Multi-Scale Process Mineralogy of Cd and Ag in a Pb-Zn Ore: Implications for Recovery Optimization

Efficient recovery of critical metals from complex polymetallic ores relies on clarifying their mineralogical occurrence. A Cd-Ag-rich Pb-Zn ore from southwestern China was investigated via a multi-scale process mineralogy approach integrating reflected-light microscopy, TIMA and LA-ICP-MS. Systematic analysis was conducted on ore texture, mineral liberation characteristics, and the occurrence and distribution of Ag and Cd. The ore is a medium–low grade Pb-Zn deposit (Pb 0.81%, Zn 4.33%) with economically recoverable associated Cd (0.066%) and Ag (5.04 ppm), dominated by sphalerite (7.74%), galena (1.39%), pyrite (3.92%), quartz (47.80%) and calcite (18.66%). TIMA analysis revealed poor liberation of sphalerite and galena, with fully liberated particles accounting for <30%. LA-ICP-MS results showed that Cd is highly enriched in sphalerite (average 5982 ppm, 98%) mainly in isomorphous form, while Ag is dispersed in pyrite (average 178 ppm, 56%), galena (average 227 ppm, 25%) and sphalerite (average 31 ppm, 19%), also primarily as isomorphs; partial Cd in pyrite occurs as micro-inclusions. The multi-scale mineralogical data provide a scientific basis for resource utilization, indicating the necessity of fine grinding and differentiated recovery strategies: “zinc depression followed by lead flotation” for Pb-Zn recovery, the establishment of a comprehensive Ag recovery system with Pb-Zn-Fe as carriers for Ag recovery, and “Zn-carried Cd” flotation for Cd recovery. This study verifies the effectiveness of combined TIMA and LA-ICP-MS in elucidating critical metal occurrence, and provides a mineralogy-based process design for the sustainable processing of such complex ores.