Programme des sessions > Recherche par auteur > El Majid Atiq

The Zgounder Ag-Hg deposit (Siroua Massif, central Anti-Atlas) is hosted within Neoproterozoic metasedimentary rocks of the Saghro Group (ca. 630–600 Ma). In addition to the Ag-Hg ore, the deposit hosts significant Zn±Pb±Cu hydrothermal vein-type mineralization (~550 Ma), dominated by sphalerite. Textural observations, combined with EPMA and µXRF, reveal that sphalerite occurs in three distinct generations: Sph I consists of Fe rich coarse grains (Feavg: 5.6 wt%, Mnavg: 0.04 wt %) exhibiting chalcopyrite exsolution and commonly displays recrystallization and annealing textures. Sph II displays rhythmic growth zoning, with light-color bands enriched in Zn and Cd. Late-stage Sph III is colorless, associated to Ag-sulfosalts and strongly enriched in Cd (up to 0.7 wt %) and Cu (up to 0.69 wt %), but highly depleted in Fe (0.5 wt%) and Mn (0.01 wt%). Trace element incorporation in sphalerite occurs via simple and coupled substitutions, primarily through Zn²⁺ ↔ Fe²⁺, Mn²⁺ in Sph I–II, and Zn²⁺ ↔ Cd²⁺ in Sph III. Mn and Cd effectively discriminate deposit types, while the highest Mn concentrations occurs within sphalerites of Magmatic-hydrothermal origin. Mn–Fe and Cd/Fe–Mn plots, along with Zn/Cd ratios (92–708; avg. 227), position Zgounder sphalerites within the epithermal field, overlapping several deposits such as Xinling (Liaodong Peninsula) and Cisma; Roșia Montană (Romania). Sphalerite geothermometry indicates progressive cooling from 299°C (Sph I) to 262°C (Sph II) and 236°C (Sph III). Given the thermometer's application limit (~240°C), Sph III temperatures are likely lower, supported by high Fe/Zn ratios (up to 6644; avg. 2114), suggesting crystallization below 150°C. Sulfur fugacity (fS₂) averages are indicating intermediate sulfidation state during sphalerite formation. Chlorite geothermometry yields consistent results, with average temperatures of ~295°C and a minimum temperature of 169°C. These results define Zgounder as an epithermal system evolving from moderate-temperature, reduced magmatic-hydrothermal fluids toward lower-temperature basin brines fluids , with Cd enrichment primarily controlled by fluid Zn/Cd ratios rather than cooling.