The Portage Island concessions are part of Doré Copper’s larger property that encompasses the Copper Rand and Cedar Bay deposits (past producing mines) and the Copper Rand mill. It covers part of the Lac Dore Complex, a stratified complex of intrusive rocks, composed principally of meta-anorthosites and meta-gabbro. See surface location map below.
Within the Portage Island concessions are three of Chibougamau mining camp’s most productive former mines:
|Portage mine (1959-1997): 6.2 Mt at 1.77% Cu and 3.91 g/t Au|
|Henderson I mine (1960-1971): 1.8 Mt at 2.23% Cu and 1.54 g/t Au|
|Henderson II mine (1960-1988): 6.5 Mt at 1.60% Cu and 1.41 g/t Au|
|Total ore extracted: 14.45 Mt at 1.73% Cu and 2.47 g/t Au|
Portage Island also hosts a number of the area’s most underexplored and prospective surface showings: McKenzie Vein, Baie du Commencement Zone and the Hematite Bay Gold Zone. Other zones which have also shown potential for economic mineralization include Hematite Bay and Magnetite North and South Zones.
Originally discovered in 1903, the McKenzie Vein is located just north of the Portage mine. It has all the characteristics of a typical shear-hosted Archean gold-quartz-tourmaline-sulphide vein. The vein was stripped over a length of 110 meters and interpreted to extend to 250 meters. The vein was never mined from surface due to the erratic nature of the veining and sulphide concentrations. It was mined from the 700 ft (213 meters) to the lowermost 3,600 ft (1,097 meters) level as part of the Portage orebody. The upper 213 meters of the vein remains sparsely explored. A few holes completed in the 1950s to a depth of 170 meters vertical returned encouraging values, including 1.8 meters at 1.2% Cu and 1.37 g/t Au (hole 107). The vein structure continues to the southwest across Portage Island, cut by a set of northeast faults.
The Baie du Commencement Zone is located on the southwest part of Portage Island. In 1956, seven drill holes tested the Baie du Commencement area with two holes intersecting quartz veins containing high copper and gold grades: 0.46 meter at 6.85% Cu and 119 g/t Au and 0.3 meter at 3.90% Cu and 111.4 g/t Au. Several drill programs afterwards were not successful in defining the zone. It is mentioned that much of the core collected between 1956 and 1963 (>35 holes) was never sent for lab analysis.
In 1991, 13 shallow holes were completed with five holes returning narrow high-grade gold values. This drilling defined an east-west structure over 450 meters in length dipping 35-55 degrees to the south with an interpreted plunge of 45 degrees easterly. In 2003-04, six holes totaling 1,660 meters were completed with no significant results. In 2013, four holes totaling 582 meters traced the primary quartz-carbonate vein to depths beyond 100 meters from surface and confirmed the interpreted plunge direction.
Within the main Hematite Bay area, located on the north side of Portage Island, there are several copper-bearing east-west zones dipping 50-75 degrees to the southeast (inferred from the 1950s drilling programs). Chalcopyrite, pyrite and local quartz-carbonate veinlets occur as lenses 30-60m long and 3-5 meter wide in a zone 240-365 meters long and up to 90 meters wide, extending west from the north side of Hematite Bay. Interpreted geology indicates that copper mineralization is found in the nose of a drag fold. An historical resource (non NI 43-101 compliant) of 363,000 tonnes at 2.01% Cu was reported by Patino Mining*.
*This estimate is considered to be historical in nature and should not be relied upon. A Qualified Person has not completed sufficient work to classify the historical estimate as a current mineral resource or mineral reserve. The Company is not treating the historical estimate as current mineral resources or mineral reserves.
This area is located just south of Hematite Bay and was drilled on a widely spaced pattern in 1956-57. Gold-copper mineralization was intersected in 4 of 6 holes with the best hole intersecting 4.5 meters at 0.228 g/t Au and 0.32% Cu (hole P120). The mineralization is associated with a structure traversing a known iron formation. Its extent is unknown and there has not been any other work completed in the area since the mid-50s drilling campaign.
Two parallel magnetite bodies outcrop on Portage Island. The magnetite occurs as disseminations and stringers in serpentinized pyroxenite. The North Zone extends for 1.5 kilometers with a maximum width of 150 meters. It strikes 80 degrees and dips 65 degrees to the north. The South Zone is 2.3 kilometers long, 90 to150 meters wide and has a strike of 65 degrees and dips 65 to 75 degrees to the north. Patino Mining reported an iron resource for both zones in 1966.
Source: Portage Island Properties Summary – Nuinsco Resource Ltd. & Ocean Partners by RadonEx Ltd. (April 2011).