Mt. Milligan Mine, British Columbia, Canada

The Mount Milligan mine is a copper-gold project in central British Columbia, Canada. The mine is located about 150km northwest of Prince George. It is owned and operated by the North American miner Thompson Creek Metals Company.

Mt Milligan was owned by Placer Dome in the 1990s. The company intended to develop the mine in 1993. The development was, however, stalled due to low metal prices and the mining permits expired in 2003.

The property was acquired by Terrane Metals Corporation, a subsidiary of Thompson Creek Metals Company, in 2006. A feasibility study and mining permits were completed and acquired by 2009. An Environmental Assessment (EA) certificate for the mining project was received in March 2009. British Columbia awarded the Mines Act Permit in September of that year.

Construction work on the copper-gold mine was started in June 2010. Production from the mine is expected to begin in the third quarter of 2013. Full commercial production is scheduled for 2014. The project is expected to generate 1,000 jobs during construction and about 350 full-time positions during operations. The total estimated cost for developing the mine is about C$1.6bn.

The property is accessible by road from Mackenzie and Fort St. James. It is served by a 92km power line.

Mt. Milligan mine details

The copper gold mine will be developed as a conventional open-pit mine with a capacity of 110,000t per day. The mine is expected to produce 194,500oz of gold and 81 million lbs of copper a year. It is expected to have a mine life of 22 years.

The project will help train and employ local people for various positions to boost regional employment. Thompson Creek Metals will provide the training courses in collaboration with the College of New Caledonia.

The mine site will have an ore processing plant with a capacity to handle around 60,000t/day of throughput. The produced copper concentrate will be exported for further processing.

Geology, mineralisation and reserves

The mining property lies within the Quesnel Terrane volcanic arc of the Intermontane Belt. The geology is made of oceanic plates formed in the Early Jurassic Period and low metamorphic grade magmatic arc segments. The mine is an alkalic porphyry deposit of copper and gold.

The deposit is tabular and measures approximately 1,500m east-west, 2,500m north-south and 400m in thickness. The mine consists of Southern Star (SS) Zone with monzonite stock, and Main Zone comprising Rainbow Dyke and MBX monzonite stocks. The mineralisation is of chalcopyrite, magnetite and pyrite oxides. Bornite is localised along intrusive-volcanic contacts.

The proven and probable reserves at the Mt. Milligan mine are estimated at 482 million tonnes graded at 0.39 grams gold and 0.20% copper per tonne.

Ore processing at the British Columbian mine

The Mt. Mulligan mine will produce ore of low grade copper-gold. The planned semi-autonomous grinding (SAG) mill will be the largest in North America. It will have a capacity to grind about 2,717t per hour at 92% availability. The 12m SAG mill will be powered by a 23.5MW gearless motor drive.

An IsaMill machine, the largest in Canada, will be used for fine grinding the ore. It is considered to be one of the most energy efficient grinding machines on the market. The majority of operations will use hydro-electric generated power from the grid.

The open-pit mine development operations will have a smaller footprint of about 4km x 3km. Water used for the entire mining activity will not be discharged into local water bodies.

Contractors for the copper-gold project

The engineering, procurement, construction and management (EPCM) contract for the copper-gold project was awarded to the British Columbia Mining Joint Venture (BCMJV), in August 2011. BCMJV is a 50:50 joint venture between AMEC Americas and Fluor Canada.

The scope of work includes construction of the copper flotation process plant, storage facility for tailings, 92km of electrical cabling, a housing camp for 600 workers and ancillary plant facilities.

ABB was contracted to provide power technology equipment for the project. The company will supply the gearless mill drive for the SAG mill, as well as two dual pinion mill drives for ball mills. ABB will also provide transformers, motors, electrics and synchronisers under a C$28m contract awarded in May 2009.