TMAC Resources has announced results of a preliminary feasibility study (PFS) of expansion of mine production from 2,000 metric tons per day (mt/d) to 4,000 mt/d at its Hope Bay operations in Nunavut, Canada, including development of a new 4,000-mt/d processing plant and development of underground mines on the property’s Madrid and Boston deposits.
The PFS suggests that 16.9 million mt of ore containing an estimated 3.5 million ounces (oz) of gold at an average grade of 6.5 grams/mt could be processed over a 15-year operating life. Total recovered gold is estimated at 3.1 million oz. Life-of-mine cash costs are estimated at $841/oz, and all-in sustaining cost are estimated at $986/oz.
Expansion capital expenditures for 2020 to 2023 of are estimated at C$683 million, including C$184 million for a new processing plant.
The TMAC announcement cautions that the PFS does not take into account potential significant delays relating to the spread of the Covid-19 virus, including being able to order long-lead items or to complete critical test work, analysis, and engineering necessary to maintain the schedules presented in the PFS.
Underground mining at Hope Bay will incorporate long-hole mining methods in order to address deposit geometries and anticipated ground conditions. Mining will take place in permafrost where the mineralization is located away from water bodies and also in unfrozen ground, known as talik, situated adjacent to and under lakes.
The deposits will be accessed by ramps from surface. The ramps will also be used for ore and waste haulage from the underground operations. The Doris deposit is currently in production, with an existing decline reaching active mining areas. Mining will continue as per current methods until depletion. Transverse and longitudinal long-hole mining are planned for Doris.
Madrid North and Boston will be mined using long-hole stoping methods, with sublevels placed at 20-m vertical intervals. Both longitudinal and transverse accesses will be used, depending on the width of the ore zones. Madrid South, where ore zones are much narrower, will be mined using the long-hole stoping method, with sub-levels placed at 16-m intervals. The majority of stopes at Madrid South will have longitudinal accesses.
The new processing plant will recover gold from the ore through conventional crushing, grinding, and cyanide leaching.
Mine waste rock produced from underground mining will be temporarily stored on surface before being used as mine backfill. No mine waste rock will remain on surface post mining activities. Final closure activities are planned to ensure affected areas remain chemically and physically stable.