Cerro Negro

The high-grade gold and silver project is located in the Santa Cruz province of Argentina.

An October 2008 positive pre-feasibility study reported that probable reserves were estimated at 7.2 million tones at 6.4 g/t gold and 75 g/t silver for 1.5 million ounces of gold and 17.3 million ounces of silver.

The plan is to mine the Eureka West deposit at a nominal rate of 2,000 tpd using conventional underground mining methods and to mine the Vein Zone deposit at a nominal rate of 2,000 tpd using open pit mining methods.

Mining in Vein Zone will be with open pit methods in two phases with a 90 tonne truck fleet. For the Vein Zone deposit, an open pit design was developed that had a strip ratio of 5.6 tonnes of waste to every tonne of ore based on an economic cut-off grade of about 1 g/t gold.

The Eureka deposit will be mined with conventional cut and fill underground methods along the length of the vein and in a transverse fashion perpendicular to the vein where vein thickness permits. The underground mine will be accessed via a decline.

Eureka is anticipated to be depleted after four years, leaving the remaining production for the last two years from Vein Zone open pits only.

The 4,000 tpd, or 1.35 million tonnes-per-annum, processing plant will be located close to the Vein Zone deposit, and a 19km road will be constructed from the Eureka portal to the crusher stockpile. Ore grade material from both deposits will be stockpiled at the crusher pad and blended before being fed to the mill.

The process plant design incorporates the following unit process operations: single stage crushing with a jaw crusher; comminution circuit, using a SAG mill followed by a closed circuit ball mill grinding to a P80 of 63 ìm; gravity recovery of free gold from the cyclone underflow to produce a gravity concentrate; intensive leaching of gravity concentrates; conventional leaching circuit consisting of six agitated and air sparged leach tanks in series, providing 72 h residence time; four stage CCD circuit to provide recovery of pregnant solution and tailings washing; Merrill Crowe circuit to recover gold and silver from solution; cyanide destruction of tailings stream using the SO2/air process.