The main Corner Bay vein is a north/south striking, dipping 75 degrees to the west vein, hosted within a strike/slip shear zone. The Corner Bay deposit is considered to be the first economically significant copper discovery on the south flank of the Lac Doré complex. Twenty-six years of exploration, mainly by Corner Bay Exploration Ltd., resulted in the discovery of the Corner Bay deposit in 1982 by a joint venture between Corner Bay Exploration Ltd. and Rio Algom Inc. In 1995, the property was acquired by MSV Resources Inc. (MSV) whom subsequently merged with Campbell Resources that carried out several exploration drilling programs up to 2008.
An initial Mineral Resource estimate was prepared in 2006. In 2008, an underground bulk sample program was initiated and approximately 40,000 t was collected, trucked and milled at the Copper Rand concentrator with a copper recovery of 94.04%.
The 2017/2018 drilling program expanded known areas and identified additional resources and new targets. The main vein at Corner Bay was drilled in two locations: 1) at depth around hole CB-95-02 and, 2) under the dyke at approximately 800 meters depth on the southern side of the main vein’s strike where three good historical high-grade intercepts occurred. Both programs confirmed the continuation of the mineralization with the results from the second area being standout with all 8 intercepts intersecting economic mineralization.
The mineralization is focused within the main shear zone and the chalcopyrite ore along with other sulfides (Po & Py) exhibit replacement textures. Quartz veins are also present within the shear zones and seem to be syn-mineralization as they overprint the textures within the shear but are sometimes also replaced by the sulfides. The veins themselves do not seem to have an effect on mineralization as they do not host the sulfides exclusively but are present as part of the mineralized package.
Chalcopyrite content ranges from 5% where it occurs interstitially between clasts and along veinlets to around 90% as massive sulfides in several discreet zones.
Alteration extends up to 10 m away from the ore zone and comprises sericite and chlorite, the alteration is represented by slight bleaching of the host anorthosite and gradually dissipates away from the shear zone just as the shearing fabric.
Because of the strike/slip movement along the main fault that hosts the mineralization, the open space created by jogs along the structure is vertical in nature, which enabled the formation of ore chutes that are very steeply dipping to sub-vertical. This is currently confirmed by the grade distribution in the upper part of the vein where drilling is most dense.
There is the occurrence of other veins in the Corner Bay District and the focus of the company is to increase the resources at the Main vein but also to define economic parallel structures.
Cedar Bay is a set of extensional shear veins that formed perpendicular to and from the displacement along the Lac Doré fault. The parallel zones are located north-west of the Lac Doré fault striking 130 degrees and have a sub-vertical dip.
Cedar Bay was mined to the 2,200-foot level during operations from 1958 to 1990 with a total of 3.8 million tonnes mined at a grade of 1.63% Cu and 3.1 g/t Au. The majority of the ore mined was from the main zone and the north-easternmost parallel structure of the 10-20 zone up to a depth of 2,200 feet where the mineralization pinched in. There is a shaft descending to the 3,400-foot level. More recent exploration has identified a high-gold grade area in the 10-20 zone at approximately the same level as the bottom of the shaft. The goal of the 2018 program was to follow up on that high-grade area.
The drilling identified the potential of the Main vein but more importantly confirmed high-grade intercepts in the 10-20 zone. These areas are open in various directions.
There were exceptional intercepts in the most recent program such as 2.4 meters @ 1.7% Cu and 19.5 g/t Au, and 2.1 meters @ 4.5% Cu and 15.4 g/t Au.
The structural setting is very similar to other deposits along the Lac Doré fault which have been historically mined. There is very little shearing along the main mineralized normal fault structure, but the ore chutes are currently interpreted as shallow plunging along strike. In this deposit pinching of the veins at a depth of 2,200 feet occurred and now it is evident that the veins re-emerged at depth, however, with much higher gold grades.
The mineralization comprises sulfides such as Po, Py, and Cpy which occur as veinlets and as massive sulfide zones. Alteration is mostly sericite and chlorite and is proximal to the mineralized structures. The gold occurs within the same structures that host the sulfides but is most likely related to a later orogenic overprint.
Drilling here will focus on extending the parallel zones down dip and along strike, as well as identifying new deep parallel zones (such as the extension of the historical mined “Main Zone”).
Copper Rand was the principal source of ore for Campbell Mines when it terminated operations. Historically it was also the biggest source of ore from the Lac Doré camp. The current resources are in two areas: the CR5000 zone and the Hanging Wall zone. The majority and higher-grade resources are in the CR5000 zone and these are the resources that Doré Copper could target in a latter year of a restart scenario.
The CR5000 project was started by MSV in 1997 and then completed after the merger with Campbell in 2001. The ore from the CR5000 zone is accessed from Shaft 4 which descends to the 3,980-foot level and then accessed via a 1,500-meter 16o decline. During the last few years of the Copper Rand operation, very little exploration work was done due to the company’s financial position as there was sufficient ore for years of operation ahead of the mine. The CR5000 zone is still open at depth and along strike, however, due to its depth, there are no plans or additional exploration until mining returns to Copper Rand.
Copper Rand is hosted in the same style mineralized system as Cedar Bay but lies on the southeastern side of the Lac Doré fault. It was formed by the same processes with movement along the Lac Doré fault creating perpendicular down dropped extension faults which host the mineralization. The depth potential of these structures is several kilometres vertically so the Copper Rand mineralization has large potential below the current resources, as most deposits around the camp.
The Lac Doré deposit was accessed with a double ramp by Westminer in the late 80s and early 90s. The deposit is shallow and located close to the Copper Rand mill. Upon commencing mining, they found the structures to be heavily faulted in two directions and the ore lenses were discontinuous resulting in higher cost and less ore than originally thought. Limited drilling immediately beneath the known resources at approximately 400 meters depth, did not result in the identification of additional ore. Since the majority of the value of Lac Doré is in gold and not in copper, Westminer decided to mothball the operation.
The NNE faults that off-set the ore at the Lac Doré deposit continue on into Copper Rand but only affect the upper portion of the mine and are lesser in their magnitude. The deeper portions of the Lac Doré deposit could be unaffected or less displaced, as the depth potential of these deposits exceeds 1.5 km, and there is a lot of room for more economic ore at Lac Doré down dip. Historically it has been noted that the deposits formed from the Lac Doré fault have a high-grade core near the intersection with the Lac Doré fault. This area has been poorly explored previously and may hold large quantities of economic ore, as other similar deposits in the area (Cedar Bay & Copper Rand).
The mineralization here is the same as at Cedar Bay (off-set along the Lac Doré fault) and hence high-grade gold ore can be expected to occur in lenses down to at least 1 km below the surface.
Due to its location under the lake, this will likely have to be a winter drilling target from the ice to explore this deposit at depth and a possible high-grade zone plunging along the Lac Doré fault as has been historically posited.
The Devlin deposit is a flat-lying (horizontal) magmatic massive sulfide deposit close, <100 m, to surface. It differs from the other deposits around the area because it is hosted within the Chibougamau pluton itself. The other deposits are all hosted within the surrounding anorthosite. The magmatic fluids most likely exploited a plane of weakness within the pluton and the ore was emplaced. A bulk sample was taken in the 1980s so ramp access already exists. Devlin’s exploration potential relies on the possibility of identifying a feeder system and off-set lenses under the lake. Three deeper holes down to 700 meters have been drilled and another deeper parallel system was not intercepted. The feeder structure is likely to be one of the main NE trending faults (Lac Doré parallel) and could be very similar to the Henderson mines in the north of the property which are hosted within these main structures.
Doré Copper’s subsidiary CBAY Minerals owns 50% of Gwillim. The other 50% is owned by Argonaut Gold. Doré Copper is the operator.
The Gwillim mine operated between 1974 and 1976 and again from 1980 to 1984. In total 245,245 short tons were mined at a grade of 0.142 oz/t Au (4.86 g/t Au) and 0.06% Cu. In 1987 two high-grade intercepts were drilled by the then operator Greenstone Resources at moderate depths of 200 to 300 meters at the KOD zone (300 m south of the mined Main zone). The intercepts were 7 meters at 33 g/t Au and 7.9 meters at 17.9 g/t Au. A further 25 holes were drilled from the surface before a ramp was developed and the zone was further explored from underground in 1988 but not mined (some development through ore). In 1989 three more surface holes were drilled to depths of 400 m with one failing to hit the east plunging ore zone because of deviation. Greenstone did not follow-up afterwards as they went ahead and built gold mines in Central America.
The mineralization here is hosted in quartz-carbonate veins with limited amounts of massive sulfides. The ore is mainly gold with trace amounts of copper which points to a different style of mineralization than Cedar Bay for example. There are two vein zones identified parallel to each other <50 m apart with the mineralization predominantly occurring in the northernmost vein. The structure is oriented E-W which sets it apart from the main deposits in the camp and because of its unique structural nature not as much is known about it compared to other deposits which can be tied into a similar structural system.
The KOD zone was only briefly explored before being abandoned but presents a very high potential zone that is not very deep and already has ramp access.
A report from 1989 outlines the last calculated resource for the KOD zone as 216,000 tons at 0.334 oz/t Au – which roughly equals 70,000 oz. This is considered historical in nature and not 43-101 compliant.
Further drilling will focus on defining the limits of the ore up-dip and down-dip, as well as extending it along plunge to the east.
The Hematite Bay Gold Zone is located at the northern end of Portage Island and presents a sub vertical semi massive sulfide vein. Six holes were drilled in the 1950s with 4 intersecting copper-gold with best intersections of 4.5 m at 0.32% Cu and 7.8 g/t Au.
Further exploration work will be focused on defining a more continuous economic vein by drilling below current intercepts (<150 m) and constraining it along strike.
Growing Mineral Resources
The Shaft 3 zone, known as the Merrill East zone at the time of the CBAY acquisition, contains a historical resource of 411,000 short tons with a copper grade of 2.2%. This is not considered 43-101 compliant. It is located on the westernmost edge of the Lac Doré land package.
It is a similar deposit to Cedar Bay and the likes along the Lac Doré fault. A steep dipping extensional shear vein with massive sulfide and carbonate mineralization striking approximately 130 degrees.
The potential at Shaft 3 lies mostly at depth below the known/mined resources as most deposits in the camp have depth extensions to almost 1km and several beyond.
The Baie du Commencement area was first drilled in a 1956 program. Baie du commencement is located on the Western side of Portage Island. Of the 7 exploration drill holes, 2 intersected sub-vertical quartz veins containing high copper and gold grades: 6.85% Cu, 3.48 oz/t Au, 0.4 oz/t Ag & 0.32% Co over 1.5 ft. & 3.90% Cu, 3.25 oz/t Au, 0.34 oz/t Ag and 2.16 % Co over 1 ft.
Shallow hole programs were also done by Westminer in 1991, with 13 holes, and by MSV in 2003/2004 with 6 holes. Westminer’s results were promising in that they encountered narrow but high-grade gold intersections.
NUINSCO’s work at the Baie du Commencement in 2013 totaled 4 holes for 582 m and appears to have traced the primary quartz-carbonate vein to depths beyond 100 m from the surface, and to have confirmed the interpreted plunge direction of the very prospective structure. Results were described as somewhat disappointing in terms of the grades encountered, but quite encouraging in demonstrating the probability that the structure will persist to significant depth and extend eastward based upon observed widths and the intensity of alteration present. They also stated that over 35 holes from historic drilling were never sent for assay (possibly because of a lack of visible thick mineralization) which adds to the potential of the zone in areas previously drilled.
The BDC vein is currently interpreted to be related to the McKenzie vein to the NE near the past producing Portage Mine. They are of very similar grades and mineralization styles. They could be one and the same vein on either end of a structural jog of a NE major structure, the jog being the largest displacement zone of the off-set fault underneath lake Portage.
The Jaculet Mine produced gold and copper in the 60’s and 70’s from surface to 1,200 feet. However, development potential is present as the Jaculet deposit is suspected to be the offset extension of the prolific Copper Rand shear along the Lac Doré fault.
The mineralization at Jaculet is typical of the Lac Doré deposits comprising massive sulfides (Py, Cpy, Po), but also has smaller amounts of galena, sphalerite, and magnetite, with veins dipping steeply or sub-vertically. The similarities continue with the deposit hosted in several parallel vein/ore zones just like at Cedar Bay and Copper Rand. Discovery of new parallel zones could multiply the potential of the deposit.
The mineralization here has the same potential as Cedar Bay, Lac Doré, and Copper Rand to be mineralized down to 5 000 ft or more. A MegaTEM survey was conducted over the area and may help identify ore at the main or parallel zones when the results are processed.