The depositional environment for the mineralization at Lalor and the 1901 deposit are similar to present and past producing base metal deposits in felsic to mafic volcanic and volcaniclastic rocks in the Snow Lake mining camp. The deposits appear to have an extensive associated regional hydrothermal alteration.

The mineralized envelopes are shallow dipping, with zinc mineralization defined to date beginning at approximately 600 m from surface and extending to a depth of approximately 1,100 m. The mineralization trends about N320° to N340° azimuth and dips between 30° and 45° to the north. It has a lateral extent of about 1,400 m in the north-south direction and 800 m in the east-west direction.

Sulphide mineralization is dominated by pyrite and sphalerite. In the near solid (semi-massive) to solid (massive) sulphide sections, pyrite occurs as fine to coarse grained crystals ranging one to six millimetres and averages two to three millimetres in size. Sphalerite occurs interstitial to the pyrite. A crude bedding or lamination is locally discernable between these two sulphide minerals. Near solid coarse-grained sphalerite zones occur locally as bands or boudins that strongly suggest that remobilization took place during metamorphism.

Disseminated blebs and stringers of pyrrhotite and chalcopyrite occur locally within the massive sulphides, adjacent to and generally in the footwall of the massive sulphides. The hydrothermally altered r ........

Lalor mine is a ramp and shaft accessible mine.

At Lalor, lateral development is horizontal or near horizontal tunnelling, travelable by rubber tired mechanized equipment. Ramps are typically mined at up to +/- 15% grade to provide access between levels. Rounds are 4m long and typical dimensions are 6m wide by 5m high. Standard ground support, consists of resin grouted rebar and welded wire mesh across the back and to within 1.8m of the sill on the walls and face. Mine services, including compressed air, process water and discharge water pipelines, paste backfill pipeline, power cables, leaky feeder communications antenna and ventilation duct, are installed in main levels and stope entrances.

At Lalor, main ventilation raises and ore pass raises are developed by a mining contractor using a raisebore and/or Alimak climber. Ground support and ladder ways are installed as required. Longhole slot raises, transfer ore passes, and auxiliary ventilation raises are limited to approximately 35m long and are developed using longhole conventional drop raise techniques. Drain, paste backfill and electrical cable holes are drilled using longhole or raisebore drills and are reamed to designed diameter.

There are two mining methods used at Lalor mine: variations of cut and fill and longhole open stoping (predominantly transverse longhole mining with minor longitudinal retreat).

Cut and Fill Mining
Single pass overhand mechanized cut and fill ........

STALL MILL
Crushing
Crushing Coarse ore from the mine is transported to a primary crushing plant located at the Chisel mine site and is operated by a third-party contractor. The product from the crushing plant is then trucked to the Stall mill and placed in coarse ore bins or a stockpile. Material from the bins is reclaimed via vibrating feeders and conveyed into a Hewitt Robins 762mm x 1220mm jaw crusher. The discharge is combined with that of the secondary Symons Standard cone crusher to feed a Tyroc 2.4m x 6.1m double deck vibrating screen. The undersize from the bottom deck is conveyed to the fine ore bins (FOB) while the oversize of the two decks is combined to feed the Symons cone crusher and then recirculated to the screen deck in a closed loop.

The described crushing circuit is in the process of being decommissioned and replaced with an external crushing circuit to service both the Stall and New Britannia mills. The new external crushing circuit start-up is aligned with the New Britannia mill commissioning schedule.

Grinding
From the fine ore bins, crushed ore is conveyed to the two independent Stall and Chisel circuits. The Stall circuit, which processes approximately two thirds of the mill feed, includes a 3.2m diameter x 4.9m rod mill and a 3.8m diameter x 5.5m ball mill. The Chisel circuit has a 2.1m diameter x 3.0m rod mill and a 3.2m diameter x 4.0m ball mill.

Each rod mill discharges into a dedicated hydrocyclone feed pump box where it is combined with the ball mill discharge and with dilution water. Each hydrocyclone underflow returns to their respective ball mill. The hydrocyclone overflow from each circuit combines and discharges into the hydrocyclone overflow pump box. The product reports to a flotation feed pump box through a trash screen. Lime is added to each rod mill to control the pH in the flotation feed.

NEW BRITANNIA MILL
Grinding
The crushed material is reclaimed from the FOB via conveyors into the rod mill and then discharged into a hydrocyclone feed pump box, where it is combined with the ball mill discharge and dilution water. A variable speed hydrocyclone feed pump feeds a the hydrocyclones cluster. The hydrocyclone underflow returns to the ball mill while the overflow flows via gravity to a trash screen and then is pumped to the flotation circuit.

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