193
∼535 Ma (Selley et al. 2018). The succession is divided into three regionally mappable groups,
which from oldest to youngest are named the Roan, Nguba, and Kundelungu Groups.
Most of the known CACB deposits in the DRC are hosted by dolomitic rocks of the Mines
Subgroup in the lower part (Roan Group) of the succession (Francois 1973, Cailteux et al.
2005), whereas Kamoa occurs at the base of a stratigraphically higher diamictite, the Grand
Conglomérat of the basal Nguba Group (Broughton & Rogers 2010, Schmandt et al. 2013).
Timing of mineralisation in the CACB has been a matter of debate for decades. In the
context of exploration, however, the absolute timing of mineralisation is less crucial, as the
distribution of deposits is fundamentally controlled by chemical (reductant) and permeability (aquifer) considerations upon which ore fluids were superimposed (Selley et al. 2018).
Incorporation of these controls during grade estimation has been a key objective.
2.2 Local geology
At Kamoa, haematite-bearing sandstone and siltstone of the Mwashya Subgroup (upper
Roan Group) form the oxidised lower strata, and the pyritic rocks of the basal diamictite and
interbedded siltstone-sandstones form the reduced host rock (Twite et al. 2018).
Although often associated with glacial origins, the diamictites of the Grand Conglomérat
at Kamoa are interpreted as the deposits of cohesive debris flows, with the sandstone and
siltstone units the product of turbidity flows in a rapidly subsiding and evolving rift (Kennedy
et al. 2018). The abundance of framboidal pyrite, which can only form under anoxic conditions, suggests there was little shallowing of the basin even with the substantial sedimentary
input (Kennedy et al. 2018). This pyrite played a critical role in providing the reductant for
copper sulphide mineralisation in diamictites and siltstone units at the base of the Grand
Conglomérat (Schmandt et al. 2013).
The mineralisation at Kamoa is broadly stratiform, but zones of elevated copper grades
appear to be related to inferred growth faults that were active during sedimentation, underscoring an important link between extensional fault architecture and localisation of orebodies. These are marked by abrupt changes in stratigraphic thickness, steepened bedding and
rotated mesoscopic faults (Twite et al. 2018). Syn-sedimentary normal faults have been documented as first-order ore controls at several deposits in the Zambian Copperbelt, such as
Mwambashi B, Chambishi, Konkola, Musoshi and Fishtie (Selley et al. 2005, Hendrickson
et al. 2015).
Units are deformed into dome and basin patterns, resulting from the interference of NE-,
ENE-, and WNW-trending, mainly gentle to open, upright folds. This relatively weak deformation contrasts greatly with the complex strain patterns of the neighbouring Kolwezi system (Selley et al. 2018). A much younger extensional fault set, known as the West Scarp
Fault, transects the project in an approximate north-south orientation (west block down) to
the west of Kamoa and separating Kakula from Kakula West. This is the only brittle fault
system identified to date on the project with significant offset.
2.3 Mineralisation
Copper mineralisation at Kamoa-Kakula is typically bottom-loaded, with a vertical transition from chalcocite at the base progressing upwards through bornite, chalcopyrite and
pyrite. Mineralising fluids in the CACB have been modelled by Muchez & Corbella (2016) to
advance slowly, laterally and across stratigraphic layers away from the fluid source, driving
the reactions between a copper-rich fluid and the host rock reductant (anhydrite or pyrite),
precipitating copper sulphides. This mineralising front is also capable of dissolving some of
the earlier copper sulphides, with the stratigraphically lower, more copper-rich sulphides partially replacing the overlying, more copper-poor sulphides (Twite et al. 2018). A characteristic
zonation develops whereby pyrite is replaced by chalcopyrite, chalcopyrite by bornite, and
bornite by chalcocite. This zonation is evident at Kamoa-Kakula (Fig. 1) and elsewhere on
the CACB (Van Langendonck et al. 2013).
∼535 Ma (Selley et al. 2018). The succession is divided into three regionally mappable groups,
which from oldest to youngest are named the Roan, Nguba, and Kundelungu Groups.
Most of the known CACB deposits in the DRC are hosted by dolomitic rocks of the Mines
Subgroup in the lower part (Roan Group) of the succession (Francois 1973, Cailteux et al.
2005), whereas Kamoa occurs at the base of a stratigraphically higher diamictite, the Grand
Conglomérat of the basal Nguba Group (Broughton & Rogers 2010, Schmandt et al. 2013).
Timing of mineralisation in the CACB has been a matter of debate for decades. In the
context of exploration, however, the absolute timing of mineralisation is less crucial, as the
distribution of deposits is fundamentally controlled by chemical (reductant) and permeability (aquifer) considerations upon which ore fluids were superimposed (Selley et al. 2018).
Incorporation of these controls during grade estimation has been a key objective.
2.2 Local geology
At Kamoa, haematite-bearing sandstone and siltstone of the Mwashya Subgroup (upper
Roan Group) form the oxidised lower strata, and the pyritic rocks of the basal diamictite and
interbedded siltstone-sandstones form the reduced host rock (Twite et al. 2018).
Although often associated with glacial origins, the diamictites of the Grand Conglomérat
at Kamoa are interpreted as the deposits of cohesive debris flows, with the sandstone and
siltstone units the product of turbidity flows in a rapidly subsiding and evolving rift (Kennedy
et al. 2018). The abundance of framboidal pyrite, which can only form under anoxic conditions, suggests there was little shallowing of the basin even with the substantial sedimentary
input (Kennedy et al. 2018). This pyrite played a critical role in providing the reductant for
copper sulphide mineralisation in diamictites and siltstone units at the base of the Grand
Conglomérat (Schmandt et al. 2013).
The mineralisation at Kamoa is broadly stratiform, but zones of elevated copper grades
appear to be related to inferred growth faults that were active during sedimentation, underscoring an important link between extensional fault architecture and localisation of orebodies. These are marked by abrupt changes in stratigraphic thickness, steepened bedding and
rotated mesoscopic faults (Twite et al. 2018). Syn-sedimentary normal faults have been documented as first-order ore controls at several deposits in the Zambian Copperbelt, such as
Mwambashi B, Chambishi, Konkola, Musoshi and Fishtie (Selley et al. 2005, Hendrickson
et al. 2015).
Units are deformed into dome and basin patterns, resulting from the interference of NE-,
ENE-, and WNW-trending, mainly gentle to open, upright folds. This relatively weak deformation contrasts greatly with the complex strain patterns of the neighbouring Kolwezi system (Selley et al. 2018). A much younger extensional fault set, known as the West Scarp
Fault, transects the project in an approximate north-south orientation (west block down) to
the west of Kamoa and separating Kakula from Kakula West. This is the only brittle fault
system identified to date on the project with significant offset.
2.3 Mineralisation
Copper mineralisation at Kamoa-Kakula is typically bottom-loaded, with a vertical transition from chalcocite at the base progressing upwards through bornite, chalcopyrite and
pyrite. Mineralising fluids in the CACB have been modelled by Muchez & Corbella (2016) to
advance slowly, laterally and across stratigraphic layers away from the fluid source, driving
the reactions between a copper-rich fluid and the host rock reductant (anhydrite or pyrite),
precipitating copper sulphides. This mineralising front is also capable of dissolving some of
the earlier copper sulphides, with the stratigraphically lower, more copper-rich sulphides partially replacing the overlying, more copper-poor sulphides (Twite et al. 2018). A characteristic
zonation develops whereby pyrite is replaced by chalcopyrite, chalcopyrite by bornite, and
bornite by chalcocite. This zonation is evident at Kamoa-Kakula (Fig. 1) and elsewhere on
the CACB (Van Langendonck et al. 2013).