Zgounder is a Neoproterozoic age, sedimentary rock-hosted, low-sulphidation epithermal silver deposit. [TR 2021, 79]

Epithermal Au deposits are classified on the basis of the sulphidation state of the sulphide mineralogy as being one of three sub-types (Hedenquist, 2000; Taylor, 2007):
- Low-Sulphidation: previously called adularia-sericite, these low-sulphidation subtype deposits are considered to be formed by near-neutral pH fluids, as a result of being dominated by meteoric waters but containing some magmatic C and S.
- High-Sulphidation: previously called quartz-(kaolinite)-alunite, alunite-kaolinite, enargite-Au, or high-sulphur deposits, these highly acidic deposits generally occur proximal to magmatic sources of heat and volatiles and form from acidic hydrothermal fluids containing magmatic S, C and Cl.
- Intermediate-Sulphidation: some deposits with mostly low-sulphidation characteristics have sulphide mineralized assemblages that represent a sulphidation state between that of high-sulphidation and low-sulphidation deposits. [TR 2021, 79]

In low-sulphidation epithermal systems, silver and gold occur in vein deposits that contain only up to a few percent sulphides. The principal gangue minerals are calcite, chlorite, adularia, barite, rhodochrosite, fluorite and sericite. Calcite is characteristic, because of the low acidity of the hydrothermal mineralizing fluids. Low-sulphidation deposits form in fault zones, sedimentary rocks and vein complexes relatively more distal from magmatic intrusions (Taylor, 2007). [TR 2021, 79]

The silver mineralization occurs at the top of the Brown Formation (sandstone), predominantly along the contact and within the dolerite sill. The economic silver concentrations at Zgounder are present mainly as vertical columns, complex clusters, shear zones, veinlets and at the intersection of the E-W and N-S fractures. Though preferentially at the contact zones between schist and dolerite, (Petruk, 1975; Popov et al., 1989).

Tension gashes originally trapped the silver mineralization within a NNE-oriented shear zone affecting the shale-sandstone beds (Brown Formation) that contain anomalous Ag values. The silver was then likely remobilized by EW-oriented structures forming isolated Ag-mineralized lenses and fissures. The silver mineralization extends laterally over 1,000 m with a subvertival dip to the south. The vertical extension of the body is offset by sub-horizontal faults with a northward movement of 10 to 30 m, pushing the mineralized zones in steps or blocks (Bounajma, 2002).

Two successive stages of Zgounder paragenetic sequence were discussed by Marcoux and Wadjinny (2005): An early Fe-As stage (silver-bearing pyrite and arsenopyrite), followed by an Ag-bearing polymetallic (Zn, Pb, Cu, Hg; sphalerite and chalcopyrite) event. The late polymetallic event involved the formation of two generations of sphalerite with Fe-poor and Fe-rich components devoid of silver. Native silver is by far the most common form, representing 65 up to 90% of the total amount of silver at Zgounder. The silver mineralization consists of an Ag-Hg amalgam in the shape of 25 to 480 µm blebs (average 150 to 250 µm). Marcoux and Wadjinny (2005), revealed the presence of two generations of silver amalgam: large Ag-rich patches (85–95 wt% Ag, Ag17Hg) presumably corresponding to remobilized mineralization, and “normal” blebs containing 72 to 80 wt% Ag (Ag5Hg; close to eugenite), which represent the majority of the native silver deposit at Zgounder. Acanthite (Ag2S) is the major silver sulphide but far less abundant than native silver and often includes several micropatches of native silver.

The Zgounder deposit is located in competent rock and has a steep overall dip. The historic mining method used at Zgounder is shrinkage stoping. To increase selectivity and ore recovery the cut and fill method is under development for new mining stopes. The main ramp is at the 2,000 m level and connects all existing levels to the east above the 2,000 m up to 2,100 m level. An access ramp from the 2000 level to the 1975 lever was also built. In the future, another access ramp to the 1,800 m level below the 2,000 m level will be built to reach the developed levels down to 1,925 m and the future levels down to 1,800 m. This will facilitate the development and the transportation of backfill when required above 2,100 m elevation.

As the mine has previously been in production, few new developments are required above 2,000 m. The total of additional development required is estimated at 20% of mineralized material tonnage with an average of 3.0m linear meters per working day. There is a provision in the sustaining capital for an average of 6.0m linear per working day, including the ramp (3.4m x 4m section), for a total of 4,691m for the major access and a 315m internal shaft for the life of mine (“LOM”). According to the historical and current mine production, the mining dilution is 10% and the mining recovery is 97%.

EXISTING FLOTATION PLANT
Run-of-mine ore containing 2.5% moisture content, is fed into a bin either by haul trucks or by a front-end loader. The mineralized material is withdrawn from the bin by a feeder to feed a 75-kW primary jaw crusher. The jaw crusher crushes the mineralized material, which is then conveyed to a dry crushing product screen with two decks. The oversize of the top deck falls by gravity into a 37-kW jaw crusher. The crushed product from this smaller jaw crusher is combined with the screen bottom deck’s oversize. Both streams combined are conveyed to a 160-kW secondary cone crusher.

The secondary cone crusher product combines with the primary jaw crusher product and is circulated back to the double-deck screen in closed circuit. This screen undersize is the crushed product from the crushing area and is conveyed to a crushed mineralized material stockpile.

From the crushed mineralized material stockpile, the product is reclaimed by vibrating feeders to be conveyed to the primary grinding circuit. This circuit comprises of a 320-kW primary ball mill, which operates in closed circuit with a spiral classifier. The overflow product from this primary grinding circuit contains the fines and is transferred to a secondary grinding circuit.

The secondary grinding circuit consists of a 280-kW ball mill in closed circuit with a cyclones cluster. The primary grinding circuit product combines with the secondary ball mill discharge into a pump box. The slurry is pumped to the cyclones cluster. The purpose of this last grinding step in the existing process plant, is to reach the final particle size for the flotation process. The cyclones underflow is reground in the secondary ball mill, whereas the cyclones overflow gravitates to an agitated tank.

EXISTING CYANIDATION PLANT
Silver mineralized material from the mine is crushed using a 55-kW jaw crusher and a 75-kW cone crusher.

Crushed mineralized material is stored in two silos, each dedicated to the two (2) identical production lines (North and South). The crushed mineralized material is further reduced in size by being conveyed to a grinding circuit in closed-circuit with cyclones. The pump box receives the 132-kW ball mill discharge and a downstream thickener overflow. The slurry is pumped to the cyclones where the underflow is fed to the ball mill feed chute along with the conveyed crushed ore from the silo. The cyclones overflow is transferred a thickener prior to cyanidation.

This section provides a summary of the current operations at Zgounder processing facilities; i.e. the flotation and cyanidation plants. A Feasibility Study is forecast to be completed in year 2021 for a new process plant with capability of treating 2,000 tpd of mineralized material.

EXISTING FLOTATION PLANT
The existing flotation plant beneficiates ore from the mine into a silver concentrate that is bagged on-site. In order to achieve concentrate production, the main steps are crushing, grinding, beneficiation and dewatering.

The cyclones underflow is reground in the secondary ball mill, whereas the cyclones overflow gravitates to an agitated tank. Reagents are added to the agitated tank in order to condition the material prior to the flotation process.

The conditioned slurry flows to the rougher flotation bank that contains three (3) mechanically agitated cells to start the beneficiation process. Rougher concentrate overflows from the flotation ce ........