Summary:
The Tamarack Igneous Complex (“TIC”), which sits within the Tamarack North Project boundaries, is an ultramafic intrusion that is associated with the early evolution of the failed, Midcontinental Rift (dated at 1105ma +/- 1.2). This age is significantly older than the Duluth Complex Intrusions which consistently date at 1099ma and is consistent with other earlier intrusions of the Midcontinental Rift that are often characterised by more primitive melts.
The TIC has intruded into Thomson Formation siltstones and sandstones of the Animikie Group and is preserved beneath shallow Quaternary glacial sediments.
The various mineralized zones at the Tamarack North Project occur within different host lithologies, exhibit different types of mineralization styles, and display varying sulphide concentrations and tenors. These mineralized zones range from massive sulphides hosted by altered sediments in the massive sulphide unit (MSU), to net textured and disseminated sulphide mineralization hosted by the coarse-grained ortho-cumulative (CGO) intrusion in the semi-massive sulphide unit (SMSU); to a more predominantly disseminated sulphide mineralization, as well as layers of net textured sulphide mineralization, in the 138 Zone. Mineralization in the 138 Zone, where interlayered disseminated and net textured mineralization occurs, is referred to as Mixed Zone Olivine (MZNO) mineralization. All these mineralization types are typical of many magmatic sulphide deposits around the world. The current known mineralized zones of the Tamarack North Project (SMSU, MSU,138 Zone and the recently discovered CGO East and CGO West) that are the basis of the resource statement are referred to as the Tamarack Resource Area. Also located within the Tamarack North project are currently lesser defined mineral zones, namely the 480 Zone, the 221 Zone, and the 164 Zone, which have not been evaluated for the Mineral Resource Estimate.
The Ni-Cu-Co-PGE mineralization at the Tamarack North Project, occurs as various types ranging from disseminated to net textured to massive sulphides. Sulphide mineralogy is dominantly pyrrhotite (Po), pentlandite (Pn), chalcopyrite (Cpy), with minor cubanite. Pn occurs as coarse grains and as intergrowths with Po.
Although some of the mineralization names at the Tamarack North Project are used to describe mineralization lithologically in terms of sulphide concentration, they have historically been used at the Tamarack North Project to describe specific mineralized materials. These deposits have different mineralization styles, with different metal tenors, genetic implications, and different resource potential.
The 164 Zone
The mineralization type within the 164 Zone, which is located around 1.5 km S of the 138 Zone typically occurs as variable massive sulphide veins and pods < 2 m thick with blebby disseminated mineralization occurring at the base of the fine grained ortho-cumulate olivine (FGO) intrusion on the wallrock contact (500 m depth), and often within hornfelsed and partially melted sediments near the chilled contact with the FGO. Mineralization is generally low tenor and has been interpreted as early cumulate mineralization associated with the base of the FGO. In the 164 Zone, the base of the FGO is more complex. Thick intervals of variable textured gabbro, magmatic breccia, and thin sills or dykes occur within the partially melted meta-sediment where coarse blebby disseminated mineralization occurs in variable textured gabbro with granophyric patches.
The 138 Zone
A wide range of disseminated to net-textured and patchy net-textured sulphides typically occur in the 138 Zone. This type of mineralization is referred to as MZ mineralization. In the 138 Zone, MZtype sulphides appear to form a wedge-like zone of 200 m length, 120 m to 160 m height and a width of approximately 50 to 90 m, starting at ~350 m depth. The mineralization is hosted in FGO and contaminated FGO, i.e. in MZNO and FGO lithologies.
The SMSU
The SMSU forms the bulk of the defined mineral resource and occurs in the upper part of the CGO intrusion as an elongated boudin-aged tubular-shaped zone at the top of the CGO. Two SMSUs (Upper and Lower) have been modelled. The Upper SMSU body dimensions are 400 m long, 40 m to 80 m wide and 40 to 70 m vertically at a depth of 300 m to 325 m. The Lower SMSU body dimensions are 350 m long, 40 m to 65 m wide and 40 to 70 m vertically at a depth of 445 m to 485 m.
The MSU
MSU-type mineralization is defined as containing 80-90% sulphide. The MSU also refers to a mineralized body hosted by intensely metamorphosed and partially melted meta-sediments occurring as fragments or wedges of country rock at the base of the FGO with typical dimensions of 10 to 30 m wide by 0.5 m to 18 m thick. The MSU has a strike length of 550 m at a depth of 275 m (N) to 550 m (S).
CGO East and CGO West New Discovery
The sulphide mineralization consists of a thick sheet of disseminated sulphide 1 to 38 m, with an accumulation of primary sulphides in the FGO Keel and basin that vary in thickness from 0.2 m to 13.92 m, strike length of 500 to 900 m, at a depth of 150 m to 250 m, and a weak plunge to the south at 15°. The sheet-like mineralization in the CGO East has a span of 500 m (east to west) by 900 m (north to south), whereas the CGO West has a span of 400 m (east to west) by 500 m (north to south). The sulphides are disseminated to blebby to massive in texture. In some instances, a vertical increase in sulphides has been observed with depth.
The 480 Zone
Drilling in a narrow linear, E-W trending, positive magnetic anomaly at the northern portion of the Tamarack North Project, referred to as the 480 Zone, has intersected disseminated and net textured sulphide mineralization at a relatively shallow depth. The host olivine cumulates visually resemble olivine cumulates of the FGO intrusion to the S and include intervals of quartz xenolith rich magmatic breccia similar to those in the 164 Zone.
Mineralization in the Weathered Laterite Zone
A weathered lateritic profile is irregularly preserved in the northeastern part of Tamarack North project beneath Cretaceous and Quaternary cover and has concentrated Ni, Cu, Cr, and Fe. The weathered profile is up to 10 m thick, at 35 m depth and consists typically of a 0.5 m pisolithic, limontic hard cap, underlain by massive greenish saprolite, and saprock with remnant igneous textures. Native Cu up to 2% (visual estimation) can be observed as 1 to 3 mm nuggets and veinlets in the weathered profile and persists into the serpentinized upper part of the FGO (Goldner, 2011).
Quaternary and Cretaceous Cover and Weathering Profile
The Tamarack North Project does not outcrop at surface, as it underlies 20 to 50 m of Quaternary glacial and fluvial sediments and in the north of the Tamarack North Project along the east part of the intrusion. Cretaceous siltstone and mudstone are preserved and unconformably overlie the preserved paleo-weathered lateritic profile of the FGO.
Quaternary glacial-lacustrine deposits between 20 to 50 m cover the TIC with thicknesses increasing towards the south. The deposits are a complex arrangement of glacial and interglacial fluvial sands and silt and clay from lake sediments.