The mine is located in an area with well-developed infrastructure and is accessible by paved roads. Fosterville’s ore is processed at the Fosterville mill which has a capacity of 2,275 tonnes per day.
With the completion in February 2022 of the merger between Agnico Eagle and Kirkland Lake Gold, the Fosterville mine ranks as the Company’s lowest cost operation with total cash costs anticipated to be US$457 per ounce gold in 2023 on production of 305,000 ounces of gold.
Gold was first discovered in the Fosterville area in 1894 with mining activity continuing until 1903. Aside from a minor tailings retreatment in the 1930s, the field lay dormant until 1988. Between 1988 and 2001, a total of 240,000 ounces of gold were poured from heap leaching ore derived from shallow oxide open pits. The present-day Fosterville mine started underground mining operations in 2005 and, during its initial years, produced gold from near-surface, low-grade mineralization.
In 2015, high-grade visible-gold mineralization was intersected at depth, leading to the discovery of the Eagle Zone and, in 2016, the ultra-high-grade Swan Zone. The discovery of these zones, particularly Swan, significantly improved mine's overall mineral reserve grade, production profile and unit-cost performance. In 2016, exploration work found similar visible-gold mineralization in the Harrier zone. Additional exploration progress in early 2017 resulted in a new mineral reserve and mineral resource estimate for the operation being released in June 2017 that more than doubled underground mineral reserves.
With continued exploration success over the remainder of 2017, another mineral reserve and mineral resource estimate was released in December 2017 that saw mineral reserves rise another 65% from the June 2017 estimate. Continued drilling in the Lower Phoenix system during 2018 resulted in another significant increase in the Fosterville mine mineral reserves to 2.72 million ounces at an average grade of 31.0 g/t gold.
As of December 31, 2022 at the Fosterville mine, proven mineral reserves were 453,000 ounces of gold (608,000 tonnes grading 23.19 g/t gold) and probable mineral reserves were 1.2 million ounces of gold (6.0 million tonnes grading 6.39 g/t gold). Measured mineral resources totalled 125,000 ounces of gold (1.1 million tonnes grading 3.67 g/t gold), indicated mineral resources totalled 1.6 million ounces of gold (9.7 million tonnes grading 5.18 g/t gold, and inferred mineral resources totalled 1.2 million ounces of gold (5.6 million tonnes grading 6.53 g/t gold).
The above mineral reserves and mineral resources include the Robbins Hill deposit, a new gold system identified approximately 4.0 km north of the existing Fosterville mine.
Geology and Mineralization
The Fosterville Goldfield is located within the Bendigo Structural Zone in the Lachlan Fold Belt. The deposit is hosted by an interbedded turbidite sequence of sandstones, siltstones and shales. This sequence has been metamorphosed to sub-greenschist facies and folded into a set of upright, open to closed folds.
Mineralization at Fosterville is controlled by late brittle faulting. These faults are generally steeply west-dipping reverse faults with a series of moderately west-dipping reverse splay faults formed in the footwall of the main fault. There are also moderately east-dipping faults which have become more significant footwall to the anticlinal offsets along the west dipping faults. Primary gold mineralization occurs as disseminated arsenopyrite and pyrite forming as a selvage to veins in a quartz-carbonate veinlet stockwork. The mineralization is structurally controlled with high-grade zones localized by the geometric relationship between bedding and faulting. Mineralized shoots are typically 4 to 15 metres thick, 50 to 150 metres up/down dip and 300 to 1,500 metres down plunge, and have average grades of 5 to 10 g/t gold, with individual assays up to 60 g/t gold.
Primary gold at Fosterville also occurs as visible gold that variably overprints sulphide mineralization and is found as disseminated fine specks of gold within host quartz veins. The visible gold is spatially associated with antimony mineralization in the form of stibnite that occurs with quartz and varies from replacement and infill of earlier quartz-carbonate stockwork veins, to massive stibnite-only veins of up to 0.5 metres in width. The stibnite-quartz event occurs in favourable structural locations, such as the Phoenix, Eagle and Lower Phoenix structures.
The occurrence of visible gold is becoming increasingly significant at depth and is observed more frequently below approximately 800 metres depth, down-plunge within the Lower Phoenix and Harrier gold systems.
In the Lower Phoenix system, the high-grade Eagle Zone is 0.5 to 6 metres in width, 50 to 80 metres in dip length and has a down-plunge extent of 700 metres while the Swan Zone — currently the highest-grade mineralized zone at Fosterville — is 2 to 5 metres in width, dips west and is presently defined over a 275-metre strike and a 200-metre vertical extent. The Eagle and Swan zones remain open down-plunge for potential mineral-resource expansion.
Mining
Mining activities at Fosterville are currently focused on the Central, Phoenix and Harrier underground ore zones. All areas are extracted using open stoping techniques with the application of Cemented Rock Fill where practical. Selection of the specific mining method within the open stoping regime is based upon previous experience at the Fosterville mine and expectations of ore zone geometry and geotechnical conditions. In 2020, work on a twin exploration drive, capable of supporting production activities, commenced to connect the existing Fosterville mine to Robbins Hill, which is expected to be established as a second mining operation to feed the Fosterville mill over the next few years. The twin drive was completed in 2022.
Underground mining is conducted using a conventional fleet including jumbos, production drills, loaders, trucks and ancillary equipment. Open Cut (open pit) mining (when required) is conducted using a conventional fleet including excavators and trucks with a contract mining fleet and workforce.
Processing
The processing path for the ore involves crushing and grinding followed by flotation, bacterial oxidation and CIL circuits. The modern sulphide treatment plant is one of the world’s leading BIOX systems and has achieved record recoveries. In addition, a gravity gold recovery circuit was installed in 2016.
Fosterville commenced production in April of 2005 and produced its one millionth ounce of gold in December 2015.
In March 2023, Fosterville celebrated producing its 4 millionth ounce of gold.
Exploration
The Fosterville property includes approximately 1,400 sq. km of additional land package with numerous brownfield and greenfield exploration targets that are a key aspect of the Company's ongoing exploration efforts. Exploration programs to date have traced only 20 km of potential gold bearing structures, highlighting the exceptional exploration potential of this premier gold district.
In 2021, Kirkland Lake Gold carried out an $80.5 million exploration program at Fosterville, including development of a twin exploration drive from the Fosterville mine to Robbins Hill. Key exploration results in 2021 included the intersection of high-grade quartz with visible gold 500 metres further down-plunge from the Swan Zone in Lower Phoenix, in a series of splay structures sub-parallel to Swan Zone at Cygnet, and 1,000 metres down-plunge from the deepest mineral reserves at Robbins Hill.
Exploration activities in 2022 at Fosterville totaled 154,917 metres and continued to expand the mineral reserves and mineral resources as the deposit remains open at depth in the Harrier, Lower Phoenix and Robbins Hill areas.
At the Fosterville mine in 2023, the Company expects to spend approximately $20.8 million for 105,300 metres of capitalized drilling and the development of exploration drifts to replace mineral reserve depletion and to add mineral resources in the Cygnet, Lower Phoenix and Robbins Hill areas. Another $4.4 million is budgeted for 11,300 metres of underground and surface expensed exploration with the aim of discovering additional high-grade mineralization at Fosterville.
An additional $1.3 million is budgeted for regional exploration on properties surrounding the Fosterville mine.
Based on current exploration results, the Company's long-term goal for Fosterville is to establish the mine as a long-life asset through the successful replacement of mineral reserves. The Company believes there is potential to discover additional high-grade zones that could potentially support higher production levels and improvements in unit costs.