HBM&S launches program at Chisel North zinc deposit

Hudson Bay Mining & Smelting has announced a $17-million underground development program at its Chisel North zinc deposit near Snow Lake, Man.

The company plans to drive a 2.6-km decline from the 140-metre level of its Photo Lake mine to the Chisel North deposit. A reserve drilling and bulk-sampling program will attempt to confirm Chisel North’s drill-indicated resource of 2.4 million tonnes grading 10.8% zinc.

If the underground program indicates production is feasible, HudBay would carry out development work on levels between a vertical depth of 300 and 600 metres and commission a mine. Also, the Snow Lake mill would be modified to handle the zinc-rich Chisel mineralization. Capital costs for this second phase of work are estimated at $33 million.

The company expects to haul ore along the decline with 40- or 50-tonne trucks, then up the existing Photo Lake ramp to the Snow Lake mill and on to the zinc refinery in Flin Flon. The expected milling rate is 163,000 tonnes per year, with an anticipated recovery rate of 83-85%.

A decision will be made shortly on whether to employ company personnel in the first phase of development, or use contractors. HudBay currently employs 65 people at the Photo Lake mine and Snow Lake mill; of these, 25 would maintain their jobs in the event they are needed (the mine will exhaust its reserves by September). Another 15 workers would assist in completing the second phase of development, with a maximum total of 75 employees once production has started.

Because of the thickness and dip variations of the deposit’s three sulphide lenses, various mining methods are being considered. A combination of room-and-pillar and cut-and-fill methods will likely be employed.

As at Photo Lake, an optical tracking system for guiding haulage trucks will be tried. Hundreds of runs have been successfully completed, though a few kinks have yet to be ironed out. The feasibility study will not consider automated trucking.

The Chisel Lake deposit was discovered several years ago, yet its zinc-rich nature has always been an obstacle to development. Explains HudBay’s Vice-President Peter Jones: “The principal methodologies that had been applied to it over the years invariably involved the use of a [capital-intensive] shaft and consequently a high production rate. And because the deposit is principally zinc, this would flood our plant with zinc for a comparatively short period of time.”

The decline is designed to overcome these obstacles by minimizing capital costs and allowing the ore to be trucked, which will lower and create flexible production rates. Also, the ramp will make it possible to develop the uppermost — and richest — lens first, resulting in a short payback period.

Chisel North is one of many projects HudBay plans to develop in the Snow Lake and Flin Flon areas. Approval for the second phase of development partly depends on whether those other projects are given the go-ahead by parent company Minorco, a subsidiary of South African-based Anglo American.