Mount Polley is an alkalic porphyry copper-gold deposit. It lies in the tectono-stratigraphic Quesnel terrane or Quesnellia, which is characterized by a Middle Triassic to Early Jurassic assemblage of volcanic, sedimentary and plutonic rocks which formed in an island arc tectonic setting outboard of the ancestral North American continental margin. Quesnellia hosts several major porphyry copper deposits such as Highland Valley, Copper Mountain, AftonAjax, Gibraltar and Mount Milligan, all generated by early Mesozoic, calc-alkalic or alkalic arc magmatism.

In the Mount Polley region, the Triassic arc rocks are assigned to the Nicola Group and comprise alkalic basaltic to andesitic volcanics and sedimentary rocks, which are intruded by sub-volcanic stocks; all are overlain by post-Nicola, Early Jurassic clastic rocks and rare volcanics. Mount Polley itself is a complex of alkalic intermediate porphyritic intrusions and related magmatic-hydrothermal breccias. It was emplaced into the Nicola Group in the Late Triassic around 205 million years ago. The intrusive complex is about 6 km long (north-northwest) and 3 km wide, lying between Polley Lake in the east and Bootjack Lake in the west. The intrusions range from diorite (oldest) to monzonite (youngest) and are marginally undersaturated in silica. The Mount Polley Intrusive Complex is in the centre of the Mount Polley property; the remainder of the property is underlain mainly by Nicola Group volcanics and post-Nicola conglomerate, and small intrusions in which no economic mineralization has been found to date.

Mineralization in the Mount Polley Intrusive Complex (“MPIC”) is primarily hosted by irregular zones of hydrothermal breccia, which are closely related to the porphyry intrusions and were formed by magmatic devolatization processes. Mineralization and brecciation were accompanied by potassic or calc-potassic, albite, and magnetite alteration; the MPIC is bounded on most sides by propylitic country rocks. As in many alkalic porphyry systems, there is no single or simple zoned mineralization pattern, but instead a number of copper-gold zones of various size, shape and grade characteristics, distributed around the MPIC from the far north to the south. There is no clear structural control on the location of these mineralized breccia zones, although the greatest continuity and the bulk of the past and present resources occur in the centre of the MPIC (e.g. Springer, Cariboo, Bell zones) between two pre-mineral diorite intrusions. Dimensions of mineralized breccias in the MPIC range up to many hundred metres in length and width, such as in the Springer zone. Elsewhere, smaller zones (generally less than 100 m across) may form mineable bodies if grades and other factors are favourable. Post-mineral faulting probably did not disrupt the continuity of mineralized zones very significantly, except in the Northeast zone where deeper mineralization was offset along a fault a few hundred metres laterally and dropped vertically slightly.

In the deposits, the degree of brecciation and associated hydrothermal alteration is usually a reliable guide as to grade. There is relatively little post-mineralization dike dilution. Chalcopyrite is the dominant copper mineral, typically accompanied by pyrite; bornite is relatively uncommon in the centre of the MPIC. Here, copper sulfides occur as disseminations or veins and fracture coatings in brecciated intrusion, or they are disseminated in the matrix of breccias, in both cases precipitated along with alteration minerals. Mineralization has been traced by deep drilling in the Springer zone to a depth of around 900 m (from pre-mining surface).

In the north of the MPIC are much higher grade orebodies, namely the Northeast (mined in the Wight pit, 2005- 2009) and Boundary zones, where copper grades can reach several percent per tonne. Chalcopyrite and significant bornite form coarse-grained infill in breccias, and intense vein and microvein stockworks. As in the zones in the centre of the MPIC, gold and silver occur mainly as microscopic inclusions in the copper sulfides and in pyrite.

Exploration has always proceeded alongside mining at Mount Polley, leading to the expansion and deepening of known deposits, or to the discovery of new zones, or raising the status or resource category of marginal prospects, potentially towards feasibility for profitable mining. Geological and geotechnical logging of drill core is integrated with down-hole assay data and used with software for computation of the resource block model and mine design. In addition, exploration and research since the restart of operations in 2004-2005 have considerably advanced understanding of geology, structure and deposit genesis at Mount Polley, improving interpretation of mineralization geometry and the design of drill programs. New underground development is followed where appropriate by wall mapping and rib sampling to further characterize the mineralization, fill gaps in the resource model, and help guide stope design.

Airborne and ground magnetic signature is regarded as the most important geophysical tool for identifying new mineralization, although tellingly it was not effective in the Northeast zone, possibly delaying discovery of that highgrade but magnetite-poor orebody until 2003. An 11-line Titan-24 deep Induced Polarization-Magnetotelluric survey was completed by Quantec Geoscience Ltd. in Fall 2009 to potentially locate blind sulfide targets and guide exploration drilling where appropriate. Outlying parts of the Mount Polley property, away from the mine site, have been explored by geological mapping, sampling and trenching and by soil surveys over intrusive bodies, with no significant results to date. Mineral potential remains most promising within the MPIC itself, or possibly buried beneath the unconformity with cover rocks (conglomerate, breccia) immediately to its north.

Mount Polley mine has been on care and maintenance status since operations were suspended in May 2019.

The mine restart plan was updated in early 2021 to include revised pit designs, results of recent drilling, and current metal prices. The COVID-19 pandemic has had an impact on mine restart scenarios; however, MPMC took the initial steps towards recommencement of operations in late 2021 with the introduction of mine pre-stripping and plant refurbishing activities under a protective COVID-19 plan.

Mining Methods - conventional shovel, truck and open pit mine. With a developing underground mine.

Open Pit Mining Equipment
The current open pit mining operation at Mount Polley utilizes a conventional truck and shovel fleet with drilling and blasting prior to excavation. The fleet includes a mixture of diesel and electrically powered equipment for drilling, excavating and dewatering.

Material Handling
Ore mined from the pits is hauled to either the primary gyratory crusher located immediately adjacent to the mill or to nearby stockpiles.

Waste material at Mount Polley occurs in one of two types: non-acid generating waste (NAG), and potentially acid-generating waste (PAG). NAG/PAG designations are made on the basis of the neutralizing potential ratio (NPR) of a given material. This NPR is calculated by performing acid-base accounting (ABA) using carbon and sulfur assays from blasthole cutting samples. Sampling is performed on a one sample per 20,000 tonnes basis. All rock with an NPR less than 2.0 and a sulfur content greater than 0.1% is designated as PAG and stockpiled.

PAG waste is estimated to constitute approximately 27% of the waste tonnage in the life-of-mine plan. PAG waste, as a condition of operating permits, must be submerged for long-term storage at the end of mine life. As such, all PAG rock is selectively mined and temporarily stored in the Northwest PAG Stockpile. This stockpile will be rehandled into the exhausted pits at the end of mine life. NAG waste is hauled to either the southeast rock dump (SERD), or to the Tailings Storage Facility (TSF) for construction purposes.

Pit Slope Design Parameters
Bench heights in the Main Zone are 12m, while the Boundary Zone Pit will be mined with 10m bench heights in waste and 5m spilt benches in ore.

The strength of the overall rock mass around the pits is generally good with the exception of faults and late-stage mafic dykes which can be of poorer quality. Jointing in the rock mass is semi-consistent through different rock units, resulting in pit slope design criteria being dominated by the orientation of the pit face in question, and specifically how this open face interacts with the local jointing regime.

Pit wall design parameters employed for mining at Mount Polley are provided by Golder Associates Ltd., and are based on historical mining experience.

Underground Mining Methods
The Primary Underground mining method at Mount Polley is mechanized long-hole open stoping followed by backfill with cemented rock before mining the next stope.

The three noteworthy zones which are currently being mined or planned to be mined are; the Boundary, Halo and Zuke Zones. The majority of the Mineral Reserve base is contained in the Boundary Zone (81% of the 312,000 tonnes of underground Mineral Reserves).

The larger Boundary Zone with approximate dimensions of 80m long by 20m wide and 100m tall has been divided into four stoping blocks (A, B, C, and D). Individual stoping blocks are approximately 20m by 20m in plan, and between 35m and 100m in height and are aligned.

The final stoping blocks (C and D) will be filled with un-cemented rock fill as required. Mining of the smaller Halo and Zuke Zones will not require backfill.

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The mill at Mount Polley was commissioned in June 1997. The mill uses conventional rod and ball mills with a flotation and dewatering circuit to produce a copper /gold concentrate. The mill has a capacity to process 17,800 to 22,000 tonnes per day (tpd) of ore depending on hardness. Mount Polley concentrates are trucked to facilities at the Port of Vancouver and then shipped to overseas smelters.

The flotation circuit separates the valuable minerals from the rest of the ground particles. With the addition of reagents, the valuable minerals, mostly in the form of sulphides, are separated by flotation and are collected and upgraded to produce a concentrate. Initial separation is completed in a rougher/scavenger circuit, where the remaining minerals are discarded as tailings (which flow by gravity to the TSF). Rougher concentrate is reground in a regrind mill and further upgraded in a cleaner circuit to produce the final concentrate product. Cleaner tailings report to the cl ........