The 7,000-tonnes/day LaRonde mine and processing complex has produced over 6 million ounces of gold as well as valuable by-products. The mine still has 2.9 million ounces of gold in proven and probable mineral reserves (15 million tonnes grading 6.02 grams of gold per tonne) as of December 31, 2019.
LaRonde achieved commercial production of its deep extension (that is, below level 245) in November 2011, where most of its ore is now mined. LaRonde currently has a mine life lasting through to 2029.
Geology
The LaRonde property is located in the southern portion of the Archean-age Abitibi volcanic belt, within the Bousquet Formation of the Blake River Group of volcanic rocks. The LaRonde deposits occur at the eastern end of the east-west-trending Doyon-Bousquet-LaRonde mining camp, which includes the Mouska, Doyon, Bousquet 1 and Bousquet 2 gold deposits. The most important regional structure is the Cadillac-Larder Lake fault zone, located approximately 2 km south of the LaRonde property. The LaRonde deposit is a gold-rich volcanogenic massive sulphide deposit. LaRonde lenses were formed mainly by sulphide precipitation from hydrothermal fluids on the seafloor and by replacement below lenses. The stacking of the LaRonde lenses is the result of successive volcanic events, intercalated by cycles of hydrothermal activity associated with reactivation of synvolcanic faults.
Mineralization
Gold-copper and zinc-silver mineralization occurs in the form of massive and disseminated sulphide lenses. The presence of silver and base metals adds considerably to the value of LaRonde’s gold ore, reducing the total cash cost to produce each ounce of gold on a by-product basis. Five different mineralized horizons are known to exist adjacent to the Penna Shaft. The zinc-silver mineralization with lower gold values, common in the upper mine, grades into gold-copper mineralization within the lower mine. The predominant base metal sulphides are chalcopyrite (copper) and sphalerite (zinc).
Zone 20 North contains the majority of the mineral reserves and mineral resources at the LaRonde mine. The Company believes that Zone 20 North is one of the largest gold-bearing massive sulphide mineralized zones in the world and one of the largest known mineralized zones in the Abitibi region of Ontario and Quebec.
Mining
Access to LaRonde’s underground mining operation is through the 2.2-km-deep Penna Shaft, the deepest single-lift shaft in the Western Hemisphere. The LaRonde mine extension (“LaRonde 3”) allows access to even deeper ore at the lower part of the orebody. Two mining methods are used at LaRonde: longitudinal retreat with cemented rock or paste backfill; and transverse open stoping with cemented rock backfill, paste or unconsolidated backfill. In addition, to address concerns regarding the frequency and intensity of seismic events encountered at the lower levels of the LaRonde mine, a hybrid of these two methods has been used.
The risk of more frequent and larger seismic events has increased as the Company mines deeper at LaRonde. Over the years, the Company continued to adapt and manage the risk. The Company continues to adjust the mining methods, ground support and protocols to address seismic activity in the deeper portions of the mine.
Following the successful deployment of the LTE network at LZ5, an LTE network was deployed at the LaRonde mine below level 269 in late 2018. Extension of the network in the ramp area from level 269 to surface and at LaRonde 3 was carried out in 2019. The LTE network will facilitate the integration of automation technologies currently being tested at LZ5, which are expected to allow the Company to maintain similar historical productivity levels at LaRonde 3.
Infrastructure continues to be developed to provide further access to mine LaRonde 3 and construction of the level 308 East mine cooling plant is ongoing. Development continues on the access ramp to LaRonde 11-3. Production activities could potentially begin at this zone in 2022.
Processing
Ore is processed at the LaRonde mineral processing complex, which includes copper and zinc flotation as well as precious metals recovery and refining. The processing plant produces doré bars containing gold and silver, as well as zinc and copper concentrates that carry valuable gold and silver credits.
The plant has a daily capacity of 7,000 tonnes of ore and has been expanded four times since it opened in 1988. In addition, a dedicated 2,000-tonnes/day carbon-in-leach processing facility has treated ore trucked from the adjacent LZ5 mine and refined its concentrates into doré bars. This plant formerly treated ore from the now closed Lapa mine.
The LaRonde plant also treats concentrate pulp trucked from the Goldex mill. The material is sent to the LaRonde leaching/carbon-in-pulp circuit for gold recovery along with LaRonde residual pulp.
In 2019, the Company was granted a revision to the Certificate of Authorization at the LaRonde Complex, which allowed for the processing of ore from LZ5 through the LaRonde mill circuit. As a result, the Company will report the operational parameters from both LZ5 and LaRonde on a combined basis starting in 2020.
Exploration
Exploration work at the LaRonde mine is focused on conversion drilling in the LaRonde 3 project below 3,100 m depth. The LaRonde 3 mineral reserves and indicated mineral resources currently extend to approximately 3,380 m depth, while the inferred mineral resources continue to down to 3,800 m.
Below approximately 2.8 km depth, the LaRonde mine divides into two parallel lobes called the "East mine" and the slightly offset "West mine". New high-grade gold drill intersections in the West mine area in 2019 support and improve the geological model, and are expected to result in conversion of inferred mineral resources to indicated mineral resources in the western portion of the LaRonde 3 project.