Summary:
Ajax is an alkalic copper-gold porphyry deposit hosted within the Iron Mask Batholith. Mineralization extends to depths exceeding 700 m, widths exceeding 1,000 m, and has a strike length that exceeds 2,000 m. The mineralization in the project area is associated with structural corridors of highly fractured and albite-altered sections of Sugarloaf Diorite (SLD) and Sugarloaf Volcanic Hybrid (SVHYB) units.
The Iron Mask Batholith is host to more than 20 known mineral deposits and occurrences. Copper-gold mineralization within the Iron Mask Batholith is associated with the younger intrusive phases of CHMZ and SLD. Mineralization is generally localized along major fault zones, at the contacts with the older PHD and IMH units and associated with albite and potassium feldspar alteration.
The mineralization in the project area is associated with structural corridors of highly fractured sections of SLD and SVHYB phases of the Iron Mask Batholith. Chalcopyrite is the dominant copper mineral and occurs as veins, veinlets, fracture fillings, disseminations and isolated blebs in the host rock. Concentrations of chalcopyrite rarely exceed 5%. Accessory sulphide minerals include pyrite and molybdenite.
Copper mineralization in the Ajax area consists predominantly of chalcopyrite and is hosted primarily in the SLD and SVHYB units. This mineralization appears to have greater concentration within the Sugarloaf units near the contact with IMH. Some mineralization is also seen within the IMH, MAFV, PXPP and PICR units near the contacts with Sugarloaf units, but mineralization drops off quickly with increasing distance from the contact. Chalcopyrite occurs as blebs and disseminations, in fractures, veinlets and micro-veinlets, as well as in occasional breccias and vugs with calcite. High-grade copper mineralization (>1.0% Cu) is confined to chalcopyrite vein systems. High-grade mineralization can extend several metres from the vein structure. Low-grade copper mineralization (0.10% to 0.50% Cu) is generally associated with the SLD-IMH contact. Drilling on the Ajax property has shown that mineralization extends to depths exceeding 700 m, widths exceeding 1,000 m and has a strike length exceeding 2,000 m.
Sulphide mineralization at Ajax also consists of pyrite and molybdenite. Pyrite is ubiquitous, occurring with chalcopyrite but also peripherally to the copper mineralization. Molybdenite is occasionally observed in SLD and SVHYB units, associated with potassium feldspar ± carbonate veins. Tetrahedrite has also been observed in trace amounts. Secondary copper oxides bornite and chalcocite occur infrequently.
Very minor amounts of the copper oxides malachite and azurite occur near surface. Native copper has also been observed locally.
As albite alteration was a precursor to mineralization, not all altered areas are mineralized. Where albitization is intense and texturally destructive, typically no copper mineralization is present. Intense albitization is interpreted to have rendered the SLD impermeable to mineralized fluids.
There are three copper mineralization/albite relationships:
- High-grade copper with weak to moderate albitization
- Low-grade copper with high albitization
- Barren copper with high albitization.
Gold mineralization is common and has a significant correlation with copper, but is very finegrained and visible gold has not been observed in the core. Gold mineralization increases slightly in areas where strong albite alteration occurs (Wardrop, 2009). It is common for gold concentrations to be directly correlated with copper concentrations. It is infrequent for gold mineralization to occur without associated copper; however, in areas of moderate to strong potassium feldspar alteration, this can occur. Variable gold-copper ratios throughout the deposit suggest a series of pulses of gold-copper mineralization were emplaced. Spatial distribution of copper-gold ratios has pointed to at least three phases of mineralization in the Ajax West Pit but possibly only one in the Ajax East Pit (Bond, 1988). In addition, northwest trending faults seem to be offsetting copper mineralization and concentrating gold, possibly due to later remobilization along structures.
Minor palladium mineralization is associated with copper near the contacts of the IMH and SLD units (Wardrop, 2009). Minor amounts of silver have also been found.