Within the Project area, the main rock types are Archean granites and metasedimentary rocks of the Quetico Subprovince, and Keweenawan Supergroup mafic to ultramafic intrusive rocks and related intermediate to mafic hybrid intrusive rocks of the Mid-continent Rift.

The Current Lake, Bridge and Beaver Lake Zones collectively form the nickel–Cu–PGE deposit at Current Lake. However, the different zones display different morphologies, are disproportionately mineralized, and have slight differences in mineralization tenors.

The Current Lake and Bridge Zone portions of the deposit form a narrow, almost flat-lying conduit ranging in dimensions from 30 m x 30–50 m wide and as much as 70 m tall. The olivine melagabbro in the magmatic conduit is variably mineralized. The sulphide mineralogy consists of pyrrhotite, pentlandite, chalcopyrite, pyrite and rare cubanite and violarite.

The Current Lake zone lies beneath Current Lake and is sub-horizontal, narrow, sinuous, and tube-like in morphology. The width, thickness and orientation of the host body, and its contained mineralization, changes along its length as it follows intersecting, sub-vertical and sub-horizontal fractures and faults. The magmatic conduit exhibits a slight southerly plunge with the base of the mineralized body at 45-50 m depth in the north and 90–95 m depth in the south, where it joins with the Bridge Zone.

The Bridge Zone is hosted by granitoid rocks and is completely preserved and tubelike in form; however, it exhibits a steeper east– southeasterly plunge, when compared to the Current Lake Zone, and has a relatively well- defined strike. The top of the magmatic conduit in the Bridge Zone is 60 m below surface in the west and 125 m below surface in the east. The thickness of the conduit averages 50 m and ranges from 35 m to 65 m in width. Mineralization is continuous and relatively high-grade throughout the zone.

Beaver Lake exhibits a shallow (15°) east– southeasterly plunge and is tabular in form. The morphology of the Current Lake Intrusive Complex system changes from tube-like to tabular when it crosses the contact between the granitoid rocks north of the contact, and the metasedimentary rocks south of the contact. Mineralization typically occupies basal depressions.

The Beaver Lake zone host intrusion increases from 100 m width and 15 m thickness to 550 m width and 200 m thickness towards the east. Beaver Lake sulphide mineralization is largely hosted by olivine melagabbro; however, significant mineralization can occur within lherzolite, which forms the core of the Beaver Lake Intrusion. The sulphide mineralogy is similar to Current Lake.

The morphology of the sulphide mineralization at Beaver Lake differs from Current Lake in that the entire conduit is not mineralized. The sulphide mineralization is typically located around the margins of the conduit within the olivine melagabbro and may wrap around the northern margin of the intrusion.

Basal mineralization is the most dominant and appears to have thermally eroded into the Quetico Subprovince meta-sedimentary rocks. Typically, mineralization is thickest and highest grade in depressions on the floor of the intrusion. This basal mineralization generally forms a complex mesh of mineralized depressions and varies in thickness from 2 m to as much as 30 m and in widths from 20 m to >50 m. The term “Spine Zone” is a term used by Magma Metals geologists for basal mineralization present within the central Beaver Lake portion of the Current Lake Intrusive Complex.

The sulphide tenor is, in general, consistent in the mineralization along the upper and lower contacts; however, some higher-tenor “cloud” mineralization has been identified along the upper contact of the Beaver Lake Intrusion. This style of mineralization, referred to as the “Cloud Zone”, consists of very finely- disseminated chalcopyrite.

Mineralization within the lherzolite occurs where the upper and lower contact mineralization are thickest, and therefore continues into the lherzolite. Additional mineralization is developed in chromium-rich horizons within the core of the Beaver Lake intrusion. Typically, the olivine melagabbro and lherzolite contains 2,000–3,000 ppm chromium; however, two continuous zones 4,000– 5,000 ppm chromium with thicknesses of 2–5 m contain significant sulphide mineralization. Chromite has not been observed in the horizons; however, bright green chlorite is present and may host the chromium.

Current Lake and Bridge Zones.
In general, within the Current Lake and Bridge Zones, sulphide mineralization is disseminated, ranging from a few percent to >25% sulphides.

Disseminated sulphide grains can range in size from 0.5 mm to as much as 1 cm in size and consist of pyrrhotite, chalcopyrite, pentlandite, minor pyrite and rare cubanite and violarite.

Basal net-textured (25–50%) sulphide and massive sulphide intervals have been intersected in core drilling locally and are more common in the Bridge Zone than the Current Lake Zone.

Significant massive sulphide veins, generally 1–2 cm wide, occur within the Current Lake Zone. These veins are typically either sub- horizontal or near-vertical, and are interpreted by Magma Metals geologists to be the result of segregation of molten massive sulphide during the cooling of the intrusion. Plagioclase occurs in these veins, which indicates that plagioclase had also not yet crystallized completely and was still partially molten.

Beaver Lake Zone.
The Beaver Lake sulphide mineralization is disseminated, ranging from a few percent to >25% sulphides, and is also interstitial to the silicate gangue. Disseminations can range in size from 0.5 mm to as much as 1 cm in size. Blebby sulphides are common and classic net- textured and massive sulphide mineralization has been intersected regularly in core drilling within the western portions of the Beaver Lake Zone, particularly where it merges with the Bridge Zone.

The conceptual mine plan was developed using only open pit methods. Mining would be at a rate of 1.5 Mt/a over a seven-year mine life.

Initially the company studied two mining scenarios, a standalone open pit and a hybrid case with a smaller open pit mine and underground operation, utilising a drift-and fill mining method. As the study progressed and the economic parameters became better defined, it became apparent that the stand alone open pit presented better economic results then the hybrid scenario.

The overall slope angles account for the likely future ramp configuration. All of the ramps in the Current Lake area will be placed on the east wall. An 18° overall slope angle was used in the overburden material.

The Thunder Bay North deposit displays very low sensitivity to the slope angles with respect to the contained amount of mineralization; however, the stripping ratio varies considerably with the change in the slope angles. The relatively shallow Current Lake area would not be particularly sensitive to pit slope changes; however, the high strip ratio Beaver Lake area would be more sensitive to slope changes.

Phase volumetrics by bench were manually scheduled, using maximum descent rates of ten 2.5 m benches per period in selective mining areas. Selective and bulk zones were tracked to allow individual costing on an annual basis.

Due to the relatively short life-of-mine, a contract mining scenario is recommended. Initial mining at the north end of Current Lake will require small equipment, which can mine selectively. This fleet would consist of typically two, but up to three 4 m3 to 5 m3 excavators, matched to 50 t to 60 t trucks. The initial pre-stripping of the later phases that stretch south to the Beaver Lake zone, will be performed with larger bulk mining equipment. This fleet would consist of typically one, but up to two ~18m3 excavators working on 10 m benches, matched to ~145 t trucks.

The three-stage process selected as the preferred process route is as follows:
- Crushing, grinding and flotation to extract the sulphides from the ore to produce an initial bulk concentrate. A gravity circuit would extract a significant proportion of the gold, which is output to the bulk concentrate.
- The bulk concentrate is then treated by PlatsolTM pressure oxidation to produce a pregnant leach solution (PLS), which contains the dissolved metals.
- The PLS is then treated via relatively simple and commercial process routes (reduction with metal (cementation) to produce both precious metals bullion and copper, followed by electrowinning of nickel and cobalt).

Four high value products will be made and either sold to metal refineries or direct to end-users:
• A high-grade precious metals (PGM and gold) bullion product to a PGM refinery.
• A high-grade silver product to a silver refinery
• Copper briquettes to market, and
• A nickel-cobalt alloy to market.

A sample of flotation concentrate from the Thunder Bay North project was tested in a 2 L Parr titanium batch autoclave, under standard Platsol™ pressure oxidation operating conditions. The concentrate was oxidized for two hours at a temperature of 225°C, under an oxygen partial pressure of 100 psi and in the presence of 10 g/L chloride ions in solution.

Greater than 90% of the platinum and about 90% of the palladium in the concentrate were solubilized, along with >90% of the nickel and cobalt. Four tests were carried out in which the effects of fine grinding the concentrate, increasing the acid concentration in solution, and lowering the chloride concentration to 5 g/l were examined. None of these changes had a significant effect on metal recoveries, except for lowering the chloride strength, which had an adverse effect on platinum recovery.

Several methods were considered at the conceptual level for recovery of revenue metals from the Platsol™ pregnant leach solution (PLS) within the constraint of keeping the hydrometallurgical operation simple and economical but providing upgraded products which would improve Project revenue due to reduced impact of smelter deductions.

The Platsol™ pregnant leach solution is treated with copper powder (an internal recycle stream) to reduce solution Eh by reduction of ferric iron, PGM and part (approximately 5%) of the copper. The resulting dilute suspension of PGM and cuprous chloride is thickened and filtered to produce a cake containing essentially all of the PGM (about 10 kg/day) with about 200 kg/day of copper chloride. The thickened pulp is contacted with fresh Platsol™ PLS to dissolve most of the CuCl. The precipitate leach solution recycles to the PGM precipitation.

The PGM–AgCl–CuCl residue from the PLS leach (15–20 kg/day net product) is heated in a strong chloride solution (salt or ferrous chloride from copper precipitation) to dissolve silver and copper. Filtration produces a PGM + gold cake which is vacuum dried, de agglomerated and packed for shipment to a refinery.

Filtrate is cooled to precipitate an AgCl–CuCl precipitate, >65% silver, for sale to a silver refinery or chemical producer.

Copper remaining in the Platsol™ solution after PGM precipitation is precipitated quantitatively as CuCl by reduction on copper powder. CuCl is thickened and further reacted with scrap iron to produce copper powder (“cement” copper). Copper powder equivalent to net production, about 7.8 t/d, is filtered, washed and briquetted for sale. Approximately 8 t/d of copper powder is recycled to reduce ferric, precipitate PGM, and CuCl. Net ferrous chloride product is recycled to the Platsol™ feed, partly replacing salt as a source of chloride ion.

Precipitation of copper as copper chloride from an acid sulphate–chloride leach solution using copper powder and cementation of copper from the precipitate slurried in ferrous chloride brine was commercially practiced for many years at Chuquicamata (McArthur and Leaphart, 1961).

Essentially copper-free solution passes to limestone neutralization and iron oxidation/jarosite precipitation; iron precipitate and gypsum are filtered and pass to tailing. Nickel (and cobalt) is then precipitated as hydroxides/basic sulphates, along with gypsum, by lime adjustment to pH 8. The gypsum-nickel hydroxide precipitate is thickened, filtered and repulped with a nickel sulphate pH 6 electrolyte and passed as a slurry through EMEW® cells to plate nickel cobalt alloy which is stripped and sold. For revenue computation, cobalt is valued at the price of nickel and marketing is limited to manufacturers of non-nuclear grades of stainless steel. The precedent for this is cobalt recovery from leach solutions in the Congo (Bouchat and Saquet, 1960).

Acid generated by plating of nickel is consumed by hydroxide so the pH and Ni(Co) contents of the circulating solution remain constant. Gypsum, with any residual nickel hydroxide, is removed from the circulating electrolyte by filtration and recycled to the jarosite precipitation. The final step in solution treatment is pH adjustment with lime to precipitate magnesium as its hydroxide and the associated sulphate as gypsum to prevent discharge of an excessive level of soluble magnesium sulphate.