Name: Mount Milligan mine.
Location: Mount Milligan is located about 145 km north-west of Prince George, in central British Columbia, Canada.
Controlling Company: Centerra Gold.
Brief Description: The Mount Milligan mine is a conventional truck-and-shovel openpit copper/gold mine and concentrator. The mine has a mine life of 22 years.
Brief History: Prospector Richard Haslinger and BP Resources Canada located claims on the site in 1984. Two years later, Lincoln Resources optioned the claims and in 1987 completed a diamond drilling programme that led to the discovery of significant copper/gold mineralisation. In the late 1980s, Lincoln restructured, amalgamated with Continental Gold Corp and continued ongoing drilling in a joint-venture (JV) with BP Resources.
In 1991, Placer Dome acquired the project from the JV partners, resumed exploration drilling and completed a prefeasibility study for the development of a 60 000 t/d openpit mine and flotation process plant.
Barrick Gold Corporation bought Placer Dome in 2006 and sold its Canadian assets to Goldcorp, which, in turn, sold the project to Atlas Cromwell. Atlas Cromwell changed its name to Terrane Metals Corp and initiated a comprehensive work programme.
Thompson Creek Metals (TCM) acquired the Mount Milligan development project through its acquisition of Terrane in October 2010, and subsequently built the Mount Milligan mine, which started commercial production in February 2014.
In October 2016, TCM was acquired by a subsidiary of Centerra and, inconnection with that acquisition, Terrane and certain other subsidiary entities of TCM were amalgamated into TCM. The Mount Milligan mine is now indirectly owned by Centerra.
Products: Copper/gold.
Geology/Mineralisation: Mount Milligan is a tabular, near-surface, alkalic copper/gold porphyry deposit, measuring an estimated 2 500 m north to south, 1 500 m east to west and is about 400 m thick. It comprises the Main and Southern Star (SS) zones. The Main zone includes four adjoining subzones – MBX, WBX, DWBX and 66 – all of which are spatially associated with the MBX monzonite stock and Rainbow dyke. The SS zone is centred on a monzonite stock of the same name and is about 1 000 m south of the Main zone.
Main zone mineralisation and associated alteration are primarily hosted in volcanic rocks, whereas in the SS zone, mineralisation is hosted equally in monzonite stock and volcanic rocks. Mineralisation in both zones encompasses pyrite, chalcopyrite and magnetite with bornite localised along intrusive-volcanic contacts. The pyritic 66 subzone is notable in that it is comparatively gold-rich.
Copper/gold mineralisation is primarily associated with potassic alteration, which decreases in intensity outwards from the monzonite stocks. Pyrite content increases significantly outward from the stocks where it occurs in association with propylitic alteration, which forms a halo around the potassic-altered rocks.
Reserves: Total proven and probable reserves as at December 31, 2017, were estimated at 467.94-million tonnes grading 0.19% copper and 0.3 g/t gold.
Resources: Total measured and indicated resources as at December 31, 2017, were estimated at 229.73-million tonnes 0.3 g/t gold. Inferred resources were estimated at 35.04-million tonnes grading 0.3 g/t gold.
Mining Method: Large-scale openpit mining. A 15 m bench height has been selected for mining ore and waste.
Major Infrastructure and Equipment: The mining operations equipment fleet comprises:
- two 311 mm electric blast-hole drills,
- one 203 mm diesel blast-hole drill,
- two 41 m3 electric cable shovels,
- two 19 m3 front-end loaders, and
- thirteen 217 t trucks and two 190 t trucks.
These major units are supplemented with a back-up equipment fleet of graders, track and rubber-tired dozers, backhoes and water trucks.
Key equipment includes:
- a primary crushing plant with a 1.525 m x 2.794 m gyratory crusher;
- a secondary precrushing plant with two cone crushers, each powered by one 1 000 kW
- a motor prior to the grinding circuit;
- a semiautogenous (SAG)/ball mill/crusher grinding circuit;
- flotation circuits; and
- regrinding and gravity concentration circuits.
Prospects: Mount Milligan continues to examine potential flowsheet modifications to further improve performance and results.
Contact Details:
Centerra Gold
Tel +1 416 204 1953
Fax +1 416 204 1954
Email info@centerragold.com