MINERAL EXPLORATION
Drill hole MH25-08 – 71.21 g / t Au ( 39.24 g / t cut ) over 21.33 m – in addition to MH25-04 ( 28.97 g / t Au ( 26.89 g / t cut ) over 21.76 m ) have true widths approximately four times greater than the average width of the large high-grade inferred resource block defined upplunge of them ( graphic : Alamos Gold
“ It really all hinges around the quality of the orebody and our understanding of the deposit and the controls and the mineralisation ,” he said . “ Knowing we require a certain drill spacing to be able to define inferred mineral resources , we strategically target the down-plunge extensions of the ore shoots .”
At Island , these ore shoots – which are the high-grade portions of the deposit – are laterally extensive in the lateral and vertical sense , Parsons explained .
“ With the surface directional drilling , we are able to specifically target these down-plunge extensions ,” he said . “ With one or two pilot holes and branch patterns , we can evaluate a large area down-plunge and along strike of the existing mineral reserves and resources . In some cases , other gold deposits can have ore shoots that are less predictable , or are not as extensive , so it would be a challenge to apply surface directional drilling without having a strong understanding of the controls of these shoots for targeting .”
And , it should not be forgotten , it requires an investment in exploration that goes beyond simply reserve and resource replacement on an annual basis . Richmont , a much smaller company , was unable to bankroll such a strategy .
Alamos has made a commitment to do this , as evidenced in the 16-year mine life outlined in the Island Phase III study and the $ 25 million it intends to invest in exploration this year .
The use of surface directional drilling looks set to continue paying off beyond this study , with the company recently drilling its best-ever hole to date by leveraging the technique .
Drill hole MH25-08 – 71.21 g / t Au ( 39.24 g / t cut ) over 21.33 m – is the hole in question . This hole , in addition to the previously reported MH25- 04 ( 28.97 g / t Au ( 26.89 g / t cut ) over 21.76 m ), have true widths approximately four times greater than the average width of the large high-grade inferred resource block defined up-plunge of them . This , the company said , demonstrates the
zone has widened in this area , providing even further potential beyond the company ’ s current growth plans .
“ That one – MH25-08 – is the best drill hole ever drilled at Island ,” Parsons said . “ And that is after 1.3 million metres of drilling and over 7,000 drill holes dating back nearly 100-years .
“ That speaks to the potential of this deposit to continue to grow through exploration , and also highlights the prospectivity of the Michipicoten Greenstone Belt .”
More to come
With 27,500 m of surface directional drilling scheduled for 2021 – and only 6,683 m carried out as of May 31 – more of these high-grade intercepts could soon come to the fore .
And Parsons says the company can continue to use surface directional drilling some 500 m below where it is currently drilling down to at Island .
On top of that , the company , having established the necessary underground exploration infrastructure , is equipping its underground drill rigs at Island for directional drilling , with 24,000 m of underground directional drilling planned this year ( 3,233 m completed as of the end of May ).
“ This is allowing us to reduce our cost per metre compared with surface directional drilling and allowing us to drill more targets in a shorter amount of time ,” Parsons said . “ We will continue applying directional drilling technology as long as the orebody is continuing at depth to drill off those ore shoots .”
At Young-Davidson , the company ’ s other core asset in Ontario , Canada , the company is also making plans to use underground directional drilling .
“ One of our plans going into 2022 is to
evaluate opportunities to utilise directional
drilling from underground exploration drifts established in lower and mid mines at Young-
Davidson to target mineralisation down-plunge at depth ,” Parsons said .
More broadly , Parsons thinks the company ’ s exploration team can leverage their understanding of the technology at other assets .
“ For us , it is a competitive advantage ,” he said . “ With a solid geological understanding of the deposit you are looking at and an understanding of the application and the benefits of directional drilling , we can recognise opportunities of what could be occurring at depth where others might not see potential until well into the future after underground infrastructure is established at depth .”
There are obvious cost , time and accuracy benefits to using directional drilling , yet there is another benefit that may get lost along the way . Without the need to constantly move the surface drill rigs between drill pads , the footprint of these rigs is reduced .
McCluskey says the technology has brought another ESG advantage to Island too .
By being able to quickly drill off more targets and convert these into the resource base , Alamos has been able to think long term with its Island Gold Phase III Expansion and justify the expense of a shaft and paste backfill plant .
This comes with a 35 % reduction in emissions compared with using the mine ’ s existing ramp and diesel-powered truck haulage , he said , explaining that much of the Ontario grid is powered by renewable hydroelectricity .
“ This technology has given us the exploration success that has been converted into scale and allowed us to think longer term and afford the infrastructure to make it a ‘ greener ’ operation ,” he said .
With such a long list of benefits , more companies will be looking at directional drilling to prolong the life of their assets and make longterm decisions that make economic and
sustainable sense .
IM
32 International Mining | SEPTEMBER 2021