Mining

Mining Overview

A combination of conventional, contractor operated open pit and underground mining at both the Hammerdown and the Orion deposits was selected as the basis for this PEA.  Both open pits will utilize 5 metre high benches and a mobile fleet of 7.0 m3 hydraulic excavators, 6.5 m3 front end loaders and 55 tonne haul trucks, supported by 455 kW track dozers and graders to maintain pit floors, dumps and road surfaces. Pit slope angles applied to the pit designs included inter-ramp angles ranging from 48-55 degrees (65-70 degree bench face angles) and were based on the Company‚Äôs geotechnical investigations during 2019.  The mine designs and scheduling were engineered to provide a nominal 1,400 tpd of ROM feed to the sorting plant to produce 700 tpd of feed for the gold circuit.  At Hammerdown a total of 1.88 Mt grading 4.23 gpt Au with 28.8 Mt of waste rock is expected to be moved over the LOM (Figure 1).  A smaller satellite pit at the Orion deposit (Figure 2) is expected to produce 0.58 Mt grading 2.38 gpt Au with 4.87 Mt of waste rock moved.   Open pit dilution has been factored at 50%.  Waste rock from both open pits will be stored in a waste storage facility located between the two pits, with a portion backfilled at the end of the mine life with reject material from the sorting plant.  

Underground mining is envisioned at both the Hammerdown and Orion deposits. The mine design is based on utilizing narrow vein longhole open stoping to extract the mineralized veins, with stope widths varying between 1.5-3.0 metres.  Sublevels were set at 16 metre intervals.  Mineralized material will be extracted and hauled to surface where it will be transported to the sorting plant by the surface mine fleet.  At Hammerdown the mine plan anticipates making use of some of the existing underground development below the open pit to provide access to the mineralization.  Backfilling of open stopes will be completed using rock fill supplied with crushed, uniform reject material from the sorting plant. Over the LOM the total ROM production from the Orion underground workings includes 1.74 Mt of mineralized material grading 3.86 gpt Au from and 0.21 Mt of mineralized material grading 7.58 gpt Au from Hammerdown, respectively. A summary of the mine outputs is highlighted in Tables 7 and 8.  
 

Table 7. Hammerdown Open Pit and Underground Design

Open pit mineralized tonnes (Mt)

1.88

Open pit Au grade (gpt)

4.23

Open pit Au ounces contained (oz)

256,100

Strip ratio (waste:mineralized)

15.3

Underground mineralized tonnes (Mt)

0.21

Underground Au grade (gpt)

7.58

Underground Au ounces contained (oz)

51,500

Table 8. Orion Open Pit and Underground Design

Open pit mineralized tonnes (Mt)

0.58

Open pit Au grade (gpt)

2.38

Open pit Au ounces contained (oz)

44,200

Strip ratio (waste:mineralized)

8.4

Underground mineralized tonnes (Mt)

1.74

Underground Au grade (gpt)

3.86

Underground Au ounces contained (oz)

216,600

Figure 1. Hammerdown PEA Mine Design

Figure 2. Orion PEA Mine Design


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