The copper-silver occurrences of Rahmani (Western Sahara, Algeria) are located in paleochannel facies of Cambrian sandstones deposited onPan-African volcanics and intrusives. Sulfur isotope analyses were performed on pyrite and copper sulfides in order to trace the origin of the copper-silver mineralization. S isotopic data preclude that bacterial reduction of Cambrian sulfate could have induced the formation of the sulfides. Non-bacterial reduction of sulfate during burial diagenesis is the most valuable explanation for disseminated pyrite. Isotopic ratios on copper sulfides indicate that they result from the reaction of actual or subactual sulfate-bearing surface water with the disseminated pyrite. The origin of copper and silver remains unclear. They are thought to be brought by the downward migrating surface water but their origin could be either the leaching of the Cambrian sandstones or of the weathered volcanics.