A reconsideration of Pan African orogenic cycle in the Anti-Atlas Mountains, Morocco

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

“…They consist of ophiolites and island arc-related gneiss and intrusions accreted to the northern edge of the West African craton during the climax of the Pan-African orogeny (ca. 850-540 Ma) (Kröner and Stern 2004;D'Lemos et al 2006;Linnemann et al 2008;Timmerman 2008;El Hadi et al 2010;Hefferan et al 2014;Soulaimani et al 2014). During the Ediacaran, at the end of the Pan-African orogeny, the Anti-Atlas experienced post-orogenic collapse resulting in tilted basement blocks and continental basins filled by the Upper Ediacaran volcaniclastic series of the Ouarzazate Group (Gasquet et al 2008;Soulaimani et al 2014).…”

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

“…More recently Gasquet et al (2008), El Hadi et al (2010 and Walsh et al (2012) have proposed three events (PA1, PA2, PA3), however the timing of the distinct orogenic events was not pinpointed. Recently Hefferan et al (2014) incorporating concepts developed by numerous researchers summarized the individual orogenic events establishing the following Neoproterozoic evolution of the Anti-atlas during Pan-African orogenesis: firstly, the initial rifting of the supercontinent Rodinia (885-760 Ma) generated the WAC passive margin and ocean floor. During PA1 event (named Iriri orogeny by Hefferan et al, 2014), between 760 and 700 Ma, the Bou-Azzer Group developed as an oceanic crust or as a juvenile arc complex (TazigzaoutTichibanine island arc) on the margin of the WAC, coeval with a north dipping subduction of the ocean lithosphere beneath the Iriri island arc.…”

“…El Hadi et al (2010) reported metamorphic conditions above 600°C and 10 kbar. PA2 event (named Bou Azzer orogeny, Hefferan et al, 2014), 680-640 Ma, is characterized by the end of the northward dipping subduction, the obduction of the Tasriwine and Bou Azzer ophiolites onto the margin of the WAC, and the collision of the Iriri and TazigzaoutTichibanine island arc complexes with the WAC. During this tectonic phase ophiolite was metamorphosed under greenschist-facies (Bousquet et al, 2008;El Hadi et al, 2010;Walsh et al, 2012).…”

“…During this tectonic phase ophiolite was metamorphosed under greenschist-facies (Bousquet et al, 2008;El Hadi et al, 2010;Walsh et al, 2012). Finally, PA3 event (WAC Cadomian orogeny, after Hefferan et al (2014)), 620-655 Ma, was the final stage of Pan-African tectonism producing a large volume of volcanic and sub-volcanic plutonic rocks and was marked by the initiation of southward dipping subduction beneath the Cadomian volcanic arc, located north of the WAC.…”

“…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.…”