The Superior Lake zinc project is an underground mine located in north-western Ontario, Canada. It includes the redevelopment of the historic Superior Lake zinc project, which comprises two deposits namely Winston Lake and Pick Lake.

Ophiolite Holdings owns the project, which is being developed by Superior Lake Resources, a company which holds 70% stake in Ophiolite and entered binding agreements with other shareholders to acquire up to an additional 15% stake in the project. The remaining 15% share in Ophiolite is free-carried, unti.

The Superior Lake zinc project is expected to produce 38,000 tonnes per annum (tpa) of Zn and 1,400tpa of copper  (after ramp-up) through its initial mine life of approximately nine years.

Bankable feasibility study of the project was completed in August 2019. Construction is anticipated to be commenced in the first half of 2020, with first zinc production slated for 2021. The initial project development is estimated to cost £70.7m ($86.7m).

Superior Lake zinc project location, geology, and mineralisation

Located approximately 180km to the east of Thunder Bay, the Superior Lake project is made up of a single contiguous group of claims consisting of 81 mining claims extending in 175km².

The zinc project is a part of the Big Duck Lake Volcanic Belt located within the Archean ShebandowanWawa Volcanic Belt of the Superior Province.

The Winston deposit is classified as a single massive sulphide sheet and has a strike length of 500m. Two primary ore types are identified at Winston with the first ore type being a mixture of pyrrhotite and sphalerite and the second type made of course grained sphalerite.

The Pick deposit lies beneath the Winston deposit and has a strike length of approximately 250m. The deposit hosts fine-grained sphalerite, pyrrhotite, chalcopyrite, and pyrite.

Superior Lake zinc project reserves

The probable reserves of Superior lake zinc project are estimated to be 1.96 million tonnes (Mt), grading 13.9% zinc (Zn), 0.6% copper (Cu), 0.2 grams per ton (g/t) gold (Au), and 26.2g/t silver (Ag).

Mining at Superior Lake zinc project

Longhole open stoping (LHOS) mining method, along with introduced cemented paste fill, will be used at the Superior Lake zinc deposit.

The project will be accessed through a decline ramp to be located adjacent to the historical Zenmac workings. It is further divided into three mining areas namely Pick Upper, Pick Middle (A&B), and Pick Lower (A&B), which include between four and five levels of panels.

Ore drives are proposed to be developed by using resue firing method, which involves separate blasting and removal of ore and waste.

Ore processing

The processing facility at the Superior Lake zinc project is capable of treating 325,000tpa. It will comprise one comminution circuit and two-stage flotation circuits one each for copper and zinc.

The run-of-mine ore will undergo single stage crushing followed by grinding in a semi-autogenous grinding mill within the comminution circuit.

The first stage of flotation will involve regrinding of the copper rougher concentrate and final stages of cleaning to produce copper concentrate. The copper rougher and cleaner tails will be conditioned resulting in the production of a zinc concentrate in the second stage of flotation.

The plant produces an average of 73,000tpa of zinc concentrate and 5,200tpa of copper concentrate. The resultant concentrates will be thickened before being filtered in two pressure filters, loaded into sealed containers, and transported to the rail siding in Schreiber for export to the ports.

Infrastructure at Superior Lake zinc project

Access to the project is through the TransCanada Highway, followed by a 20km unpaved road.

The existing 115kV transmission line will be used to meet the power needs of the project. A new 10MW substation will be constructed, consisting of primary transformers (10MVA) and switchgear.

The project site already has a freshwater dam and a water treatment plant. The mill is expected to use reclaim water from the tailings storage facility and polishing pond, while fresh water will be used for reagent mixing alone.

Workers will be accommodated at the 180-person camp located on the site of an existing motel on the Trans Canadian highway.

Contractors involved

Primero Group prepared the plant design and operating and capital expenditure estimates for the project, as part of the BFS.

Superior Lake Resources also received inputs for the BFS from consultants such as Orelogy Consulting, Massa Geoservices, SGS Canada, Mine Design Engineering, Nordmin Engineering, and Wood Canada.