Constraining ore-forming processes of the sediment-hosted Dolostone Ore Formation copper-cobalt mineralization, northwestern Namibia: a sulfide trace element study

Exploration was recently carried out on the sediment-hosted Dolostone Ore Formation (DOF) Cu-Co mineralization, in the Kunene Region of northwestern Namibia, in the pursuit of new sources of Co. Sharing several key similarities to the Central African Copperbelt, the DOF has potential of becoming Namibia’s first Co mine. Due to the mineralization being recently explored, aspects of the mineralizing system are yet unconstrained. In the scope of the project, several analytical methods are being deployed; LA-ICP-MS trace element analyses of sulfides being one of the main methods. Trace elements analyses of sphalerite, chalcopyrite, pyrite and pyrrhotite of the six mineralization styles (disseminated, clustered, nodular, “sigma”, veins and “events”) reveal a multi-generational ore-forming history of the DOF. Elements such as Fe, Co, Ni, Ga, Se and Cd in sphalerite and Co, Ni, Se and Bi in chalcopyrite show discrete grouping of element concentrations between (1) dissemination, cluster, nodule and “event” styles and (2) “sigma” and vein styles. Trends in sulfide geochemistry and geothermometry of sphalerite (which formed above 310 ± 50 °C) indicate that metamorphism strongly influenced the DOF mineralization. Metamorphism in the Kunene Region is attributed to the Damara Orogeny. Many questions remain, e.g. the role of pre-existing pyrites and the possibility of an early, diagenetic mineralization. Understanding when and why these Co-bearing sediment-hosted mineralizations formed is of key-importance for the exploration of new deposits and securing new Co-resources for our green-technology future.