RNC and Bikermann Engineering (2002) consider the Cerro Quema deposits to be high-sulphidation epithermal deposits. Corral et al. (2011) also consider that the mineralogy and spatial distribution of hydrothermal alteration observed in Cerro Quema fit well within the classical high-sulfidation epithermal gold deposit model. Hydrothermal alteration is interpreted to be related to the circulation of acidic fluids of magmatic origin and to the presence of a porphyry copper system at depth in a calc-alkaline volcanic arc in both, sub-aerial and submarine environment (Sillitoe et al., 1996). Corral et al. (2011) consider that despite the Cerro Quema deposit being consistent with the high sulphidation epithermal model, the presence of a porphyry copper at depth could not be proved at the time. On the other hand, a model based on an oxidized gold and copper deposit that shares characteristics of both epithermal and volcanogenic massive sulphide deposits (Nelson, 2007) is not preferred, as no signs of bedded massive sulphides have been found in the alteration zones, in the vicinity of the dacitic lava domes or associated hyaloclastitic sediments.

In the Cerro Quema Project area, several gold mineralized zones are located along a 15 km long, east-west trend. These zones include the La Pava Quemita-Quema and La Mesita deposits. RNC and Bikerman Engineering (2002) describe the mineralized zones as hosted in a belt of hornblende-pyrite pyroclastic flows and lavas of dacitic and andesitic composition. The volcanic belt is up to 1.5 km wide and conformably bounded to the north and south by epiclastic submarine sediments. The sequence dips south at 45o to 60o north. The main rock types within the mineralized zones are saprolitic dacitic clay, silicieous dacite with various degrees of acid leaching and iron-oxide cemented breccia.

Gold occurs as disseminated submicroscopic grains and as invisible gold within the crystalline structure of pyrite (Corral et al., 2011), especially in the advanced silica alteration zone. Strong supergene alteration results in the formation of an oxidation cap or gossan and released the gold contained in the pyrite. The highest grades of gold mineralization are near the surface and decrease toward the lower limit of oxidation.

The gold and copper mineralization are associated with disseminated pyrite, chalcopyrite, enargite and a stockwork of quartz, pyrite, chalcopyrite, and barite with traces of galena and sphalerite. The presence of vuggy silica, alunite, natro-alunite and enargite in addition to the hydrothermal alteration pattern is compatible with a high-sulfidation epithermal system.

At Cerro Quema, RNC and Bikerman Engineering (2002) reported that the silica-pyrite alteration is characterized by a highly fractured, vuggy, locally brecciated rock composed of silica and iron-oxides at the surface. The oxidized rock extends from surface to a depth of up to 150 m. Beneath the oxidation boundary, pyrite is abundant and accounts for up to 35% of the rock. With few exceptions, gold mineralization above the cut-off grade is restricted to the silica-rich alteration type within the oxidized and leached cap. RNC and Bikerman Engineering (2002) also report that on the south side of the La Pava deposit, steeply-dipping chalcopyrite veins appear to be associated with late stage fracturing. In this area, a zone of high grade supergene mineralization (0.5 to 5.0% copper) is present beneath the oxidation surface.

A large network of steeply-dipping NW-SE and NE-SW trending normal faults have been observed in the Rio Quema area. The east-west striking Rio Joaquin fault zone is the major mapped fault Corral et al. (2011). The fault can be easily observed about 3 km south of the Cerro Quema mineralization zone. The Rio Joaquin fault has had an apparent reverse slip sense with a minimum of 300 to 400 metres of vertical displacement (Corral et al. 2011). Fault movement has uplifted the southern block with respect to the northern block and has juxtaposed with the lower and upper units of the Rio Quema Formation.

The mining method proposed for the Cerro Quema Project will be a conventional open-pit mine. Mining will occur in two open pits; the La Pava Pit and the Quema Pit. A fleet of hydraulic excavators and trucks consisting of 50 tonne rigid frame trucks and 40 tonne articulated trucks will be used to mine the ore and waste materials. The drilling and blasting of both ore and waste rock will be required although some materials will be free-digging.

The ore production rate delivered to the heap leach pad area is approximately 3.6 million tonnes per year of silica and fresh rock type ore. Clay type ore will be stockpiled and processed at the end of the mine life since this ore requires a different crushing method and agglomeration.

Overall total annual mining rates will range from a high of 7.1 Mt of combined ore and waste to a low of 5.5 Mt with an average of about 6.4 Mt/year. This results in an average total daily mining rate of 18,000 tpd, of which 10,000 tpd would consist of ore.

The Cerro Quema project will be a 10,000 tonnes per day heap leach facility. Processing at Cerro Quema will be by conventional heap leaching of crushed ore stacked on a single use pad. Gold will be leached from the mineralized material with dilute cyanide solution and recovered from the solution using a carbon adsorption-desorption-recovery plant to produce doré bars.

Run-of-mine ore will be delivered by haul trucks from one of the open pit mines to the primary crusher. As much as possible, material will be direct-dumped by haul trucks into the primary crusher dump hopper. Ore will also be reclaimed from stockpiles by frontend loader into the dump hopper located above the apron feeder as required for either blending or haul truck availability.

The crushed ore stockpile is filled by the crushed ore stockpile stacker. The stockpile will be conical and contain about 5,300 t of live feed and a total of 26,000 t of crushed material. The stockpile will be constructed over a subterranean tunnel containing two reclaim belt feeders and the reclaim tunnel conveyor. Each belt feeder will be able to reclaim and feed crushed material to the reclaim tunnel feeder at the design rate of 556 dry tph.

The grasshopper and ramp conveyors will transport the crushed material from overland conveyor 2, onto and across the pad to the stacking conveyors. The stacking conveyors allow the radial stacker to place crushed material in 8 m lifts with minimal downtime. The radial stacker and horizontal feed conveyor together are capable of moving while slewing and stacking ore in an arc. The radial stacker can retreat approximately the length of a grasshopper conveyor.

Barren solution will report to the barren tank from the adsorption columns. High-strength cyanide solution and antiscalant will be added to the barren tank by metering pumps. The barren solution will be pumped to the heap leach pad using a split-case horizontal centrifugal pump. Strainers will be installed on the barren solution header to minimize the plugging of sprays by fine particulates. The ore will be leached using a dilute solution of sodium cyanide applied by a system of sprinklers. Leach solutions will be applied to the crushed ore heap at a nominal application rate of 10 L/h/m2 .

A trade-off study was performed to evaluate several alternative locations for the heap leach facility at the Cerro Quema Project. Upon completion of this trade-off study, the site located within the Quebrada Maricela was selected for the heap leach facility. The Heap Leach Facility (Maricela HLF, HLF), located in the Quebrada Maricela, will be a multiple-lift, single-use type leach pad designed to accommodate approximately 20 million tonnes of crushed ore. The HLF has been designed with a lining system in accordance with International Cyanide Code requirements and meets or exceeds North American standards and practices for lining systems, piping systems, and process ponds, which are intended to lessen the environmental risk of the facilities to impact the local soils, surface water, and ground water in and around the site.

The adsorption facility at Cerro Quema will consist of one train of five up-flow, open-top carbon columns (CICs). The columns are capable of holding 5 tonnes of carbon each providing a CIC process inventory of 25 tonnes of carbon. Pregnant solution will be pumped to the adsorption-feed head-tank of the CICs at a nominal flow rate of 605 m3 /h. A magnetic flow meter and a wire sampler will be installed on the feed to the CICs to allow the calculation of total gold ounces fed to the carbon columns. Pregnant solution will flow by gravity through the set of five columns, exiting the last adsorption column as barren solution. Barren solution from the last carbon column will be continuously sampled by a wire sampler for metallurgical accounting then discharged to the carbon safety screen to recover any floating carbon particles.

The desorption facility at Cerro Quema will include both an acid wash and a pressurized strip circuit. Each circuit will be capable of processing a 2.5 tonne lot of carbon. Loaded carbon will be advanced to an acid wash vessel. The acid wash vessel is a rubber lined, carbon steel vessel designed to contain 2.5 tonnes of carbon. The vessel is a contactor that allows the carbon to be treated with dilute acid to remove calcium carbonate scale.

Pregnant eluent flows to two electrowinning cells that are operated in parallel. Stripped gold is plated from the pregnant eluent onto mild steel wool cathodes. The mild steel wool cathodes are removed periodically and treated in the retort furnace which removes all of the water and most of the mercury from the cathodes. Retorted cathodes are then treated in the diesel fired, tilting smelting furnace. The cathodes are mixed with fluxes, typically a combination of borax, niter, soda ash and silica sand and melted. The soda ash and niter oxidize impurities and allow them to collect into the slag phase and the bullion settles to the bottom of the crucible. The slag and impurities are poured off into a slag mold and the molten bullion is then poured into a cascading series of molds. Off-gases from the furnace are extracted with a blower and filtered in a baghouse (furnace dust collector) to remove particulates and discharge to the atmosphere.

The bullion or doré is cooled and quenched in a water bath. Doré bars are cleaned of slag and loose bits of metal, labeled and weighed. The doré is then shipped to an offsite refiner for further processing and sale as fine gold.