Le volcanisme d'arc du massif ancien de l'ouest du Haut-Atlas occidental (Maroc), un temoin de la convergence de la branche occidentale de l'ocean panafricain

The Early-Cambrian Boho volcano of the El Graara massif, Morocco: Petrology, geodynamic setting and coeval sedimentation

“…This transition has recorded a distinct evolution of the igneous activity from calc-alkaline to alkaline intra-plate and/or continental tholeiitic volcanism (Ezzouhairi, 2001). This magmatic evolution reflects a tectonic inversion from a Neoproteorozic (Pan-African) compressive margin (Badra et al, 1992;Jouhari et al, 2001;Ouazzani, 2001) to intraplate extension related to latest Neoproteorozic-early Cambrian rifting processes (Piqué et al, 1995). As envisaged by Ezzouhairi (2001) and El Archi et al (2004), this major geodynamic modification from 'orogenic' to 'anorogenic' geodynamic episodes started earlier (latest Neoproterozoic) in the Anti-Atlas, reached the western High Atlas after the earliest Cambrian (Badra et al, 1992;Ait Ayad et al, 1998), and occurred even later in the Meseta domains (Ouali et al, 2000(Ouali et al, , 2003Ribeiro et al, 2001;El Attari, 2001).…”

Age of the Wirgane granodiorite intrusions (Western High-Atlas, Morocco): New U–Pb constraints

“…As they overlay basalts, andesites, metapelites and rhyolites without any obvious unconformity, the latter must be consequently older: either Upper Neoproterozoic or Lower Cambrian. From a structural point of view the Wirgane basalts, andesites, metapelites and rhyolites can be compared with either the Ouarzazate Supergroup in the Anti Atlas (Thomas et al, 2004), or with the well-documented volcanism from the Western High Atlas, which is either Cambrian (Badra et al, 1992) or Neoproterozoic (Ouazzani et al, 2001). A more precise determination of the age of basalts, andesites, metapelites and rhyolites (Neoproterozoic or Cambrian) will require complementary isotopic and geochemical data.…”

Metallogenic model of the Amensif Zn-Pb-Cu-Ag±Au-Bi carbonate replacement deposit (Western High Atlas, Morocco): New litho-structural and mineralogical data

“…In the Azegour-Erdouz area, situated in the western part of the High Atlas belt, the volcanic and volcano-sedimentary rocks were deposited during or after the opening of the Cambrian rift. The volcanic deposits consist of calc-alkaline basalt and andesite [27]. The U-Pb dating zircon dating of the Tizgui dacite, which is located north Azegour mine, revealed an age of 532.5 ± 4.2 Ma [28].…”