Author:

Keywords:

Cu isotopes, Dikulushi Cu-Ag deposit, Copperbelt, D.R.Congo, Science & Technology, Physical Sciences, Geosciences, Multidisciplinary, Mining & Mineral Processing, Geology, DRCongo, COPPER, FRACTIONATION, COMPLEXES, BRINES

Abstract:

Recent studies show that the largest natural variations in the Cu isotope composition are due to changes in redox conditions and occur in the weathering zones of Cu ore deposits. This study investigates the influence of supergene processes on Cu isotope variations in the Dikulushi Cu- Ag deposit, which consists of a Cu-Pb-Zn-Fe mineralisation that was partially remobilised into a Cu-Ag mineralisation. The upper part of the deposit is weathered, causing significant Cu isotope fractionation. Relict sulphides are characterised by light Cu isotope compositions (0.00 to -2.3 ‰ δ 65Cu), while the supergene mineralisation is enriched in 65Cu (1.37 to 2.65 ‰ δ 65Cu). The influence of supergene processes on the Cu isotope composition decreases as a function of depth. At depth, the Cu isotope composition for chalcopyrite from the Cu- Pb-Zn-Fe mineralisation clusters in two end members around -2.1 ‰ and -0.05 ‰ δ 65Cu. These chalcopyrite samples likely precipitated from physico-chemically distinct fluids in which Cu was transported in the form of different complexes. The results show that samples for Cu isotope analysis should not be influenced by weathering. If supergene processes can be excluded, their Cu isotope composition can be used to indicate physico-chemically distinct fluids from which the mineralisation precipitated.