Osisko Starts Construction at its Malartic Gold Project

Costing an estimated C$1 billion, Osisko Mining’s Canadian Malartic gold mine in Quebec will begin
production at a rate of roughly 600,000 oz/y in 2011, following an 18-month construction phase. In this
photo, the plant’s SAG mill foundations are being poured. (All photos courtesy of Osisko Mining)

Computer rendering of the Canadian Malartic mine’s processing and administrative facilities.

Projected facilities layout after ten years of mine operation.
Osisko Mining received Quebec government authorization in late August 2009 to complete development of its Canadian Malartic open-pit gold project and is proceeding with construction of the mine and mill. Construction is expected to take 18 months, and the project is planned to be fully operational by the second quarter of 2011. Production is planned to average 591,000 oz/y of gold over 10 years of operation based on current proven and probable reserves of 6.28 million oz and will exceed 600,000 oz/y in the initial years of operation. Production costs of $319/oz will be in the lowest quartile of world gold producers.

In addition to current reserves, Canadian Malartic’s measured and indicated resources stand at 3.6 million oz, and inferred resources total 720,000 oz. Five mineralized zones outside the planned pit and additional targets are currently being explored by six diamond drills. Drilling during 2009 will total about 200,000 m.

The Canadian Malartic mine is located at the southern edge of the town of Malartic, and mine development required movement of a neighborhood to make way for mining operations. This aspect of the project was 98% complete as of September 2009. Drilling and blasting activities have been designed to control blast induced vibrations and airblast overpressure on the town.

With overall investment of nearly C$1 billion, the Canadian Malartic project will create about 800 direct jobs during construction and 465 permanent direct jobs during the 10 years of operation. A large majority of the new jobs will be taken by residents of the town of Malartic and the Abitibi-Témiscamingue region.

Canadian Malartic mine planning is based on an ore resource of 183.3 million mt at an average grade of 1.07 g/mt gold. Mine production will total 150,000 mt/d of ore and waste, and the mill will process 55,000 mt/d of ore. Access to the pit will be via a 35-ft-wide, 10% decline ramp designed to accommodate Caterpillar 793F haul trucks. The haulage fleet initially will include 12 units and is planned to increase to 22 units by the sixth year of operation due to the deepening of the pit and higher dump levels for waste.

Two 28-m3 O&K RH340-B hydraulic shovels will load ore and waste. During the second year of operation, a 21-m3 O&K RH200 hydraulic shovel will be added to increase the mining rate from 51 million mt/y to 64 million mt/y. A Cat 994F HL front-end wheel loader will complement the shovels and re-handle ore from the stockpiles. Ancillary equipment will include two Cat 16 M graders, four track-type Cat D10T dozers, one Cat 834H wheel dozer, two water trucks, and other support equipment.

The processing flowsheet includes gyratory crushing and SAG and ball mill grinding. Cyclone overflow from the tertiary grinding circuit will be thickened to about 50% solids and fed to a leach tank circuit, where oxygen will be injected to increase the kinetics of the dissolution of gold in the leach circuit. This slurry will flow by gravity to two parallel sets of carbon-in-pulp (CIP) pump cell carousels, where activated carbon will absorb the gold in a countercurrent flow arrangement.

The loaded carbon will be screened from the slurry and transferred to the stripping circuit, where the gold will be stripped into a gold pregnant solution and deposited in the form of a sludge onto stainless steel cathodes. The deposited gold sludge will be pressure washed to the bottom of the electrowinning cells and subsequently filtered, dried, and poured into gold doré bars.

The stripped carbon will be reactivated in two kilns and re-used in the carousel pump cell CIP circuit. The slurry from the last stage of the tank series in the carousels will be barren in gold and will be directed to the tailings thickener.

The original Canadian Malartic deposit was discovered in 1926, and underground mine production started in 1935. The mine closed in 1965 after producing 1,076,000 oz of gold from 9.93 million mt of ore grading 3- to 6-g/mt gold. Osisko acquired the property in 2004.

As featured in Womp 2009 Vol 08 - www.womp-int.com