Mining Methods And Gold Processing Musselwhite Mines

   

      Mining methods and gold processing musselwhite mines initially operated both open-pit and underground mines, open-pit production having been designed to ensure mill feed at a rate of 3,300t/d for about five years following mill commissioning. Most of the mine’s ore is now sourced from underground. And gold processing from musselwhite mines processing includes crushing, grinding, leaching by cyanidation, carbon in pulp recovery and electrowinning, to achieve an overall recovery of approximately 96%.

      The stratigraphy in the Musselwhite mine vicinity is dominated by mafic volcanics, chemical sediments and felsic volcanics. External into the supracrustal sequences are a series of undifferentiated gneisses and granitoids. All mineral lithologies within the immediate mine area have been metamorphosed at mid to upper amphibolite facies. Mineralization is predominantly hosted within meta-chemical sediments (banded iron formations) and in particular within garnet-magnetite-grunerite facies meta-banded iron formations (locally termed the Northern Iron Formation). The location of mineralization is controlled by the intersection of shear zones and folded meta-banded iron formations. These geological controls result in mineralized shoots, which plunge at approximately 15 degrees to grid north, have a down dip extent of up to 150 metres, down plunge continuation in excess of 1.5 kilometres, and across-lithology width of up to 10 metres. Mineralized zones are characterized by abundant pyrrhotite, quartz flooding and, rarely, visible gold.

Mining Methods In  Musselwhite Mines

      Mining methods in Musselwhite mines is Longhole, Underhand and Overhand Cut and Fill. The Musselwhite mine which is located in Weagamow – North Caribou Greenstone Belt of the Sachigo Subprovince, part of the Archean Superior Province. In 1997 Phase first , underground production gold mine from the T Antiform (T-A) deposit, built up to a design rate of 2,700 t/d, and supplemented by ore, at a rate of 1,000 t/d, from the PQ zone. The T-A was increased to 3,300 t/d by expanding operations the fleet of 40-tonne haul trucks. The first phase of project development of the underground mine section of the T Antiform deposit involved developing a decline from surface to access some 5Mt of ore mineral reserves above the 275m level. Other infrastructure included a ventilation raise to surface.

      Mining Methods during phase two, the reserves mineral ore were accessed via a production shaft, achieving a mining rate of 3,500t/d. A new ventilation shaft was sunk and the existing ventilation shaft converted into a mining production shaft. Mining methods underground is from transverse longhole stopes where the mining width is greater than 12m, the ore being blasted using ring drilling. Cemented rockfill is used in primary stoping blocks and uncemented rockfill in secondary stopes. Longitudinal stopes use conventional longhole benching and are backfilled with waste rock and crushed material from open-pit stripping. Mineral ore is extracted via a blast hole process and moved via a series of scoop-trams and underground dump trucks to one of 2 rockbreakers, either on the surface or at a 400 meter level. The ore then travels once through a jaw crusher and through a series of conveyor belts and countinously along a cone crusher rock sizing circuit. When the ore reaches a specific size it is transported to the mill building. Ore handling underground is undertaken by remote-controlled LHDs, with 40t-capacity trucks used to haul the mineral ore to surface.

      Musselwhite ore is crushed underground in a Nordberg jaw crusher, then hoisted to another Nordberg jaw crusher on surface. Final mineral ore reduction to --9 mm is accomplished in a Simplicity cone crusher. The mineral ore is further reduced to 80% --106 microns in a grinding circuit consisting of a Nordberg rod and a Nordberg ball mill. The seven existing 40-mm Technequip hydrocyclones are soon to be replaced with four 510-mm Weir Cavex cyclones.

   

Gold processing Musselwhite Mines

     

      Gold processing Musselwhite mines uses a gold cyanidation and CIP (carbon in pulp) extraction process. The mill Musselwhite gold mines is designed to treat 3300t/d and employs conventional gravity separation, cyanide leach and carbon-in-pulp (CIP) processes to recover the gold from the ore. Gold processing first is primary mineral crushing, is carried out on surface using a jaw crusher, the output being fed directly to a secondary crushing plant. Gravity concentration using a Knelson concentrator and shaking tables recovers coarse free gold from the ore, with the remainder being leached for 32 hours in agitated tanks. The slurry is then thickened, exposed to a cyanide treatment to extract it from the ore and into the solution, absorbed from the solution with activated carbon.

      Gold in solution is recovered by absorption onto activated carbon in a CIP circuit. Loaded carbon is eluted using the conventional pressurized Zadra technique. The CIP tailing flows by gravity to a two-stage CCD washing circuit to recover cyanide. The washed tailing is pumped to a reaction vessel for cyanide destruction. The Inco/S02 air process with two stages of washing is used in order to provide an effluent containing less than 5ppm cyanide for discharge to the tailings pond. The gravity circuit includes two Knelson concentrators. The recovered free gold is placed in a ConSep Acadia reactor, also provided by Knelson. This is a patented, high-efficiency batch leaching system and EW reactor. Between 26% and 30% of the gold is recovered in the gravity/Acacia circuit.

     

      Ninety-three per cent of the remaining gold is recovered by conventional CIP means, bringing the total gold recovery rate to 95.5%. The mill houses four stirred-tank reactors in which the slurry is leached, and six CIP tanks. Loaded carbon passes through an elution column using a caustic-cyanide solution to strip the gold. The pregnant solution passes into three EW banks, where the gold is plated onto cathodes. Gold is washed from the cathodes, dried, smelted and poured into doré bars containing 85-93% Au.

      Tails from the CIP circuit are washed with reclaim water in a two-stage counter-current decantation circuit. Cyanide is destroyed using the Inco SO2 process. The final slurry is impounded behind a tailings dam. The current plans are to increase the existing tailings disposal capacity using a dry stacking method and backfill system to help accommodate the mine life that could extend up to the year 2026.Twice a year the excess water is drained off the tailings pond where it flows naturally through a series of polishing ponds and a freshwater marsh. By the time the runoff reaches the natural watershed system the cyanide content is drastically reduced and poses no environmental or safety hazard.

      Since achieving its first commercial production in April of 1997, Musselwhite mine has produced over three million ounces of gold. The 2010 discovery of the Lynx zone—a zone of higher-grade ore above the cornerstone PQ Deeps underground operation—has created the potential to significantly enhance economics and extend productive mine life. Exploration continues to test other high-potential lateral targets and extension of existing gold structures. During 2014 the operation produced 278,300 ounces of gold and is forecast to produce between 250,000 and 270,000 ounces in 2015.