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The transition from the Cambrian to Ordovician in Morocco is known to be characterized by a frequent Furongian hiatus, restricted extension of the Tremadocian marine deposits, and frequent unconformities at the base of the transgressive upper Floian deposits. In the present work, we first highlight the occurrence of Fe- and mica-rich, red silty/sandy formations in the Central and Eastern High Atlas between the Middle Cambrian and Upper Floian sequences. In the Tislyt type-locality, a synsedimentary hemigraben structure is defined, within which the red beds show frequent slump folds, debris flows and internal unconformities. The correlation with several coeval series of the Meseta domain allows us to define a shallow marine, ferruginous clastic Atlas-Meseta Red Beds (AMRB) basin during the Tremadocian-early Floian. The AMRB basin extended between the Meseta coastal block and the Anti-Atlas domain, being limited by the fault zones that became the West Meseta shear zone and the South Meseta fault, respectively, in the Variscan orogen. The AMRB basin compares with the coeval rifted basins of the central Iberian and Armorican massifs. The red beds were likely sourced from the east, from both the Precambrian basement and Early Ordovician magmatic rocks, contrary to the Ordovician deposits of the Sahara platform sourced from the south. Subsidence of the AMRB and central Iberian-Armorican basins of the NW-Gondwana border aborted during the Floian, whereas the opening of the Rheic ocean went on more to the west.

Copper mineralization in the Lower Paleozoic sedimentary cover of the Anti-Atlas (Morocco) is continually being revised not only to improve its mining capacity, but also to determine its origin, which remains a matter of debate. As evidenced by the various models proposed, the related research is fragmented, localized, and confusing. The origin of the Anti-Atlas Lower Paleozoic copper mineralization is shared between synergistic and epigenetic processes or a superposition of the two processes. Based on new tectono-magmatic data and a reinterpretation of the ore structural arrangement, we propose a link between the last concentration of copper deposits and the Late Triassic–Early Liassic CAMP (Central Atlantic Magmatic Province) tectono-thermal event, as evidenced by the significant concentration of copper mineralization in the three NE–SW corridors affected by extensional faults, some of which are filled with dolerite CAMP magma. The heat flow generated by the mafic dykes within these reactivated corridors causes mineralized fluids to up well into the sedimentary layers, depositing material rich in juvenile or leached copper, or even a mixture of the two. In some cases, these fluids are trapped by fracture systems that accompany passive folds initiated on normal faults. In other cases, these fluids can infiltrate bedding planes, and even karst caves, formed during carbonate exhumation. Notably, extensive NE–SW faults systematically cover the early Hercynian structures, suggesting that they belong to a post-Hercynian extensional episode. During the Late Triassic, the global fragmentation of the Pangaea supercontinent was manifested by the stretching of the continental crust at the margin of northwest Africa, with the simultaneous opening of the Central Atlantic Ocean and emplacement of CAMP magmatism. This last and often overlooked tectonothermal event must be considered in the remobilization and reconcentration of copper mineralization and other mineralization in Morocco. [ABSTRACT FROM AUTHOR]

Development and concentration of many ore deposits at the regional and district scales closely depend on structural geology, especially in polydeformed basements. The superposition of many deformation periods highlights the complexity of the structural context and expected potential location of mineralization zones. The formation and concentration of hydrothermal ore deposits is highly dependent on structural controls. On the NE flank of the Saghro massif (Eastern Anti-Atlas, Morocco), the Imiter silver mining region has been affected by multiple tectonic events since the Precambrian and throughout the Phanerozoic. In this investigation, a structural analysis of the different geological units revealed multi-stage deformation, beginning with the late Pan-African-Cadomian event, and ending with the last Cenozoic exhumation of the area. At least eight tectonic regimes have been identified. The Imiter basement, formed by the Cryogenian-early Ediacaran "flysch-like" Saghro Group, has been folded in low-grade metamorphic conditions, followed by an ENE-WSW brittle compressive event. These deformations occurred before to the early Ediacaran during the compressional and/or transpressional late Pan-African-Cadomian events (600–580 Ma). The unconformably overlaying deposition of the late Ediacaran Ouarzazate Group takes place in a WNW-ESE extensional setting and then involved in a NNW-SSE compressional event that occurred concurrently with a regional exhumation and erosion stages. A similar extensional event appears to have controlled the middle Cambrian sedimentation, the oldest Paleozoic deposits in this area. During the late Carboniferous, Variscan shortening was recorded by NW-SE transpressional deformation responsible for combined dextral strike-slip and southward thrusts. The Imiter silver mining region is part of the Moroccan Sub-Meseta Zone along with Paleozoic inliers of the Skoura and Tamlelt on the southern side of the High Atlas. The Mesozoic evolution began with the Late Triassic NNW-SSW transtensional tectonic regime with a northeast trending CAMP (Central Atlantic Magmatic Province) dyke during the Pangea breakup. Ultimately, the Imiter silver mining region experienced NNW-SSE Atlasic shortening during the uplift of the adjacent High Atlas. Over time, the direction of implemented tectonic stress and its effect on various geological units can elucidate the relationship between tectonism and hydrothermal silver mineralization in the Imiter region. In conclusion, structural analysis and investigation of paleostress development can be one of the most important factors for successful exploration plan and resource recovery in the Imiter region. An analysis of geological structures in determining feasible mineralization zones is crucial for future safe mining operation in the study area and can be extrapolated to other ore mining regions. [ABSTRACT FROM AUTHOR]

Abstract The Imiter inlier at the eastern Anti-Atlas chain (Morocco) hosts a world-class epithermal Ag-Hg deposit, and several occurrences of sulfide-magnetite mineralization. These occurrences are confined to transcurrent faults that cut mildly to highly potassic I- and S-type granite intrusions (e.g., Igoudrane, Bou Teglimt, Taouzzakt and Bou Fliou). In this contribution, we present new field, petrographic and microanalytical data of the Bou Fliou sulfide-magnetite mineralization in the northwestern part of the Bou Teglimt granodiorite intrusion (567 ± 6Ma). Field and microscopic investigations reveal pervasive silicification and potassic alteration associated with iron oxides-rich (>10 vol %) veins, stockworks, and breccias along NE-SW faults. The ore minerals are mainly magnetite, hematite, chalcopyrite, pyrite, sphalerite, Ag-galena, cobaltite, and less abundant Bi-sulfosalts (i.e., cosalite, galenobistmuthite, and llilanite-gustavite). The low-titanium iron oxides (magnetite and hematite), widespread iron-rich breccia, association with crustal scale fault zone, pervasive alteration, and overprinting mineral assemblages suggest a shallow level IOCG-style mineralization. High-order splays of the major fault zone could have provided effective traps for magmatic and basinal Cu and Zn-Pb hydrothermal fluids. The ∼550 Ma intrusive phases in the region could have contributed by fluid, elements or heat in a local effective blumbing. The mineralogical and ore textural criteria reflecting ore formation at a realtively shallow crustal environment, but a fluid inclusion study is needed to characterize the ore fluids and mechanism of ore deposition. [ABSTRACT FROM AUTHOR]

The Bou Azzer-El Graara inlier (BAEI) in the Central Anti-Atlas has been extensively studied due to its famous Pan-African ophiolite and its great mineral potential. In 1998, an airborne survey was flown over this inlier, providing high-resolution magnetic data. This study is concerned with reinterpreting these data to help elucidate the BAEI structure. For this purpose, the aeromagnetic data were processed through a series of filters and transformations. They were then subjected to a detailed analysis, taking into account the study area geology. Qualitative analysis of the reduced to pole data indicates that the observed anomalies are broadly consistent with outcrops of Precambrian mafic and metavolcanic rocks in the BAEI. The extension of this type of rocks below the Paleozoic sedimentary cover could explain similar anomalies found outside the inlier. Additional analysis of the processed data helped to identify various lineaments and structures organized into two main trends: ENE-WSW and ESE-WNW. Furthermore, the calculation of anomalous source depths by Euler deconvolution from aeromagnetic data shows that these vary between 0 and 1000 m within the inlier. However, deeper sources occur beneath the detached and slightly folded Paleozoic sedimentary deposits in the northern part of the inlier. Moreover, a quantitative interpretation using the 3D inverse method was applied to high-amplitude anomalies associated with the Bou Azzer ophiolite (BAO) and the Foum Zguid great dyke (FZGD). The results indicate that (i) the BAO consists of three north-northeast dipping magnetic bodies, (ii) the FZGD corresponds to a deeply rooted vertical structure with lateral thickness variations and (iii) the NE-SW FZGD structure represents the eastern limit of the BAO as indicated by geological and magnetic data. This suggests that the FZGD fracture may have played an important role during the Pan-African collages as a key structure controlling the oblique suturing of the ophiolite slices. • We perform a structural interpretation of aeromagnetic data from Bou Azzer inlier. • The anomalies are generally associated with mafic rocks and metavolcanics outcrops. • We delineated magnetic lineaments and structures dissecting the study area. • We carry out a 3D modeling of the Bou Azzer ophiolite and the Foum Zguid dyke. [ABSTRACT FROM AUTHOR]

For over 50 years the Pan African orogeny has been recognized as a Neoproterozoic tectonothermal episode affecting West Africa 800–550 Ma. As such, the Pan African events are similar to the Appalachian orogenic cycle extending from ∼1100 to 250 Ma and the Cordilleran orogenic cycle of 350 Ma to the present. A significant difference is that the Appalachian orogenic cycle has long been recognized as consisting of separate Grenville, Taconic, Acadian and Alleghenian orogenies. Similarly, the Cordilleran orogenic cycle consists of distinct Antler, Sonoma, Nevadan, Sevier, Laramide and ongoing Cascadian-Andean orogenies. Failure to distinguish individual tectonic events in the Anti-Atlas Mountains has been attributable to the dearth of radiometric dates in this region. Since 2000, precision geochronologic dating in the Anti-Atlas Mountains, Morocco, has provided a means by which it is now appropriate to designate a Pan African orogenic cycle consisting of separate distinct orogenic events. We herein propose the following distinct orogenic events in the Anti-Atlas Mountains of Morocco: Iriri-Tichibanine orogeny (760–700 Ma), Bou Azzer orogeny (680–640 Ma) and the WACadomian orogeny (620–555 Ma). [ABSTRACT FROM AUTHOR]

Abstract: Aeromagnetic data of the Anti-Atlas Mountains show an important magnetic anomaly along the ‘Major Anti-Atlas Fault’, produced by different mafic and ultramafic rocks of a Neoproterozoic ophiolite complex. The magnetic modelling of Bou Azzer–El Graara ophiolitic suture shows a deep-seated anomaly through the upper continental crust corresponding to a north-dipping subduction. The polarity of the Pan-African subduction in the Anti-Atlas is therefore compatible with the contemporaneous Pan-African orogenic belts, where polarity of subduction dipped away from the West African Craton during the amalgamation of Western Gondwana. To cite this article: A. Soulaimani et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]

Abstract: During the Late Precambrian–Early Cambrian times, the borders of the Kerdous inlier were affected by normal faults where thick conglomerates (Ouarzazate Group: PIII), grading progressively upwards into Cambrian marine sediments, were accumulated along their hanging walls. This tectonic activity persisted during the Early Cambrian and was accompanied by a magmatic activity resulting mainly in the emplacement of continental tholeiitic basalts. These tectono-sedimentary and magmatic events are related to the crustal extensional episode that affected the northwestern Gondwana margin during the opening of the Iapetus Ocean during Late Proterozoic times. To cite this article: A. Soulaimani et al., C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

Abstract This study presents new U–Pb zircon ages for three granitoid bodies in the Imiter inlier at the eastern part of the Moroccan Anti-Atlas chain, which is located in the northwestern edge of the West African Craton (WAC). Analyzes of zircon grains yield the following ages: 538 ± 6 and 575 ± 10 Ma for the Igoudrane massif, 567 ± 6 Ma for the nearby Bou Teglimt granodiorite, and 582 ± 6 Ma for the Bou Fliou granite. These new data reveal that the Igoudrane massif is younger than previously thought (677 Ma), and that all the granitoids in the Imiter area are Ediacaran in age and are related to the Ouarzazate Group. Sm-Nd isotopic data yield negative εNd(t) values (−4.5 to −0.2) and T DM model ages of 1.04–1.82 Ga. These data indicate the presence of an inherited Paleoproterozoic to Archaean component in some zircon grains and show that generation of the parent magmas involved a Neoproterozoic juvenile contribution and recycling of an older crustal component. These new data allow reinterpreting the geochemical and isotopic data of the granitoids, and revisiting the structural significance to the Igoudrane massif, which was assumed until now to be coeval with the major Pan-African event of the Central Anti-Atlas. They also bring significant constraints to discuss the context and age of deposition of the Saghro Group, which is still a matter of debate. All these data provide evidence of an emplacement of the Imiter granitoids in a subduction complex, which affected all of the Anti-Atlas chain during the Late Proterozoic time. Highlights • We provide new zircon ages for the granitoids of the Imiter inlier (Saghro, Eastern Anti-Atlas). • The crystallization age of the Igoudrane massif (575 ± 10 Ma) is younger than previously thought. • The granitoids in the Imiter inlier are Ediacaran to Lower Cambrian in age (538–582 Ma). • An Archaean to Paleoproterozoic basement is present under the Eastern Anti-Atlas. [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]

Abstract: The Anti-Atlas is reviewed and examined in the light of its geodynamic significance as a Palaeozoic basin and fold belt. Shortening is accommodated by polyharmonic buckle folding of the cover in a thick-skinned fashion without the development of any significant thrust/duplex systems. The Anti-Atlas is heavily inverted deep intracratonic basin, rather than a former passive margin of the Palaeo-Tethys Ocean. Inversion took place in Late Carboniferous to Early Permian times. Main shortening directions changed from NW–SE to north–south and maybe NE–SW through time, leading to the development of dome and basin patterns on scales from 100 m to 10 km. To cite this article: M. Burkhard et al., C. R. Geoscience 338 (2006). [Copyright &y& Elsevier]