Crushed material would be stacked on the heap leach pad by a radial stacker in 50 by 50 metre modules in layers 10 m thick. Every five layers, a geomembrane will be placed on the heap to separate subsequent layers from the underlying material. The final leach pad height will be approximately 100 m. A pad irrigation rate of 10 liters/hour/metre2 has been considered. Sodium cyanide and lime consumption are expected to be 0.24 kilograms per tonne ("kg/t") and 1.4 kg/t respectively. The pregnant leaching solution containing gold would then be pumped to a conventional carbon adsorption facility (ADR plant) where gold from process solutions would be recovered to a final gold dore product.
Average gold recoveries of 79.5% have been used in the PEA based on bottle roll and column metallurgical testing. To date, over 75 bottle roll tests and 20 column tests have been completed on material from the Cerro Maricunga deposit. The majority of the column tests have been completed on mineralization crushed to 19 millimetres ("mm"), however, 78% gold recoveries were also achieved on material crushed to 50 mm and 77% recoveries were achieved on 100 mm crushed material. In order to evaluate gold recoveries at various crush sizes, further metallurgical test work is continuing.
Capital Requirements
The PEA initially estimates capital expenditures for the potential development of an open pit mining and conventional heap leach processing operation at the Cerro Maricunga project at $514.6 million, which includes contingencies of $41.3 million and Engineering, Procurement, and Construction Management ("ECPM") costs of $28.9 million. A breakdown of these costs is provided in Table 3. Additional capital requirement during the life of the mine, including annual heap leach pad expansions and closure costs total $249.0 million, which includes a 5% contingency. The capital costs presented are based on quotes received from equipment manufactures or contractors. The PEA assumes, on the basis of quotes received, that the mining fleet will be acquired through a manufacturer lease arrangement payable over the life of the mine at a total cost of $214.1 million.
Table 3 - Preliminary Summary of Capital Expenditures--------------------------------------------------------------------------- Item US$ (millions)------------------------------------------------------------------------------------------------------------------------------------------------------Open Pit--------------------------------------------------------------------------- Pre-strip 17.1--------------------------------------------------------------------------- 1st Fleet Lease Payment 14.7--------------------------------------------------------------------------- Mining Support (incl. truck shop) 27.6---------------------------------------------------------------------------Processing--------------------------------------------------------------------------- Crushing & Stockpiles 108.2--------------------------------------------------------------------------- Leach Pads 93.2--------------------------------------------------------------------------- ADR & EW/Smelting 29.5--------------------------------------------------------------------------- Indirect 55.6---------------------------------------------------------------------------Infrastructure--------------------------------------------------------------------------- Water 84.8--------------------------------------------------------------------------- Warehouse, Office, etc. 7.7--------------------------------------------------------------------------- Roads 3.0--------------------------------------------------------------------------- Indirect 3.1------------------------------------------------------------------------------------------------------------------------------------------------------Capital Costs (without contingencies) 444.5---------------------------------------------------------------------------Contingencies(ii) 41.3---------------------------------------------------------------------------EPCM(ii) 28.9------------------------------------------------------------------------------------------------------------------------------------------------------Total Capital 514.6(i)---------------------------------------------------------------------------(i) The PEA has been completed to a level of accuracy of +35% to -10%.(ii) Contingencies are 10% and EPCM are 7% of capital expenditures excludingPre-strip and 1st Fleet Lease Payment.
