This report documents a mineral reserve update at the Gibraltar Mine, supported by increased long-term metal prices and an updated mine plan.
Report context
The Gibraltar open pit mine and related facilities are located 65 km north of Williams Lake, British Columbia, Canada. This technical report, with an effective date of March 15, 2022 and a report date of March 30, 2022, documents an increase to the mineral reserves at the Gibraltar Mine. The increase is supported by increased long-term copper and molybdenum prices and an updated long-range mine plan. The reserve update incorporates updated capital and operating cost estimates, additional resource drilling, and demonstrated operating performance. All costs are in Canadian dollars and units are imperial unless stated otherwise. The Gibraltar Mine property consists of 32 mining leases covering 2,275 hectares, 215 mineral claims covering 21,425 hectares, and 5 optioned claims covering 2,888 hectares. The mine is held in an unincorporated joint venture between Gibraltar Mines Ltd. (75%) and Cariboo Copper Corporation (25%).
Processing route
Sulphide ore processing
Sulphide ore from the Gibraltar deposits has been processed on-site since 1972. The processing facilities consist of two separate bulk sulphide concentrators operating in parallel at a combined design rate of 85,000 tons per day. Run of mine ore is fed to primary crushing, with the product reporting to a closed circuit SAG/ball comminution stage. Ground ore is processed through a rougher flotation stage. Tailings from the rougher flotation stage are pumped to a Tailings Storage Facility, while the concentrate is reground and upgraded through two further cleaner flotation stages. Final bulk concentrate contains both copper and molybdenum values.
The bulk concentrate from both facilities is combined and processed through a single molybdenum flotation plant. The bulk concentrate is floated in a rougher stage which depresses the copper minerals and selectively recovers molybdenum. The underflow from this plant is the site's final copper concentrate, which is dewatered and shipped in bulk to market. The rougher concentrate is reground and upgraded through two further cleaner flotation stages. Molybdenum final concentrate is dewatered and bagged, then shipped to market.
Oxide ore processing
Run of mine oxide ore has been leached since 1986. Oxide ore from the mine is delivered to oxide leach dumps. The SX/EW plant is designed to extract copper from the pregnant leach solutions (PLS) collected from the site's leach dumps. Acidic solution passes through the leach dump and extracts copper in the form of copper ions in the PLS. This copper-laden solution is delivered to the SX/EW plant via collection ditches, ponds, and pumping where required. The process takes PLS and selectively extracts the copper ions in solvent extraction mixer-settlers. Copper is transferred from the acid solution to an organic phase and finally to a clean electrolyte. The electrolyte is filtered and heated before passing through electrowinning cells where copper is plated onto stainless steel cathodes. The resultant high-quality cathode copper is bundled and sold to market. The barren solution (raffinate) leaving the plant is pumped back to leach additional copper from the oxide leach dumps.
Historical design and operating data
Taseko increased design mill capacity to 55,000 tons per day in 2011 through upgrades to the concentrator, and again to 85,000 tons per day in 2013 through installation of a complete independent second bulk concentrator with a stand-alone Molybdenum Separation Plant. The second bulk concentrator circuit has a nameplate capacity of 30,000 tons per day and consists of a 34-foot diameter SAG mill, a 20-foot diameter ball mill, rougher flotation tank cells, a regrind circuit, and a two-stage cleaner circuit. The Molybdenum Separation Plant processes the bulk concentrate produced in both concentrators and produces separate molybdenum and copper concentrates via a four-stage differential flotation process.
The total production from restart in 2004 to December 31, 2021 was 369 million tons milled, producing 1,711 million pounds of copper in concentrate, 18 million pounds of cathode copper, and 25 million pounds of molybdenum. Total production since 1972 is 705 million tons of ore, producing 3,575 million pounds of copper in concentrate, 102 million pounds of cathode copper, and 44 million pounds of molybdenum.
Testwork
Metallurgical testing associated with the Extension Zone returned results consistent with the larger ore body. The basis for predictions of copper concentrate flotation recovery is plant performance data from both existing concentrators based on sulphide and oxide content. Molybdenum recovery predictions are informed by historic test work and molybdenum plant production data. Predictions of copper cathode produced from heap leaching and subsequent solvent extraction are based on an economic assessment of recoverable copper using a kinetic leach curve and the oxide ore release schedule from the mine plan.
Key reported parameters
| Parameter | Design | Historical Operating | Testwork |
|---|---|---|---|
| Combined concentrator design capacity | 85,000 tons per day | , | , |
| Copper recovery (sulphide flotation) | , | 85% average over operating period of reserves | , |
| Molybdenum recovery (overall) | , | 50% predicted for remaining reserves | Informed by historic test work and plant production data |
| Oxide copper recovery (heap leach to cathode) | , | ~50% of placed oxide copper mass | Based on kinetic leach curve |
| Copper concentrate grade (nominal) | , | 28.5% Cu | , |
| Molybdenum concentrate grade (nominal) | , | 48% Mo, 3.0% Cu | , |
| Copper cathode purity (nominal) | , | 99.9%+ Cu | , |
| Annual average copper production | , | ~129 million pounds | , |
| Annual average molybdenum production | , | ~2.3 million pounds | , |
| Average strip ratio | , | 2.4:1 | , |
| Reserve mine life | 23 years | , | , |
| Average mining rate | 104 million tons per year | , | , |
Project website: https://www.tasekomines.com/properties/gibraltar-mine/
Technical qualifications
The mineral reserves referred to in this report are contained within zones which have been significantly mined, with the exception of the Extension Zone. The Qualified Person has direct knowledge of the Gibraltar mine site, having been employed by Taseko Mines since July 2018, and has visited the site on numerous occasions. The Qualified Person supervised the preparation of this report, reviewed the methods used to determine grade and tonnage in the geological model, and reviewed the long-range mine plan and capital and operating cost estimates. For the purposes of this report, the author relied on title and property ownership obtained from the Mineral Titles Online system as of March 15, 2022. Except for the purposes legislated under provincial securities laws, any use of this report by any third party is at that party's sole risk.
Source: Technical Report on the Mineral Reserve Update at the Gibraltar Mine, British Columbia, Canada, effective date March 15, 2022, report date March 30, 2022. Sections 1 (Summary), 6 (History), 13 (Mineral Processing and Metallurgical Testing), 16 (Mining Method), and 17 (Recovery Method).
