PB-ISOTOPE CONSTRAINTS ON BASE-METAL MINERALIZATION AT KIPUSHI (SOUTHEASTERN ZAIRE)

The Kipushi Zn-Pb-Cu deposit, located in the northern extension of the Central African Copper Belt in southeastern Zaire, is a discordant or e body at the contact between abreccia body and adjoining host rocks o f the Upper Proterozoic Lower Kundelungu Group. Model age data of gale na indicate a probable mineralisation age of 454+/-14 Ma which is youn ger than the peak of the Lufilian tectonism and suggests that the mine ralisation is epigenetic and post-dates the folding and brecciation at Kipushi. Pb-isotopic compositions of sulphide minerals and host rocks at Kipushi show little variation. Limited data from other deposits (L ombe, Kengere, and Kolwezi), also in the northern extension of the Cop per Belt, suggest that the Pb-isotopic homogeneity extends over a larg e region which corresponds to the northern part of the Copper Belt and also to the outer, northern zone of the Lufilian fold belt Pb from th e Kinsenda ore deposit, located in the central zone of the Lufilian fo ld belt, differs from Kipushi and displays similarities to that of Mus oshi, another deposit located in the central zone of the fold belt. Th e Kipushi data, in conjunction with other available data, form the bas is of a model involving at least two distinct mineralisation events an d which might apply to the Copper Belt as a whole: (1) an early event associated primarily with deposits of the stratabound type of Copper B elt deposit; this event occurred at or before c. 650 Ma and resulted i n the Cu-Co mineralisation of the central part of the fold belt and wa s sourced from basinal fluids, and (2) a younger event responsible for vein type deposits, at 454+/-14 Ma, which produced the Zn-Pb-Cu miner alisation of the northern part of the fold belt and derived its metals from a magmatic or volcanic source.