The Soto Norte mineral deposit is classified as a high-sulphidation epithermal deposit, with gold, silver and copper occurrences, mainly in sulphides. The deposit is related to the Miocene porphyry stocks and dikes that have been identified in the area, cross cutting the older sedimentary, igneous and metamorphic rocks.

Mineralisation within the Soto Norte Project comprises parallel anastomosing veins which occupy the composite fault system. These veins have various widths and characteristics depending upon the open spaces provided by the fault movements, which occurred over time, as evidenced by multiple mineralised events recorded within the individual vein structures and host rocks.

Veins at Mascota exhibit open-space filling textures along the Mascota related structures, indicating low overburden stress consistent with a shallow crustal emplacement typical of epithermal vein systems.

Brecciation is apparently of a hydrothermal origin (angular fragments, commonly monolithic, locally with jigsaw textures and, typically fragment-supported, dominantly cemented by hydrothermal minerals) and is observed in most mineralised zones, with the common feature that the brecciated fragments consist of local wall rock.

The mineralisation has a variety of textures of cement fill that are characteristic of an epithermal environment, with colloform bands of quartz and colloform pyrite that indicate super saturation in a relatively low temperature environment.

Veining in the El Gigante structure is mostly characterised by more compact, less vuggy and often banded textures. It is also characterised by more heavily altered wallrock and clay content consistent with the veining following the La Baja Fault and where post-mineralisation fault movement has probably taken place.

Overall, the veins cover a strike extent of 2.6 km and have been drilled to a depth of approximately 800 m below the surface. The width of the veins is variable dependent on the major and minor structures, but also pinch and swell within individual structures. On average the ranges are between 1 – 30 m width. A summary of the key dimensions of the known mineralisation for Soto Norte are shown in Figure 7.11. The mineralised structures extend to the surface and are open at depth and along strike, with high exploration potential to target the deep structures from underground drilling stations.

Gold and occasional electrum are observed in core and under the microscope as having a strong relationship with fine, crystalline pyrite (not the coarser crystalline pyrite) and occurs either free with the gold, adhering to pyrite particles or encapsulated within the pyrite crystalline lattice. Copper sulphides appear to have a partial affinity for pyrite but have much less of an association with gold than the pyrite because of its more irregular distribution. Gold also occasionally occurs within telluride minerals like calaverite and petzite, which are rarely visibly identifiable, although their possible presence is reflected in the sporadic distribution of tellurium assays. There is also a perceived relationship with quartz. Several mineralising events which introduce quartz, each time the quartz is introduced, become darker in colour (grading from white to dark grey). The fine crystalline pyrite has an association with this, either encapsulated within the darker quartz or emplaced within the darker quartz.

Silver occurs occasionally as native silver in the shallower SW end of the explored mineralisation in the El Cuatro zone and, more frequently, as silver sulphosalts, pyrargyrite and proustite.

Copper occurs principally as enargite and to a lesser extent as bornite, chalcopyrite, primary chalcocite and tetrahedrite-tennantite. Chalcopyrite is seen as being enriched on a local scale to bornite, covellite, secondary chalcocite and finally to native copper.

Arsenic (a penalty element) is principally associated with enargite. It is rarely seen as arsenopyrite but may be attributable to the presence of tennantite.

Zinc (a potential penalty element) occurs as red to black sphalerite or wurtzite and occurs associated with the distribution of lead, principally occurring as hinsdalite and occasionally as bournonite and possibly boulangerite.

Antimony (a potential penalty element) occurs occasionally as jamesonite and tetrahedrite and on a very small scale in bournonite and boulangerite.

Bismuth (a potential penalty element) occurs as a trace element within the deposits and may be related to bismuthinite or tellurobismuthite.

Tungsten occurs mainly as hubnerite and occasionally as ferberite. Hubnerite occurs as very fine, bright red transparent needles in quartz, is seen throughout the Mascota vein and is one of the indicators that mineralisation continues to the SW towards California.

The near surface to surface oxidation zone, which has an irregular depth and penetrates much deeper around major fractures and faults, is dominated by the reduction of sulphide minerals (being mainly pyrite) to haematite and goethite and limonite. Copper sulphides in the transition zone in old workings are seen commonly reduced to chalcanthite.

The parallel vein systems in the Soto Norte Project area are defined over a strike length of 2.6 km and the two main vein systems considered, Mascota and Gigante, each have strike lengths of around 2.0 km. Other minor vein structures of mining interest have strike lengths as low as 15 m.

The majority of vein structures are sub vertical, dipping from 70 to 80° and can range in true width from 1 m or less to over 30 m (typically between 3 and 18 m). There are some vein structures in the hangingwall zones which dip at 60°, and an isolated zone in the southwest where the vein lays over on a 15° dip, closer to surface.

The vein structures extend to surface, with significant variances in elevation due to the terrain, and are open at depth and along strike. The depth limit of the resources considered for mining is 2,100 mRL.

The minimum stope width defined for mining is 2.5 m and stoping blocks are categorised as follows:

- Longitudinal narrow stoping for stope widths from 2.5 to 5m;
- Bulk (or wide) longitudinal stoping for stope widths greater than 5m.

The predominant mining method considered for the Project is Modified Avoca for stoping blocks identified as longitudinal narrow and wide stopes. CRF is applied to limited specific areas of poor ground classification.

The mine plan supporting the Mineral Reserve targets a sustainable production rate of 2.6 Mtpa over a 7- year period. The ramp up to full production is five years with two years of initial ore development prior to the process facilities being operational, outlined as follows:

- The mine design is separated into a number of mining zones due to the extensive strike length and depth of the deposit. A number of underground accesses have been incorporated to enable timely entry and egress, optimise materials handling to the process facilities and provide sufficient ventilation to working areas.

- An access tunnel will be developed using a TBM from the Padilla site to the underground mine, a distance of approximately 6.9 km. The mined ore will be crushed underground and conveyed at a rate of 2.6 Mtpa to a processing facility located on the surface at Padilla. The processing facility will produce saleable gold concentrates.

- The Emboque zone is designed with decline access from surface with a separate ventilation adit from El Cuatro. The La Bodega zone is accessed through the Emboque decline on a connecting level (2,610 mRL).

- The mine utilises Modified Avoca as the primary mining method (Overhand sequence) and CRF to backfill limited areas of poor ground. A significant amount of waste is required for the mining method to use as both a working platform between levels and to maintain ground stability.

- To produce enough waste for the mining method approaches, underground quarry waste stopes are designed to supplement the development waste generated. The waste used in the mine plan will be utilised in several forms including unconsolidated, cement reinforced, and grout injected depending on the mining method applied and sequence of the mining cycle. Once the individual waste stopes are completed there is an opportunity to store dry filtered tailings underground.

The primary (mobile) crushers will be located within the mine area; ore will be withdrawn from the discharge vault by a variable speed apron feeder and transferred to the primary crusher sacrificial conveyor, which discharges onto the underground tunnel conveyor.

The tunnel conveyor provides the most direct and cost-effective route through the underground mine to transport ore from the primary crushing station to the crushed ore stockpile at the plant facilities. The crushed ore transfer conveyor tunnel will have an arch roof with a top of radius of 3.9 m and a finished cross circular section 7.8 m wide at the centre and 6.7 m high at the top of the arch.

The underground tunnel conveyor transports ore to the surface and discharges onto the coarse ore stockpile (“COS”).

The coarse ore from the primary crusher will feed a single conical, uncovered stockpile, which has a live capacity of approximately 6,600 t.The stockpile provides surge capacity between the primary crushing circuit and the downstream processing plant. The live stockpile capacity provides approximately 24 hours of mill feed capacity. The dead capacity is equivalent to about three more days of feed, and this can be recovered using equipment such as a bulldozer or front-end loader.

Coarse ore will be reclaimed from the stockpile by two apron feeders, each capable of delivering the full design feed rate, which will be fitted with variable-speed drives. A spray water dust suppression system is considered for dust generated at the processing stockpile feed conveyor discharge point as well as the apron feeder discharge points.

The apron feeders will discharge onto the SAG mill feed conveyor, which will transport the crushed ore to the SAG mill feed chute. The SAG mill feed conveyor will be fitted with a weightometer to measure new feed rate to the SAG mills for process control and metallurgical accounting.

SAG mill grinding media will be added to the SAG mill feed conveyor by a front-end loader that will load balls into a hopper located over the SAG mill feed conveyor. There will be ball storage and a ball charging system for the SAG mill.

The grinding circuit consists of a single stage SAG mill operating with a primary cyclone cluster in closed circuit. The product from the grinding circuit (primary cyclone cluster overflow) will have a typical size of 80% passing 106 ?m, with a density between 30% and 35% w/w solids.

Ore withdrawn from the stockpile will discharge from the SAG mill feed conveyor into the SAG mill feed chute. A belt weigh scale will be installed on the SAG mill feed conveyor and will be used to measure new ore feed rate and control the water addition to a fixed ratio with the solids entering the SAG mill. The water will be added at the head end of the mill feed chute to assist the material flow into the mill.

The SAG mill feed conveyor will transfer ore and grinding media (and crushed pebbles possibly starting on the third year of operation) to the SAG mill feed chute where it will be combined with mill feed dilution water and lime slurry to increase the slurry pH to approximately 9.0.

The SAG mill will be fitted with a single pinion, a liquid resistance starter (“LRS”), and discharge grates to retain grinding media while allowing smaller particles to discharge from the mill. The SAG mill will be fitted with a trommel screen to separate slurry and coarse, unbroken rocks.

If the need for a pebble crushing system is confirmed with plant throughput trials, the SAG mill will be retrofitted with discharge grates containing pebble ports to discharge from the mill, and therefore feed the pebble crushing circuit. In this case, the pebbles in the trommel oversize from the SAG mill will report to a surge bin and pebble crusher via the pebble crusher feed conveyor.

A self-cleaning electro-magnet will be installed over the pebble crusher feed conveyor belt to remove any metal present that could damage the pebble crusher. A metal detector will be installed downstream of the electro-magnet to detect any remaining metal on the belt. If metal is detected, a gate in the conveyor head chute changes position and the stream containing the metal is directed away from the pebble surge bin and the downstream pebble crusher. This gate can also be used to purge pebbles from the circuit into a pebble bunker if the recirculating load becomes too large. When the crusher is on maintenance, the gate in the pebble crusher feed conveyor head chute changes position to allow pebbles to by-pass the pebble crusher.

SAG mill trommel undersize will gravitate to the primary cyclone feed hopper, which uses a variable speed cyclone feed pump to feed slurry to the cyclone cluster. A spare feed pump wet end is available for quick repairs in the case of a pump failure. The cyclone overflow stream will gravitate to the copper flotation circuit via cross-stream samplers and boil boxes while the cyclone underflow stream reports back to the SAG mill.

Copper Concentrate Regrind
The regrind circuit consists of a single vertical regrind mill HIGmill® running in open circuit with a classifying system using hydrocyclones. The main purpose of this stage prior to the cleaner flotation circuit is to improve copper liberation and recovery by grinding rougher concentrate to a finer granulometry.

Copper rougher concentrate, Copper recleaner tailings, lime slurry and OSA sample return are the fresh feed to the regrind mill cyclone feed tank. A variable speed cyclone feed pump transports slurry to the regrind mill cyclone cluster. Fine particles in the cyclone overflow that do not require further grinding report by gravity to the regrind discharge hopper to produce a 30 µm stream; the cyclone underflow reports to the regrind mill feed hopper. The cyclone underflow stream flows by gravity to the regrind mill feed hopper.

Grinding media for the copper regrind mill will be hoisted up to the regrind media feed hopper and metered into the regrind mill feed hopper by the regrind mill grinding media feeder.

Regrind product will report to the cleaning flotation circuit, which consists of three stages: the first stage (cleaner) consists of forced air mechanical flotation tank cells, the second stage (recleaner) consist of forced air rectangular cells and the third stage is a Jameson cell.

Regrind circuit products feed the cleaner circuit via the regrind mill cyclone overflow pump and report to the cleaner feed box. The cleaner concentrate is pumped to the recleaner flotation cells. The cleaner tailings are pumped back to the rougher flotation feed.

Pyrite Concentrate Regrind
The regrind circuit consists of a classification system (using hydrocyclones) and a single regrind vertical mill. Pyrite rougher concentrate, pyrite recleaner tailings and OSA sample return are fresh feed to the regrind mill cyclone feed tank. A variable speed cyclone feed pump transports slurry to the regrind mill cyclone cluster.

Fine particles that do not require further grinding report to the cyclone overflow stream that gravitates to the pyrite regrind discharge hopper to produce a 45 µm stream. The cyclone underflow stream flows by gravity to the regrind mill feed hopper.

The flotation circuit will consist of two stages: one for producing copper concentrate and one for producing pyrite concentrate, both with high gold grade. The copper rougher flotation is followed by rougher concentrate regrind and three stages of cleaner flotation to produce a copper concentrate with high gold grade. The pyrite flotation circuit will condition copper rougher tailings in one conditioning tank followed by pyrite rougher flotation, concentrate regrind and two stages of cleaner flotation.

Copper Rougher Flotation
Primary cyclone overflow will report directly to the copper rougher flotation collection box and, along with cleaner tailings and On-Stream Analyser (“OSA”) sample return, will feed the rougher flotation circuit consisting of five 70 m3 forced air mechanical flotation tank cells.

Lime will be added to the copper rougher collection box to increase the pH to 10.5. Frother and copper collector will also be added in this collection box. ........