THE LEADER VOLUME 19 • NUMBER 7
Detour Lake mulls underground move
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Agnico Eagle is evaluating the potential for Detour Lake in Ontario , Canada , to become a million ounce per year gold operation after the completion of a recent slew of studies .
The 2024 Life of Mine plan builds on the company ’ s previously filed technical report on Detour Lake as well as the mine plan update released by the company in July 2022 . It updates the open-pit mine production profile and incorporates updated costing . The company has also completed a preliminary economic assessment ( PEA ) which contemplates the concurrent operation of the open pit and a proposed underground mining project , combined with mill throughput optimisation to 29 Mt / y . The 2024 PEA demonstrates that the Underground Project and the mill optimisation have the potential to increase the Detour Lake mine ’ s overall production to an average of approximately 1 Moz / y of gold over a 14-year period , starting in 2030 . The current open-pit operation produced 677,446 oz of gold in 2023 .
The 2024 PEA assumes an underground mining rate of approximately 11,200 t / d starting in 2030 , combined with a mill expansion to 79,450 t / d starting in 2028 . Annual production is expected to increase by approximately 43 %, or 300,000 oz / y of gold , from 2030 to 2043 . The PEA extends Detour Lake ’ s mine life by two years to 2054 , with the company saying it believes that there is a good upside potential for additional exploration to add ounces to the mine plan in future years , which could result in an increase in production in the period between 2044 and 2054 or extend the life of the mine . The preliminary mining concept for the Underground Project is based on transverse longhole open stoping , as this mining method is best suited for the sub-vertical mineral deposit . Sublevels will be 40 m apart , with the stope size averaging approximately 30,000 t . Primary stopes will be backfilled with cemented paste fill , while secondary stopes will be backfilled with either cemented paste fill or waste rock fill according to the sequence and waste material available . Approximately 130 stopes will be mined annually to sustain a mining rate of approximately 11,200 t / d ( equivalent to an annualised production rate of 4 Mt / y ).
The Underground Project is expected to use a combination of conventional and automated equipment , similar to the company ’ s Odyssey mine at the Canadian Malartic complex in Quebec . Ore and waste handling will be conducted by LHDs and trucks with a capacity of 21 t and 60 t , respectively . The ore handling system to surface will consist of ore passes , an underground jaw crusher located at level 760 and a conveyor system with a capacity of 15,000 t / d . The conveyor will be installed in a dedicated conveyor ramp , with the portal located near the primary crusher on surface , east of the open pit . A service ramp , with the portal located near the west end of the open pit , will be the main underground access for the workforce , equipment and materials .
Production could begin as early as 2030 and ramp up to the designed rate of 11,200 t / d by 2033 , which is expected to be sustained throughout the mine life until 2044 .
The Detour Lake processing facility consists of two independent milling circuits , including gravity separation , concentrate leach , agitated tank leaching , carbon-in-pulp , solvent extraction and electrowinning . Over the last four years , the processing plant has undergone significant modifications to de-bottleneck existing circuits and improve throughput while maintaining recovery and reliability . The 2024 PEA contemplates that underground ore will be blended with the open-pit ore and processed through the existing plant .
Through investments in the crushing and grinding circuits and continuous improvement efforts , the mill throughput rate has increased from approximately 62,900 t / d in 2020 to approximately 69,700 t / d in 2023 and is expected to reach 76,700 t / d by the end of 2024 . The company believes that further process optimisation can be achieved with minimal investment to reach a mill throughput rate of 79,450 t / d by 2028 .
The main initiatives to realise this potential include the implementation of advanced process control systems to optimise circuit charge , mass flow balance and recovery ; further improvements to the crushing and grinding circuits , including the implementation of variable frequency drives for the secondary crushers and pebble crushers and redesigned SAG discharge screens ; and further optimisation to the maintenance practices and improved mill runtime . An investment of approximately $ 12 million is included in the 2024 PEA to execute these initiatives .
Ammar Al-Joundi , Agnico Eagle ’ s President and Chief Executive Officer , said : “ At Detour Lake , the company continues to build on the unique potential of this world-class asset . With the development of an underground mine to complement the existing open-pit mine , we see the opportunity to transform the asset into one of the top five gold mines in the world by output . We believe the Underground Project has relatively low execution risk , and has the potential to generate a strong risk-adjusted return on capital while maintaining exploration and production upside for decades in one of the best mining jurisdictions in the world .”
He adds : “ We have adopted a phased and disciplined approach to develop this potential , with the approval of a $ 100 million investment over the next three years to further study and de-risk the Underground Project , including the development of an exploration ramp ( 2 km ) and the collection of a bulk sample .”
Daniel Gleeson Editor daniel @ im-mining . com
JULY 2024 | International Mining 3