Geochronological constraints on the polycyclic magmatism in the Bou Azzer-El Graara inlier (Central Anti-Atlas Morocco)

Zn-, Mn- and Co-rich chromian spinels from the Bou-Azzer mining district (Morocco): Constraints on their relationship with the mineralizing process

“…Modern reliable dates for oceanic crust and ophiolite formation in the Bou-Azzer-El Graara inlier range from about 760 to 700 Ma (El Hadi et al, 2010;Walsh et al, 2012;Hefferan et al, 2014;Blein et al, 2014), during Cryogenian time. This period was characterized by subduction of oceanic lithosphere beneath the Iriri island arc, generation of the Bou Azzer ophiolite and creation of an island arc (Tazigzaout-Tichibanine) followed by obduction of oceanic lithosphere and arc-continent collision, corresponding to the onset of the major phase of Pan-African orogenesis (i.e., Pan-African event PA1; Gasquet et al, 2005Gasquet et al, , 2008.…”

“…This event produced the oldest macroscopic foliation in ophiolites, characterized by schistosity and occurred at lower greenschist facies conditions (Nerci, 1988;Saquaque et al, 1992;Fekkak, 2000;Walsh et al, 2012), or greenschist to amphibolite facies metamorphism (D'Lemos et al, 2006). The PA2 deformation correspond to the second period of Pan-African orogeny characterized by the collision of the Iriri arc, the Tazigzaout-Tichibanine island arc and the Bou Azzer ophiolite complex (Hefferan et al, 2014), along with the obduction of the Bou Azzer ophiolite and calc alkaline igneous intrusions in the Bou Azzer-El Graara inlier (Blein et al, 2014). This event produced a strong foliation, which overprinted the PA1 macroscopic foliation and took place between about 680 and 640 Ma (Inglis et al, 2005;El Hadi et al, 2010;Walsh et al, 2012;Hefferan et al, 2014).…”

“…The P-T conditions of metamorphism is still a matter of debate: Hefferan et al (2002) describe blueschist-facies conditions, Gasquet et al (2008) suggest metamorphism under greenschist-facies and El Hadi et al (2010) propose amphibolite-facies conditions. The southward dipping subduction beneath de Cadomian volcanic arc with development of a continental magmatic arc marks the onset (c. 620 Ma) of the final Pan-African event, PA3 that ended about 555 Ma (Walsh et al, 2012;Hefferan et al, 2014;Blein et al, 2014) with the development of a fracture cleavage and block faulting.…”

The Bou Azzer Co–Ni–Fe–As(±Au ± Ag) District of Central Anti-Atlas (Morocco): A Long-Lived Late Hercynian to Triassic Magmatic-Hydrothermal to Low-Sulphidation Epithermal System

“…The district has been extensively studied over the last few decades resulting in the release of a wealth of geological, mineralogical, and geochemical data, in hundreds of research papers, theses, geological maps at different scales, and unpublished mining company reports. The regional and local geological descriptions presented here draw extensively from the pioneering work of Leblanc (1975Leblanc ( , 1986 together with recent studies of Hefferan et al (2000), Thomas et al (2002Thomas et al ( , 2004, Walsh et al (2002), Inglis et al (2004Inglis et al ( , 2005, Gasquet et al (2005), Soulaimani et al (2006), El Hadi et al (2010), and Blein et al (2014). Accordingly, only a summary of major conclusions relevant to the present synthesis is given below.…”

History of the West African Neoproterozoic Ocean: Key to the geotectonic history of circum-Atlantic Peri-Gondwana (Adrar Souttouf Massif, Moroccan Sahara)

“…Another region comprising several ophiolitic structures is situated in the Anti-Atlas. With ages between 762 + 1/− 2 and 697 ± 8 Ma, the rocks of the Bou Azzer, Iriri, and Sirouer mafic terranes are significantly older than similar structures in the Mauritanides, Bassarides, and Rokelides (Thomas et al, 2002;Samson et al, 2004;El Hadi et al, 2010;Liégeois et al, 2013;Blein et al, 2014). The obduction of the Iriri ophiolites is supposed to be represented by zircon overgrowth rims dated at 663 ± 13 Ma, while protolith emplacement in an island arc is interpreted to have taken place at 743 ± 14 Ma inferred from zircon cores (Thomas et al, 2002).…”