The gold-silver deposits of the Deseado Massif are hosted in silicic volcanic and volcano-sedimentary Jurassic rocks related to arc or back-arc settings in Andean or extra-Andean settings. The ore geology, textures, mineralogy, restricted alteration, and geochemistry of these mineralised occurrences indicate that they belong to the epithermal class of precious metal deposits. The deposits are mainly associated with quartz +/- calcite +/- adularia +/- illite alteration assemblages interpreted to represent low and intermediate sulphidation epithermal type deposits.

At La Paloma, the Sulfuro-Rocio vein system comprises narrow, arcuate, steeply dipping quartz- breccia veins. Drilling has defined four areas of interest:

• The Sulfuro vein, the principal deposit of economic interest, is represented by a single, well developed quartz vein typically 2 m to 4 m in thickness and has a primarily northwest-south southeast orientation with a steep southwestwardly dip. Associated sulphide minerals include pyrite and minor galena and sphalerite.
• The Ramal Sulfuro vein occurs at the northern end of the main Sulfuro vein and is strongly curved from a north-south orientation to east-west and is typically 2 m to 4 m in thickness.
• The Rocio vein occurs to the west of the main Sulfuro vein. The Rocio vein is typically 2 m to 5 m in thickness and dips steeply to the east. It is also arcuate in shape and sub-parallels the Sulfuro vein.
• The Esperanza vein system dips 75 degrees toward Sulfuro and has an average thickness of 0.3 m to 6 m.

A near-surface oxidised resource has been estimated for the Arco Iris vein, located towards the north of the Sulfuro vein system. It is represented by a series of narrow, structurally displaced, sub- parallel aligned, sheared quartz veins hosting erratic precious metal mineralisation.

The La Paloma veins remain open-ended at depth. Geological interpretation of the results of recent geophysical studies strongly suggests that the main Sulfuro vein is additionally open-ended towards the south.

At Martinetas, multiple mineralised structures occurring as “vein swarms” with minor intervening stockwork development occur. Five resource areas have been delineated. The main resource is at the Coyote and Cerro Oro deposits comprising a series of narrow, sub-parallel, anastomosing quartz veins varying in width from tens of centimetres to several metres, and typically averaging 1 m or less in thickness. Au/Ag mineralisation is variable within the veins with some minor stockwork mineralisation extending into the host volcanic lithology. Conceptually, near-surface oxidised stockwork precious metal mineralisation might provide a low grade, conventional, heap- leachable resource.

Other resource areas at Martinetas include the Lucia, Calafate and Armadillo deposits. Precious metal mineralisation associated with these deposits is also hosted by narrow to moderately thick, steep dipping quartz veins of variable tenor.

The MDN operation is currently a producing gold mine. Final construction was completed December 2017 for the 1,000 tpd operation.The mine was “designed” for 1,000 tpd and it has reached 1,200 tpd on occasion.

Commissioning of the operation began in December 2017. MDN began operations of a series of conventional open pit mines with a carbon-in-leach facility. Ramp up continued until late 2019. Currently the operation is mining from three active pits (Coyote, Cerro Oro and Sulfuro) at a rate of +1,000 tpd and the mill is able to handle the throughput. As of the effective date of the technical report, further optimisation is being done to both the mining and milling operation. MDN consists of two fully permitted mining areas, each containing a clustered, shallow pits.

Production began with removal of waste for the construction of the tailings storage facility. Marginal grade was stockpiled at the same time and now a long-term, low-grade stockpile has grown to over 500 kt. It continues to grow as all marginal material is stored here.

Mining is currently split 70% – 30% between the Martinetas pits and the La Paloma pits 60 km away, largely due to the high stripping ratio at La Paloma. The three Pantera drills typically drill out blast patterns on a double bench height of 10 m and a 5 m bench when mining mineralised material. Blast holes are typically 3.5” to 4” in diameter. Waste drilling and pre splitting against the final pit wall is done using 5.5” hole diameters. MDN uses ammonium nitrate/fuel oil (ANFO) explosives with conventional primers and a shock tube ignition system for blasting. The ANFO is charged up by hand. Fragmentation in the muck piles is good and the powder index is 0.5 kg/t.

Crushing
The crushing circuit will reduce the mined material size from a nominal top size of 500 mm to a product size P80 of 6.5 mm in preparation for the grinding process.

Haulage trucks with a nominal capacity of 28 t will bring run-of-mine [ROM] material to the dry crushing plant. The material will be dumped directly from the trucks for crushing, although provision has been made for material to be dumped onto atemporary emergency ROM stockpile in the eventof unscheduled crusher plant stoppages or breakdowns. The ROM surge stockpile will also serve as a blending facility to mix the material coming from different sources prior to feeding the plant.

The trucks will dump the ROM material onto a stationary grizzly. This grizzly will prevent oversize rocks from entering the ROM surge bin. The surge bin will have a nominal capacity of twice a truck load capacity. The surge bin will be equipped with a vibrating feeder which will feed the ROM material to the primary jaw crusher. The jaw crusher will reduce the feed size from minus 500 mm to a size less than 100 mm with a closed side setting of 70 mm. The crushed material will be deposited onto the conveyor belts together with the vibrating feeder undersize material to the sizing screen. A belt magnet will be installed to remove tramp iron, followed by a metal detector which will activate an alarm to stop the belt in the event that metal by-passes the detector. The crusher plant utilization will be 60% and the design throughput will be 68 t/h.

The sizing screen will receive the crushed material from the jaw crusher and the grizzly feeder fines, or undersize. The sizing screen will be a double-deck vibrating screen with a final product size P80 of 6.5 mm. The screen oversize will be conveyed to a cone crusher which will have a closed side setting of 15 mm. The crushed product material from the cone crusher will be returned by conveyor belt to the sizing screen feed conveyor. The screen undersize minus 7 mm material will be discharged onto a conveyor, which will transport the fine crushed material into thefine ore bin, or mill feed bin. The fine ore bin will have a live capacity of 1,000 t, equivalent to a full day’s operation.

Grinding
The grinding circuit will reduce the size of the crushed material to a final product size with a product P80 of 75 µm, suitable for the subsequent gold recovery by gravity concentration and cyanide leaching processes. The grinding process will be a single-stage operation with the ball mill in closed circuit with classifying cyclones.

The material in the mill feed bin will be drawn from the mill feed bin under controlled feed rate conditions using the vibrating feeders. These feeders will discharge the material onto a conveyor belt feeding the ball mill. A belt scale will control the feed to the ball mill. The mill will be fed at the rate of 44 dry t/h new feed. The cyclone underflow and the gravity circuit tailings will also constitute part of the feed to the mill. Process water will be added as required to maintain the slurry density of the ball mill at 72% solids. The ball mill will operate at a speed which will be 75% of critical.

The ball mill will have a classification circuit consisting of a mill discharge pumpbox, cyclone feed pumps and a classifying cyclone cluster. The discharge from the ball mill will be directed into a mill discharge pumpbox where dilution water will be added as required to adjust the slurry density for cyclone classification. The slurry in the mill discharge pumpbox will be pumped to a cyclone cluster for classification. The cut size for the cyclones will be at a particle size of P80 of 75 µm, and the circulating load will be 300%. The cyclone underflow will be returned to the ball mill together with feed material for further grinding. A 30% split of the cyclone underflow stream will be directed to the gravity concentration circuit. The mill feed rate of 44 t/h of new feed will constitute the feed to the carbon-in-leach (CIL) circuit.

The cyclone overflow from the classification circuit will be directed to a vibrating trash screen. Process water will be used to spray the deck of the screen to wash off any oversize tramp material or trash. This will be collected in a tote which will be emptied as required. The trash screen underflow will be discharged by gravity flow into the CIL feed distributor box ahead of the leaching and adsorption process. The pulp density of the screen underflow slurry will be approximately 44% solids. Provision will be made for the addition of lime to the ball mill for the adjustment of the pH of the slurry in the grinding circuit prior to the leaching process. Grinding media will be added to the mill in order to maintain the grinding efficiency and power. Steel balls will be added periodically using a ball charging kibble. A weightometer located on the mill feed conveyor will control the feeding rate of the mill feed bin reclaim feeders to the mill so as to maintain the required grinding throughput rate.

The MDN processing facility was designed to process a nominal 350,000 tonnes per annum (tpa),or 972 tpd, of gold-silver bearing material from an open pit operation. The concentrator was designed to produce a gold-silver doré product.

The process flowsheet follows conventional crushing and ball mill grinding and cyclone classification. The gravity concentration circuit in the grinding circuit includes the recovery of coarse and liberated gold using a centrifugal concentrator followed by the tabling of the gravity- gold product to up-grade the concentrate prior to smelting.

The ball mill cyclone overflow is treated in an 8-stage CIL circuit to recover gold from the feed material using activated carbon. Loaded carbon is transferred from the head CIL tank to the elution circuit on a daily basis, while regenerated and/or fresh carbon is brought from the carbon plant for adding to the CIL circuit.

The loaded carbon is initially acid-washed to remove calcium a ........