Osisko Metals has reported results from an independent preliminary economic assessment (PEA) of its Pine Point zinc-lead project near the town of Hay River in the Northwest Territories, Canada. Osisko Executive Chairman and CEO Robert Ware said, “The proposed mine plan would produce more than 450 million lb of zinc in its peak year and an annual average of nearly 330 million lb of zinc and 145 million lb of lead over its estimated 10-year mine life.
“On a zinc-only basis, Pine Point could potentially, if it entered into production, become a low-cost zinc-lead producer ranking fourth largest in the Americas and ninth in the world, yielding an exceptionally clean and high-grade zinc concentrate.
“Furthermore, the concurrent release of an updated 2020 mineral resource estimate for Pine Point demonstrates that continued drilling will improve the classification of the resources and potentially yield further expansion of known deposits. With several deposits open, I am particularly excited to continue exploring and expanding the resource base across the project. We strongly believe in the Pine Point project, and Osisko Metals will continue developing this asset within the context of improving global zinc markets.”
Osisko President and COO Jeff Hussey added, “The current PEA concept is a large-scale, 11,250-metric-ton-per-day (mt/d) operation, where the mineral resource mined would be sourced mainly from small, near-surface open pits, with additional contributions from eight high-grade, shallow deposits mined by underground methods. The PEA considers historical data from the Cominco Ltd. era and incorporates significant technological improvements in the mining industry since the closure of the Pine Point operation in 1988.”
The open-pit mineral resource inventory used in the current life-of-mine plan is contained in 47 open pits over a strike length of 50 km and is mainly located above 125-meter (m) depth from surface. Most of the deposits are characterized by multiple shallow tabular panels dipping approximately 2° to 5° to the west.
The open-pit mining method incorporates 5-m benches in mineralized material, 10-m benches in waste, and an overall open-pit wall angle of 45°. Mineral resources will be extracted using a fleet of long-haul trucks with payloads of 90 mt. The production rate will vary between 8,000 mt/d and 11,250 mt/d. The strip ratio is expected to average 5.2:1.
Underground operations will use 45-mt haul trucks with ramp access to produce at a rate of 4,000 mt/d in the project’s West zone and 1,500 mt/d in its Central Zone. Mining methods will be a mixture of long-hole stoping (80%) and room-and-pillar (20%). All mineral resources will be transported to a central concentrator located adjacent to the existing electrical substation. Additional power will be supplied by LNG fueled generators.
The Pine Point processing flowsheet includes a three-stage crushing circuit incorporating an XRT-based mineral-sorting system that will reject 40% of waste material on average. The mineral sorter concentrate will be blended with the crushing circuit fines to feed 6,700 mt/d to a ball mill, followed by conventional lead and zinc flotation circuits. The process plant will produce on average 168 mt/d of lead concentrate at 62% Pb and 687 mt/d of zinc concentrate at 58% Zn.
Overall zinc and lead recoveries, inclusive of sorting, are expected to be approximately 87% and 93%, respectively, over the life of the mine. The flotation concentrates will be filtered and trucked to Hay River for transloading into rail cars for shipment.
Concentrates will be sent by rail to North American smelters and further afield to Asian smelters by bulk sea freight.
Flotation tailings will be thickened and pumped for disposal within mined-out pits.
The Pine Point PEA was prepared by Osisko in collaboration with independent engineering firms BBA Inc., WSP Canada Inc., and Tetra Tech.
Going forward, value trade-off studies will be performed to determine the best overall processing and dewatering methods, mining schedules, and infrastructure to further optimize Pine Point operations, leading to increasingly attractive economics to be included in an eventual feasibility study.
This work will include resource expansion laterally along open-pit-constrained boundaries; 3D hydrogeological and groundwater modelling to optimize dewatering management plans; metallurgical testing and material-sorting efficiency options to further optimize recoveries and increase the sorted coarse material fraction; geotechnical testing to potentially reduce open-pit wall angles and strip ratios; and incorporation of automation to reduce camp and personnel requirements.