At the Bolivar Property, the volcanic rocks strike northwest and dip gently to moderately to the northeast.

Skarn alteration and mineralization at the Bolivar Property is hosted primarily in a package of sedimentary rocks that occur as a layer or lens within the LVS (Reynolds, 2008). All sedimentary units have undergone low grade metamorphism. The lowermost sedimentary horizon observed is a dolostone which ranges from 24 m to 40 m in thickness. The lower part of the dolostone horizon is interlayered with siltstone. To the south, progressively less of the sedimentary sequence is cut out by granodioritic intrusive rocks and the dolostone is observed to be underlain by a siltstone horizon.

The Bolivar deposit is classified as a high-grade Cu-Zn skarn and exhibits many characteristics common to this type of deposit. The term ‘skarn’ refers to coarse-grained calcium or magnesian silicate alteration formed at relatively high temperatures by the replacement of the original rock, which is often carbonate-rich.

The dikes locally cut the granodiorite, have planar, chilled contacts, and are generally finely crystalline. Both their texture and crosscutting relations suggest that the dikes are younger and shallower than the granodiorite. Both granodiorite and andesite dikes have alteration and locally skarn along their contacts. In addition, endoskarns, which are skarns of igneous origin that form within the granite mass itself, affect both the granodiorit ........

Sub-level stoping and room and pillar mining methods are currently used in the main areas of the mine to obtain a production rate of 5,000 tpd.

Using the resources estimated by SRK Consulting through December 2019, Sierra Metals performed a growth analysis to determine how the Bolívar Mine could achieve sustainable production of 7,000 tpd - 15,000 tpd. The analysis indicates that the production objectives are achievable through the expansion of the sub-level stoping mining method in the new production areas, which will allow the sustainability of the operation. A new configuration of the mining method will allow greater recovery of resources and production rates.

The longhole method is applied in the shallow dipping mineralized bodies in Bolivar West. Excavation for longholes with openings of 9.0 m and pillars of 7.0 m x 7.0 m for stope heights between 12.0 m and 15.0 m. From the access ramp, access to the mineralized material is established in the central part of the chamber and the mineral cut begins. A drive is developed within the mineralized material, then the drilling of long holes is carried out and extraction begins. Ramps are established in some cases in mineralized material to minimize waste extraction.

The longhole method is applied to the mineralized structures at the El Gallo Inferior deposit. Each level has 20.0 m of vertical stope height and is accessed through a ramp to the central part of the level. A mineralized material driv ........

- subscription is required.

- subscription is required.