Lithostratigraphic and structural controls on sulphide mineralisation at the Kamoa copper deposit, Democratic Republic of Congo

Abstract

The Kamoa copper deposit, 25 km west of the Kolwezi CuCo district in Democratic Republic of Congo, is one of the largest high-grade copper deposits in the world. Kamoa is a recent discovery on the western edge of the Congolese part of the Central African Copperbelt (CACB). Two main rock units are present at Kamoa, sandstone and siltstone of the Mwashya Subgroup (Roan Group), and overlying diamictite and interbedded siltstone-sandstone of the Grand Conglomérat unit (Nguba Group). The deposit is at a redox boundary at the base of the Grand Conglomérat.Drill-core data indicate that the Kamoa deposit includes areas of higher and lower grade, some of which appear at the deposit-scale to be related to known or inferred faults. In the southern part of the Kamoa deposit, a NNW-trending zone of abrupt change in stratigraphic thickness named the “Mupaka fault” correlates with elevated copper grades. Thickness variations, facies changes, steep bedding, and rotated mesoscopic faults demonstrate that the Mupaka fault is a syn-sedimentary normal fault that was active during deposition of Nguba Group rocks. Similar to syn-depositional and subsequently inverted extensional faults known to localise ore at other CACB deposits, particularly in the Zambian Copperbelt, the Mupaka fault was an important control on mineralisation at Kamoa.