First Quantum Minerals Ltd (FQM) has filed an NI 43-101 Technical Report with an updated Mineral Resource estimate for the La Granja copper project. La Granja is located in northern Peru and is 55% owned by First Quantum and 45% by Rio Tinto.
“I am pleased to share this resource update on La Granja, highlighting the Project’s position as the second-largest greenfield copper resource in the world, with the potential to become a Tier 1, multi-generational copper mine. By working collaboratively with the surrounding community, our partner, Rio Tinto, and leveraging First Quantum’s core strengths in project development, we expect La Granja will add meaningful growth to our project pipeline,” said Tristan Pascall, Chief Executive Officer of First Quantum. “La Granja has the potential to become a significant new source of the copper supply required for the global energy transition.”
Katie Jackson, Chief Executive, Copper at Rio Tinto, said: “The updated Mineral Resource estimate further reinforces our increasingly positive view of La Granja’s significant long-term potential. While the project remains at an early stage and there is considerable work ahead, we are encouraged by the scale and quality of the resource and look forward to continuing to work with First Quantum to better understand the opportunity.”
La Granja is a large-scale copper porphyry-skarn-epithermal system with two adjacent mineralised domains at Paja Blanca and Mirador, both of which transition to porphyry-style mineralisation at depth. The updated Mineral Resource represents a substantial copper endowment, underpinned by improved geological confidence resulting from targeted drilling, detailed geological mapping and modelling, and geochemical test work to enhance spatial definition of the mineralised domains.
It includes approximately 4.831 billion tonnes of Measured and Indicated Resources at 0.48% copper, comprising 23 Mt of contained copper, and approximately 5.206 billion tonnes of Inferred Resources at 0.40% Cu, comprising an additional 20.7 Mt of contained copper (0.16% Cu cut‑off grade). The updated Mineral Resource estimate was prepared in accordance with NI 43-101 and the Canadian Institute of Mining, Metallurgy and Petroleum (CIM) Definition Standards.
The current concept envisages mineralised material being mined from the Paja Blanca and Mirador deposits at La Granja by conventional open-pit methods, with waste deposited in a storage facility located adjacent to the pit. Mineralisation will be crushed and milled at La Granja before being transported via tunnel to a flotation plant situated on a flat, dry, Pacific coastal plain approximately 100 km from the mine site.
Water supply for milling and mineralised material transportation would be sourced primarily from coastal desalinated water, supplemented by captured site contact water and tailings storage facility (TSF) decant return. Following conventional flotation, concentrate will be transported by truck to a port facility for export, with tailings deposited in a conventional TSF located adjacent to the flotation plant.
As the report is focused on the Mineral Resource, there is little additional detail on the proposed mining and processing methods. However, it does state: “The geometry, depth, and continuity of mineralisation at La Granja indicate that the deposit is amenable to conventional large-scale open pit mining. Alternative methods, including strip mining or underground-only approaches, are not considered appropriate at the current level of study given the deposit scale, geometry, and production rate requirements.”
The report adds: “Mining operations are expected to employ conventional open pit methods incorporating drill-and-blast, hydraulic or electric shovel loading, and off-highway truck haulage. This approach provides operational flexibility for continuous bench-scale mining while accommodating material blending and management of deleterious elements, including arsenic and zinc.”
The mining concept includes consideration of in-pit or near-pit primary crushing to reduce haulage distances and improve truck cycle efficiency, with haul road design incorporating straight segments to accommodate potential future trolley-assist infrastructure.
FQM is the most experienced trolley operator anywhere to the point where it has its own Quantum Electra-Haul system with which it has reduced fuel consumption on trucks from 650 l/h to 60 l/h and upped speeds on ramp to 22 km/h from 11 km/h. Its Kansanshi and Sentinel copper mines in Zambia today have 15 km of trolley lines between them but this is being increased significantly. FQM develops & maintains its own pantographs & mountings plus has perfected rapid trolley relocation. It has achieved results through a strong haul road maintenance focus plus having traffic light systems & zoned approaches to assist operators as much as possible.
In terms of processing, metallurgical testwork on representative mineralisation samples from across the deposit began at a conceptual level in 1997. From 2011, Rio Tinto expanded the program significantly, documenting results in an internal report dated 24 September 2014 entitled ‘Variability Flotation and Comminution Testing on La Granja Ore – Full Potential Case Study – Project P13039.’
Comminution and flotation testwork on two master composites, Skarn and Porphyry, established an
optimum grind of 80% passing 100 µm. Individual sample testwork defined an 80% confidence interval for SAG mill pinion energy requirements of 5.4 to 5.9 kWh/t, corresponding to a SAG mill power draw of 44.25 MW at a design throughput of 60 Mt/y (7,500 t/h). Softer mineralised material during the initial period of operation could reduce SAG mill power requirements significantly below this range.
Bond work index values ranged from 9.0 to 14.2 kWh/t, pointing to ball mill power requirements of 82.7 MW for a target grind of 80% passing 100 µm. These results support a comminution circuit comprising two SAG mills of 28 MW each and four ball mills of 22 MW each.
Rougher flotation testwork on 80 individual samples assessed variability across the deposit. Twenty of these samples and composites advanced to batch cleaner flotation, followed by four cleaner locked cycle tests, supporting the development of a geometallurgical model and the derivation of nine material types. At 15 minutes residence time, rougher and scavenger flotation of geometallurgical domain composites returned copper recoveries of 81% to 93% to rougher concentrates, averaging 88% across all 80 samples.
Mass pulls ranged from 14% to 22%. Many material types produced elevated arsenic or zinc grades in rougher concentrates, with only porphyry and primary sulphide domains yielding clean, low-impurity concentrates. Batch cleaner tests at pH 11 and a regrind of 80% passing 50 µm revealed significant copper losses during cleaning, driven by high mass pull in the roughers due to elevated pyrite levels, which caused high mass rejection in the cleaners and carry-over of fine copper minerals.
Four composites advanced to locked cycle testwork: three representing the dominant mineralisation styles and one representing a blend reflective of early production feed. All tests used a primary grind of 80% passing 94 µm and regrind sizes of 80% passing 52 to 73 µm, with rougher and scavenger flotation at pH 9.0 and cleaner flotation at pH 11.5.
Recycling cleaner tails between cleaner stages improved average copper recovery from 67.3% in batch
cleaning to 77.3% in locked cycle tests, without compromising concentrate grades. Bulk flotation of two
master composites (high and low pyrite content) using 4 kg and 14 kg samples respectively returned copper recoveries of 77.5% and 80.6% at concentrate grades of approximately 25% Cu.
Testwork data indicates potential for variable arsenic levels in final concentrates. The intended operating philosophy envisages two parallel mineralisation streams: one higher-arsenic and one lower-arsenic, with the mine plan optimised to supply these streams as required. Each stream would feed a dedicated parallel processing circuit, producing two final concentrates that would be filtered, stored separately, and blended prior to dispatch to maintain arsenic concentrations within smelter offtake limitations.
Blending with low impurity third-party concentrates presents an additional option to further reduce final arsenic levels. FQM is currently progressing work on arsenic recoveries and the direct separation of arsenic-bearing minerals, including enargite, from chalcopyrite and chalcocite, targeting a process to reduce bulk concentrate arsenic and minimise smelter penalties. Based on currently available smelter offtake parameters, arsenic penalties are not expected to be material to treatment economics.
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