the Variscan belt which extended from the Meseta plateau in the north to the Mauritanides in the south resulted in thick-skinned inversion and folding of the Anti-Atlas basement (Piqué et al 1987;Helg et al 2004;Burkhard et al 2006;Michard et al 2010). After the Variscan orogeny, the inherited Precambrian and Paleozoic structures were supposedly reactivated during Late Mesozoic-Cenozoic times, contemporaneously with the deformation and uplift of the Atlas Mountains to the north (Malusà et al 2007;Sebti et al 2009;Frizon De Lamotte et al 2009;Soulaimani et al 2014).…”

Section: Figmentioning

confidence: 99%

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Post-Variscan evolution of the Anti-Atlas belt of Morocco constrained from low-temperature geochronology

Gouiza

Charton

Bertotti

et al. 2016

Int J Earth Sci (Geol Rundsch)

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Section: Paleozoic Evolutionmentioning

confidence: 96%

Section: Figmentioning

confidence: 99%

Post-Variscan evolution of the Anti-Atlas belt of Morocco constrained from low-temperature geochronology

Gouiza

Charton

Bertotti

et al. 2016

Int J Earth Sci (Geol Rundsch)

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“…This event produced a wide variety of tectonic structures including folds and associated schistosity, multidirectional faulting, shear zones, and thrusts. Regional metamorphism, developed contemporaneously with ductile deformation during Late Carboniferous crustal shortening (Hoepffner et al 2005;Michard et al 2010), ranges from low-grade greenschist to amphibolite facies. Conversely, thermal metamorphism produced by emplacement of the bimodal suite and late Hercynian intrusions, gave rise to a regionally developed metamorphic aureole that consists predominantly of hornblende-and pyroxene-hornfels, and spotted-textured schists with porphyroblasts of cordierite, andalusite, chlorite, muscovite, and biotite ± sillimanite ± garnet (Bouloton 1992).…”

Section: Stratigraphymentioning

confidence: 99%

Geologic, Hydrothermal, and Geochemical Relationships Between Bimodal Magmatism and Massive Sulphide Mineralization in the Central Jebilet-Guemassa Province (Western Moroccan Hercynides)

Bouabdellah

Hibti²,

Maacha³

et al. 2016

Mineral Deposits of North Africa

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The Jebilet-Guemassa volcanic-hosted massive sulphide (VHMS) province comprises four sheet-like, polymetallic deposits. These are referred to as Kettara (>20 Mt at 0.6 % Cu with traces of Pb and Zn), Hajar (*20 Mt at 10.5 % Zn, 3.2 % Pb, 0.6 % Cu, and 60 g/t Ag), Draa Sfar (*11 Mt at 5.9 % Zn, 2.2 % Pb, and 0.3 % Cu), and Koudiat Aicha (3-5 Mt at 3 % Zn, 1 % Pb, and 0.6 % Cu), which collectively total >80 Mt of Pb-Zn-Cu ore. Host rocks consist predominantly of variably altered, mafic to felsic, submarine volcanic and tuffaceous volcaniclastic rocks within the metasedimentary Visean Sarhlef Series composed of black argillite with interbedded carbonate, siltstone, and sandstone. Hydrothermal alteration is distinctly asymmetric, occurring regionally in rocks of the stratigraphic footwall, immediate footwall, and hanging wall. In order of decreasing abundance, alteration assemblages consist of varying proportions of sericite, chlorite, quartz, carbonates (calcite, siderite, ankerite, and dolomite), talc, and epidote, with minor albite and tremolite-actinolite. These assemblages were controlled mainly by temperature and pH of the hydrothermal fluids. Mass-balance calculations indicate that hydrothermal alteration of the footwall rocks was accompanied by pervasive leaching of K 2 O, Na 2 O, and CaO, moderate loss of SiO 2 , and addition of FeO, MgO, and MnO under a high-temperature (>150°C) regime and high water/rock ratios (>10). In contrast, sericite-and calcite-rich alteration of hanging wall rocks involved lower temperatures (<150°C) and water-rock ratios of <5. Sulphide ores are dominated by pyrrhotite with variable proportions of sphalerite, chalcopyrite, galena, and pyrite ± tetrahedrite ± arsenopyrite ± marcasite ± bismuthinite ± cassiterite ± stannite ± cobaltite ± cubanite ± electrum. Overall, the ore and host rocks were strongly deformed, foliated, and mylonitized under greenschist-facies metamorphic conditions. Lithogeochemistry, alteration mineralogy, mineral chemistry, fluid inclusion data, and stable and radiogenic isotope constraints indicate that the Jebilet-Guemassa VHMS deposits formed in the Upper Visean (*330 Ma) from an evolving hydrothermal system that was initiated by regional-scale convection of magmatic-hydrothermal fluids and ambient seawater. Compared to classical VHMS systems, the Jebilet-Guemassa deposits possess a number of distinctive attributes that set them apart. These include (1) a banded sheet-like morphology, (2) predominance of pyrrhotite (up to 90 vol.%) over pyrite, (2) lack of well-developed stockwork zones, (4) absence of barite, (5) high Zn/Cu ratio, and (6) volumetrically minor igneous rocks.

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“…Variscan orogenesis there is recorded by NW-verging thrust faults, greenschist-to amphibolite-facies metamorphism, and widespread syn-to late orogenic magmatism. Tectonic polarity is predominantly oriented WNW (Michard et al 2010). Crustal extension occurred repeatedly during the Cambrian, Ordovician, Devonian, and early Carboniferous.…”

Section: Moroccan Hercynides or Variscidesmentioning

confidence: 99%

“…For more details on the stratigraphy and tectonic evolution of the Moroccan Hercynides or Variscides, the reader is referred to Guiraud et al (2005), Hoepffener et al (2005Hoepffener et al ( , 2006, and Michard et al (2010).…”

Section: Moroccan Hercynides or Variscidesmentioning

confidence: 99%

Geologic and Metallogenic Framework of North Africa

Bouabdellah

Slack

2016

Mineral Deposits of North Africa

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North Africa is noteworthy for having a great diversity of geology and mineral resources. Geologically, the region contains numerous terranes that contain rocks ranging in age from Archean to Quaternary, including diverse igneous, sedimentary, and metamorphic lithologies. Major geological features were built during the main phases of Proterozoic and subsequent Phanerozoic orogenies, the break-up of the supercontinents Rodinia, Gondwana, and Pangea, and during the opening and closing of major ocean basins such as the Iapatus, Atlantic, Pacific, and Tethys. Three major tectono-stratigraphic domains are recognized (1) the Precambrian province that includes the African-Nubian Shield (ANS) to the east and the West African Craton (WAC) to the west, and the intervening Tuareg Shield and "Saharan Metacraton"; (2) the Variscan (Paleozoic) fold belt; and (3) the Atlas-Alpine (Mesozoic-Cenozoic) system. Mineral deposits of North Africa formed in a variety of geologic settings at different time periods from Archean to Quaternary. Mineral commodities including gold, silver, cobalt, nickel, chromium, arsenic, copper, lead, zinc, iron, and many other elements. Major deposit types present in the region are (1) orthomagmatic Cr-Ni-platinum group elements (PGE); (2) rare-metal granites and related rare-element pegmatites; (3) volcanic-hosted massive sulphide (VHMS); (4) sedimentaryexhalative (SEDEX); (5) orogenic and intrusion-related gold; (6) iron oxide-copper-gold (IOCG); (7) banded iron formation (BIF); (8) Mississippi Valley-type (MVT) lead-zinc; (9) sediment-hosted stratiform copper;Electronic supplementary material The online version of this chapter

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The South-Western Branch of the Variscan Belt: Evidence from Morocco

Cited by 242 publications

References 80 publications

Post-Variscan evolution of the Anti-Atlas belt of Morocco constrained from low-temperature geochronology

Post-Variscan evolution of the Anti-Atlas belt of Morocco constrained from low-temperature geochronology

Geologic, Hydrothermal, and Geochemical Relationships Between Bimodal Magmatism and Massive Sulphide Mineralization in the Central Jebilet-Guemassa Province (Western Moroccan Hercynides)

Geologic and Metallogenic Framework of North Africa

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