Africa-focused project developer Ivanhoe Mines last week said it had started construction on the box cut for the initial portal to planned decline ramps that will provide underground access to the proposed Kamoa copper mine, in the Democratic Republic of Congo’s Katanga province.
The TSX-listed firm on Thursday reported that the construction contract was awarded to Lubumbashi-based Mining Company Katanga (MCK), which had extensive local experience in contract mining and earthworks and had worked on other significant Katanga copper mining projects, including Kinsevere, Kipoi and Kolwezi.
Construction of the box cut was expected take about five months, after which the first set of twin declines would be developed. The declines were designed to intersect the high-grade copper mineralisation in the Kansoko Sud area, about 150 m below surface. Ivanhoe’s drilling programme in this area had defined a thick, near-surface zone of high-grade copper mineralisation in Kansoko Sud, where a recent drill hole intercepted 15.7 m (true width) of 7.04% copper, at a 1.5% total copper cutoff.
“This first development step is an important milestone in Ivanhoe’s schedule to begin realising the tremendous potential of Kamoa’s high-grade resource to deliver meaningful benefits to all our stakeholders. Industry experts recognise that Kamoa is a world-class copper deposit, both in terms of size and grade.
“In our mine planning, Kamoa’s tabular form and relatively undeformed geometry, allows [the use] of simple and low-cost mining methods; no complex metallurgical processes are required and the inherent scalability of the deposit means that it can provide significant returns over a range of production scenarios,” founder and executive chairperson Robert Friedland said in a statement.
Kamoa is the world’s largest high-grade (greater than 2.5% copper) copper resource. Ivanhoe’s independent preliminary economic assessment (PEA) was based on an initial mining rate of three-million tonnes a year, which could be scaled up in phases to a steady-state rate of up to 15-million tonnes a year.
Ivanhoe CEO Lars-Eric Johansson noted that it was important for the company to strike the correct balance between capital efficiency and operational risk.
“This principle will be adopted during the project’s first phase, which is being scoped to target several high-grade areas in Kansoko Sud in the initial build-up. The approach is to target early cash-generation opportunities, while allowing organisational learning and operational refinements to be incorporated into the subsequent expansion phases,” Johansson added.
Ivanhoe said given the favourable geological characteristics of the Kamoa deposit as derived from the December 2012 mineral resource – including its relatively undeformed, continuous mineralisation – the deposit was considered amenable to large-scale, mechanised, room-and-pillar and drift-and-fill mining.
The overall dip and geometry of the resource made it conducive to room-and-pillar mining in the shallow portions of the deposit, which would transition to drift-and-fill mining in the deeper or steeper sections. These methods were the accepted industry standards for mining deposits such as Kamoa.
Infill drilling of the planned initial mining area from the PEA had confirmed the overall grade and thickness of the December 2012 resource estimate in these areas and provided invaluable refinement within localised areas. While traditionally modelled on a 1% total copper cutoff to define a selective mineralised zone (SMZ), the deposit had shown that grade continuity also existed at an elevated 1.5% total copper vertical cutoff and a 2% total copper vertical cutoff may be feasible in certain areas.
Applying higher cutoffs to define the SMZ had shown that higher-grade, narrower intervals would improve intial mine economics, as it would create more expansive, contiguous zones of high-grade mineralisation.
In line with the phased approach to project development outlined in the 2013 updated Kamoa PEA, the Kamoa prefeasibility study (PFS) was currently progressing on the basis of an initial three-million-tonne-a-year mine and concentrator. Development plans would be refined after completing the PFS