The Magino Mine is an orogenic gold occurrence related to longitudinal shear zones (greenstone-hosted quartz-carbonate vein deposit). Greenstone-hosted quartz-carbonate vein deposits are a subtype of lode-gold deposits (Poulsen et al., 2000). They correspond to structurally controlled, complex epigenetic deposits hosted in deformed metamorphosed terranes (Dubé and Gosselin, 2007).

Gold mineralization at the Magino gold mine occurs primarily within the Webb Lake granodiorite Stock. The Webb Lake Stock underwent variable metasomatic alteration during deformation and gold mineralization (Heather and Arias, 1992).

Gold mineralization occurs in several sub-parallel high-strain zones striking 070° to 080° within the Webb Lake Stock and within mafic metavolcanic rocks immediately along the northern margin of the stock (Heather and Arias, 1992). Deevy (1992 and 1994) distinguished and described two types of mineralized material shoots, namely “zones” and “veins”. The “zones” are usually 2 to 4.5 m wide and have a strike length of 25 to 70 m. They consist of foliated, bleached and silicaflooded granodiorite. The zones are folded in places, which, during underground mining, produced mineable widths of up to 10.5 m. The “zones” dip at about the same angle as the foliation and have a vertical plunge. The vertical continuity of the “zones” is at a vertical to horizontal ratio of 2.5:1 (Deevy, 1994). Weak bleaching and silica flooding are the distinguishing features of the “zones” (Deevy, 1994). Silica flooding consists of incipient pale gray quartz occurring within the foliated granodiorite. Gold content is directly related to the amount of silica flooding and quartz veining. (Deevy, 1994).

The “veins” consist of discrete pale grey to pale green to almost white quartz veins varying in width from a few to 45 cm. They have a strike length of several to 35 m. Gold values are distributed erratically within the veins, but overall grades can be quite high. The veins are folded in places, with gold sometimes concentrated in fold noses (Deevy, 1992 and 1994). Vertical continuity of the “veins” is similar to that of the “zones”, and the plunge is also vertical.

Native gold occurs in zones of pervasive silicification and in narrow (i.e. less than 1 to 20 cm wide) quartz veins that form complex systems 1 to 3 m wide. Gold occurs within both quartz veins and foliated and altered wall rocks, but the better gold grades are in the veins (T. Deevy, Magino mine geologist 2001, pers. comm., as cited in Heather and Arias, 1992). Finely disseminated leaflike visible gold can be observed in quartz veins exposed in diamond drill cores. (Koskitalo, 1983). The gold tends to form plates or leaves along fractures in quartz rather than coarse nuggets. The quartz hosting the gold tends to be fine-grained and dull milky grey (Koskitalo, 1983). Up to 10% disseminated pyrite is also present, most commonly found in alteration haloes around the gold-bearing quartz veins (Heather and Arias, 1992).

The Magino deposit is amenable to development as an open pit (OP) mine. Mining of the deposit is planned to produce a total of 105.4 Mt of ore and 398.5 Mt of waste (includes low grade material) for a 3.8:1 overall strip ratio, over a ten and a half year mine production life (including one year of pre-production). The current life-of-mine (LOM) plan focuses on achieving consistent ore production rates, and mining of higher grade material in the production schedule, as well as balancing grade and strip ratios. The average open pit ore gold mill head grade is estimated to be 0.89 g/t and contain 3.0 Moz of gold. Lower grade material is planned to be stockpiled and is not included in the Mineral Reserves or processed ore tonnages reported.

The process plant was designed based on a throughput of 10,000 tonnes of ore per day with an average gold head grade of 1.25 g/t and to achieve an overall 92.0% gold recovery.

The process plant flowsheet design utilizes primary jaw crushing followed by a single stage semiautogenous (SAG) mill for grinding. The SAG mill is in closed circuit with cyclones for classification and a gravity circuit to remove coarse gold. Prior to the leaching and Carbon-in-Pulp (CIP) circuit, the ground product (cyclone overflow) will be thickened in a pre-leach thickener to reduce the slurry volume and reagent requirements. The thickener overflow will be recirculated to the process water tank for re-use as process water. The thickener underflow will be pumped to the leach circuit, be dosed with lime and cyanide, leached for 36 hours, and will then flow into the CIP circuit to recover dissolved gold and silver from the leached slurry.

Loaded carbon from the CIP circuit will be acid washed, followed by carbon stripping using a split AARL (“split Anglo”) elution circuit and electrowinning circuits to recover the gold and minor silver. Stripping will be done daily. Carbon will be reactivated prior to return to the CIP circuit.

Smelting of the filtered electrowinning sludge to produce gold doré will occur two to three times a week.

CIP tailings will be washed in a tailings wash thickener to recover cyanide for reuse in the leach circuit and to reduce the amount of residual cyanide that is required to be destroyed during cyanide destruction. The tailings wash thickener overflow will be recirculated to the process water tank. The tailings thickener underflow will be pumped to the cyanide destruction tanks to reduce the Weak Acid Dissociable (WAD) cyanide concentration to acceptable environmental levels prior to pumping of the plant tailings to the TMF.

Leach thickener overflow, tailings wash thickener overflow, and reclaim water from the TMF will supply the majority of the required process water for the plant. Raw water from Goudreau Lake will be used as makeup as necessary. Raw water will be used for all process uses requiring higher quality water including screen sprays, pump gland service, stripping water, and reagent preparation.

The 10,000 t/d process plant will consist of the following unit operations and facilities:
- Run of mine (ROM) material receiving;
- Primary crushing;
- Crushed ore stockpile and reclaim;
- Single stage SAG mill in closed circuit with cyclones and gravity concentration;
- Pre-leach thickening;
- Agitated tank leaching with a residence time of 36 hours;
- Carbon-In-Pulp (CIP) gold recovery;
- Split AARL elution and carbon reactivation;
- Electrowinning;
- Smelting (to gold doré);
- CIP tailings washing and thickening;
- Cyanide destruction (SO2 / air method);
- Tailings deposition / management;
- Raw and process water circuits;
- Reagent preparation facilities; and
- Utilities including air, potable water, fire water etc.