Supergene Metallogenesis and Its Prospecting Significance of the Ruashi Cu-Co Deposit in D.R.Congo
The Ruashi copper-cobalt deposit in the Central African Metallogenic Belt has undergone supergene oxidation and secondary enrichment,but the related research is weak.This work analyzed the composition of supergene zoning and its metallogenesis based on geological surveys,mineralogical observations and production resource exploration of this deposit.The primary orebodies contain sulfide minerals of chalcopyrite,bornite,chalcogenite,and the ore grade ranges in 1%～2%for copper and 0.1%～0.3%for cobalt.The upper oxidation belt can be further divided into three sub zones,i.e.,the complete oxidation subzone,the leaching subzone and the secondary oxide enrichment subzone.The complete oxidation subzone develops the"gossan"with cobalt-rich oxide accumulation(cobalt grade is 1%～3%,locally reaching up to 12%).The leaching subzone contains almost no copper and cobalt metal minerals.The secondary enriched oxide subzone includes oxide minerals of malachite,silicomalachite,azurite,chalcopyrite,and water chalcopyrite,as well as carbonate minerals.The ore grade is 5%～10%for copper and 0.8%～1.0%for cobalt,which is enriched by 3～5 times than the primary ore.The lower part is the secondary sulfide enrichment including chalcopyrite and chalcocite.The ore grade is within the range of 3%～5%for copper and 0.3%～0.8%cobalt,which is 1～3 times enriched than the primary sulfide ore.The study reveals that the Ruashi deposit has experienced multi-period and multi-stage metallogenic evolution,and the supergene oxidation zoning is controlled by factors such as rock stratum,geological structures,and groundwater.The secondary enrichment has significantly improved the ore grade and development value,which formed high to ultra-high grade ore bodies such as the Cu-Co-enriched oxide ore,Cu-Co-enriched sulfide ore,Cu-enriched oxide ore near the contact zone of carbonate rock and black Co-enriched ore.Exploration indicates that the newly discovered high-grade ore resources in the deep edge of the deposit are 2.56 million tons,with an average grade of 3.68%copper and 0.44%cobalt.The recoverable reserves are 1.43 million tons,with an average grade of 3.53%copper and 0.32%cobalt.This study can provide scientific basis for the epigenetic enrichment of sulfide deposits evolving into oxide deposits in the same type of mines and region,as well as for deep edge exploration prediction.
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