Summary:
The mineralisation identified to date within the Project is typical of sediment-hosted stratiform copper deposits. Such deposits can be hosted in either marine or continental (red-bed) sediments. Major global examples of these deposits include the Kupferschiefer (Poland), most of the deposits within the Central African Copperbelt (such as Konkola, Nkana, Nchanga, Mufulira, Tenke–Fungurume, and Kolwezi), Redstone (Canada), and White Pine (USA).
The modelled Kamoa deposit is located in a broadly-folded terrane, with the antiform centred on the Kamoa and Makalu domes. The central portions of Kakula are located on the southern extension of this antiform, with Kakula West located on the top of a separate, but parallel trending antiform. The domes form erosional windows exposing the redox boundary between the underlying haematitic (oxidised) Roan sandstones (Mwashya Subgroup), and the overlying carbonaceous and sulfidic (reduced) Grand Conglomérat diamictite (N’Guba Group), which comprises diamictites with minor interbedded sandstone, siltstone, and conglomerate. The mineralisation at Kamoa-Kakula is hosted towards the base of the Grand Conglomérat unit (Ki1.1).
Mineralisation at Kamoa-Kakula has been defined over an irregularly-shaped area of about 28 km x 23 km. Mineralisation is typically stratiform, and vertically zoned from the base upward with chalcocite (Cu2S), bornite (Cu5FeS4) and chalcopyrite (CuFeS2). The nature of the copper grade distribution is related to its stratigraphic position, proximity to the Roan aquifer (or structures that may have focussed fluid flow), and the localised development of lithological units. The earliest sulfide mineralisation at Kamoa-Kakula was deposited during diagenesis and formed abundant framboidal and cubic pyrite in the laminated siltstones (Schmandt et al, 2013). This pyrite mineralisation above the mineralised horizon could possibly be exploited to produce pyrite concentrates for sulfuric acid production (needed at oxide copper mines in the DRC).
Kamoa Deposit
Mineralisation at Kamoa has been defined over an irregularly-shaped area of 24 km x 14 km. Mineralisation thicknesses at a 1.0% Cu cut-off grade ranges from 2.3–21.6 m (for Indicated Mineral Resources). The deposit has been tested locally from below surface to depths of more than 1,560 m, and remains open to the west, east, and south.
At Kamoa, the clast-rich diamictite (Ki1.1.1.1) is considered to be only weakly reducing, and thus generally hosts only low-grade (<0.5% TCu) mineralisation. The intermediate siltstone (Ki1.1.1.2) and clast-poor diamictite (Ki1.1.1.3) are considered to represent significantly better reducing horizons and thus host the majority of the primary mineralised zone. Some of the most consistent and highest-grade intervals are intersected where the clast-rich diamictite is absent, and the clast-poor diamictite rests directly on the Roan contact.
The nature of the copper grade distribution is related to its stratigraphic position and the localised development of lithological units. Where the mineralisation is located on the Roan contact, the mineralised interval is thick, and has a very strongly-developed bottom-loaded profile. Where the mineralisation is located at the base of the clast-poor diamictite (Ki1.1.1.3), the profile is typically bottom-loaded (if no intermediate siltstone is developed), or complex if one or more siltstone layers are developed. In the Kansoko Sud and Makalu areas, numerous siltstone layers developed within the diamictite cause the grade profile to become bimodal or even top-loaded. Where the mineralisation is hosted at the base of the KPS, it is typically narrow (but often high grade), with a middle-loaded profile.
At Kamoa, chalcopyrite is the primary sulfide mineral, and usually occurs as fine-grained disseminations in the diamictite matrix. However, very coarse-grained chalcopyrite can form as elongated grains up to 5 mm in length rimming clasts, or defining strain shadows to clasts. Bornite is typically fine-grained and disseminated in the matrix of the diamictite. When well developed, the fine-grained bornite is visually recognised through a significant darkening of the diamictite matrix. Chalcocite almost always occurs as fine-grained disseminations, particularly within the intermediate siltstone (Ki1.1.1.2).
Kakula Deposit
The Kakula deposit is currently delineated over an area of 14 km by 5km. The vertical thickness of the mineralisation at a 1.0% Cu cut–off grade ranges from 2.9 m to 42.5 m (in the indicated Mineral Resource area). The deposit has been tested locally from below surface to depths of more than 1,000 m, and remains open to the southeast and west.
At Kakula, the narrow (<3 m) clast-rich diamictite immediately above the Roan contact is only weakly reducing and thus has low copper grades. The basal siltstone overlying the clast-rich diamictite is a very strong reductant, contains very high grades (>6% Cu), and accounts for the majority of the deposit. The lateral continuity of this reductant allows for the unique lateral continuity of grades >6% TCu. The diamictite overlying the basal siltstone is clast-poor and is also a good reductant; however, it hosts low-grade copper mineralisation relative to the basal siltstone. This relationship is considered to represent the distribution of the pyrite reductant prior to mineralisation, and has been incorporated into the domaining used in the estimation for both Kakula and Kakula West.
Mineralisation at Kakula is dominantly hypogene chalcocite with gradual transition upward to bornite. Bornite and chalcopyrite zones are not as well developed as at Kamoa, and supergene chalcocite zones do not occur at Kakula. The chalcopyrite and bornite zones are very narrow, with a very gradual transition downward from bornite to chalcocite, followed by a zone that is typically within the basal siltstone, which is chalcocite-dominant. Whilst still dominantly fine-grained, numerous examples of coarse to massive chalcocite are evident in the highest-grade intersections. Chalcopyrite is observed in the core, but typically occurs outside of the defined mineralised zone, except in peripheral areas at Kakula West where the overall mineralised zone has narrowed, incorporating the full zonation.
In the south-eastern portions of Kakula, the highest-grade intersections trends 115°, and aligns with the different stratigraphic, and lithological units. To the north-west, the mineralisation turns to the west, with alignment along 105°. At Kakula West, well-developed growth faults control the alignment of thickness and grade trends that vary around north-easterly orientations. The orientations of the controlling growth fault features have been incorporated into the search orientations used during grade estimation.