Microtectonics and fluid evolution in the Katanga Supergroup (Tenke Fungurume Mining District): Evidence of pre- to post-orogenic Cu-Co mineralization in the Central Africa Copperbelt

Abstract

The sediment-hosted stratiform copper-cobalt deposits in the Central African Copperbelt (CACB) are renowned for their resource potential, encompassing Cu-Co (Ni, U) and Cu-Zn-Pb (Ag, Ge, Mo, Cd) mineralization. Microstructural and microthermometric analyses of carbonate-quartz veins from the Tenke Fungurume mining district, situated in the central part of the Katanga Copperbelt (KCB), have delineated a pre- to post-folding paragenesis of vein formation and hypogene Cu-Co ore mineralization. The mineralization primarily consists of chalcopyrite, chalcocite, carrollite, and bornite.Pre-folding veins comprise bedding-normal veins related to the extension stage, occasionally linked with mullion development during the following compressional stage, as well as bedding-parallel beef veins. Syn-folding mineralization manifests as saddle reef veins within fold hinge zones, fracture-filling veins aligned with tangential longitudinal strain in hinge zones of folded bedding-parallel veins, thin veinlets forming parallel to an axial-planar and shear-band cleavage, and bedding-parallel shear veinlets with oblique fiber orientations. The post-folding Cu-Co mineralization consists of veins that cross-cut earlier veins and folds.Microthermometric analysis of fluid inclusion assemblages from the pre-, syn-, as well as post-folding veins reveals the presence of different fluid types. A high-temperature (180–340 °C) and high-salinity (27–52.5 wt% NaCl + (KCl) eq.) fluid was responsible for the Cu-Co mineralization during the pre- to syn-folding stages. A hypersaline fluid (27.0–42.1 wt% NaCl eq.) with a broad range in temperature (45–387 °C) circulated during the post-folding stage of the Lufilian orogeny. A fluid exhibiting low to moderate homogenization temperatures (28–215 °C) and low to moderate salinity (3.4–23.0 wt% NaCl eq.) is related to fluid circulation during the post-Lufilian epoch. The wide range and variations in salinity of these three fluid types associated with Cu-Co mineralization provide evidence for a multistage fluid flow and a complex hydrothermal system linked to the deposition of Cu-Co ores within the Tenke Fungurume Mining District and the broader Katanga basin. This hydrothermal system has operated during diagenesis, the basin development stage to the Lufilian orogeny and the subsequent post-Lufilian period.