Summary:
Sulphide mineralization discovered to date in the Project area can be characterized as Komatiite-hosted Ni-Cu-Co-(PGE) deposit type, which recognizes two sub-types (Lesher and Keays, 2002):
Type I: Kambalda-style: channelized flow theory; komatiite-hosted; dominated by net-textured and massive sulphides situated at or near the basal ultramafic/footwall contact with deposits commonly found in footwall embayments up to 200 m in strike length, 10s to 100s of metres in down-dip extent, and metres to tens of metres in thickness; generally on the order of millions of tonnes with nickel grades that are typically much greater than 1% nickel; tend to occur in clusters (e.g., Alexo-Dundonald, Ontario; Langmuir, Ontario; Redstone, Ontario; Montcalm, Ontario; Thompson, Manitoba; Raglan, Quebec).
Type II: Mt. Keith-style: sheet flow theory; thick komatiitic olivine adcumulate-hosted; disseminated and bleb sulphides, hosted primarily in a central core of a thick, differentiated, dunite-peridotite dominated, ultramafic body; more common nickel sulphides such as pyrrhotite and pentlandite but also sulphur poor mineral Heazlewoodite (Ni3S2) and nickel-iron alloys such as Awaruite (Ni3-Fe); generally on the order of 10s to 100s of million tonnes with nickel grades of less than 1% (e.g., Mt. Keith, Australia; Dumont Deposit, Quebec).
The Crawford Project is situated in Northeastern Ontario, in the western portion of the mineral-rich Abitibi Greenstone Belt (AGB) (2.8 to 2.6 Ga), which is within the Superior Province, Canada.
Historical work in Crawford and Lucas townships has generated several generations of geological maps with geology inferred almost entirely from diamond drill core, overburden bedrock interval sampling, and the interpretation of geophysical surveys.
The principal target, the CUC, is entirely under cover but based on geophysics and drilling is an approximately 8.0 km long by 2.0 km wide body (original estimated shape) of dunite, peridotite (and their serpentinized equivalents), and lesser pyroxenite and gabbro, as confirmed in historical diamond drillholes (Spruce Ridge Resources, 2018) and the current extensive drilling program by CNC. Historical diamond drilling in the 1960s and 1970s also reported intersections of gabbro, peridotite, pyroxenite, dunite and serpentinite (e.g., George, 1970). Descriptions from drill core logs record localized brecciation in the Main Zone at the northern contact between mafic volcanic rocks and dunite.
Mineralization
The Abitibi Greenstone Belt affords a mineral exploration company with several target deposit types and commodities, including Ni-Cu-(PGE), VHMS, and orogenic gold.
Within Crawford Township, several prominent mafic-ultramafic intrusions (i.e., sills) offer the potential for sulphideassociated nickel, copper, cobalt, and platinum-group element (PGE) mineralization. Intrusion-hosted nickel sulphide mineralization is the principal target on the Crawford Project where it has been intersected by drilling, hosted in units of dunite and peridotite (largely serpentinized).
Mineralization has been drill-delineated in two principal zones of nickel sulphide mineralization, the Main Zone and the East Zone. Other areas of similar mineralization have been identified through diamond drilling by CNC, including the West Zone (Lane et al., 2022) and North Zone.
Within the Main Zone, drilling to date allows for the delineation of two higher grade (>0.30% Ni and >0.35% Ni) regions (modelled grade shells) within a larger core high-grade zone (>0.25% Ni), which in turn are within the larger enveloping low-grade zone (>0.15% Ni), all contained within the host ultramafic body of the CUC. The high-grade zone (>0.25% Ni) has a minimum modelled strike length of about 3.3 km, is between approximately 70 and 250 m wide, and contains regions of incrementally higher grade nickel (i.e., >0.30% Ni and >0.35% Ni). The high-grade zone and internal regions of higher grade nickel remain open along strike to the north-northwest and extend to a depth of at least 800 m (open at depth).
Located within the northern margin of the ultramafic to mafic body of the Main Zone, is a PGE Reef potentially 2 km long and up to 9 m wide, that is associated with a contact between a peridotite unit to the south and a pyroxenite unit to the north. Additional drillholes will be required to better define the PGE Reef.
Located about 1.2 km northeast of the Main Zone is the East Zone. The East Zone extends for about 2.6 km east-west, is open to the east but is truncated to the west by a large regional north-northwest trending fault. Like the Main Zone, mineralization in the East Zone is characterized by a relatively high-grade nickel core between approximately 70 and 200 m wide and at least 800 m deep (open at depth), within a low-grade nickel envelope and hosted by an ultramafic body comprising variably serpentinized dunite and peridotite, with lesser pyroxenite and minor gabbro.
Within the layered ultramafic unit of the East Zone, two PGE reefs have been differentiated: (1) a higher grade reef potentially 1.5 km long and up to 8 m wide at the northern boundary of the nickel-rich domain, and (2) a lower grade reef potentially 2 km long and up to 6 m wide, near the northern margin of the ultramafic body.
Although magmatic nickel sulphide (pentlandite) is present in the Crawford deposits, nickel grades have been significantly upgraded through the serpentinization (alteration) process, producing secondary minerals that are not magmatic in origin, such as heazlewoodite, awaruite, and godlevskite.
Where visible, nickel sulphide mineralization is dominated by fine-grained, disseminated pentlandite (magmatic) and heazlewoodite (hydrothermal). In general, pentlandite is the dominant nickel sulphide, except in regions of higher grade nickel (i.e., dunite core) where heazlewoodite is the dominant nickel species. This reflects a hydrothermal upgrading of nickel concentration in the CUC, also suggesting very low sulphur conditions. Overall, pyrrhotite occurs at about the same average percentage as awaruite but was identified in less of the drill holes. This suggests that although pyrrhotite occurs less often than awaruite, when it does occur, it is by far the dominant mineral phase.