Germanium in carbonate-hosted Cu-Pb-Zn mineralization in the Otavi Mountain Land, Namibia

摘要

The Otavi Mountain Land (OML), Namibia, hosts a large number of base-metal sulfide deposits, some of which are enriched in germanium. Mineralogically simple Zn-Pb - dominated deposits of the "Berg Aukas-type" carry less germanium than polymetallic, Cu-rich "Tsumeb-type" deposits. Both types are hosted by Neoproterozoic platform carbonates of the Otavi Group. In addition, clastic sediments under-and overlying the Otavi Group carry base metal mineralization. Germanium occurs as Cu-thiogermanate minerals (e.g. germanite, renierite, Ge-colusite) in the massive As-rich copper ore (tennantite-enargite association) of Tsumeb-type deposits. Deposits in the OML formed by the reaction of hot fluids passing through a variety of aquifers, becoming saline and metal-rich, and depositing metals in structural traps such as karst pipes and breccia horizons. Sources of metals and sulfur are discussed using isotope data.