Genesis of As-Pb-Rich Supergene Mineralization: The Tazalaght and Agoujgal Cu Deposits (Moroccan Anti-Atlas Copperbelt)

Abstract

In the Moroccan Anti-Atlas, sulfide deposits hosted by Neoproterozoic to Cambrian formations underwent significant weathering, leading to the formation of supergene profiles. In the Tazalaght Cu-As deposit, three mineralogical steps are distinguished: (1) the replacement of hypogene sulfides (chalcopyrite, pyrite, tennantite) by supergene sulfides (bornite, chalcocite) in the large cementation zone; (2) the formation of oxidized minerals (malachite, azurite, olivenite, and chenevixite, mainly) in a more oxidizing and neutral environment; and (3) the precipitation of goethite, hematite, and quartz in the gossan. In the Cu-As-Pb-V deposit of Agoujgal, the mineralogical units are spatially less confined than at Tazalaght. The narrow cementation zone hosts chalcocite, resulting from the weathering of hypogene chalcopyrite, pyrite, tennantite and galena, while the much more extended and diversified oxidized zone is rich in Cu and Pb carbonates, arsenates, sulfates, phosphates, vanadates, and oxides. Goethite, hematite, mottramite, and late calcite occur in the gossan. Both deposits are characterized by As-rich secondary ores that were formed through similar processes, despite some mineralogical and chemical variations highlighting the influence of the host rocks on weathering. The restricted oxidized mineralization at Tazalaght and the Agoujgal cementation zone most likely arise from the contrasting omnipresence of quartzite at Tazalaght that could not enable a fast and effective neutralization of the fluid’s acidity, and the large amounts of dolomitic host rocks that could be dissolved at Agoujgal. At both sites, the weathering of tennantite through a boxwork texture records the transition from the cementation zone (chalcocite), the oxidized zone (arsenates), and the gossan, and reflects the fluids evolution with time.

(U-Th)/He Dating of Supergene Iron (Oxyhydr-)Oxides of the Nefza-Sejnane District (Tunisia): New Insights into Mineralization and Mammalian Biostratigraphy

“…. ), allowing the fluids to percolate within sediments, as it has been previously suggested for numerous weathering profiles in various areas (e.g., [28,29]). The 14MnTAM sample, showing GHe ages between 8.9 ± 0.9 Ma and 8.4 ± 0.8 Ma (Table 1), is clearly related to weathering, as suggested by (i) its botryoidal texture ( Figure 3A) and (ii) the δD and δ 18 O data highlighting its formation in equilibrium with meteoric waters [4].…”

Application of the deterministic block theory to the slope stability design of an open-pit mine in Morocco

“…The Tazalaght deposit, located on the eastern border of Ait Abdellah inlier, occupies an anticline structure oriented northeast (NE) with a length of approximately 500 m. As shown in Figure 5a, b, it is composed of two major lithological formations: Neoproterozoic formations and early Cambrian unit (also called Tata-Taroudant Group). The Neoproterozoic formations consist of quartzites unconformably overlain by conglomerates that may represent a succession of paleoshoals and paleobasins [50], [51]. While the early Cambrian unit consists of Base Series (composed of alternating sandstones and siltsones) and Cambrian carbonates of the "Lower Limestone Series," including the thick "Tamjout dolomite" layer [52]- [54].…”

Unravelling the Temporal and Chemical Evolution of a Mineralizing Fluid in Karst-Hosted Deposits: A Record from Goethite in the High Atlas Foreland (Morocco)

“…One particularity of the High Atlas range is that the present-day foreland basins are poorly deformed but contain numerous ore deposits [17,18]. Some of them are affected by later weathering processes (e.g., [19,20]), in particular the southern foreland basin host Mn ore deposits in Cretaceous rocks [14]. In the Ouarzazate basin, the Imini ore deposit forms lenses aligned along a WSW-ENE direction over 25 km, hosted in a ~10 m-thick Cenomanian-Turonian dolostone, extending to the Tasdremt ore deposit to the west in the Souss basin (Figure 1b,c).…”