Kansanshi Mine

 copper mine, gold mine

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The Kansanshi mine is the largest copper mine in Africa and is 80% owned by Kansanshi Mining PLC, a First Quantum subsidiary. The remaining 20% is owned by a subsidiary of ZCCM. The mine has undergone several expansions since it began operating in 2005 at an initial production capacity of 110,000 tonnes of copper. As of 2014 it had a capability of producing 340,000 tonnes of copper and more than 120,000 ounces of gold per year, with a multi-stage expansion project which aims to increase copper output capacity to approximately 400,000 tonnes by 2015.

The current large-scale mining licence LML 16 was first issued to Kansanshi Mining plc on 7th March 1997 and is valid until 7th March 2022 whereupon renewal can be applied for. The licence allows the holder to explore and mine the minerals of copper, cobalt, gold, silver, tellurium, selenium and sulphur. On 14th June 2000, the company applied to have the mining licence re-oriented and expanded to 21,593 ha from the original 4244 ha. The Chief Mining Engineer (Mines Development Department) approved the application on the 28th December 2000. The area covered by LML 16 now forms a square.

The deposit outlines a well mineralised, north-south striking zone. The zone is characterised by complicated faulting, abundant injection vein networks, development of brecciate units and down-dropped rock structures. Vein-specific copper mineralisation that is either stratiform or concordant is hosted within and directly adjacent to mesoscopic veins, in thin bands and veinlets oriented parallel to rock bedding or foliation. It also occurs as disseminated mineralisation related with albite-carbonate alteration. The main veins and vein swarms plunge sub-vertically, perpendicular to the fold axis.

Mineralisation within the brecciate zones occurs within oxidised and supergene enriched layers. Secondary copper minerals are distributed in a complex manner across these layers. The primary copper sulphide mineralisation is chalcopyrite-dominated and is associated with trace amounts of bornite, minor pyrite and pyrrhotite. The oxide mineralisation is largely dominated by chrysocolla. It also hosts malachite, limonite and cupriferous goethite. The mixed zone, a combination of both oxide and primary-style mineralisation, also hosts significant amounts of chalcocite, minor local copper and tenorite.

Mining at the Main and NW open pits is done by conventional open pit methods involving hydraulic excavators and a mining fleet of haul trucks. Processing of the three ore types, namely leached ore, mixed float and sulphide, is through either an oxide circuit or a sulphide and transitional ore mixed float circuit. Treatment of the sulphide ore involves crushing, milling and flotation to produce copper in concentrate.

A HPL circuit is used to convert the flotation concentrate to final cathode. The HPL circuit processes the copper concentrate in the autoclaves. The operation involves oxidation and leaching. The circuit residue is treated through a gravity gold circuit that replaced the gold circuit in 2009. Contained gold was originally planned to be recovered into bullion through cyanide leaching and elution, but the gold circuit was not put into operation due to technical problems. In the gravity gold circuit, the efficient gravity concentration is combined with pyro-metallurgical of lower grade gravity concentrate.

Expansion of the mine is being carried out over three phases. The $32m Phase 1 involved capacity enhancement of the oxide circuit by 20% to 7.2 million tonnes (mt). It resulted in a flexible operation that allows easy switch between mixed and sulphide circuits to suit the mining operations.

Phase 2, which was completed in November 2013 at a cost of $200m, increased the annual oxide treatment capacity by 15mt. The mixed ore and sulphide ore are milled together by a second sulphide circuit (S2) following the phase 2 expansion.

The third phase of expansion includes construction of a new 16mtpa sulphide concentrator through a single stage Semi-Autogenous Grinding (SAG) mill, which can be extended up to 25mtpa by adding a ball mill in the future. This phase has been budgeted at $565m. The new Sulphide concentrator (S3) is expected to be operational by 2015. The sulphide ore will be milled by the new S3 following the third phase of expansion, while the mixed ore will be milled by the S2 circuit. The copper concentrate produced from the S3 will be supplied to the new smelter.