Torex Gold Resources has announced a maiden underground reserve for the El Limón Deep zone (ELD) at its El Limón Guajes mining complex (ELG), in southwest Mexico, and revealed plans to mine it with its newest innovation, the Muckahi system.

The probable mineral reserve at ELD contains 86,000 oz of gold in 487,000 t of material at an average grade of 5.5 g/t Au (cutoff grade of 3.7 g/t). This is a subset of an indicated mineral resource at ELD that contains 141,000 oz in 797,000 t at an average grade of 5.52 g/t Au (cutoff grade of 2.5 g/t).

The mineral resource at ELD is the downdip extension of mineralisation in the El Limón open pit, some 400 m north-northwest of the Sub-Sill deposit (already being mined) and is open in three directions.

Fred Stanford, President and CEO of Torex, said, while small in comparison to the open-pit mineral reserves, the ELD provides a “nice sweetener to the open-pit production”.

He added: “It is also indicative of the potential to add further underground mineral resources. With ELD open in three directions, the Sub-Sill underground deposit still open at depth, and the potential for down dip extensions of Guajes, we are upbeat about the potential to further expand underground reserves and resources through multiple sources.”

ELD will be accessed through the existing underground development and will use the existing site infrastructure, according to Torex. This infrastructure includes, but is not limited to, electrical facilities, maintenance facilities, main ventilation exhaust fans and the backfill plant. Depending on material availability and geotechnical requirements, all mining areas at the ELD will be backfilled with either cemented aggregate fill or uncemented rockfill.

While the mineral reserves for the ELD deposit have been estimated using conventional mining techniques and costs, the intention is to mine the deposit with the Muckahi mining system, Stanford said.

“If as expected, the costs associated with Muckahi mining are lower than conventional mining costs, we may be able to lower the cut-off grade and increase the size of the mineral reserve.”

Excavation of the 30° down ramp to access the lower parts of the ELD deposit is underway, with four rounds taken, according to Stanford. “In the upper portions of the deposit, the excavations are nearly completed for the initial long hole stopes that will be mined utilising the production aspects of the Muckahi system.”

Stanford also provided an update on the Muckahi system, which is currently undergoing trials at ELG. The first tunnelling blast of the field trials was taken on March 26 and the round was successfully drilled from the monorail mounted Muckahi jumbo drill. The second piece of equipment, the Muckahi service platform, was at the Mexican border as of April 3 and was expected to be in service this by the end of June.

The goal of the trial is to demonstrate Muckahi’s capabilities over the full development cycle for tunnelling, including on a minus 30° gradient, and to demonstrate the capability of the system to lower costs in long hole open stope mining.

Stanford said on June 20: “To date the Muckahi system has performed as expected, we are all eager to progress through the next stages of the testing program and, if proven, then move forward with the strategic options it has the potential to unlock.”

The Muckahi concept is an alternative to established underground mining processes that, Torex says, can create a more continuous mining process able to accelerate return on investment.

Learn more about the concept and technology by clicking here.