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Gold ore in Red lake mines
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The Red Lake Mining is one of the largest gold mines in Canada and largest gold mines in the world. Located in the Red Lake Mining Division within the District of Kenora, northwestern Ontario this mine cover approximately 2335 hectares, the mine is comprised of the Red Lake Complex and the Campbell Complex one of the world’s most prolific gold districts and the mine has estimated reserves of 3.23 million oz of gold
Red Lake Mining is owned and operated by Goldcorp Inc, operations are situated in the eastern part of the Red Lake Greenstone Belt in the Birch-Uchi Lake Subprovince of the Superior Province, within the core of the Canadian Shield and In 2014 Red Lake mine yielding 414,400 ounces. Gold rush in Red lake was first began in 1926, resulted in the discovery and development of several reasonably successful, former producing mining operations (i.e. >10 years production, >200,000 oz produced)
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| Mine site geology for red lake mining |
The Red lake high grade zone is the backbone of the Red Lake mines operation, with an average grade of more than two ounces of gold per tonne. Mining from the High Grade Zone began in early 2000 and test milling in July. By year-end, full rated production was achieved with a small stockpile of several thousand tons of crushed ore remaining on surface. Since production restarted in 2000 the exploration to increase resources has focussed on the High Grade Zone (HGZ).
The mineralisation at Red Lake may be classified as an Archaean greenstone-hosted quartz carbonate vein deposit (GQCV).
The GQCV deposits correspond to structurally controlled complex epigenetic deposits characterized by simple to complex networks of gold-bearing, laminated quartz-carbonate fault–fill veins.
These typically occur in deformed basalts and ultramafic komatiite flows intruded by intermediate to felsic porphyry intrusions, and sometimes with swarms of albite and lamprophyre dykes.
These veins are hosted by moderately to steeply dipping, compressional brittle-ductile shear zones and faults, with locally associated shallow-dipping extensional veins and hydrothermal breccias.
Gold is largely confined to the quartz-carbonate vein network but may be present in significant amounts within iron-rich sulphidized wallrock selvages or within silicified and arsenopyrite rich replacement zones.
The diagnostic features of the greenstone-hosted quartz-carbonate vein type gold deposits are arrays and networks of fault and shear-zone related quartz-carbonate laminated fault-fill and extensional veins in associated carbonatized metamorphosed greenstone rocks.
The deposits are typically associated with large-scale (crustal) compressional faults. They have a significant vertical extent (~2kms), with very limited metallic zonation. They can coexist regionally with iron-formation hosted vein and disseminated deposits as well as with turbidite-hosted quartz-carbonate vein deposits.
Greenstone hosted quartz-carbonate vein deposits are one of the most significant sources of gold and account for more than 13% of all world gold. Of the 14 world class deposits of this type within Canada, 6 are found within the Abitibi greenstone belt and include Timmins, Kirkland Lake and Larder Lake within Ontario.
In general, there are three types of mineralisation zones encountered at the Red Lake Gold Mines, namely vein type ore, disseminated sulphide ore and replacement ore.
Structures at the mine exhibit three trends: conformable northwest, north-south and east-west.
The conformable structures are most common and are subparallel to the foliation. The vein systems follow these structures. Complex vein arrays are those which also include the north-south and east-west components. The arrays are most common near high angle mafic-ultramafic contacts.
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| Red lake gold mines ore zone |
The main mineralized zones at the Red Lake Complex Zones
The High Grade Zone at Red Lake Complex Zones occurs in such an environment where enhanced dilatency developed and was sustained over a long period of time. Its geometry will combine both conformable and complex vein arrays overprinted by replacement mineralisation.
The High Grade Zone (HGZ) in Red Lake gold mines consists of quartz-carbonate veins and breccia structures and arsenopyrite replacement mineralisation within altered basalts and altered ultramafic rocks. The alteration consists of chlorite, biotite, silica, carbonitization and minor actinolite.
The mineralisation is characterized by consistent distribution of both coarse and fine flecks of native gold, fine acicular arsenopyrite and pyrrhotite. Accessory mineralisation includes chalcopyrite and sphalerite.
Vein mineralisation has been dominant in the upper levels at the northwest end of the mine. With depth, vein dips become shallower and change in mineralogy from quartz-carbonate-arsenopyrite-pyrite to quartz-carbonate-pyrrhotite-arsenopyrite assemblages.
The main mineralized zones at the Red Lake Campbell Complex are
The A1 Zones is located on the hanging wall (HW) side of the central ultramafic rock unit, south of the shaft. The zone is approximately 1500 ft (460m) long and extends from surface to the 26 level (3850 ft). The type of mineral in this zone, foliation parallel type vein system which varies from 0.3 to 1m wide and consists of quartz and carbonate material with pyrite, pyrrhotite, arsenopyrite, and gold.
The AU Zone It consists of quartz lenses and pipes containing pyrite, pyrrhotite, arsenopyrite, gold, sphalerite, stibnite and fuchsite. This type of zone varies in length from 10 ft-250 ft (3m – 75m).
The B Zone consists of quartz and carbonate material with pyrite, pyrrhotite, sphalerite, cinnabar, fine arsenopyrite and gold, type vein system averaging 5.0 ft (1.5m) wide that extends up to 900 ft (275m)
The DC Zone is comprised of multiple stacked vein structures and localized high grade 10-20ft (3-6m) podiform structures. The structure is essentially quartz-carbonate veins with arsenopyrite replacement mineralisation. The alteration minerals consist of chlorite, biotite, silica, carbonitization and minor actinolite.
The F Zone is is located west of both shafts and south of the G Zone. It is bounded by the rhyolite to the west and intersects the central ultramafic unit in the east.
The F zone consists mainly of quartz with lesser amounts of quartz/carbonate and is mineralized with pyrite, pyrrhotite, sphalerite, stibnite, fuchsite, and gold, type vein system which varies from 1 to 3 ft (0.3 – 1m) wide and is approximately 1000 ft (300m) in length and extends from surface
The F2 Zone It consists mainly of quartz and quartz carbonate and is mineralized with pyrite, pyrrhotite, sphalerite, stibnite, fuchsite, and gold. The F2 Zone is a foliation parallel type vein system which varies from 1 to 3 ft (0.3 – 1m) wide. It is approximately 600 ft (180m) in length and extends from the 2 level to below the 27 level.
The G Zone is located north of both shafts at the contact of the basalt (andesite) and a nose in the north (ultramafic) unit. The zone consists of quartz and quartz/carbonate with silicified replacement sections overprinting the carbonates and is mineralized with heavy pyrite and pyrrhotite, arsenopyrite, sphalerite, stibnite, fuchsite, and gold. type vein system foliation oblique approximately 500 ft (150 m) long and varies from 10 to 70 ft (3m – 21m) wide. This zone extends from surface to 22 level and although the structure continues at depth the vein is uneconomic.
The H Zone is a series of foliation parallel veins which varies from 1 to 3 ft (0.3m – 1m) wide and is approximately 1400 ft (430m) in length. This zone extends from the 3 level to the 10 level and is open to depth. The zone consists mainly of quartz with lesser amounts of quartz carbonate and is mineralized with pyrite, pyrrhotite, arsenopyrite, and gold. The H Zone is located west of the G Zone and north of the Reid Shaft.
The L Zone is a complex series of foliation parallel to foliation oblique veins situated along a fold in the central komatiite-mafic contact, varying in length from 50 to 150 ft (15 – 45m) and striking northwest. The zone consists of quartz and quartz/carbonate with silicified replacement sections overprinting the carbonates and is mineralized with pyrite, pyrrhotite, arsenopyrite, sphalerite, stibnite, fuchsite, and gold.The main L Zone vein is approximately 300 ft (90m) in length and varies in width from 1 to 120 ft (0.3 to 35m) and extends from surface to the 22 level. Additional veins vary in length from 50-150 ft (15-45 m) and upto 10ft (3 m) wide
North L Zone is a foliation parallel vein structure similar to the A zone, 1-3 ft (0.3-1 m) in width and 200-300 ft (60-90 m) in strike length, extending from surface to 22 Level, where the gold grade becomes uneconomic.
The MM Zone is a sulphidic replacement-dominated mineralisation zone with a sulphide, quartz and silicate (biotite+/- amphibole) + magnetite assemblage mainly over-printing carbonate -altered metabasaltic hosts and less commonly in metasediments. It typically exhibits fewer carbonate and siliceous veins than other styles.
The N Zone extends from the 14 level to the 27 level and located west of the shaft between the L & P Zones. This zone is similar to the AU with half the ore in andesite and the other half in altered rock.The N Zone is a foliation parallel vein in the basalt and foliation oblique vein in the ultramafic rock and varies from 5 to 20 ft (1.5 - 6m) wide and 100 to 250 ft (30m to 75m) long.
The O Zone is located north of the shaft and the G zone and is developed on the 11 and 12 levels. The zone consists mainly of quartz/carbonate and is mineralized with pyrite, pyrrhotite, arsenopyrite, and gold. The O Zone is a foliation parallel type vein system which varies from 1 to-5 ft (0.3 – 1.5m) wide and approximately 350 ft (105m) long.
The P Zone is situated west of the shaft, south of the G Zone and west of a nose in the central ultramafic rock unit. The zone consists of quartz and quartz/carbonate with silicified replacement sections overprinting the carbonates and is mineralized with pyrite, pyrrhotite, arsenopyrite, sphalerite, stibnite, fuchsite, and gold. The P Zone has three main veins radiating west from the basalt-ultramafic contact. The P Zone is a combination of foliation parallel veins and foliation oblique type veins approximately 450 ft (140m) long which vary in width from 1 to 65 ft (0.3 – 20m), extending from the 18 level to the 27 level.
The TP Zone and PCB Zone are characterized by intense silicification, arsenopyrite, pyrite and/or pyrrhotite, and base metal sulphide mineralisation ranging from <5% total sulphides to semi-massive sulphides. These replacement type mineralised zones extend a thousand feet into the footwall of the 56, 56-1 vein structures, and the DC Zone to depth.
The 56 zone is a basalt hosted quartz-carbonate vein and is typically between 2 to 4 feet (0.6-1.3 m) wide. Auriferous mineralization may be present where strong silicification and sulphide mineralization (pyrite and pyrrhotite) occur with the vein
The 56-1 zone auriferous structure (hangingwall to the 56 vein) is hosted in both basalt and komatiite lithologies. Within the basalt the structure may consist of one ore more narrower mineralized
All this 56 zones are both horizontally and vertically extensive, striking for approximately 2000 feet (600 m) and extending vertically for 1800’ (550 m) veins, commonly 0.5 to 1.0 feet (0.15-0.3 m) wide. The structures are generally auriferous with both grade and width decreasing away from the basalt-komatiite contact. Ore grade mineralization is typically found proximal to the contact or within the komatiite unit. Within the komatiite, gold mineralization is found where strong carbonate and biotite alteration, and abundant veining is present. Ore mineralization is associated with strong silica replacement and suphide mineralization (predominantly aresenopyrite). Visible gold is common, with ore width commonly from 2’ to 4’ (0.6-1.3 m) wide, although widths of 6’ to 8’ (1.8- 2.3 m) aren’t uncommon.
Source : U.s. Securities and Exchange Commission
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