Deposit Geology
The Cerro Blanco deposit is a classic hot springs-related, low-sulphidation quartz-adularia-calcite vein system. It is localised along a complex fault intersection created during late Miocene-Pliocene tectonic extension within the active Central American volcanic arc. Local igneous activities that drove the Cerro Blanco hydrothermal system include a vesicular andesite dike swarm and mineralization stage rhyolite / dacite flow dome eruption and cryptodome intrusion.

The Cerro Blanco vein systems are best developed (widest and most continuous) within the 300 to 500 m elevation ranges. Principal host rocks include a lithic tuff–calcareous shallow marine- volcaniclastic sequence and, to a lesser extent, the overlying volcaniclastic-hydrothermal breccia sequence of probable Pliocene age. Vein zones often appear to transition to barren calcite beneath the ±300 m elevation in the northern half of the deposit. To the south, high-grade quartz-adularia-calcite vein zones continue at least another 100 m down to 200 m elevation. Some veins remain open at depth.

Mineralization
The Cerro Blanco gold deposit occurs within a large hydrothermal alteration zone covering an area about 5 km long and 1 km wide. This zone exhibits the effects of strong, pervasive hot spring type hydrothermal alteration.

Gold mineralization is hosted within a broadly north-south striking sequence of westerly-dipping siltstones, sandstones, and limestones (Mita Group) that are capped by silicified conglomerates and sediments with contemporaneous dacite/rhyolite flow domes or cryptodomes (Salinas Unit). The Salinas rocks are synmineral and believed to have accumulated progressively in a low-relief graben characterised by a shallow groundwater table. The Salinas conglomerate was presumably derived by erosion of the flanking horst blocks as relief was created during active faulting. The topographic inversion required to explain the current prominent position of the graben fill is ascribed to the silicic character of the Salinas unit and its consequent resistance to erosion.

The west and east sides of the Cerro Blanco ridge consist of flat agricultural plains characterised by Quaternary basalts, interbedded with boulder beds and sands. These rocks also appear down-faulted to lower elevations, implying major post-mineral extensional movements on such faults; and they may be neotectonic (active).

The current gold resource occurs under a small hill and is confined within an area about 400 m x 800 m. The gold deposit is characterised by both high-angle and low-angle banded chalcedony veins, locally with calcite replacement textures. High-angle mineralised faults and discontinuous stockwork zones host some of the highest gold grades. Gold-bearing structures in the Cerro Blanco project area extend 2 km to the northwest of the gold deposit and occur largely confined within the hydrothermal alteration zone. Exposures are poor and locally covered by alluvium and post-mineral rocks. Gold-bearing structures extend at least 1 km south and southwest of the deposit under valley fill and post-mineral rocks. Geothermal well MG7, located about 0.5 km east of the deposit, encountered a 27 m zone averaging 6.3 g Au/t and 22 g Ag/t at a depth of 634 m. The upper 6 m of this zone averages 23.9 g Au/t and 79 g Ag/t

Gold and silver occur almost exclusively in quartz-dominated veins of low-sulphidation epithermal origin and in low-grade disseminated mineralization within the Salinas conglomerates and rhyolites.

Deposit types
The low sulphide content and near absence of base metals in the Cerro Blanco veins confirm it as a classic hot springs-related low-sulphidation epithermal deposit. In common with most low-sulphidation deposits, it appears to be linked to compositionally bimodal, basalt-rhyolite volcanism, the hallmark of intra- and backarc rift settings worldwide. The hydrothermal system seems likely to have been initiated during rhyolite dyke and cryptodome emplacement, at the base of the Salinas unit, with the rhyolitic magma and magmatic input to the mineralising fluid both being derived from the same deep parental magma chamber.

Adularia-sericite epithermal gold-silver deposits characteristically occur as banded fissure veins and local vein / breccias which comprise predominantly colloform banded quartz, adularia, quartz pseudomorphing carbonate, and dark sulphidic material termed ginguro bands. Examples of adularia-sericite epithermal gold-silver deposits include Waihi and Golden Cross, Pajingo, Vera Nancy, Cracow, Hishikari, Sado, Konamai, Tolukuma, Toka Tindung, Lampung, Chatree, Cerro Vanguardia, Esquel, El Peñon.

At near surficial levels, many are capped by eruption breccias and sinter deposits. Eruption (phreatic) breccias, which form by the rapid expansion of depressurized geothermal fluids, are characterised by intensely silicified matrix and generally angular fragments including sinter, host rock and local surficial plant material. Although sinter deposits formed distal to fluid upflows commonly associated with eruption breccias, sinters tend to be barren with respect to gold but may be anomalous in other elements such as boron, arsenic and antimony.

Cerro Blanco shows all the characteristics of a completely preserved, non-eroded epithermal deposit. The occurrence of hot springs (sinters, silicified reeds, pisoliths) directly above the presumed feeder veins at Cerro Blanco implies a high water table and swampy conditions (cf. McLaughlin, California). In areas of high topographic relief, outflow springs (sinter) are usually found several kilometres from the upflow zones. The widespread occurrence of lacustrine and fluvial clastic sediments in the Salinas Group and accretionary lapilli, typical of water-rich pyroclastic surges, supports this interpretation. Sedimentation probably kept up with subsidence. Mudstone dykes and geopetal structures—open fractures filled by horizontally bedded chalcedonic and sulphide-rich sediment—reinforce the interpretation. The hydrothermal breccia in the south part of the South Ramp may be a diatreme.

The Cerro Blanco Gold Project will be mined by conventional open pit mining techniques using trucks and diesel-powered hydraulic excavators supported by production wheel loaders. Trucks will haul the ore to the primary crusher and to a run-of-mine (ROM) pad where it will be rehandled and processed through the concentrator.

The objective of pit phasing is to improve the economics of the Project by feeding the mill with higher-grade material during the earlier years and/or delaying waste stripping until later years. Internal phases are designed to have a lower stripping ratio than the subsequent phases. The Cerro Blanco deposit is split into two separate pits: the main pit and the satellite pit. The main pit is split into seven phases; three are in the north end, three are in the south end, and one is the final pit that includes both the north and south ends. The satellite pit has one phase.

Drill and blast specifications are established to effectively drill and blast a 10 m bench with a single pass. Loading in the pit will be performed by two 15 m3 face shovels and two 11 m3 wheel loaders. The loading units will be matched with a fleet of 90-tonne payload capacity mine haul trucks.

Over the mine life, the Project will produce 53.9 Mt of mill feed and 145.4 Mt of waste at an overall stripping ratio of 2.70. The total in-situ gold and silver ounces contained in the ultimate pit design are 2.85 Moz and 12.60 Moz, respectively, including the existing stockpile from the previous underground workings.

Mining activities for the Project take place over ~12 years. This includes a ramp-up period of two years; eight years of mining at peak capacity; and a two-year post-peak production ramp down. The peak mining rate is 21 Mt/a (57,500 t/d) at an average stripping ratio of 2.1:1 (waste to ore).

Ramp & Road Design
The ramps are designed specifically for the primary hauling equipment, a 90-tonne truck, in accordance with SME Standard, the ramp with needs to be 2.0 x (for single lane) and 3.5 x (for double lane) of the vehicle operating width. The operating width of the 90-tonne truck is 5.98 m. The ramp includes adequate distance for the vehicles to operate, a safety berm on the pit side, and a drainage ditch on the wall side. The safety berm is designed to be at least half the height of the tallest tire to be used on site, in this case the tires of the 90-tonne truck.

Mine Design Parameters
A minimum mining width of 30 m was used to safely and optimally mine between phases or at the bottom of a pit. This value is determined by the operating width of the primary excavator, the width required for a double lane road with berm, and the area required for the 90-tonne truck to safely complete a three-point turn.

Single lane ramps were used in the bottom 40 to 60 m of the final pits to reduce stripping and capture more ore. Single lane ramps can cause bottlenecks and reduce the fleet productivity. This method is only used sparingly at the bottom of the pits. Reductions in productivity stemming from single lane ramping is captured in reduced production or compensated by mining in other pits or phases. To attain additional ore at the bottom of the pit, 10 m box cuts are used.

Open Pit Designs
Ramps for the pits are designed to exit east of the pits to better access the primary waste dump and the ore crusher.

The main pit consists of seven phases. For the north and south end, each phase is deeper than the previous one. All the phases exit to the east side of the pit, providing access to the crusher and the primary dump. Using the pushback method, a new ramp will be needed for each phase.

The south portion of the main pit consists of three phases in the main orebody. Parts of the west wall are shared among phases 2, 3, and 4. The fourth and final phase includes both the south and north phases.

Phase 1 defines part of the west wall of the main pit. A geotechnical berm is planned on the north part of this phase. There are 60 m of single-lane ramping at the bottom and a 10 m box cut.

Phase 2 reaches the final wall on parts of the west wall. There is a 10 m box cut at the bottom and 60 vertical meters of single-lane ramping.

Phase 3 expands on the final wall of the west wall of phase 2. It also contains the phase 3 north, which will be mined first. There is a 5 m box cut at the bottom and contains 50 m of single-lane ramping.

Phase 1 south has a depth of 200 m and is approximately 440 m long and 360 m wide. Phase 2 South has a depth of 250 m and is approximately 470 m long and 510 m wide. Phase 3 South has a depth of 305 m and is approximately 780 m long at its longest and is 580 m wide. Phase 4 is the final phase of the pit and includes both south and north phases. It has a depth of 360 m and is approximately 1.2 km long and 660 m wide.

The north phases are not the located where the main ore body is and are therefore second in importance. Phase 3 north is also only a small portion to be mined at the end of Phase 2 north and the beginning of Phase 3 south. It is not represented here as it is part of Phase 3 south. Phase 1 north has a depth of 150 m and is approximately 400 m long and 340 m wide. Phase 2 north has a depth of 200 m and is approximately 510 m long and 370 m wide. Phase 3 north is a small part on the north-west end of the pit.

The satellite pit consists of one phase. As the ore is a lower grade than the main pit, it will be mined last. The ramp is located on the east side to take advantage of the natural topography. The satellite pit is 80 m deep with a length of 220 m and width of 160 m.

- subscription is required.

The process plant will treat 4.0 million tonnes per year (Mt/a) of ore and will consist of comminution, cyanide leach, carbon adsorption via carbon-in-pulp (CIP), carbon elution and gold recovery circuits. CIP tailings will be treated in a cyanide destruction circuit and dewatered to produce a filtered tailings product.

Pre-Leach Thickening
Hydrocyclone overflow, at the target size of P80 of 53 µm, will flow onto two vibrating trash screens in parallel, one in duty and one standby, to remove trash material. Oversize material will discharge into a trash bin, while screen undersize will flow by gravity to a 32.0 m diameter high-rate pre-leach thickener. Flocculant solution will be added to the pre-leach thickener feed to promote the settling of fine solids. The thickener will dewater the slurry to 42% solids. The pre-leach thickener underflow will be pumped to the pre-oxidation tank, while the pre-leach thickener overflow will report to the process water tank.