Atacama Pacific has received a positive, NI 43-101-compliant preliminary economic assessment (PEA) for its 100%-owned Cerro Maricunga oxide gold project in Chile from NCL Ingeniería y Construcción SA, of Santiago. The PEA describes an open-pit/heap-leach project producing 2.7 million oz of gold over a 10-year mine life at estimated operating cash costs of $652/oz. Production over the first five years is projected at 298,000 oz/y.
Capital cost to develop the project is estimated at $514.6 million, with sustaining capital of $249 million.
The Cerro Maricunga project is located in the high Andes 140 km northeast of Copiapo, Chile, and 40 km west of the Chile-Argentina border at elevations ranging between 3,800 and 5,000 m above sea level. The PEA is based on a pit-constrained resource estimated at 185.8 million mt measured and indicated grading 0.41 g/mt gold and containing 2.46 million oz of gold and 75.4 million mt inferred grading 0.39 g/mt gold and containing 938,000 oz of gold.
Conventional open-pit mining methods are considered for mining the Cerro Maricunga deposit, utilizing a fleet of 16 haul trucks (Komatsu 9300E – 290 mt), five diesel shovels (Komatsu PC5500 – 38 yd3), five production drills (Sandvik DR460 – 10 5/8 in.), and various ancillary equipment. No additional production fleet equipment is considered during the mine life. The preliminary open-pit design incorporates 10-m-high benches, with 40-m-wide main haul roads at a maximum grade of 10% and pit walls at an average 42° angle.
The PEA envisions trucking of oxide mineralization to a primary gyratory crusher, with a minimum capacity of 4,200 mt/hr, where it will be crushed to 165 mm. The primary crushed material will then be conveyed 3.4 km to feed three secondary cone crushers and three tertiary cone crushers. The final crushed product, measuring (P80) 19 mm, will be conveyed 2.8 km to the heap leach pads.
Crushed material will be stacked on the pads by a radial stacker in 50 x 50-m 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/hr/m2 is considered. Sodium cyanide and lime consumption are expected to be 0.24 kg/mt and 1.4 kg/mt, respectively. The pregnant leach solution will be pumped to a conventional carbon adsorption facility, where gold will be recovered to a final gold doré product.
Average gold recoveries of 79.5% were considered in the PEA based on bottle roll and column metallurgical testing.
Atacama Pacific President and CEO Carl Hansen said, “With the PEA completed, we will move toward a feasibility study and will examine the opportunities to potentially improve the results of the PEA by increasing the overall resource through additional drilling and by leaching coarser crushed material in a valley‐fill heap leach scenario.”
