Two types of gold mineralization styles have been identified to date on the Property. The first, host to the bulk of mineralization in the Detour Lake area (Detour Lake and West Detour deposits), occurs as orogenic greenstone-hosted hydrothermal lode gold deposits.

A second style of gold mineralization was identified in the Lower Detour area, which is localized into three spatially related mineralized horizons known as the 58, 58N, and 75 Zones. These mineralized lenses share characteristics with both syenite-associated oxidized intrusion-related deposits of the Kirkland Lake area (Robert, 2001) and the Sigma-Lamaque deposits of the southern Abitibi (Robert, 1986), the latter of which are thought to be borne of the orogenic model described above. Still in the early stages of exploration and research, a clear genetic model has not yet been determined.

At the Detour Lake mine, the gold mineralization is characterized into two main zones: hangingwall mineralization and footwall mineralization.

The mineralization forms a 200 metre wide (locally up to 350 metres) corridor within a broad assemblage of mafic volcanics with an overall east-west trend. To date, Detour Gold has drill tested this mineralized corridor for a distance of over five kilometres, west from the former Campbell pit. The bulk of the mineralization within this corridor is concentrated along a highly strained corridor of a moderate to strong potassic alteration envelope at the contacts between the pillowed mafic flows and massive flows.

At the eastern end of this corridor at the Detour Lake mine, the main mineralized zone is referred to as the Main Zone (terminology of the former Detour Lake mine). The Main Zone was the largest gold-bearing mineralized zone and consists of gold mineralization occurring in the CMH or in quartz and quartz-carbonate vein systems splaying from the SLDZ. Placer’s Quartz Zones Q50, Q70, Q100, and Q120 zones are typical quartz veins arrays splaying off the SLDZ into the hangingwall (Barclay, 1993). These quartz veins are typically less than one metre in width. Gold occurs generally as free gold with these veins. The quartz veins commonly occur with a frequency of greater than one vein per metre.

West of section 19,620E, the mineralization mainly straddles the lower massive flow-pillow flow contact and is commonly associated with increased biotite alteration, shearing, narrow quartz veining and minor pyrite or pyrrhotite. Local zones of strong brecciation with sulphide infilling have also been recognized along with minor chalcopyrite, telluride minerals and visible gold. Visible gold is usually found as specks, clusters or fracture coatings. The gold mineralization is associated with a series of sub-vertical to arcuate deformation zones characterized by enhanced strained fabrics, well defined open-space breccias, and to a lesser degree sheeted shear-hosted veins and extensional veins.

From sections 16,160E to 17,160E, Placer intersected the QK Zone along a massive flowpillow flow contact between 600 metres and 750 metres below surface. This mineralization is associated with narrow parallel to sub-parallel quartz veins, quartz boudins and sulphide rich veins/breccias with adjacent silicification and potassic alteration envelopes. Gold is directly associated with sulphides.

The footwall mineralization (Talc Zone) commonly contains boudins of quartz veins and felsic as well as intermediate dyke slivers. It is generally intensely sheared, especially in the area adjacent to the contact with the volcanoclastic sediments. Gold in the Talc Zone occurs dominantly within pyrite-pyrrhotite and minor chalcopyrite along foliation planes, narrow discrete shears or strain zones and in irregular lenses (Barclay, 1993). The zones also contain short deformed lenses or boudinaged quartz veins. In some cases, it appears that the mineralization is controlled by strong fault structures containing several centimetres of gouge material.

Conventional open pit mining methods are used to mine the Detour Lake deposit utilizing a current fleet size of 34 haul trucks (CAT 795F - 300 tonnes), 2 electric cable shovels (48 m3), 4 hydraulic shovels (28 m3), 10 drills and various ancillary equipment to support the mining operation. The mining fleet will be increased in the next few years in order to meet the mine production schedule of the new life of mine plan.

The mining operation is using a conventional gravity, cyanidation and carbon-in-pulp processing facility currently operating at approximately 60,000 tpd.

The crushing circuit includes a larger gyratory crusher (60"X113" HD equipped with 1,000 kW) and the addition of a secondary crushing circuit (2X750 kW crushers). In addition, this system is complemented with additional crushing capacity in the pebble crushing circuit (2X750 kW pebble crusher).

The grinding circuit consists of two parallel lines, each having one twin pinion semi-autogenous (SAG) mill (36'X20') and one twin pinion ball mill (26'X40.5'). The gravity circuit is expected to recover approximately 30% to 40% of the gold. The remaining gold in ore is sent to cyanidation followed by carbon in pulp (CIP) gold recovery. After carbon stripping, the gold is processed through electro-winning cells prior to gold pouring. The overall gold recovery is estimated to average 90.6% for 2017 and 2018, and 92.7% for the life of the mine.

The cyanide solution is recycled to the head of the circuit to reduce operating costs and environmental impact. The remaining stream is detoxified through an SO2/air system before tailings deposition. The Company is initially using the same location for the tailings impoundment facility as the former operation. The design will be expanded to a second and then a third containment system with capacity for approximately 650 million tonnes.