Nguba Group hosted the Lonshi Copper Deposit: Perspective for the discovery of new deposits in the vicinity of the Lonshi Mine

Abstract

The Lonshi is a newly discovered copper deposit located in the southeastern region of the Central African Copperbelt, in the Democratic Republic of Congo. The deposit is hosted in the Nguba Group of the Katanga Supergroup. This paper analyzes the lithostratigraphy of the Nguba Group, structures, ore host rock, and mineralization characteristics of the Lonshi deposit. The lithostratigraphy of the Lonshi area is comprised of the Mwashya sandstone of the Roan Group; conglomerate, dolostone, shale, mudstone, and siltstone of the Nguba Group; and conglomerate, pink dolostone, and siltstone of the Kondelungu Group. Geological structures identified within the mining zone encompass the N-S and W-E trending folds, the NW-trending fault, E-W sinistral shear structures, and various fractures and veins. The Lonshi deposit exemplifies a characteristic of hydrothermal stratiform mineralization, comprising two main orebodies situated within the Mwale conglomerate (lower orebody) and the underlying Lonshi dolostone (upper orebody). The ore deposited during three mineralization stages, wherein the first hydrothermal stratigraphically-controlled stage that deposited chalcocite 1, bornite, chalcopyrite and pyrite. The structurally-controled stage 2 is further divided into chalcocite 2 and bornite stage 2a, and chalcopyrite, bornite and native copper stage 2b; and the supergene alteration stage 3 results in the formation of chalcocite 3, malachite, cuprite, azurite, and native copper 2. The gangue minerals associated with copper sulfide minerals consist of ankerite, feldspar, quartz, muscovite/sericite, kaersutite, barite, and illite. The sulfide minerals associated with ore stages display zonation both vertically and laterally, transitioning from chalcocite to bornite to chalcopyrite to pyrite±sphalerite. Copper sulfide minerals manifest as fine- to coarse-grained disseminations within the conglomerate, exhibiting a replacement texture. The mineralizing fluids at the Lonshi deposit were likely enriched in Fe, Ca, Mg, Si, S, and Cu, with additional magnesium within the ore hosted dolostone and cobalt and potassium within the ore hosted conglomerate.The Nguba Group shows the distinct lithologies of light-gray conglomerates and dolostone, provide valuable insights for potential new deposits near the Lonshi mine. The observed mineral zoning, hydrothermal alterations, and multi-stage mineralization events suggest favorable conditions for copper mineralization. Targeting similar stratigraphic settings and alteration signatures in the vicinity could enhance the likelihood of discovering new deposits, particularly in areas exhibiting similar geological characteristics and structural features.