Summary:
The Elder property is located in the southern part of the Abitibi subprovince, composed of volcanic rocks with zones of clastic sediments. The volcanic and sedimentary rock units are of Archean age and form alternating bands that generally run in an east to westerly direction. The Archean rocks of the Abitibi belt are cut by numerous post-metamorphic diabase dykes of Proterozoic age having variable widths (5 to 50 metres), they may be found as dyke swarms sometimes with extensions up to 100 km. Directions of these dykes vary from N-S to NE-SW with a sub-vertical dip. One of these dykes crosses the Elder property approximately 200 metres west of shaft No. 1.
The Elder gold deposit occurs within the south-eastern margin of the Flavrian Batholith. In the western part of the Elder mine, gold is mainly associated with the No. 1 vein where mineralization is found above, within and under an altered dioritic dyke, referred to as the "basic dyke" in the mine’s terminology, that cross-cuts the Flavrian Batholith at low angle. The basic dyke is extensive and it can reach widths along strike of up to 10 metres, although locally it is discontinuous and narrow. Between 1947 and 1966, most of the 2,024,420 tonnes of ore grading 5.33 g/t Au were mined from the No. 1 vein, outside of the basic dyke area.
The No. 1 vein strikes N 60° E at surface and about N 80° E on the 13th level and dips southward at an average angle of 25°. This is the dominant structural trend of the mine area and it is also seen in the attitude of the basic dyke as well as the No. 2, and 3 veins. Another structural trend observed in the mine is faulting trending north to NNW and dipping at a shallow angle to the east. The No. 4 vein, located in both the hanging wall and footwall of the No. 1 vein, follow this trend (340°N/28°E).
The alteration is stronger in the auriferous areas and extends up to 25 metres into the wall rock, being more pronounced in the footwall. The average sulphide content in the ore is only 1% and varies widely along the No. 1 vein. The amount of pyrite is closely related to gold enrichment.
The structure that hosts the No. 1 vein is filled with white to smoky quartz and pyrite, minor amounts of chalcopyrite, bornite, and hematite as well as traces of galena, molybdenite and telluride. The vein is notably consistent and carries economic gold values over two thirds of its length. By contrast, the other veins have a more erratic gold content. This would appear to be related to their lower degree of silicification, pyrite enrichment and alteration (Hinse, 2003). Although the No. 1 vein is generally a very consistent structure, the width of economic mineralization may vary from a few centimetres to 7.5 metres. The ore occurs in lenses that display a distinctive geometry with long axes plunging to the southwest at low angles. These lenses seem to be in "en echelon" pattern along the main controlling structure, possibly as rhythmic undulations along the shear plane.
Gold particles are very fine grained with 86.9% of them having a diameter lower than 0.03 mm and 47.4% a diameter lower than 0.01 mm. Their composition is quite pure since the average percentage of silver associated with gold is 10% in weight. The grains are generally associated with pyrite in altered wall rocks of the veins and within fragments enclosed in the veins. The majority of these gold grains (84%) are closely associated with pyrite surfaces or in inclusions within chlorite or carbonate bordering the pyrite grains (5%). Gaulin (1988) also mentioned that 16% of the observed gold grains are intimately related with plagioclases of the altered wall rocks and in the mafic dyke. Clusters of fractured, cataclastic and fine grained (< 2 mm) pyrite are more likely to contain gold. Magnetite, ilmenite and sphene are less abundant in unaltered wall rocks. These minerals were probably replaced by pyrite, rutile and hematite during the mineralizing events.
The origin of Archean gold deposits is a controversial subject. The three following models are generally proposed in the scientific literature:
1. Gold mineralization is associated with magmatic hydrothermal activities related to the crystallization of felsic magmas (Burrows and Spooner, 1984);
2. Gold mineralization is associated with metamorphism and the fluids originated from the dehydration of any rocks exposed to a deep seated transition between greenschist and amphibolite metamorphic facies (Kerrich and Fyfe, 1981); and
3. Gold, fluids and lithophile elements were liberated and concentrated in open structures located in the upper part of the crust during the crystallization of the lower part of the crust (Colvine et al., 1984).
Studies carried out by Gaulin (1988) on fluid inclusions and stable isotopes at the Elder mine are not corresponding with any of these models. Gaulin stated that two immiscible fluids were probably involved in the mineralizing process. The first fluid was introduced in open structures under oxidizing conditions (hematization) and it was progressively expulsed by the second metallic-rich fluid which was under reducing conditions (pyritization). The proposed model is in accordance with petrographic observations showing that carbonates were introduced later than early stage quartz veins in the mineralizing process.
Production
On August 1, 2022, the Company ceased operations at the Elder mine which was placed in care and maintenance mode.
| Commodity | Units | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 |
|
Gold
|
oz
| ....  | .... | .... | 15,067 | 15,380 | 13,405 |
All production numbers are expressed as metal in doré.