The Meliadine gold project is located in the Archean Rankin Inlet Greenstone Belt, in the Churchill Structural Province of the northern Canadian Shield. This belt consists of mafic volcanic rocks, felsic pyroclastic rocks, sedimentary rocks and gabbro sills of about 2.7 billion years old that have been polydeformed and metamorphosed. The Meliadine trend is defined by northwest-trending rock units as well as a major fault zone known as the Pyke Fault: a high-strain zone characterized by multiple foliations and regionally important shear zones.

The Meliadine gold district comprises a combination of orogenic greenstone- and banded iron formation (“BIF”) hosted gold mineralization. Gold in the district is associated with hydrothermally altered and sulphidized BIF (Lawley, et al., 2013).

Seven gold deposits have been identified at the Meliadine project, of which Tiriganiaq is the most significant. The other deposits are the Discovery, F zone, Wesmeg, Normeg, Wolf and Pump. The Normeg deposit, discovered in 2012, is a southern expansion of the Tiriganiaq deposit, and extends as far as the Wesmeg deposit. Gold mineralization in these seven deposits is mostly mesothermal quartz-vein-dominated gold systems in strongly sheared and complexly folded host rocks of Archean turbidites, iron formation and volcanic rocks. Within each deposit are many gold-bearing lodes of quartz vein stockwork, laminated veins and sulphidized iron formation with strike lengths of up to 3 km. The stratigraphic units generally strike northwest-southeast, dip steeply to the north and are overturned, with the oldest units to the north. All seven deposits remain open at depth.

Mineralization
Mineralization in the Tiriganiaq gold deposit is strongly associated with shearing and quartz veining, which likely developed during the Proterozoic third deformation event. The most intense and consistent gold mineralization is present within both the Upper Oxide Iron Formation and proximal to the Lower Fault in the siltstones of the Tiriganiaq Formation, but minor amounts of mineralization have been reported in all rock types. Areas of intense shearing are ‘healed’ by quartz veining and there is generally little to no brittle deformation.

Gold mineralization is directly associated with syn- to post-deformational quartz veining. Vein appearance is highly variable from a several-metres-thick laminated vein along portions of the Lower Fault to wispy, apparently erratic quartz stringers and stockwork in the Tiriganiaq Formation. With some exceptions, quartz-only and quartz-ankerite veins tend to be mineralized with gold, while quartz-calcite veins are commonly barren in all lodes. This observation implies to multiple veining events.

Sulphide minerals in the Tiriganiaq gold deposit are of two distinct generations: primary and late sulphides.

Primary sulphides consist of wispy, discontinuous, bedding-parallel laminations of pyrrhotite, pyrite and chalcopyrite in oxide iron formations and black argillite. Fine-grained, web-textured sulphides in oxide iron formations close to quartz veins may represent remobilization of primary sulphides, but may alternatively signify sulphur introduced during mineralization. Gold values are generally low to absent in this sulphide assemblage, in the absence of quartz veining.

Late sulphides consist of coarse-grained (sub-centimetre-size) clots of arsenopyrite crystals and pyrrhotite associated with highly gold-bearing zones located in and close to quartz veining. The coarse arsenopyrite crystals rarely show signs of strain, having suffered little post-depositional deformation. Arsenopyrite of this type, in association with quartz veining, is a good visual indicator of elevated gold values.

Visible gold is common in all lodes in the deposit and is present in quartz veins, pyrrhotite, and along the margins and late fractures of arsenopyrite crystals.

Mining at Meliadine will be carried out through ten open pits and two underground mining operations. Underground access is by decline, with long-hole mining methods. Each stope is backfilled, with cemented pastefill and/or cemented rockfill used in primary stopes and dry rockfill for the secondary stopes. A conventional truck/shovel operation is used for the open pits. Mining in 2021 occurred by both underground and open pit at Tiriganiaq.

An underground portal allowing access to an exploration ramp was built at the Tiriganiaq deposit in 2007 and 2008 to extract a bulk sample for study purposes. This ramp now provides access for services, underground activities and personnel transportation. The construction of a second portal was completed in 2018. The main purpose of this second portal is for production activities, including bringing ore to the crusher feeding the mill.

Crushing and Ore Handling
The ore is trucked from the underground mine to a surface crusher located in the vicinity of the process plant. The trucks dump into a hopper equipped with a static grizzly and a hydraulic rock breaker that can handle any oversize rocks. An apron feeder is located under the dump hopper. The ore is fed to a reciprocating grizzly feeder via the apron feeder. Oversize rock from the grizzly feeder is fed to a jaw crusher. The jaw crusher product and the undersize from the reciprocating grizzly feeder are both transferred by gravity to the jaw crusher discharge conveyor, which then carries the material to a 2,500-tonnes-capacity ore bin adjacent to the process plant. The ore is reclaimed from the bin using an apron feeder that discharges onto the SAG mill feed conveyor at an average feed rate of 136 t/h.

Grinding
Grinding is performed by a single-stage mill in closed circuit with a cyclone cluster. Cyclone underflow recirculates to the SAG mill, while the overflow reports to the thickener. The thickener underflow is fed to the CIL circuit and the overflow reports to the process water tank, which is the source of water for most applications in the plant. It should be noted that the layoutproposed for the SAG mill discharge area takes into consideration the potential future retrofit of a vibrating screen and recycle conveyors, should the plant throughput be increased and the circuit expanded to a two-stage circuit. The expansion would be located to the east of the primary grinding circuit (refer to the Item 18 Infrastructure for more detail).

In 2018, Metso sold one hydrocyclone cluster with three MHCTM 250 hydrocyclones and a VTM 500 Vertimill® grinding mill to Agnico Eagle for its Meliadine gold project. The equipment is used for regrind application of gold ore. The combination of the Vertimill 500 grinding mill and the MHC 250 hydrocyclones provides with a total comminution solution.

During development, more than 39 metallurgical test programs were conducted at Meliadine. Based on the results of these tests, a conventional gold circuit was built, comprising crushing, grinding, gravity separation and cyanide leaching, with a CIL circuit, followed by cyanide destruction and filtration of the tailings for dry stacking. The mill was completed in early in 2019 and has a name-plate capacity of 3,750 tonnes per day.

A summary description of processing at Meliadine is provided below (Technical Report, 2015).
The process plant will consist of three separate facilities:
- a crushing facility, including primary and related material-handling facilities that can crush ore from either underground or open pit operations;
- a main processing facility including a coarse ore surge bin and related feeding and reclaim systems, grinding, gravity concentration and an intensive leaching reactor, leaching feed thickening, CIL cyanide circuit, loaded carbon acid ........