Name of the Project
Windfall gold project.

Location
Abitibi greenstone belt, Québec, Canada.

Project Owner/s
Osisko Mining and Gold Fields.

Project Description
The Windfall deposit is currently one of the highest-grade resource-stage gold projects in Canada and has world-class scale. Mineralisation occurs in three principal areas – Lynx, Main and Underdog.

The project is expected to produce 306 000 oz/y of gold, with peak production of 374 000 oz of gold expected in year two.

The process flowsheet comprise primary crushing, followed by a grinding circuit consisting of a semiautogenous grinding mill (in closed circuit with a pebble crusher) and ball mill (in closed circuit with cyclones – semiautogenous ball mill crusher circuit). A gravity circuit followed by intensive leaching recovers coarse gold from the cyclone underflow, while the cyclone overflow is treated in a carbon-in-pulp circuit.

Gold is recovered in an adsorption-desorption-reactivation circuit, followed by electrowinning  cells. The tailings filtration plant is located less than 1 km south-east from the Windfall process plant building.

The plant consists of pressure filters and their ancillaries, paste mixers, paste pumps, a clarifier, a binder storage and dosing system, as well as a dry-stack storage facility. The totality of the process tailings is filtered. Based on the mine plan, about 39% of the tailings are transformed in paste backfill. The remaining tailings are disposed of as dry stack.

Potential Job Creation
The project is expected to create more than  1 100 direct and indirect jobs during construction and more than 670 direct permanent jobs during operation.

Net Present Value/Internal Rate of Return
The project has an estimated after-tax net present value of C$1.17-billion and an internal rate of return of 33.8%, with an after-tax payback of 2 years from the start of production.

Capital Expenditure
The project will require capital expenditure of $607-million.

Planned Start/End Date
Process plant construction is planned for the second quarter of 2024, with ramp-up beginning in the third quarter of 2025.

Latest Developments
Gold Fields CEO Martin Preece has reported in its results for the six months ended June 30 that the JV will start and finalise permitting for the project, hopefully by the fourth quarter of 2024. The JV can then start building that into production.

He has further noted that an environmental-impact assessment was submitted in March this year, and is expected to take 12 to 18 months to be approved.

Key Contracts, Suppliers and Consultants
A2GC (rock mass characterisation and rock engineering, in support of the underground mine design); BBA Inc (historical data review; current and historical geology, exploration and drilling; sample preparation, quality assurance and control, and data verification; geological modelling and mineral resource estimate; metallurgical testwork management and analysis, crusher and process plant mass and water balance; crusher and process plant design, capital costs and operating costs; electrical infrastructure design and costs; information technology and communications infrastructure design and costs; integrated remote operations centre design and costs; general and administration operating costs; financial analysis and overall NI 43-101 integration); Entech Mining (underground mine design, underground infrastructure, ventilation, production scheduling, underground capital costs and operating costs); Golder Associates (waste rock, tailings and ore geochemical characterisation; surface tailings management facility designs and costs; site-wide water balance; hydrogeology and groundwater quality input into environmental studies; hydrogeology input for underground mine design); WSP Canada (design and costs of surface infrastructure for Windfall site, site utilities, on-site roads and pads, site infrastructure electrical distribution, surface mineralised material, waste rock, overburden and topsoil management facility, surface water management infrastructure, tailings filtration plant and dry tailings storage/handling, as well as underground paste backfill distribution, infrastructure design and costs); GCM Consultants (water treatment design, capital and operating costs).

Contact Details for Project Information
Osisko Mining, tel +1 416 363 8653 or emailinfo@osiskomining.com.