FIELDTRIP 5: CRATONS AND MOBILE BELTS: KEYS FROM THE NORTHERN BOUNDARY OF THE WEST AFRICAN CRATON (CENTRAL AND EASTERN ANTI-ATLAS BELT OF MOROCCO)

Summary: Cratons are characterized by a rigid behavior during younger subsequent oogenesis. The strong rheological contrast with surrounding mobile belts induces a favourable context for magmatism and mineralization. Also, the craton boundaries may be partly affected, showing characteristics and behavior intermediate between a craton in the strict sense and a mobile belt, which has been called “metacraton”. Metacratonic boundaries remain poorly understood, as they do not fit the classical models.
The oldest rocks of Morocco Archean in age crop out in the Reguibat Shield, being part of the West African Craton (WAC).The Anti-Atlas belt of Morocco that occupies the northern boundary of the West African Craton (WAC) is an excellent area to raise that issue. A large part of this area is constituted by Eburnian (c. 2 Ga) formations that have been reactivated during by Pan-African (0.8 - 0.55 Ga) orogenies constituting a metacratonic boundary. It is important to note the new discovered late Palaeoproterozoic/Mesoproterozoic doleritic rocks.
The Anti-Atlas includes important mineral deposits that are currently mined. The Bou Azzer inlier in the Central Anti-Atlas is of particular importance to the understanding of Pan-African events, because its ophiolitic complexes are considered as relics of a Neoproterozoic suture zone marking the boundary between the Paleoproterozoic Eburnean basement and Neoproterozoic accreted arcs to the north. Neoproterozoic diamictites are also of important interest as well as the effects of the Variscan orogeny to be compared with that to the north, in the Meseta region. The western Anti-Atlas area is characterized by a palaeoproterozoic and panafrican cristalline and sedimentary rocks with the interfered eburnean, panafrican and Variscan orogenies (Kerdous and Ighrem inliers). The High Atlas is the current mountain range formed along the WAC metacratonic boundary in response to the Alpine constraints. The Meseta region, to the north of the High Atlas comprises mainly Palaeozoic rocks and was affected by the Variscan orogeny and could constitute a link with the peri-Gondwanan terranes.
Field trip itinerary
18/10/2020: Arrival at Marrakech at night
Day 1 - 19/10/2020: The traverse of the High Atlas mountains through the Tizi n’Tichka pass (2260 m)
Departure from Marrakech at 8 h am
Stop D1.1. Introduction to the regional geology and panoramic view of the High Atlas Mountains.
Stop D1.2. Taguergoust syncline an example of perched synclines in the area.
Stop D1.3. Panoramic view of the Tizi n’Tichka Paleozoic inlier (optional)
Stop D1.4. Arg n’Ouannou Pan-African granodiorite: facies and contact metamorphism
Stop D1.5: Proterozoic/Paleozoic boundary in the eastern border of Tircht.
Overnight at Tazenakht village.
Day 2 - 20/10/2020: Zenaga inlier: Example of a Palaeoproterozoic basement in the Central Anti-Atlas belt
Stop D2.1. Tazenakht Palaeoproterozoic granite
Stop D2.2. Basic dykes witness of the Break-up of the WAC during the pre-Pan-African orogeny
Stop D2.3. Pre-Pan-African Taghdout passive margin series
Stop D2.4. Ediacaran diamictites (Siroua Inlier).
Overnight at Tazenakht village.
Day 3 - 21/10/2020: Bou-Azzer inlier: Pan-African ophiolites complex
Stop D3.1. Tizi-n-Taguergoust unconformities between the Paleoproterozoic and the Neoproterozoic formations and between the Late Neoproterozic and the Cambrian formations.
Stop D3.2 Bou-Azzer ophiolite - An example of an accretionary prism and melange zone. Bou-Azzer Mine. Stop D3.3 Aït Ahmane Neoproterozoic ophiolites.
Stop D3.4 Ediacaran diamictites.
Overnight at Ouarzazate city
Day 4 - 22/10/2020: Contacts Neoproterozoic - Cambrian
Stop D4.1 Jbel kissane Ordovician formations
Stop D4.2 Contact Late Neoproterozoic-Cambrian (Aït Saoun village)
Stop D4.3 Late Neoproterozoic stromatolithes.
Overnight at Ouarzazate city
Day 5 - 23/10/2020: Metacratonisation of the Northern Edge of the West African Craton during the Neoproterozoic time. An example from the Eastern Saghro (Anti-Atlas of Morocco)
Drive along the Dadès Valley where the lush green villages contrast greatly with the rocky canyons surrounding them).
Stop D5.1 Cross section through the Saghro Group sedimentary series, the interbedded basatic pillow-lavas and the intrusive granodioritic rocks.
Stop D5.2 The famous Imiter Silver mine.
Stop D5.3 Cross section through the M’gouna and Ouarzazate Groups.
Stop D5.4 Foum El Kouss plio-quaternary basalts.
Geotouristic visit of the Jurassic Todra gorges
Overnight in Boumalen city
Day 6 - 24/10/2020: Return to Marrakech
Route Boumalene-Marrakech
Visit of Aït Ben Haddou Kasbah (32 km NW of Ouarzazate).
End of the field trip.
Leaders: Ezzoura Errami and Nasser Ennih
Fees: 600 euros all inclusive