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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]

Three microbialite forms are recognized in the Lower-Cambrian succession of Irherm area in the western Anti-Atlas (Morocco). Stromatolites, which correspond to non-calcified shallow marine laminated microbialites, are well developed in the basal Lower-Cambrian succession. Occurrence of calcified microbial thrombolites, in the middle part of this succession, reflects an increasing sea level from the peritidal zone to the subtidal environment. In the upper part of this succession, a second increasing water depth event and the development of branching archaeocyathan reefal framework lead to dendritic microbialite emergence. To cite this article: M. Benssaou, N. Hamoumi, C. R. Geoscience 336 (2004). [Copyright &y& Elsevier]

In the Moroccan western Anti-Atlas, the combined extensive tectonic events with a long-term sea-level rise is the main factor on building vertical stacking transgressive–regressive sequences. In the Ait Abdallah-Boussafene axis, the subsidence processes, relayed by a brutal platform tilting generated an elongated NE–SW graben. This is an evidence of the persistence of the Anti-Atlasic rifting process during the last part of the Lower-Cambrian succession. [Copyright &y& Elsevier]

• Ironstones of Morocco are economically attractive because of low P and high Fe. • Found at points in sequence stratigraphic cycle where clastic supply is minimum. • Favored at top of the highstand and on ravinement surfaces. • Fe sourced from older BIF, carried in rivers as particles, deposited at coast. • Solid Fe3+ converted to soluble Fe2+ in sediment, waves reworked into Fe3+ ooliths. In Morocco, iron deposits of sedimentary origin are mainly developed in the Ordovician where they are interbedded at different levels of the stratigraphic column. A detailed analysis of the sedimentary facies shows that the iron ores are not randomly distributed but are concentrated at omission surfaces of the sequences thus raising the question of their sedimentological significance within the sequences that shelter them. This study determines three morphological types of ore, which provide a possible avenue for economic exploitation. These morphological types are: firstly, from metric to decametric bodies of regional extension (examples are "Caid Rami" and "Tachilla"), consisting of a set of detrital facies organized in two stratigraphic stages that cyclically recur to form genetic sequences. Within each sequence, the maximum mineralization is at the top of the prograding basal stage and is expressed by diagenetic iron cement and at the base of the regressive stage in the form of strata of iron oolites, or in massive beds. Secondly, lenses with a thickness up to 30 m over a kilometer width (example of "Imi n'Tourza" field), corresponding to incisions cut along the ravinement surfaces. The maximum mineralization of this second type is within the median sandstone stage in connection with a large transgressive event. Thirdly, there is a type of reworked material consisting of discontinuous layers of ferruginous conglomerates and bioclastics lining the ravinement surface that separates the higher order sequences. It is this third type that has generated the most economic interest. The iron-bearing mineral phases identified are: magnetite, hematite, iron chlorite, maghemite, iron hydroxides (goethite, lepidocrocite) and siderite. The ultimate source of iron would probably be the large reserves of banded iron formation of the West Africa Craton (Mauritania in particular). Intense tropical weathering would have leached the silica and left a highly enriched iron residuum that was carried as particulate iron to shallow marine shelf environments where Fe3+ was converted to Fe2+ during early diagenesis. This reduced iron was recycled into the water column by tidal currents or storm waves where it precipitated as ferric oxide or ferrous silicate ooliths. This depositional mechanism accounts for the positioning of ironstone beds at times of stasis and reworking. [ABSTRACT FROM AUTHOR]