In the Superior Province, major gold deposits are spatially associated with large-scale regional deformation zones and associated Timiskaming-type metasediments (LeClair et al., 1993). These regional structures are interpreted as zones of transpressive terrain accretion.

Typical greenstone-hosted, mesothermal gold deposits are associated with structurally controlled quartz-carbonate veins hosted by moderately to steeply dipping shear zones displaying brittle to ductile deformational features in low-grade (greenschist) metamorphic rocks. In contrast, the Sugar Zone gold deposit is hosted in medium-metamorphic-grade (amphibolite) rocks that exhibit ductile deformation. The Sugar Zone host rocks have been intruded by felsite and porphyry sills, and exhibit strong association of gold with silica-sulphide-potassic alteration.

The Sugar Zone is interpreted as an orogenic, mesothermal gold deposit located in the SDZ, which is an area of high strain. The auriferous zones of the Sugar zone are interpreted to be highly strained altered mafic flows, intermediate to felsic porphyritic intrusions, and boudinaged auriferous quartz veins. Alteration consists primarily of silicification, biotization, and sulphidization. Hydrothermally altered basalt is recognized as a key component of mineralized zones. Commonly in contact with porphyries within mineralized zones, it is strongly silicified biotitic basalt containing significant amounts of pyrrhotite, and pyrite.

The Upper, Lower, and Footwall mineralized subzones range in thickness from 0.2 m to 6 m, strike at 140° and dip between 65° and 75° to the west.

The mineralized Upper, Lower, and Footwall Subzones of the Sugar Zone lie within the SDZ. They occur within a highly strained assemblage consisting of variously altered mafic volcanic flows, intermediate porphyritic intrusions, and boudinaged auriferous quartz veins. The three zones range in true thickness from about 0.2 to 6 m, and are separated by 20 to 30 m of un-mineralized metavolcanics.

Each Subzone is made up of one or more porphyritic intrusions, flanked by altered basalt, and hosting conformable quartz veins. Alteration within the mafic metavolcanic portions of the subzones consists primarily of silicification that occurs both as pervasive alteration, and as quartz veining, diopsidation, and biotization. The porphyry units of the zones exhibit biotite and silica alteration, but lack diopside alteration.

Gold mineralization mostly occurs in quartz veins, stringers, and quartz-flooded zones predominantly associated with porphyry zones, porphyry contact zones, hydrothermally altered basalts and, rarely, weakly altered or unaltered basalt within the Upper, Lower, and Footwall Subzones. Fine to coarse-grained specks and blebs of visible gold are common in the Sugar Zone quartz veins, usually occurring within marginal, laminated, or refractured portions of the veins. The visible gold itself is often observed to be concentrated within thin fractures, indicating some degree of remobilization. Quartz veins and floods also contain varying amounts of pyrrhotite, pyrite, chalcopyrite, galena, sphalerite, molybdenite, and arsenopyrite. The presence of galena, sphalerite, and/or arsenopyrite is a strong indicator of the presence of visible gold. Pyrite, chalcopyrite, and rarely molybdenite form a minor component of total sulphides, and do not appear to be directly related to the presence of gold mineralization.

The Middle Zone, located between the Sugar and Wolf Zones, may represent the extension of the Sugar Zone to the north. The zone occurs within a highly strained package of massive and pillowed flows exhibiting various degrees of biotite alteration. Gabbro sills and flows are common about the zone. Similar to the Sugar Zone, a weak Upper and Footwall Zone may locally be developed. The zone typically ranges from 0.2 to 6 m in thickness. Middle Zone gold mineralization is often associated with quartz veins and veinlets hosted within a package of altered mafic volcanic and feldspar porphyry. The gold mineralization is often accompanied by 1%–5% pyrrhotite, and pyrite with local sections of minor galena and sphalerite. Galena is normally indicative of higher grades and the presence of visible gold.

The auriferous Wolf Zone lies along strike of the Sugar Zone, and may represent the northern extension of the SDZ. It is defined as highly strained packages consisting of variously altered mafic volcanic flows and gabbros. The zone ranges in true thickness from 0.2 to 3.0 m. The Wolf Zone is made up of highly sheared mafic metavolcanics and a network of intrusive, intermediate quartz-feldspar porphyry dykes/sills. Alteration in the mafic volcanic and gabbro units consists mainly of silicification (both pervasive and quartz veining), diopside alteration, and magnesium-rich, brown biotite alteration. Alteration within the intermediate porphyry units consist of mostly silicification, with small amounts of magnesium-rich brown biotite, and no diopside. The zone is observed in trenches to pinch and swell over 30 m. Wolf Zone gold mineralization mostly occurs in quartz veins, stringers, and quartz-flooded zones predominantly associated with porphyry zones and hydrothermally altered basalts and gabbros. Fine-grained specks of visible gold are occasionally observed in the Wolf Zone quartz veins. The visible gold itself is often observed to be concentrated within thin fractures, indicating some degree of remobilization. Quartz veins and floods also contain varying amounts of pyrrhotite, pyrite, and occasional galena. The presence of galena is a strong indicator of the presence of visible gold. Pyrite and pyrrhotite form most of the total sulphides, but do not appear to be directly related to the presence of gold mineralization.

The Sugar Zone and Middle Zone mineralization typically comprises tabular, narrow veins, approximately 1.5 m to 3 m thick, and dipping at around 70° to the southwest. Excessive dilution is potentially a major risk to operating success in narrow mineralization. Longitudinal longhole retreat stoping was selected as appropriate for this Deposit based on the favourable geometry, current geotechnical knowledge and success of the Bulk Sample trial mining. Both the ore and the host rock are sufficiently competent to facilitate the void sizes required for effective longhole stoping.

The longhole open stoping mining method provides the following advantages:
- Safe – personnel do not enter the production mining voids (remote-controlled equipment only).
- Proven – many instances of the methods application throughout the world.
- Highly mechanized – reduces personnel exposure to health and safety risks.
- Easy access to resources – skilled labour and equipment are readily accessible locally and around the world.
- Low cost – leverages off large drill and blast scale and minimization of development.

Empirical stope stability analyses by RockEng concluded that, for typical conditions, stopes are expected to perform well:
- Stress in the major influence on stability variability:
-- Above 200 m mining depth stress conditions are favourable (A factor is 0.8–1.0).
-- Between 200 and 500 m mining depth is a transition zone.
-- Below 500 m mining depth,stress conditions are less favourable (A factor drops to 0.4–0.1).
- HW geometry becomes more favourable with depth as the dip steepens (C factor increases from 5.7–7.9).
- Side walls and backs are expected to perform well due to low HR.
- HW stability will be the control factor for design.
- Current stope dimensions are expected to see good HW performance, and routine cable bolting of the HW is not expected to be required.
- There is an opportunity for larger stopes with cable bolting

Paste backfill is the primary fill type and has the following advantages:
- Reduces the need for rock pillars, maximizing ore recovery.
- Reduces the duration of the stoping cycle.
- Reduces the number of diesel powered loading and hauling units underground thereby reducing the overall primary ventilation.
- Reduces the size of the surface tailings storage facility.

The paste backfill plant was designed to generate paste backfill at a rate of 320 m3 of backfill per day. The schedule calls for an average paste backfill rate of 210 m3 of total backfill per day, implying a 65% utilization factor of the paste backfill plant. An agitator truck (typical concrete delivery truck) will transport the paste backfill from the paste backfill plant to various paste backfill holes located along strike directly above the orebody. All critical paste backfill lines will be duplicated or “twinned” to permit filling activities to continue in the event of line blockage. Underground reticulation lines will direct the paste backfill from the bottom of the surface delivery hole along the levels and into the stopes and will comprise drilled holes, steel pipe and HDPE pipe. Paste backfill barricades will be constructed in the lower sill drives using predominantly waste rock that is sealed with dry-mix shotcrete. Each barricade will be removed prior to blasting the next stope.

The mine layout is based on ramp development from surface to access the mine workings and production levels. Ramp development will extend down from both the existing North and South Zones. Two ramps are required in this area due to the large strike extent (up to 650 m), while a single ramp access is planned for mining the Middle Zone. The two Sugar Zone ramps incorporate several linking ramps at approximately 180 m vertical intervals that will facilitate ventilation, pumping, equipment movement, and escape routes.

The crushing area consists of three modules, a jaw/primary crusher unit, a sizing screener unit, and a cone/secondary crusher unit. The ROM material from underground is fed directly to the primary jaw crusher (through a grizzly) and ROM bin. This material is then passed through a vibrating screen with a 13 mm aperture; the undersize reports to the crushed fine ore feed stockpile, and the oversize to the secondary crusher.

The jaw crusher unit includes a ROM bin, vibrating grizzly feeder, and Metso C80 jaw crusher to reduce the material from a 400 mm top size to a P80 of 45 mm. The jaw crusher is fed by a vibrating grizzly feeder set to scalp at 5 cm (2); its oversize reports to the jaw and the undersize -5 cm (-2") bypasses directly to the screen feed conveyor. The screen feed conveyor is equipped with a self-cleaning crossbelt magnet and a metal detector that will automatically stop the belt when triggered. There is also a manual cleaning magnet on the existing HP100 cone crusher feed conveyor. Tramp metal will then be manually removed from this magnet. The Metso double-deck vibrating screen is a model ES202 (1.87 x 4.9 m) with a 38 mm top deck and a 15 to 16 mm bottom deck.

The current cone/secondary crusher circuit consists of an intermediate surge bin, vibrating feeder, and HP100 cone crusher. The material from this cone crusher is returned to the jaw crusher discharge belt to return to the classification screen. The secondary crushing circuit configuration requires an upgrade of the secondary cone crusher from an HP100 to an HP200 or equivalent to sustain 1,200 t/d.

The C80 jaw crusher closed side setting of 55 mm will serve the nominal feed rate; however, it is recommended to open it to 75 to 85 mm to choke feed the secondary cone crusher. The secondary cone crusher will work in a closed circuit with the ES202 vibrating screen (1.87 m x 4.9 m); at 120 t/h the screen shows low loading and will not become a constraint. Thus, a screen upgrade is not required.

The existing mill feed conveyor is fitted with a weightometer to monitor and control the feed rate to the ball mill. The weightometer is also used to proportionally add water to the milling circuit based on feed tonnage.

The grinding area is currently made up of a single 3.05 x 5.79 m (10 ft diameter x 19 ft long), 800 kW ball mill in closed circuit with a cyclone pack. The mill is designed to produce a P80 75 µm grind size. Ore is fed to the existing ball mill at a controlled rate, and water is added to the feed chute to achieve the desired milling density. Product from the ball mill discharges through a trommel with the oversize reporting to the scats bunker, where it is periodically removed by the skid steer loader and returned to the circuit. Trommel undersize gravitates to the guard screen feed hopper where it is further diluted to achieve the required cyclone feed density before entering the pair of gravity concentrators. The gravity concentrators operate so that their backwashing and flushing cycles are staggered.

A new ball mill (BM2) operating with the existing ball (BM1) mill will provide the expansion capacity. A ball mill was chosen given that the site is familiar with operating the existing mill, and as mentioned above, previous testwork and financial considerations showed that there would be no advantage in adding a SAG or rod mill. A 3.09 m diameter x 4.60 m EGL ball mill with a 550-kW variable-speed drive (VSD) was chosen as the second ball mill and will operate in series downstream of the existing ball mill with 800 kW VSD.

The mill sizing relies on the BWi of 16.1 kWh/t (106 µm screen) and a grind target of 75 µm, as per the original design. Although recent testwork samples of ball mill feed show a significantly lower BWi of 9.9 kWh/t (106 µm screen) to 11.6 kWh/t (150 µm screen) for the Sugar Zone, future ore zones including the proximal Middle Zone and deeper reaches of the North and South Zones have yet to undergo robust comminution testwork, hence a higher design BWi of 16.1 kWh/t provides a conservative basis for the design.

The ball mill discharges to the gravity circuit and is conveyed by pump to a guard screen that protects the gravity concentrators from >3 mm particles. The underflow from this screen subsequently goes to a pair of Falcon SB1350 gravity concentrators. The cycle times of the gravity concentrators is staggered so that they do not flush simultaneously and overload the hopper in the gold room.

The process plant stages for the existing and future expanded plant are as follows:
• Primary jaw crushing and secondary cone crushing with intermediate screening;
• Fine ore feed storage (stockpile);
• Grinding circuit with classification tower;
• Gravity concentration circuit;
• Gold room with furnace;
• Flotation circuit (addition of a cleaner flotation cell for expanded circuit);
• Concentrate thickening and filtration with transportation loadout;
• Tailings thickening circuit;
• Reagents area;
• Associated services such as water and air.

The gravity concentrators were previously sized to recover 75% of the gold with a grade of 1,875 g/t Au. This is dependent on the quantity of free gold reporting to the mill. The existing pair of Falcon SB 1350 gravity concentrators and existing guard screen have capacity to accept the expanded throughput with a drop in the recovery percentage expected accordingly.

The expansi ........