The Guaico and Guayabito occurrences can be classified as a mesothermal lode-gold deposit (Hodgson, 1993). “Mesothermal gold deposits are mostly quartz-vein-related, gold only deposits with associated carbonatized wall rocks. They occur in low to medium-grade metamorphic terranes of all ages, but only in those that have been intruded by granitoid batholiths.

The deposits are characterized by a high gold/silver ratio, great vertical continuity with little vertical zonation, and a broadly syn-tectonic time of emplacement. They are commonly associated with pyrite, arsenopyrite, tourmaline and molybdenite. Mineralization may occur in any rock type and ranges in form from veins, to veinlet systems, to disseminated replacement zones. Most mineralized zones are hosted by and always related to steeply dipping reverse- or oblique-slip brittle-fracture to ductile-shear zones. In mechanically anisotropic host-rock sequences, the shear zones typically are controlled by pre-existing anisotrophies like volcanic flow contacts, dykes and early veins. Shear zone dilation is commonly the result of interference between intersecting sets of shear zones and is part of bulk inhomogeneous flattening in the seismogenic regime of the crust where fluid pressure varied cyclically between sub-lithostatic and supralithostatic.

On a regional scale, the deposits occur in prograding arc-trench complexes in association with major transcrustal fault zones, linear belts of fluviatile to shallow-marine sedimentary rocks, and small felsic alkali and trondhjemitic intrusions, a co-spatial assemblage of structures and rocks that developed after the main period of accretions-related contractional deformation, but before much of the metamorphism and penetrative fabric. Ore fluids are CO2 rich and have been variously attributed to magmas, metamorphic devolatilization of supracrustal rocks and mantle degassing; the most current opinion favours devolatilization of subcreted volcanic and sedimentary rocks, with modification by interaction with the crustal column between the sites of fluid generation and ore deposition”.

Mineralization at the Cisneros Project is structurally controlled and gold is associated with shear zones, breccias and veins. The main directions of the structures are between 10º - 30º (Guaico Structures) and between 70º -90º (NUS Structures). The host rocks are mainly granodiorite, quartz-diorite and tonalite. Hydrothermal alteration of the host rock is narrow around the veins, with phyllic, propylitic and potassic alteration being the main alteration, but these are not a significate characteristic.

The minerals present are: gold, pyrite, chalcopyrite, quartz, carbonates, chlorite, sericite, potassium feldspar, heulandite, bismuthinite, galena, sphalerite and molybdenite. However, the order of events (paragenesis) is not yet defined.

Native gold and electrum (alloy of gold and silver) show anhedral, subangular to subrounded forms and sizes between 0.001 to 0.082 mm. Gold appears as inclusions in pyrite and chalcopyrite or in veinlets associated with chalcopyrite and bismuthinite.

Based on mineral associations, gold mineralization occurred in two stages. In the first stage, gold is associated with chalcopyrite and in pyrite veinlets, in the second stage, veins of chalcopyrite, bismuthinite and gold cut the pyrite veinlets.

The Cisneros Project consists of two operating, underground mines, Guaico-Nus and Guayabito. The Guaico-Nus Mine is currently accessed by the Guaico portal and decline (4.5 x 4.5 m and 12% gradient) and the Guayabito Mine is also accessed by a portal and decline (4.5 x 4.5 m and 12% gradient).

MINING METHOD
The underground mining methods are cut & fill and Longhole Open Stopping. The selection of the mining methods was determined primarily by deposit geometry and geomechanical features. Cut and fill mining is the preferred mining method for the Guaico and Guayabito veins and longhole mining for the Nus mineralized structure.

The Nus structure is suitable for mining by Long Hole Open Stopping. The 12-metre-long blast holes have been planned by benches from the upper to the lower sublevel. Blast holes will be drilled parallel to the vein’s dip along the entire defined block and following a regular pattern. The aim of the first sequence is to create a free face by blasting and mucking activities.

The preferred mining method for Guaico is a variant of cut and fill, using vertical drillholes for selective mining due mainly to the thickness of veins, rock mass conditions of the hostrock and grade distribution of the Guaico veins.

The main advantage of this method is that it allows selective mining, thereby reducing dilution and increasing mining recovery. Drilling and blasting will be done in two rounds. In the first round only mineralized material is fired, with a minimum width of 0.80 m while in the second round, the waste rocks are fired at 1.20 m width.

Blast hole drilling, to produce horizontal slices, will be drilled parallel to the vein’s dip (70°) with drillholes having a 3.0 m length and 51 mm diameter. Optimal blasting should produce free faces and help control dilution. Waste material will be used as backfill in the stopes. Considering a 50% swell factor for waste rock, it would be enough to backfill a 2.7 m high cut along the 80 m stope. Selective drilling, blasting, mucking and loading is a repetitive cycle up to the end of the stope.

MINE DESIGN
The following underground mine workings are planned for development in the Guaico and Guayabito mines:

• Main access ramps or declines: These constitute the main infrastructure of the operations and allow for deepening of the mine. Typical dimensions are 4.5 metres x 4.0 metres and the maximum and minimum slopes will be +/- 12%;

• Secondary access ramps: permit direct access to the mineralized body with dimensions of 3.0 metre x 3.0 metre and gradients around ± 15%;

• Ore pass and fill pass: primary transport system in the mining operation that allows the descent of mineralized material from a higher level to a lower one. The dimensions for this infrastructure will be 1.5 metre x 1.5 metre;

• Ventilation raise: consists of a 2.4 metre diameter raise drilled by a raise boring machine. These raises allow an open circuit for air ventilation;

• Bypass: built every 100 metres parallel to the vein dip (close to vertical) to accommodate the mining infrastructure required such as the main pumping chambers, ventilation chambers and everything related to the services and auxiliary work needed inside the mine. The dimensions of these underground workings will be 4.0 metres x 4.0 metres and the maximum and minimum slopes will be ± 1%.

Drilling
There are four principal drilling devices selected for Guaico and Guayabito:
• Electric-hydraulic jumbos for development. Two-booms and a single boom, are planned for large dimension development rounds, and smaller development headings.
• Raise Boring Machine used for all conventional raise boring, down reaming and box holing needs.
• Jackleg Drills, for underground support installation and general-purpose drilling, and
• Mucking rock loader (air rock loading machine) for C&F production drilling.

Blasting
Accessories for blasting consist of boosters, detonators, shock tube, detonation cord among other auxiliary supplies. Bulk explosives are stored in secure underground and surface powder magazines in accordance with current Colombian explosives regulations. The blasting crews will pick up the estimated explosives and accessories during each shift and return any excess to the magazines as necessary.

Mucking
Mucking is expected to be done by secondary entry or draw point using scooptrams and It will be fully outsourced. Planned loading equipment consists of a scooptram with a 6.8 tonne bucket capacity.

Hauling.
Haulage will be by conventional low-profile Caterpillar 730 underground mining articulated trucks with a 28 tonne capacity (the number of trucks will be increased according to the increase in production over time), the nominal payload of this equipment is 28 metric tons. All material dispatching will be done through the ore pass openings that are connected with the bypasses, then the material is loaded directly onto the articulated trucks by means of the hoppers and is hauled to the surface.

Backfill
Backfilling is expected to work from the upper sublevel to the lower sub-level.

- subscription is required.

The objective of the metallurgical process is to obtain gravity and flotation concentrates in a plant with a capacity of 500 tonnes per day (tpd). The plant will be composed of a single production line in two conventional processes namely gravity followed by flotation to obtain sulphide concentrates containing gold.

The process path involves a dry section consisting of crushing (primary and secondary stages) and milling and a wet plant comprising gravity concentration, flotation and filtration of concentrates where gold is recovered.

The process plant has been designed to operate 347 days per year and treat 500 tonnes of material daily. The average head grade is estimated to be 6.43 g/t Au. An overall recovery of 90% is anticipated. Resources have been estimated at 784,763 tonnes with a life-of-mine (LoM) of 5.0 years. A stockpile of 19,402 tonnes resulting from the development of stopes in the Guayabito and Guaico-Nus areas will be maintained for the commissionin ........