Castle Mountain is classified as a low-sulfidation epithermal gold deposit (Scott et al., 2018), a sub-type of the epithermal class of gold and silver deposits (Sillitoe and Hedenquist, 2003). Epithermal gold-silver systems are driven by magmatic activity and form high-level vein, stockwork, disseminated and/or replacement deposits that may be mined by open-pit and/or underground methods. Some deposits also contain substantial resources of Ag, Pb, Zn, Cu and/or Hg.

Structure and associated rock porosity-permeability characteristics are the first-order control on the distribution of gold. Flow-dome breccia margins, phreatic diatremes, fault cataclasite and fractures focused provided conduits for hydrothermal fluids and contain the highest gold grades. Unfractured coherent flow-dome facies, clay altered volcaniclastic facies, and clay altered phreatomagmatic diatremes with low or variable permeability are weakly mineralized due to lower fluid interaction. Lower permeability units that are mineralized have been cut by structures such faults, fractures, or phreatic diatremes that promoted hydrothermal fluid interactions.

Gold is focused along structures and margins of facies contacts. It is believed that sub-vertical structures acted as pathways for magma and are responsible for the emplacement of the felsic volcanic package. These same structures also acted as conduits for gold-bearing hydrothermal fluids. Intersections of the steep structures with more per ........

Mining will be an open pit operation using conventional diesel-powered truck and shovel mining equipment. The current Phase 1 operation consists of a 14,000 ton/d (12,700 t/d) ROM operation with a focus on mining backfilled material that was placed in the JSLA pit from the previous mining operation 20 years ago. The Phase 2 expansion will increase production to 53,500 ton/d and extract hard rock material from open pits which will be drilled, blasted, and loaded to mine trucks using hydraulic shovels and wheel loaders. Phase 2 mine production is split with 50,000 ton/d (45,400 t/d) to the heap leach and 3,500 ton/d (3,200 t/d) to the mill.

The Phase 2 mine plan includes 14 years of operation expanding the overall life of mine (LOM) to 19 years and delivering 266.6 Mton (241.9 Mt) of ROM heap leach ore with an average diluted grade of 0.012 oz/ton (0.40 g/t) gold to the leaching operation. The mill will commence operation one year later and will process 17.7 Mton (16.1 Mt) of ore with an average diluted grade of 0.067 oz/ton (2.28 g/t) gold. In some years, a small portion of ROM ore will be crushed and re-directed to the mill when availability permits.

Phase 2 mining depends on several things including permits and is expected to commence two years prior to full production. The expanded heap leach and mill are anticipated to reach full production by the start of Year 6, designated as Year 1 for Phase 2.

The mine plan will depend on several activ ........

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For Phase 2, the heap leach pad will be designed to process 18.2 Mton (16.5 Mt) annually at an average life of mine grade of 0.012 oz/ton (0.41 g/t), while the mill will be designed to process 1.3 Mton (1.2 Mt) annually at an average LOM grade of 0.068 oz/ton (2.32 g/t). When considering both Phase 1 and Phase 2, operations will extend to approximately 19 years with an additional estimated three years of heap rinsing as part of reclamation where gold will continue to be leached and recovered.

Heap leaching
ROM ore will be delivered to the leach pad by the mining fleet. Pebble Quicklime (CaO) will be added for pH control of the process from two 100 ton silos. The lime will be metered into a clamshell and dumped into the loaded trucks which will then deliver the ore to the active stacking area.

Phase 2 design considered both use of a single pad to be adjoined with the current Phase 1 pad as well as construction of a separate pad. Both options would use a soluti ........