Stratigraphic control on Co mineralization heterogeneity in sediment-hosted stratiform Cu-Co deposits: evidence from the Kamoya Cu-Co deposit, Democratic Republic of Congo (DRC)

The mechanism controlling Co heterogeneity in different host rock units in sediment-hosted stratiform Cu-Co (SSC) deposits remains ambiguous. This study investigates the SSC mineralization in the Kamoya deposit, Democratic Republic of Congo, through integrated petrographic, sulfide (chalcopyrite, pyrite, carrollite) major, trace elements and S, Fe isotopic analyses to discuss the factors controlling Co mineralization heterogeneity among different host rocks in SSC deposits. Two stages of mineralization are identified in the Kamoya deposit: the diagenetic stage formed fine-grained disseminated pyrite and chalcopyrite, likely representing an initial stage of metal pre-enrichment with metals, and the syn -orogenic stage generated vein-type chalcopyrite, cobaltian pyrite, and carrollite through tectono-hydrothermal activity, which caused elemental redistribution and Co upgrading. Both stages contributed to the stratigraphic variations in Co enrichment. In the diagenetic stage, the R.S.F. and R.S.C. dolostone strata of the Lower Roan Group exhibit significantly higher Co contents due to substantial red bed input and strongly reducing conditions indicated by lower redox-sensitive elements in pyrite (e.g. Se and Mo), which facilitated the relative Co enrichment in these strata. In the syn -orogenic stage, initial Co heterogeneity during diagenesis was amplified by metal element remobilization in tectonic-hydrothermal activity. Lower δ 56 Fe values in chalcopyrite associated with Co-rich minerals also indicate the different redox condition of ore-forming fluid in different strata. Influence of syn -orogenic tectonic-hydrothermal activity resulted in the concentrated Co orebody development in fold and fracture belts. These results help refine the metallogenic model of cobalt in SSC deposits and provide clues for deep cobalt prospecting in the Katanga Arc belt.