Gold Fields (GFI) to triple Tarkwa plant, Ghana
Allan Seccombe
Posted: Wed, 26 Apr 2006
[miningmx.com] -- GOLD Fields is conducting a prefeasibility study into tripling capacity at its Tarkwa carbon-in-leach (CIL) plant in Ghana, the company said in a media visit to its west African mine.
If approved, the expansion will take the plant to 11 million tons/year as well as investigating at least three potential underground targets, company officials said on Tuesday.
The CIL plant has a nameplate capacity of 350,000 tons, but can handle up to 420,000 tons of ore a month. The thinking at this stage is to add a ball mill to join the SAG mill, said Gary Chapman, the head of mineral reserves and resources at Tarkwa.
The prefeasibility could be completed by the middle of 2006 and a bankable study by the end of the year, he told Miningmx during a visit to the operation.
“This plant is designed to accept a extra ball mill and there is no need to add that much extra tankage so it should be a fairly quick process,” he said.
The open cast operation’s two heap leach pads are to be consolidated to deal with the softer ore, handling some 800,000 to 900,000 tons/month. The CIL plant will deal with the nearly one million tons/month of harder ore. However, gold output will not rise.
“The aim is to keep us as a steady 700,000 oz/year producer,” Chapman said.
Machinery would be diverted from the discontinued heap leach pad to supply the extra demand from the CIL plant.
It makes good sense to switch to increased use of the CIL plant where recoveries are 95-97% versus the 64% at the heap leach operations. Rain, of which there is plenty at Tarkwa, adversely affects recoveries at the heap leach units.
Headgrade is expected to remain constant at 1.3 grams/ton for the foreseeable future.
“We are also looking at shallow underground potential,” Chapman told journalists.
Tarkwa management is evaluating old underground plans and samples as part of a process to generate fresh targets to mine.
Any underground targets will be mined once the cheaper nine existing open cast operations are depleted in 20 years time.
“The underground grade will be higher but it will be more expensive to integrate,” he said. “This is a scoping project at the moment and in the next phase we will drill more holes to confirm what is there.”
Tarkwa will investigate hydrothermal prospects next year.
A Johannesburg-based analyst said the heap leach facilities at Tarkwa were world class and said the mine was “going like a Boeing.”
Tarkwa is struggling to keep costs in check as the price of diesel, tyres, cement, cyanide and steel have all shot up. The mine uses 110,000 litres of diesel a day and prices have risen to $0.86 a litre from a budgeted $0.68.
“These rising prices have added another $4m to our expenditure in the six months to the end of December,” said Ludwig Eybers, Tarkwa’s manager.
Theft of diesel is a bigger problem on the mine than the theft of gold, he said, adding new security and monitoring systems similar to those on South African mines were being installed at Tarkwa.
The mine is targeting efficiencies to counteract rising input costs. Interestingly, procurement of tyres is not going to be a problem for at least another 18 months, he said, explaining Tarkwa had foreseen the looming global shortage of yellow-machinery tyres and had stockpiled them.
