In early March 2022, the Company released details on the recently completed conceptual mining study by AMC Consulting. This study and the recently reported high metallurgical recoveries (ASX Announcement 25 February 2022) are seen as positive steps towards development in the district for production of gold and silver from high-grade resources defined at the El Refugio–La Soledad.
Conceptual Exploration Access – Mine Design
AMC Consultants commenced and completed a mining concepts design study for the El Refugio-La Soledad maiden JORC mineral resource estimate in 1Q 2022. The study considered open pit potential and various underground mining techniques. The positioning of the underground mine development was also assessed.
The study work shows that there is some open pit potential requiring further drilling work to better define near surface high-grade material at El Cometa. The most likely scenario from the study indicates that the resource would be most effectively mined by underground methods.
For the underground mining, the preferred mining method recommended is mechanised Avoca bench (a variant of long hole open stope benching with rockfill) using a bottom-up extraction sequence as shown in the schematic on the right.
Geotechnical
Some geotechnical logging of exploration holes has been undertaken and historical workings are present. AMC notes that rock mass conditions indicate “good” to “very good” rock but can generally be categorised as “fair” until recommended geotechnical assessment work has been undertaken. AMC has recommended geotechnical work, which includes geotechnical logging of existing drill core on site, geotechnical diamond core drilling, structural modelling and structure confirmation drilling (to coincide with resource infill drilling) to be completed prior to further mining study work.
Preferred conceptual exploration access – mine design
The preferred conceptual exploration access – mine design was constructed, and sequence animated based on:
- Twin mine area accesses from twin southern adits connected to a valley-to-valley exploration access developed in the footwall of the El Refugio orebody. A separate eastern adit exploration access is developed in the footwall of the Soledad orebodies with maximum access gradient reduced to 1:8,
- Primary infrastructure developed off the exploration access, with primary infrastructure positioned within the footwall.
- Mine access layout based on Avoca benching with rockfill.
- Mine design to avoid ventilation raises to surface, provide a cost-efficient flow-through primary ventilation circuit as soon as possible and provide emergency secondary egress as soon as possible within the mine plan.
Figure 1 provides an isometric view of the mechanised Avoca bench with rockfill mine design and in Figure 2, a plan view is shown.
