A study on the morphological characteristics of geo-electrochemical halo-forming materials in the Luoboling copper–molybdenum polymetallic deposits of Zijin Mountain, Fujian Province

This study investigates the sources and migration mechanisms of geo-electrochemical halo-forming materials in polymetallic sulfide deposits through elemental chemical speciation analysis in various media. The research utilizes the modified BCR method and ultrasonic extraction to analyze the chemical speciation of Cu and Mo in ore samples, soils above ore bodies and non-ore bodies, and geo-electrochemical extraction samples from the Luobuling Cu–Mo polymetallic deposit along profile 264 in the Zijinshan area, Fujian Province. The findings indicate that: (1) Bornite exhibits spontaneous electrochemical dissolution in aqueous solutions, with Cu and Mo primarily present in the water-soluble fraction (WS–F). (2) In soils above ore and non-ore bodies, Cu predominantly exists in the reducible fraction (RED-F), while Mo is mainly found in the oxidizable fraction (OX-F) and residual fraction (RES-F). (3) Scanning electron microscope (SEM) and Energy dispersive spectroscopy (EDS) analyses reveal that geo-electrochemical extraction primarily targets ionic halo-forming materials, which predominantly form stable complexes and ion associates through chelation with organic material in the geo-electrochemical extraction device. Based on Spearman correlation analysis and these findings, the study suggests that the various forms of halo-forming materials extracted through geo-electrochemistry do not directly correspond to their soil forms but undergo transformation through complex processes including electrochemical dissolution, activation, and secondary enrichment. The halo-forming materials in the soil surrounding the electrodes originate from deep-seated ore bodies and migrate continuously to the surface under various geological forces. These materials are subsequently adsorbed by organic matter and iron-manganese oxides in the soil, ultimately achieving stable existence. The geo-electrochemical extraction process specifically targets these deep-originated halo-forming materials.