Modern Mining June 2019

REGIONAL FOCUS: WEST AFRICA

2,0 Mt/a of primary ore. For production sched- uling, ore processing rates of 2,8 Mt/a for oxides and 2,1 Mt/a for primary ore were targeted on the basis of a higher plant availability than pre- sented in the design criteria. The higher plant availability was based on Teranga’s operating experience with its Sabodala processing plant, which utilises a similar flowsheet and pro- cesses similar ore types. Flexibility in the plant design layout provides for a future increase of ore treatment to greater than 4,0 Mt/a. Ore delivered to the plant will undergo sin- gle stage primary crushing with a single toggle jaw crusher to produce a crushed product size of P80 ranging from 100 mm to 140 mm, based on differing weathering types. The crushed ore stockpile will have a live nominal capacity of 2 000 tonnes. The crushed ore will be subjected to SAG and ball milling in closed circuit with a pebble crusher and hydrocyclones (SABC) to produce a P80 grind size of 106 µm. The leach and CIL circuit incorporates eight stages, with one stage of leaching without carbon and seven stages with carbon for gold adsorption. A Split Anglo American Research Laboratory (SAARL) elution circuit, electrowin- ning and gold smelting are employed to recover gold from the loaded carbon to produce doré. The average predicted plant gold recovery is 92 %, with soft (oxide) material recoveries from some zones reaching as high as 95 %. The tailings storage facility (TSF), located east of the processing plant, has been developed as a high-density polyethylene geomembrane-lined paddock-type facility. It consists of a zoned, downstream constructed embankment with the design utilising natural ridges to reduce the volume of embankment

7 km, 17 km and 26 km, respectively, from the plant. The average annual production of Wahgnion over its currently estimated 13-year life of mine (LoM) is estimated to be 114 koz at an aver- age all-in sustaining cost (AISC) of US$904/ oz. During the first five years, however, it is expected that the mine will produce an average of 132 koz/a at an AISC of US$761/oz. Mining will be by way of open-pit mining techniques using drill and blast with mate- rial movement by hydraulic excavators and 50-tonne class rigid haul trucks. Mining will be undertaken directly by Teranga (as it does at Sabodala). Given that Wahgnion is character- ised by numerous narrow orebodies that have variable orientations and widths (but good continuity along strike and down dip), a highly selective mining operation is planned. Multiple backhoe excavators equipped with 5,7 m 3 buck- ets are specified as the primary loading units, allowing for a high level of mining selectivity from multiple production faces. It is anticipated that 289,8 Mt of material will be mined over the LoM. The LoM stripping ratio is 8,3:1 (waste to ore) but this reduces to 7,1:1 over the first five years of mining. Mining activities at Wahgnion have been ongoing since August 2018, with material sourced from the Nangolo and Nogbele North pits. The early start on mining production has provided construction material for the tailings storage facility. It also allows the Nangolo pit to be used for water storage starting in mid- 2019 and for the build-up of an ore stockpile in advance of plant commissioning. The process plant design is based on a nominal capacity of 2,7 Mt/a of oxide ore and

Above: Installation of CIL top of tank modules.

Centre: Another view of the plant with the elution circuit in the foreground. Right: The crushed ore will be subjected to SAG and ball milling in closed circuit with a pebble crusher and hydrocyclones (SABC) to produce a P80 grind size of 106 µm.

28  MODERN MINING  June 2019