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 underground workings in Guaico-Nus mine had 5.3 km of development, mainly declines, drifts and cross-cuts. In the Guayabito Mine, the mine portal is complete and the main decline is 110 m long. The excavation is continuing in both mines.

The underground mining methods, selected for Cisneros are Cut & fill (C&F) and Longhole Open Stopping (LHOS). Mining method selection was determined primarily by deposit geometry and geomechanical features. C&F mining was the preferred mining method for the Guaico and Guayabito veins and longhole stoping for the Nus mineralized structure.

The general flow chart of the plant process consists of four sections to produce gold concentrates. These include primary and secondary crushing, grinding and gravity, flotation and concentrate filtration.

Primary and Secondary Crushing
The underground mineralized material will be fed to a coarse chute of 150 tonnes capacity using dump trucks of 25 m3 capacity and will pass through a hopper with a grill of 8 inches (200 mm) before entering the crushing circuit. The material will be extracted from the bottom of the hopper by means of a vibrating grizzly with rails of 2" (50 mm) that classifies the load into coarse and fine. The coarse fraction (> 2") feeds a 20" x 32" jaw crusher while the fines (< 2") are fed into the product of the jaw crusher.

This product will be moved by means of a conveyor belt to a 6' x 16' double-deck vibrating screen. The upper floor of the screen will be composed of mesh with a 68 mm opening, while the lower floor mesh will have a 39 mm opening. The over-sizes of the upper floor of the vibrating screen will be sent to a conical crusher, while the fine material will be sent to the fine’s chute. The product of the conical crusher will be returned to a conveyor belt to pass through the vibrating screen again in closed circuit.

The crushing circuit will have a dust suppression system located at the points of transfer between belt and equipment, in order to control the emission of suspended fine particles produced in the process of size reduction.

Grinding
The material coming from the crushing stage, will be extracted from the stockpile by means of two belt feeders (one operating and the other on standby) then it will be unloaded in a conveyor belt that will feed a ball mill of 8'x10' diameter.

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 ........