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).

Mineralization
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 permeable volcanic rocks created an environment for enhanced gold precipitation from hydrothermal fluids, possibly due to processes of boiling and interaction with meteoric water.

Lithologic controls are dependent on the host rock texture. Tuff be ........

Castle Mountain is being developed by Equinox Gold in two stages. Phase 1 construction was completed in 2020 with commercial production achieved in November 2020. Equinox Gold completed a feasibility study for the Phase 2 expansion in March 2021, outlining plans to extend the mine life and expand production to more than 200,000 ounces of gold annually.

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.

There are five pit areas with pits at JSLA (3 phases), Jumbo, Oro Belle, East Ridge (2 phases) and South Domes (2 phases). There is a total of nine phases of open pit mining starting with JSLA backfill and moving north, and then to South Domes to complete the operation. The mining sequence of the phases allows for backfilling of waste as the pit reaches final limits.

Phase 1 mining is being conducted by contract mining services. Mine supervision and technical ........

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