Geology and Mineral Resources

Eastmain Gold Project > Geology and Mineral Resources

Geological Setting

The property is located in the South branch of the Upper Eastmain River Greenstone Belt. The UERGB extends east-west for 100 km and varies from 2.5km in width on the west side to 10km in width on the east. The greenstone belt consists of several mafic to felsic metavolcanics and metasedimentary rock cycles surrounded and / or intruded by granite and granite gneiss. Widespread rock geochemical anomalies nickel-copper, nickel chromium, copper-zinc and gold suggest that these rocks are highly prospective for both gold and nickel-copper-platinum deposits similar to those found elsewhere in Canada and Western Australia. On a regional scale, the area of Northern Quebec north of Chibougamau includes multiple greenstone belt hosted gold deposits, including several new discoveries since 2019 (see figure 1)

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Figure 1 – Selected Greenstone belt hosted gold deposits in Northern Quebec and Ontario

The Eastmain property

The Eastmain Mine property is located on a Southern branch of the Greenstone Belt that is broadly Northwest striking (figure 2). Gold occurs in mineralized quartz veins with massive to semi massive sulphide lenses, veins and silicified zones. The mineralized zones are 3 to 10m wide and contained in strongly deformed and altered Mine Series assemblage of felsic, mafic and ultramafic rocks. The Eastmain deposit currently consists of three gold-rich zones known as the, “A”, “B” and “C” Zones, of which the A and B zones have been traced for over 1km in length and are found at surface to a vertical depth of 400m. These three zones strike southeast and dip and plunge to the northeast at 45dg to 50dg .

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Figure 2 – The local geological setting of the Eastmain mine

Mineralization

The deposit occurs as massive sulfide lenses, stringers, veins and disseminated sulphides in quartz veins and strongly deformed and altered rocks. The veins and lenses are between 10cm and 13m wide, with up to 15 to 20% sulphide content. In order of decreasing abundance, sulphides consist of pyrrhotite, pyrite and chalcopyrite with traces of magnetite, sphalerite and molybdenite. Visible gold occurs in mineralized quartz veins as small (<1 mm) grains associated with quartz and / or sulphides in the A, B and C zones. Mineralized quartz veins range from massive to banded or brecciated with a sulphide-rich matrix. The veins are parallel to the main foliation, are commonly folded and are boudinaged. Within the Mine Series and more rarely in the hanging wall, gold mineralization dominantly occurs in an associated deformed and recrystallized silicified and sericitized unit identified historically as a chert layer, containing massive to semi massive sulphide lenses and veins.

 

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Mineralisation typical of the mine horizon from Zone B. This photograph shows a semi-massive vein consisting mostly of pyrrhotite with minor pyrite and chalcopyrite within a deformed quartz vein and silicified rocks. Patches and stringers of sulphides are visible.  This intersection yielded 29.3 g/t Au, 16.56 g/t Ag between 218 and 219 metres as part of a 7-meter intersection averaging 10 g/t Au.

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Mine horizon mineralisation from hole EM-17-120. Again, more small veins and  stringers of pyrrhotite and chalcopyrite are visible within a deformed quartz vein and silicified rock.  This sample yielded 20 g/t Au, 36.5 g/t Ag and 1.17 % Cu between 154.5 and 155.5 as part of a mineralized intersection that yielded 14 g/t over 2 metres.

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Grab sample taken from an ore stockpile. This grab yielded 79.42 g/t Au, and is believed to have originally been mined from Zone A or B.  Visible in the image are semi massive sulphides with large pyrrhotite crystals (40% sulphides) along with chalcopyrite (5% sulphides) and pyrite (5%). Also observable is biotite alteration, and the presence of quartz veining with patchy sulphides and dissemination. 

Geological Model

Genetic models for the Eastmain Gold Deposit have ranged from a synvolcanic and stratabound deposit hosted in a recrystallized chert horizon (Boldy et. al. 1984) to an epigenetic, orogenic deposit that is structurally controlled in a silicified shear zone (e.g. Tourigny, 1989). Recent geological work and research has led to a preferred syngenetic model although there is no doubt that it has been extremely deformed. The Eastmain Gold Deposit is a copper-gold-silver, sulphide-rich deposit consisting of three high-grade, gold-rich zones known as the “A,” “B” and “C” Zones. Eastmain Resource’s exploration focus at Eastmain Mine was on the expansion of known Mineral Resources in the three zones and around the historic mine infrastructure and discovery of additional deposits along a regional 10 km long Mine Trend. Previous exploration of the Property confirmed surface copper-gold-silver mineralization in rocks and soils within the key mine horizon extending four km northwest from the Eastmain Mine Gold Deposit to the Julien, Hillhouse, Suzanna and Michel Targets. These well-defined targets present Eastmain Mine Gold Copper metal signature rock outcrops within the extension of the Mine Trend and along secondary parallel units within the Mine Series.

Mineral Resource

On the 24th May 2023 Benz Mining released an Updated Independent Mineral Resource Estimate (MRE) in accordance with NI 43-101 guidelines defined on Eastmain Project at a 2.5 g/t Au cut-off:

Classification Tonnes (M) Au (g/t) Au (koz)
Indicated 1.3 9.0 384
Inferred 3.8 5.1 621

Note: rounding errors apply

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The Eastmain core shack

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Core racks from historical drill campaigns under previous operators