TORONTO (miningweekly.com) – Canadian explorer Belo Sun Mining on Thursday said it had received positive results from preliminary metallurgical leach testwork on samples from the South Block deposit of its Volta Grande gold project, located in Brazil’s Para state.

The purpose of the preliminary metallurgical testwork programme was to verify whether the South Block ore was amenable to the same optimum leach process conditions recently confirmed for the Grota Seca and Ouro Verde deposits.

A total of six South Block composite samples were tested, with the head grades varying from 2.2 g/t to 6.5 g/t gold, which achieved an average gold recovery of 95%. These results were found to be consistent with previous results of 94% gold recovery reported for the Ouro Verde and Grota Seca deposits.

"These preliminary metallurgical leach testwork results indicate that the ores from the Grota Seca, Ouro Verde and South Block deposits can all be blended and treated in the same plant under the same optimum process conditions while achieving excellent gold recoveries,” Volta Grande project metallurgical manager Omar Antunes said.

The last mineral resource for the South Block was released in December, which estimated and inferred pit-constrained resources of 5.37-million tonnes at an average grade of 2.73 g/t of gold, containing 471 000 oz, and an inferred underground mineral resource of 408 000 t at an average grade of 3.89 g/t of gold, containing 51 800 oz for gold.

Ongoing drill results from the three deposits would be incorporated in the feasibility study that Belo Sun expects to complete at the end of the year.

"We are very encouraged with these metallurgical results, which demonstrate the ability to add the higher grade South Block material to the existing planned Volta Grande material through the company’s processing facility,” CEO Mark Eaton added.

Belo Sun recently announced results of a prefeasibility study for Volta Grande.

The study placed a potential after-tax net present value of $474.2-million on the project, using a 5% discount rate. The study had also indicated an internal after-tax rate of return of 15.2%.

The mine would cost $749.11-million to construct, after which costs to sustain operations, including closure costs, would total $19.62-million a year.

The study confirmed a ten-year life-of-mine, producing 313 100 oz/y.

The Volta Grande mine would have a seven-million-ton-a-year throughput with an average waste-to-ore strip ratio of 6.88:1.

The average grade of the Canadian National Instrument 43-101-compliant measured and indicated resources was 1.72 g/t, declining to 1.48 g/t after mining dilution was accounted for.

The total cash operating cost, including royalties, totalled $711.50/oz.