Revisiting the genesis of Au-Cu-Bi mineralization at Talat n'Imjjad, western High Atlas (Morocco): Constraints from mineral-chemical mapping and sulfur isotope data

The Talat n'Imjjad Cu–Au–Bi mineralization is controlled by a NW–SE–trending sinistral shear zone cutting the Cambrian Al Medinet quartz diorite in the western High Atlas, Morocco. This study addresses the origin of Au associated with Bi–Te–Se enriched hydrothermal system, a process that remains poorly constrained in intracontinental orogenic settings. We integrate automated mineral–chemical mapping, SEM–EDS analyses, whole-rock geochemistry, and sulfur isotope data to refine the paragenesis and constrain fluid sources and ore-forming conditions. The mineral assemblage is dominated by Bi-chalcogenides (bismuthinite ± Cu–Bi sulfosalts), native bismuth, and minor tellurides and selenides, with a notable absence of Pb sulfosalts. Textural relationships record progressive replacement from native Bi to Bi sulfides and Cu–Bi sulfosalts, reflecting increasing sulfur fugacity and evolving redox conditions. Gold occurs as native Au and electrum, systematically associated with Bi-bearing phases, supporting efficient gold scavenging by Bi-rich melts or fluids. Chalcopyrite δ³⁴S values (+7.9 to + 9.3‰) indicate a dominantly magmatic sulfur source with limited crustal contribution. The deposit is interpreted as a shear-zone-hosted magmatic–hydrothermal Cu–Au–Bi system formed under evolving redox and sulfur fugacity conditions, sharing mineralogical affinities with intermediate-sulfidation systems but lacking diagnostic epithermal alteration. The results of this study highlight the role of granitophilic metals-rich fluids in gold transport and provides new constraints on structurally controlled Au mineralization in intracontinental orogens.