The uranium deposits at Elliot Lake are contained in the sediments of the westward plunging (~15°) Quirke syncline. The mineralization is surrounded to the north and east by Archean granites and to the south by Archean mafic metavolcanic and metasedimentary rocks. Depth from surface to the centre of the Quirke syncline is estimated at approximately 1,500 metres.

Mineralization at Eco Ridge is contained in the conglomerate beds of the Ryan Member, which is roughly 100 metres thick and consists of quartzite of a distinctly green colour (sericite alteration) and quartzite with intercalated quartz-pebble conglomerates. The quartz-pebble conglomerate beds containing uranium and REOs are located in the west-northwest channels of the Matinenda Formation. The Ryan Member represents the lower Matinenda and is characterized by an increase in the amount of pyrite. Low-grade mineralization is generally contained within the coarser-grained quartzite beds while higher grades are contained in quartz-pebble conglomerates with disseminated pyrite. A 30-metre thick Nipissing diabase dyke strikes east-west across the entire property and cross cuts mineralization.

The reefs inside the Pardee Channel on the south limb of the Quirke syncline hold the Eco Ridge deposit. It is believed the stratigraphy of the mineralized reef in the Pardee Channel can be correlated to those of the Nordic Channel, where much of the region’s historic mining was conducted. The mineralized zones of the Nordic Channel are separated into Lower, Middle and Upper conglomerate reefs. The Lower Reef is thin and discontinuous; the Middle Reef has been the most historically mined while the Upper Reef has had more limited mining. The Upper Reef is thought to be correlated to the MCB at Eco Ridge.

The MCB and the quartzite floater reefs 6 to 15 metres above it contain the Eco Ridge mineral resources. The MCB contains quartz, quartzite and dark cherty pebble in a fine-grained, pyrite rich matrix. Uranium content is concentrated at the base of the MCB and decreases moving toward the top of the bed. The MCB ranges from 1.3 to 4.4 metres in thickness. The floater reefs are generally thinner, ranging from 0.1 to 2.0 metres in thickness, and generally contain uranium grades of less than 0.04%. The zone of quartzite with floater reefs above the MCB is referred to as the Hanging Wall Zone (HWZ). The thickness of the HWZ is variable, but U3O8 and REO grades appear relatively consistent.

Uranium mineralization in the Elliot Lake region is generally contained within uraninite and brannerite. Coffinite, thorite and an unidentified uranium silicate carry yttrium oxide (Y2O3) and Heavy REO, while monazite typically carries Light REO. It has been generally observed that there is a correlation between pyrite content and uranium (pyrite content historically being used as an ore cue) at Elliot Lake and that REO mineralization drops off less rapidly than U3O8 mineralization
above the MCB.

A number of mining methods have been assessed by RPA and others for extraction of the MCB mineralization. The selected mining method was room and pillar, with both development and production contained within the mineralized zone. The development and production tonnage will be loaded into trucks and transported to surface for processing.

Although the MCB average mining thickness is 2.7 m, in RPA’s opinion, the deposit will support a high production rate. The lateral extents are such that multiple accesses from surface are feasible, providing many independent workplaces.

The use of conveyors instead of haul trucks for material handling, while not included in the base case, may provide economic advantages, and is worth consideration in future studies. Particular attention should be paid to impacts on grade distribution in production schedules for each option, as there may be less flexibility with conveyors, offsetting the cost advantage that they provide.

The processing flow chart used in the PEA included pre-concentration by flotation and highintensity magnetic separation, acid baking and leaching, and solvent extraction/precipitation. Mill daily throughput is designed at 9,143 tonnes, operating 350 days per year.

The processing flow chart in the PEA calls for ore to be crushed to 100% passing 300µm. Ore beneath 25µm is directed to the froth flotation and ore larger than 25µm is routed to the magnetic separation circuit. The magnetic separation concentrate is ground to 100% passing 74µm and then mixed with the concentrate from the flotation circuit. The final concentrate is then filtered to remove moisture and directed to the acid baking process. Thickened tailings from the magnetic separation and flotation circuits are sent to a paste backfill plant.

The concentrate is mixed with sulphuric acid at an acid-to-concentrate ratio of 0.3:1 and is cured for one hour. The mixture is then baked in a rotary kiln at 310°C for three hours. The solids from baking are then discharged into the leach circuit for three hours. During leaching, the uranium and rare earth sulphates are dissolved and the slurry is pumped to a solid/liquid separation circuit. The pregnant leach solution is then sent for purification and recovery of valuable metals – treatment of the pregnant leach solution was beyond the scope of the PEA but certainly needs to be defined further by future testwork.