Overview
Stage | Production |
Mine Type | Underground |
Commodities |
|
Mining Method |
- Longhole stoping
- Transverse open stoping
- Longitudinal retreat
- Paste backfill
|
Processing |
- Carbon re-activation kiln
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
|
Mine Life | 14 years (as of Jan 1, 2021) |
World’s sixth highest grade gold mine. |
Latest News | Alamos Gold Provides Notice of Completion of Annual Filings March 30, 2022 |
Source:
p. 16
Alamos holds 100% of all mining titles related to the Island Gold property, which comprises approximately 15,000 ha.
Deposit Type
- Vein / narrow vein
- Orogenic
Summary:
The Island Gold Property is located in the Michipicoten Greenstone Belt (“MGB”) which is part of the Wawa Subprovince within the Archaean Superior Province.
A major regional deformation zone called the Goudreau Lake Deformation Zone (“GLDZ”) is situated throughout the area at the interface of the Wawa and Catfish Assemblage cycles. It is a north-easterly trending structure which has been traced along strike for 30 km with a width of 4.5 km and believed to be the main control of gold mineralization for the Project area. It is a high angle oblique-slip fault zone with an overall dextral movement cutting stratigraphy at a shallow angle.
There are three main splays to the GLDZ in the area, the southernmost of which hosts the Island Gold Mine structure which contains a stacked sequence of east-northeast striking, steeply dipping, and subparallel zones of gold mineralization.
The Island Gold Mine is an Archean orogenic lode gold deposit. It is a structurally hosted quartzcarbonate vein system situated within the Goudreau Lake Deformation Zone (“GLDZ”), a major regional brittle-ductile structure. The host terrane is a sequence of felsic to intermediate volcanic rocks of the Wawa Assemblage which are in the greenschist metamorphic range as is common for this type of deposit. High strain zones associated with the GLDZ have the tendency to develop at variable scales along lithologic unit contacts where complex geology and related competency contrasts can control stress patterns and facilitate shearing and the consequent development of dilatancy zones and concomitant quartz carbonate vein formation. It is generally accepted that these Archean orogenic lode gold deposits are related to compressional and transpressional tectonics and the associated metamorphic dewatering and devolatization of magma processes from which the gold bearing fluids are derived.
Gold mineralization in the Goudreau-Lochalsh area is not restricted to any rock type with the general exception of the late intruding north-west trending Matachewan diabase dykes which show no evidence of mineralization. Deposits may be hosted by one or several rock types, with past-producing mines and numerous other gold occurrences in the area exhibiting a close spatial association with felsic, intermediate, and even mafic intrusive rocks. East of the Island Gold Mine, in Jacobson Township, the past producing Edwards and Cline Lake gold mines are associated with felsic intrusive complexes and dykes. The past producing Magino Mine to the immediate west of the Island Gold property is hosted by the Webb Lake stock, a trondhjemite intrusive. The past producing Kremzar Mine, located on the Island Gold property, is hosted by a regional gabbroic sill.
Mineralization in the Goudreau Camp occurs along a 30 kilometre strike length of the GLDZ which transects the Island Gold property area in a roughly east-west direction. The GLDZ is a major regional deformation structure and it is believed to be the main control on gold mineralization for the area. The GLDZ and subsidiary splays have been subdivided into four structural domains (Southern, Northern, Eastern and Western) based on the style of deformation, lineation patterns, and the orientation and sense of shear displacement on sets of shear zones. The Island Gold mine mineralized zones are within the Southern domain of the GLDZ (Heather and Arias 1992). Most mineralization in this domain is hosted by quartz veining and/or shear zones with an orientation of 075°. The zones with this orientation are roughly parallel with the overall deformation zone and are considered to have formed along shear planes related to the dextral oblique slip movement of the GLDZ.
Typical alteration mineralogy associated with gold deposits of the Goudreau Camp includes variable amounts of carbonatization (Fe-carbonate ± calcite), silicification, sulphidization, biotitization, sericitization, feldspathization, and chloritization. Deposits and gold occurrences with a felsic rock association are generally associated with a quartz-sericite-pyrite ± pyrrhotite alteration package. Deposits and occurrences hosted by mafic host rocks, such as the Kremzar Mine and the historic showings along this trend are generally altered to biotite, Fe-carbonate, pyrrhotite ± pyrite, quartz, and minor K-feldspar. Chloritization is common throughout the belt. Gold presence in the Goudreau-Lochalsh area is primarily associated quartz stringers, fracture fillings and veins. Gold can be associated with pyrite disseminated in alteration envelopes but generally only in low grade levels.
Mining Methods
- Longhole stoping
- Transverse open stoping
- Longitudinal retreat
- Paste backfill
Summary:
The Island Gold deposit is accessed via a single decline from surface down to the 425 Level, at which point multiple ramps are utilized to access the main IG, IG West, Extension and East zones. These ramps are also connected at numerous points throughout the mine allowing for easy travel between mining zones.
The LOM plan includes the addition of a mine shaft which will be constructed between 2021 and 2025. Once commissioned, the shaft will be utilized to hoist ore and waste from the 1305 Level to surface. Additionally, the shaft will used to transport personnel and materials to any of the three shaft stations. From the shaft collar location ore and waste will be trucked to either the mill or the surface waste stockpile.
Level accesses are typically developed at 20 m intervals (floor to floor) and are designed south of internal ramps providing access to the footwall of the deposit. Once the ore is reached, sills are developed along the ore contact, with their direction controlled by geology. Sill development is used as a drilling, mucking and backfilling platform for stope extraction. On some levels, additional footwall and cross-cut development is required when the width of the mineralization exceeds 10 metres.
The mining method for a particular stope is selected based on a variety of factors such as overall geometry of the mineralization, width of the ore zone, local stresses, mapping and geotechnical data, spatial location of the stope, and existing nearby development and infrastructure. Other factors considered include equipment size and limitations as well as available fill type. Ultimately, each stope is evaluated individually, and a stope package is produced to include detailed drilling plans, blast letters, ventilation, and gas check instructions, mucking plans as well as backfilling directives.
Longhole Open Stoping
The predominant mining method used at the Island Gold mine is longhole open stoping. This mining method is conducive to tabular, steeply dipping orebodies and is considered to be highly productive with low mining costs. The average dip of the orebody at Island Gold ranges from 75 to 85 degrees, making this a favorable mining method for ore extraction.
There are two types of longhole stoping methods utilized at Island Gold: longitudinal open stoping and transverse open stoping. These two methods employ the same mining principles mentioned above; however, they differ by the stope’s mining direction. Longitudinal stopes are mined along the strike of the ore vein and follow either a modified Avoca technique or a traditional blast hole stoping technique, whereas transverse stopes are mined perpendicular to the vein.
Longitudinal Open Stoping
Stopes are typically mined longitudinally when the ore width is narrow (usually under 10 m). For every first stope on a horizontal sublevel, a primary slot raise is drilled at the extremity of the ore contact. This raise is drilled using an in-the-hole (ITH) drill with a large reaming head that produces a large diameter hole. This large hole is used as a free face for the first blast. The stope is then fired towards the open void in several blasts (2-3 typically) which is achieved by retreating longitudinally towards the main level access (retreat is done in east/west direction). The broken ore is extracted after each blast is taken to ensure ample void for the following blast. Once the stope is empty, UCF, CRF or paste fill is placed in the void to fill the opened excavation.
Transverse Open Stoping
Stopes are typically mined transversely when the ore width is too wide to mine efficiently and safely using a longitudinal retreat method. Island Gold employs transversal mining where the mining direction runs perpendicular to the strike of the orebody (North/South). Stope mucking is done via multiple draw points that allow for line-of-sight mucking from the remote stand which optimizes mucking productivity. Furthermore, this method allows for production holes to be drilled parallel to the hanging wall and footwall and only requires fanning into the vertical stope ends which are inherently more stable. Each block is split into different panels employing a true primary/secondary sequence. This mining method requires the use of a raise as initial void for blasting. This raise is typically designed in line with the drawpoint, which facilitates mucking as the material is blasted towards the drawpoint. Once the stope has been blasted and emptied, the void must be backfilled with UCF, CRF or paste fill. The primary stopes require a consolidated fill that creates solid end walls to withstand the blast energy while extracting adjacent stopes. The secondary stopes can be filled with UCF if there is no remnant mineralization nearby. One advantage of this method is it allows concurrent activities to take place on a single level improving mining cycle times.
Backfill
Island Gold is currently using two types of backfill methods: unconsolidated rock fill (UCF) and cemented rock fill (CRF) with the addition of paste fill planned as part of the Phase III Expansion plan. Both USC and CRF fill methods are dumped from the top cut of a stope by an LHD. In the event of a hanging wall failure, a Rammer Jammer is employed to “ram” (push) muck tighter against the hanging wall to fill the voids.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Jaw crusher
|
|
18' x 54'
|
|
1
|
Cone crusher
|
|
|
200 HP
|
1
|
Ball mill
|
|
9' x 11'
|
500 HP
|
2
|
Summary:
Crushing
The ore from the mine is stockpiled. A haul truck transports ore from the stockpile to a grizzly. A primary conveyor conveys the material to the coarse ore bin. A vibrating feeder feeds the coarse ore to the jaw crusher, the crusher discharge falls onto the screen feed conveyor. The crushed ore is screened and the oversize goes to the cone crusher to be reduced and goes back to the screen feed conveyor. The undersize of the screen is conveyed to the fine ore bin by conveyors.
Grinding Circuit
The crushed ore is sent to the primary ball mill where it discharges to the primary ball mill discharge pump box. The pulp is pumped to the cyclone to be classified; the underflow is split between the primary ball mill and the regrind ball mill. The regrind discharge is send to the primary ball mill discharge pump box. The cyclone overflow is sent to a static trash screen and pumped to the thickener. Cyanide is added to the primary ball mill discharge pump box to start the leaching reaction in the grinding circuit.
Processing
- Carbon re-activation kiln
- Agitated tank (VAT) leaching
- Carbon in pulp (CIP)
- Elution
- Solvent Extraction & Electrowinning
- Cyanide (reagent)
Flow Sheet:
Summary:
The Island Gold Mine ore is processed at the Kremzar Mill. The mill is composed of a two-stage crushing section followed by a two-stage grinding section. The mill uses cyanide leaching and a carbon-in-pulp process to recover gold. Some improvements were made to the plant in recent years such as replacement of crushers, cyclone replacement, and piping and pumping upgrades.
Thickening, Leaching, CIP
The pulp from the thickener underflow is pumped to the leaching tanks train where five leaching tanks are supplied with compressed air. The pulp is directed to a vibrating trash screen prior to the CIP circuit where carbon is added to CIP tanks to adsorb the gold in solution.
Tailings
The tailings from the CIP circuit are collected in a pump box and pumped to the tailings pond. Water from the tailings pond is pumped back to the plant to be reused as reclaim, gland seal and process water.
Acid Wash, Elution & Regeneration
When the gold adsorbed ........

Recoveries & Grades:
Commodity | Parameter | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
Gold
|
Recovery Rate, %
| ......  | ......  | ......  | 96 | 97 | 96.5 | 96.8 |
Gold
|
Head Grade, g/t
| ......  | ......  | ......  | 9.2 | 9.36 | 9.02 | 7.31 |
Production:
Commodity | Units | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Gold
|
koz
| ...... ^ | ......  | ......  | ......  | 106 | 99 | 83 |
All production numbers are expressed as metal in doré.
^ Guidance / Forecast.
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Operational Metrics:
Metrics | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 |
Ore tonnes mined
| ......  | ......  | 380,266 t | 344,336 t | 374,962 t | 318,045 t |
Daily milling rate
| ......  | ......  | 1,099 t | 1,013 t | 928 t | 814 t |
Daily ore mining rate
| ......  | ......  | 1,042 t | 943 t | 1,027 t | 869 t |
Tonnes processed
| ......  | ......  | 401,276 t | 369,767 t | 338,603 t | 297,757 t |
Total tonnes mined
| ......  | ......  | | | | 650,417 t |
Waste
| ......  | ......  | | | | 332,372 t |
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Reserves at December 31, 2021:
Mineral Reserves Cut-off - 2.89-4.22 g/t Au.
Mineral Resources Cut-off - 4.0 g/t Au.
Category | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
834 kt
|
Gold
|
9.33 g/t
|
250 koz
|
Probable
|
3,278 kt
|
Gold
|
10.33 g/t
|
1,088 koz
|
Proven & Probable
|
4,112 kt
|
Gold
|
10.12 g/t
|
1,338 koz
|
Measured
|
20 kt
|
Gold
|
4.92 g/t
|
3 koz
|
Indicated
|
1,076 kt
|
Gold
|
8.18 g/t
|
283 koz
|
Measured & Indicated
|
1,096 kt
|
Gold
|
8.12 g/t
|
286 koz
|
Inferred
|
7,906 kt
|
Gold
|
13.59 g/t
|
3,454 koz
|
Corporate Filings & Presentations:
- Subscription is required.
News:
News | Date |
Alamos Gold Provides Notice of Completion of Annual Filings
|
March 30, 2022
|
Alamos Gold Reports Fourth Quarter and Year-End 2021 Results
|
February 23, 2022
|
Alamos Gold Reports Mineral Reserves and Resources for the Year-Ended 2021
|
February 22, 2022
|
Alamos Gold Extends High-Grade Gold Mineralization 300 Metres Down-Plunge from Mineral Resources in Island Gold East
|
November 11, 2021
|
Alamos Gold Reports Best Hole Drilled to Date at Island Gold (71.21 g/t Au (39.24 g/t cut) over 21.33 m true width), Extending High-Grade Gold Mineralization Down-Plunge from Existing Mineral Resources
|
June 15, 2021
|
Alamos Gold Reports Mineral Reserves and Resources for the Year-Ended 2020
|
February 23, 2021
|
Alamos Gold Extends High-Grade Gold Mineralization Laterally and Down-Plunge at Island Gold
|
January 27, 2021
|
Alamos Gold Reports Best Surface Exploration Hole to Date at Island Gold with High-Grade Gold Mineralization Intersected across Significantly Greater Widths Down-Plunge...
|
September 17, 2020
|
Alamos Gold Reports Additional High-Grade Intercepts Beyond Existing Mineral Resources Across Multiple Areas of Focus at Island Gold
|
July 13, 2020
|
Alamos Gold Announces 14 Day Suspension of Operations at Island Gold and Provides Update on Other COVID-19 Measures
|
March 24, 2020
|
Alamos Gold Continues to Intersect High-Grade Mineralization in New Area of Focus Between Eastern and Main Extensions at Island Gold
|
June 10, 2019
|
Alamos Gold Receives Phase II Expansion Permit for Island Gold
|
May 28, 2019
|
Alamos Gold Intersects High-Grade Mineralization in New Area of Focus Between Eastern and Main Extensions at Island Gold
|
May 9, 2019
|
Alamos Gold Reports Additional High-Grade Intercepts at Island Gold Including Best Surface Directional Intersection to Date within Western Extension
|
January 10, 2019
|
Alamos Gold Completes Acquisition of Richmont Mines
|
November 23, 2017
|
Aerial view:
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