Epithermal Au and Ag mineralization at Cerro Bayo is contained in veins, stockworks, and breccias. The deposits show multiple stages of mineralization and display open-space filling and banding, typical of lowsulfidation style epithermal mineralization. Mineralogy is complex and is associated with alteration assemblages that suggest at least three types or stages of precious depositional environments.

The principal epithermal gold-silver mineralization event with local bonanza grades is hosted mainly in NNW and N-S to NNE structural trends, such as the Cerro Bayo, Cascada and Coigues Este (in the Laguna Verde sector) veins.

This event was predated by a more likely mesothermal event with silver, gold and base metal mineralization hosted in arcuate N-S to NNE veins and tectonic breccias. This style of mineralization is only known to exist in the Laguna Verde sector and is interpreted to be a result of igneous intrusions, doming, and subsequent collapse. A third mineralizing event is interpreted to coincide with the emplacement of a porphyritic stock and related apophyses at Rodados Colorados, which is characterized by a porphyry-style alteration pattern. This includes moderately extensive propylitic alteration with chlorite, epidote, disseminated cubic pyrite, and specular hematite. Structures contain gangue dominated by calcite with locally abundant oxides and relict pyrite.

Epithermal mineralization is characterized by Au and Ag associated wi ........

Currently there no any mining activities at Cerro Bayo. Commenced trial processing of mineralized waste dump material.

The mine design for the Cerro Bayo vein systems includes the main access via 4.0 m by 4.5 m decline ramps because most veins are less than 200 m below surface. The ramps are typically driven in the footwall of the target vein at a gradient of -12.5%. The access drifts driven from the ramp to the ore are three metres by three metres as are the access drifts to the ventilation raises. The ground conditions were very good in all areas visited in the past. All of the portals are located within a radius of one kilometre of the processing plant.

As a result of the very good ground conditions, a longhole mining method without backfill is employed although shrinkage stoping was used in the past by Coeur. Production development includes driving the drifts on ore at a minimum dimension of three metres by three metres, which is required for the standard equipment sizes utilized. The appropriate name for the type of stoping method is “longhole retreat stoping”. The average production rate over the LOM is 1,000 tpd.

Stoping is carried out with the drilling of 54 mm diameter production holes upwards from the drill drift towards the upper drift. Production drill holes are drilled to within approximately one metre of breakthrough and stopped at that point in order to avoid blockage of the hole from loose material on the overcut floor. Typica ........

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