Lalor Gold Mine

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HudBay Minerals constructed the Lalor Mine from 2010 thru to 2014, with construction being completed at the end of 2014. Full production is expected by 2015 and the mine is estimated to have a production life of 20 years. In 2010 the board of directors authorized the expenditures required and committed to putting a mine into production. In 2011 construction started on a new concentrator and in 2012 initial ore was produced from the ventilation shaft. Dumas was awarded the contract to sink the production shaft in April, 2011 and it is 6.7 meter diameter concrete lined shaft which is 1000 meters deep. The shaft was sunk “bald” with shaft furnishings installed afterward. As of the 3rd quarter of 2014 Hudbay completed underground development and all work will be done by the end of 2014. Full production is expected to be achieved by 2015. It is estimated to have a production life of 20 years.

The Lalor deposit lies along a stratigraphic horizon in the Flin Flon Greenstone Belt. The top of the deposit is located near a decollement contact featuring overturned hanging wall rocks. The rock units of the hanging wall include mafic and felsic volcanic rocks, mafic to felsic volcaniclastic units, crystal tuff units and fragmental units. The footwall rocks are hydrothermally altered and metamorphic recrystallisation has created mineral assemblages. These assemblages include chlorite dominant schists, sericite dominant schists and cordierite+anthophyllite gneisses.

Stacked mineralised zones three to 17m thick have been identified at the mine. Six zones are of the base metal, five are gold bearing zones and one is a copper bearing zone. Mineralisation at Lalor occurs in the form of disseminated to solid sulphides which include medium to coarse grained sphalerite, pyrite, chalcopyrite and arsenopyrite. The mineralisation is flat lying and trends 260° to 310° and dips 10° to 30° to the north.

The mine is being accessed through a 3,200m underground ramp from the Chisel North mine. The underground infrastructure will include main levels, ore and waste raises, ventilation raises and rockbreaker stations. Construction of the ramp was completed in early 2012. A 6.1m diameter ventilation shaft at a depth of 835m is providing air flow into the mine. Sinking of the shaft was completed in the second quarter of 2012. The production shaft is 6.7m in diameter and is sunk to depth of 1000m. In 2011 a decision was made to build a new concentrator with a capacity of 4,500t a day that is adjacent to the production shaft.

Three stope mining methods will be used at Lalor: mechanized cut & fill, post pillar cut & fill and longhole open stope. At the end of ore zones, where resources narrow, cut & fill mining will be used. Where the dip exceeds 35° and the orebody is of sufficient thickness, longhole open stope mining will we used. All stopes at Lalor will be backfilled to maintain long term stability and to provide a floor to work from for subsequent mining. The majority of backfill will be paste backfill. Paste backfill is an engineered product comprised of mill tailings and a binder (3% cement by weight) mixed with water to provide a thickened paste that is delivered by borehole and pipes to stopes. Hudbay has experience with the design and operation of a paste backfill system, currently in use at the Flin Flon concentrator and 777 mine.

Ore will be loaded by scooptram to underground haul trucks and hauled to the production shaft. Ore will be dumped onto a grizzly at 910m level for sizing to -0.4m by a rockbreaker. A 40m raise below the grizzly will provide approximately 1,200 tonnes of coarse ore storage. A chute at the bottom of the raise at 955m level will feed ore to a conveyor that will load a measuring flask with 15 tonnes of ore. Ore will be skipped to a surface bin by two skips in balance. Ore from the surface bin will be conveyed to the primary crusher at the onsite
concentrator. Underground development for waste and ore drifts, crosscuts and ramps will be done using two boom electric hydraulic jumbos.

Reference:

www.hudbayminerals.com/English/Our-Business/Development...