Young-Davidson Advancing to Feasibility Study

Northgate Minerals announced on July 14, 2009, that it had received positive results from a pre-feasibility study of its Young- Davidson gold project in Matachewan, Ontario, and AMEC Americas, which completed the pre-feasibility study, has been commissioned to complete a feasibility study on the project by year-end 2009. The studies are based on proven and probable reserves of 2.8 million oz of contained gold. Mine life is projected at 15 years at a mill throughput of 6,000 mt/d. Commissioning is currently targeted for late 2011, with full production in early 2012.

Life-of-mine production is projected to average 170,000 oz/y of gold at a net cash cost of $333/oz. After the first two years of production from a small open-pit, production from an underground mine will increase to over 190,000 oz/y for the next 10 years at a net cash cost of $326/oz. Initial capital cost is estimated at $293 million.

Production from the Young-Davidson underground mine will be phased in during year three of operations as the pit ore reserve is exhausted, and during the last 12 years of the projected mine life, mill feed will be provided exclusively from the underground mine. The underground ore deposit is located between depths of approximately 210 m and 1,500 m. A new 6-m-dia shaft will be sunk to the east of the deposit to a depth of 1,500 m. The mine will also be accessed by a ramp, which will be extended to the bottom of the mine from the existing exploration ramp, currently at a depth of 460 m below surface.

The mine will operate 20-mt LHDs to load and haul stope production to an ore pass system. Ore will be hoisted to the surface in 18-mt skips. Waste rock for mine backfill will be distributed underground by gravity through a waste pass system extending from surface to the lower levels and hauled to the stopes by 20-mt LHDs.

The 6,000-mt/d plant will incorporate conventional gravity, flotation, and carbonin- leach (CIL) circuits. The grinding circuit will be a single-stage autogenous mill sourced from Northgate’s Kemess plant in British Columbia. Metallurgical evaluations have indicated that gold recoveries will average 92.5% over the mine life.

The Young-Davidson underground mineral reserves have been estimated within a detailed underground mine design based on the use of three bulk mining methods: longhole shrinkage for 8-m to 40-m-thick ore zones at depth, sublevel longitudinal retreat for 5-m to 10-m-wide zones, and sublevel caving for the 20-m to 40-m-wide near-surface Upper Boundary Zone. The stopes will be backfilled with unconsolidated waste rock from the open-pit and from development, except for the longhole retreat stopes in the upper levels, which will be left open in combination with rib and sill pillars. The sublevel cave zone will be connected to the open-pit, and waste rock backfill will be added from the pit as the zone is mined.

Environmental baseline studies have been completed to support the permitting process, and permit applications are currently being finalized to support the project timeline. Testing to date on the Young- Davidson mineralization has confirmed that the mill tailings will be non-acid generating, which will allow them to be impounded at the same location as the historic tailings from the two mines that previously operated on the property.

As featured in Womp 2009 Vol 07 -