REEY characteristics in hydrothermal gangue carbonates within the sediment-hosted Nkana-Mindola Cu-Co deposit (Zambia) and in two polymetallic vein-type deposits (Kipushi and Dikulushi, Democratic Republic of Congo)

摘要

The Central African Copperbelt is a world class metallogenic province characterized by sediment-hosted stratiform Cu-Co ore deposits and polymetallic vein-type deposits. This project investigates the rare earth element and yttrium (REEY) compositions of the hydrothermal gangue carbonates associated with these mineralizations. In the Nkana-Mindola Cu-Co deposit, layer-parallel to irregular veins display variable REEY patterns, which can be explained by interaction with different sources and varying amounts of remobilization. The uniform REEY composition in the late massive mineralizations at Nkana-Mindola likely reflects similar sources and physicochemical conditions. Their heavy rare earth element (HREE) enrichment is inherited from their sources or generated during precipitation of a light rare earth element (LREE)-selective mineral phase. In the vein-type Kipushi deposit, Fe- and REEY-poor dolomites display upward-convex REEY-patterns while REEY- and Fe-rich dolomites show square-root shaped patterns with prominent negative Eu-anomalies. Both cement phases are closely associated with the main mineralization phase, and likely reflect interaction with different sources at distinct physicochemical conditions. This bimodality is absent at the polymetallic Dikulushi deposit, where the REEY in the Cu-Ag phase are likely remobilized from the earlier Cu-Pb-Zn-Fe phase.