Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Open stoping
- Room-and-pillar
|
Processing |
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 4.25 years (as of Jan 1, 2019) |
Latest News | Abcourt Mines Inc.: All Share Purchase Warrants of 2018 Have Been Exercised December 29, 2020 |
Source:
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The Elder mine is owned 100% by Abcourt.
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.
Mining Methods
- Open stoping
- Room-and-pillar
Summary:
Veins generally have a dip angle of 22o and a 2-meter thickness.
The mine is serviced by 2 shafts and 16 levels. Shaft #1 is used for the ventilation of the mine and as an escape way. Shaft #2 is used for production. The distance between levels varies between 41 and 61 meters. Drifts (2.7 m x 2.8 m) give access to the mineralized zone. Then, drifts follow the zone to give access to stopping sites. On levels 3, 4 and 6, drifts will follow the mineralization over a distance of 240 meters.
Mining is done with the room and pillar method. The roof and part of the walls are secured with rock bolts and screen. With this method of mining, about 15% of the resources are left in pillars. Part of these pillars will be recovered at the end of the mine.
The width of rooms and the size of pillars were determined by a geotechnical study done by Golder Associates in 1986 and by an inspection in 2014.
A stope team is made up of two drillers, 2 scrapping operators and one mucker.
The monthly rate of production of Elder is about 8 000 to 11,000 tonnes. Our objective is to get 12,500 tonnes per month. The life of the mine, based on the existing measured and indicated resources, is 4.25 years. The eventual conversion of inferred resources into measured and indicated resources would add about 3.5 years for a total of 7.75 years. Several exploration targets that remain to be explored could increase these resources substantially.
In his preliminary economic study in 2012, Roche used a factor of 85% for the recovery of resources. We used the same factor.
In the mining operation, to be sure to extract all the mineralization, it is necessary to take some waste. If we take only 0.15 m above and below the ore in an 1.8 m face, we get 15% dilution. In addition, frequent changes of dip of the mineralization result in getting some uncontrolled dilution. We also have to adjust to variations of grade in veins. Blasts in sheared zones also produce unwanted overbreaks. All these factors combined account for an apparent 40% dilution. We give no grade to the dilution material.
However, Roche used only 20% of dilution with a grade of 0.69 g/t Au. The Roche estimate was made without the benefit of test mining, as the mine was flooded at that time.
Processing
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Carbon adsorption-desorption-recovery (ADR)
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
Among the assets that Abcourt has acquired, there is a mill (located at the Sleeping Giant mine) with a capacity of 700 to 750 tonnes of ore per day, or 250,000 tonnes per year. This capacity is adequate to treat the Elder and the Sleeping Giant production. The process is carbon in pulp.
Recoveries & Grades:
Commodity | Parameter | 2019 | 2018 | 2017 |
Gold
|
Recovery Rate, %
| ......  | ......  | ......  |
Gold
|
Head Grade, g/t
| 4.34 | 4.38 | |
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Reserves at May 31, 2018:
Category | Tonnage | Commodity | Grade | Contained Metal |
Measured
|
56,131 t
|
Gold
|
5.52 g/t
|
|
Indicated
|
409,695 t
|
Gold
|
6.57 g/t
|
|
Measured & Indicated
|
463,826 t
|
Gold
|
6.45 g/t
|
96,126 oz
|
Inferred
|
380,251 t
|
Gold
|
6.12 g/t
|
74,872 oz
|
Heavy Mobile Equipment as of November 12, 2012:
HME Type | Size | Quantity |
Drill
|
|
1
|
Jumbo
|
|
1
|
Scoop Tram
|
5 cu. yd
|
1
|
Truck (haul)
|
30 t
|
1
|
Mine Management:
Job Title | Name | Profile | Ref. Date |
.......................
|
.......................
|
|
Jun 8, 2020
|
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