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The Saghro Group (SG) is a folded, low-grade volcano-sedimentary series up to 8 km thick that crops out within and to the north of the Pan-African suture zone in the central and eastern Anti-Atlas. Here we describe the SG of the Ougnat inliers that are exposed in the easternmost Anti-Atlas beneath the unconformable, Late Ediacaran Ouarzazate Group (OZG) volcanic rocks. The Ougnat SG mostly consists of volcaniclastic greywackes accumulated in a peritidal-to-shallow basin. The basin infilling was deformed by NNE-trending, mostly upright folds with axial-planar slaty cleavage and low-grade metamorphism. The deformed SG rocks were intruded by the ∼550 Ma Mellab hypovolcanic granodiorite. The latter also crosscuts the lowest OZG rocks that are dated to 574–571 Ma in the western Saghro region. The SG rocks that form the Siroua and Saghro inliers have an oldest age of 620–610 Ma and were folded at ∼610–580 Ma at the onset of the Cadomian orogenic events. We show that the SG rocks are similar to the “Série verte” (SV) rocks that are exposed in the Ougarta and western Hoggar east of the Pan-African suture. We infer that the SG and SV rocks accumulated in a same, continuous basin that was bounding the West African Craton to the north and the east. This strongly subsiding basin formed close to a volcanic arc and was folded during the last Pan-African synmetamorphic events. Fold orientation and age of folding differ however along the edge of the West African Craton. The orogenic greywackes that form the remnants of the SG-SV basin thus constitute a precious record of the diachronic Cadomian event s.l. along the West African Craton northern margin. [ABSTRACT FROM AUTHOR]

Located along the northwestern edge of the West African Craton, Morocco exhibits a wide variety of magmatic events from Archean to Quaternary. The oldest magmatic rocks belong to the Archean Reguibat Shield outcrops in the Moroccan Sahara. Paleoproterozoic magmatism, known as the Anti-Atlas granitoids, is related to the Eburnean orogeny and initial cratonization of the WAC. Mesoproterozoic magmatism is represented by a small number of mafic dykes known henceforth as the Taghdout mafic volcanism. Massive Neoproterozoic magmatic activity, related to the Pan-African cycle, consists of rift-related Tonian magmatism associated with the Rodinia breakup, an Early Cryogenian convergent margin event (760–700 Ma), syn-collisional Bou-Azzer magmatism (680–640 Ma), followed by widespread Ediacaran magmatism (620–555 Ma). Each magmatic episode corresponded to a different geodynamic environment and produced different types of magma. Phanerozoic magmatism began with Early Cambrian basaltic (rift?) volcanism, which persisted during the Middle Cambrian, and into the Early Ordovician. This was succeeded by massive Late Devonian and Carboniferous, pre-Variscan tholeiitic and calc-alkaline (Central Morocco) volcanic flows in basins of the Moroccan Meseta. North of the Atlas Paleozoic Transform Zone, the Late Carboniferous Variscan event was accompanied by the emplacement of 330–300 Ma calc-alkaline granitoids in upper crustal shear zones. Post-Variscan alkaline magmatism was associated with the opening of the Permian basins. Mesozoic magmatism began with the huge volumes of magma emplaced around 200 Ma in the Central Atlantic Magmatic Province (CAMP) which was associated with the fragmentation of Pangea and the subsequent rifting of Central Atlantic. CAMP volcanism occurs in all structural domains of Morocco, from the Anti-Atlas to the External Rif domain with a peak activity around 199 Ma. A second Mesozoic magmatic event is represented by mafic lava flows and gabbroic intrusions in the Internal Maghrebian flysch nappes as well as in the external Mesorif. This event consists of Middle-Upper Jurassic MORB tholeiites emplaced during opening of the Alpine Tethys ocean. The Central High Atlas also records Early Cretaceous alpine Tethys magmatism associated with the aborted Atlas rift, or perhaps linked to plume activity on the edge of the WAC. Cenozoic magmatism is associated with Tertiary and Quaternary circum-Mediterranean alkaline provinces, and is characterized by an intermittent activity over 50 Ma from the Anti-Atlas to the Rif Mountain along a SW–NE volcanic lineament which underlines a thinned continental lithosphere. [ABSTRACT FROM AUTHOR]

Highlights: [•] U–Pb baddeleyite and zircon ages on dolerites in the Anti-Atlas inliers, which represents a major step towards a complete West African Craton intraplate magmatic “barcode”. [•] First evidence of a widespread 1750Ma bimodal magmatic event in the Anti-Atlas. [•] Distribution of a widespread 1750Ma Large Igneous Province within the Columbia (Nuna) supercontinent. [ABSTRACT FROM AUTHOR]

Precambrian inliers of the Anti-Atlas belt in the southern part of Morocco contain numerous dolerite dyke and sill swarms which were previously poorly dated. Four dykes and two sills dated by the U–Pb TIMS method on baddeleyite and zircon provide the first steps toward a magmatic ‘barcode’ for the West African Craton (WAC) and constraints on the timing of breakup of the WAC from Precambrian supercontinents. A 2040±2Ma (U–Pb zircon) age for a WNW dyke in the Zenaga inlier, matches the published age of a dyke in the Tagragra of Tata inlier, and also those of Eburnean granites observed in several inliers, which are collectively interpreted to represent ca. 2040Ma bimodal magmatism due to a mantle plume. Based on the presence of matching 2040Ma ages, the WAC may have been connected to the North Atlantic Craton at the initial stage of fragmentation of a late Archean continent. U–Pb baddeleyite ages of 1656±9Ma and ca. 1655Ma from sills in the Zenaga inlier and 1654±16Ma from a NE-trending dyke in the Agadir Melloul inlier are similar to intraplate magmatic ages in eastern and northern Baltica, and support the SAMBA reconstruction (part of the Nuna supercontinent) of the WAC adjacent to Baltica. Approximate U–Pb ages of 885Ma for two dykes in the Iguerda-Taïfast and Zenaga inliers date a NE trending swarm (named herein the Iguerda-Taïfast swarm) which is connected to the initial breakup of the supercontinent Rodinia, and a specific link with the São Francisco/Congo and North China craton is considered. [ABSTRACT FROM AUTHOR]

In the Bas-Drâa Inlier (Anti-Atlas, Morocco), the Paleoproterozoic basement which is cut by the Ediacaran Taourgha granite is also crosscut by numerous dykes of a variety of trends, mostly of uncertain age. Two doleritic dykes are dated by the ID-TIMS U–Pb method on baddeleyite and yield emplacement ages of 1381±8Ma (MSWD=0.84) and 1384±6Ma (MSWD=1.4) determined for a N135°E and a N40°E trending dyke, respectively. These dates represent the first geochronological evidence of a Mesoproterozoic magmatic event in the Anti-Atlas. This magmatic event falls in the previously considered ca 1.7–1.0Ga (Mesoproterozoic) gap in geological activity in the Anti-Atlas. The poorly dated Taghdout and Taarotihate sequences could represent remnants of the ca. 1380Ma magmatism and rift-related sedimentation. The Mesoproterozoic sedimentary succession of the Atar Group in the Taoudeni basin (Mauritania) could also represent a good candidate for rift-related sedimentation but it postdates the 1380Ma magmatic event by 270Ma. The dated 1380Ma dykes are transitional to mildly alkaline basalts, not unlike some Hawaiian lavas. However, these dykes have a distinct negative Nb anomaly (a common features in many Large Igneous Provinces, LIPs), and this requires interaction with the lithosphere. This interaction may have occurred at the level of the lithospheric mantle or the crust. These newly dated 1380Ma dykes may converge to the north, speculatively suggesting a magmatic center (associated with a 1380Ma mantle plume?) along the northern margin, and possibly linked to rifting and possible breakup on that margin, and also to a regional uplift that largely removed the evidence of a 1380Ma cover sequence. Contemporaneous 1380–1390Ma magmatism is reported elsewhere on other crustal blocks, and that in northeastern Laurentia (northern Greenland), northern Siberia (Anabar shield), and Baltica (southern Urals) can be reconstructed with that of the Bas Drâa Inlier (Anti Atlas region of the West African Craton, WAC) into a single Large Igneous Province (LIP) extending over an area of >1millionkm2, and associated with the final fragmentation of the Columbia (Nuna) supercontinent. [ABSTRACT FROM AUTHOR]

Baddeleyite (ZrO2) is today recognized as the key mineral for dating the emplacement of mantle-derived igneous rocks, primarily gabbro and dolerite dykes and sills. The comment by Michard and Gasquet calls for a discussion on the significance of baddeleyite U–Pb TIMS dates of two dykes in the Bas-Drâa inlier, dated at 1381±8 and 1384±6Ma, presented in El Bahat et al. (2013-in this issue). They suggest that the U–Pb systematics were “seriously perturbed in the Bas-Drâa region” with the main argument being a lack of age matches between the ca. 1385Ma dykes in Bas-Drâa and the 2040, 1650 and 885Ma dykes in adjacent inliers to the east. To infer an older age for these dykes, as suggested by Michard and Gasquet, and explain the ca. 1385Ma TIMS results would require two separate events of perturbation, in the Mesoproterozoic and a subsequent Variscan event. However, such an alternative is improbable from basic theoretical reasoning using U–Pb isotopic systematics and our current understanding of the behaviour of baddeleyite in metamorphic systems. In addition, we present new LA-ICPMS U–Pb age data of baddeleyite from one of the dated dykes from Bas-Drâa. The new LA-ICPMS U–Pb age of 1416±7Ma is slightly but significantly older than our TIMS 1384±6Ma upper intercept age, nevertheless confirming this dyke could not correspond to any of the other mafic intrusions dated in the inliers to the east. The LA-ICPMS result also contributes to a deeper understanding on the effects of secondary processes in baddeleyite in general, and suggests a modified methodological approach for samples with complex geological histories. [ABSTRACT FROM AUTHOR]