Overview

Deposit type

• SEDEX

Summary:

The Cardiac Creek, Cirque, Driftpile deposits and other lead-zinc-silver occurrences within the Kechika Trough are characterized as sedimentary exhalative (SEDEX) type deposits.

The lead-zinc-silver-barium deposits and occurrences found within the Kechika Trough (Cirque, Driftpile and Cardiac Creek), as well as the deposits and occurrences in the Selwyn Basin (Howards Pass, Tom, Jason, Faro and Grum), the Belt-Purcell District (Sullivan), and in Australia (HY, Century, Mount Isa and Broken Hill) and the Brookes Range in Alaska (Red Dog) all share common characteristics and are typically grouped as SEDEX deposits (Goodfellow and Lydon, 2007). The SEDEX deposit type was first proposed by Carne and Cathro (1982) in their early description of the Selwyn Basin and Kechika Trough deposits. This type of deposit shares many similar characteristics with VMS (volcanogenic massive sulphide) and MVT (Mississippi Valley Type) deposits suggesting a shared genetic link (Goodfellow and Lydon, 2007).

Much research has been completed on this type of deposit examining the geological characteristics, genetic models and the physiochemical controls (MacIntyre, 2008). From this work, a general consensus concerning the formation of SEDEX deposits has been made. It is generally agreed that SEDEX deposits are formed from the precipitation of sulphide and sulphate minerals from metalliferous brines exhaled out onto the seafloor along re-activated rift faults that generate rapidly subsiding graben or half-graben structures (MacIntyre, 2008; Goodfellow and Lydon, 2007). However, recent work by Gadd et al. (2015) on the Howards Pass deposit in the Selwyn basin is beginning to test this theory which may not apply to all SEDEX deposits in the Selwyn Basin and or Kechika Trough. The metal-bearing fluids are likely derived from dewatering of fine- to coarse-grained clastic sediments or carbonate hydrothermal reservoirs (Goodfellow and Lydon, 2007) where leaching has scavenged the zinc and lead and other elements. In the Selwyn Basin and the Kechika Trough, the coarse clastic grits of the Windermere Super Group are thought to have acted as the hydrothermal reservoir for the mineralizing fluids (MacIntyre, 2008).

The geology of the Akie property can be subdivided into east and west segments by Silver Creek. To the west of Silver Creek, the wavy-bedded mudstone with nodular limestone rocks of the Kechika Group, the Ospika volcanics and siltstones, black graptolitic shales, limestones and calcareous siltstones of the Road River Group form a series of southeast-striking, southwest-dipping imbricated thrust panels that are in thrust contact with a thick, approximately 500 m panel of southeast-striking, southwest-dipping Earn Group rocks.

The geology of the Akie property can be subdivided into east and west segments by Silver Creek. To the west of Silver Creek, the wavy-bedded mudstone with nodular limestone rocks of the Kechika Group, the Ospika volcanics and siltstones, black graptolitic shales, limestones and calcareous siltstones of the Road River Group form a series of southeast-striking, southwest-dipping imbricated thrust panels that are in thrust contact with a thick, approximately 500 m panel of southeast-striking, southwest-dipping Earn Group rocks comprised primarily of Gunsteel Formation shales that are the host to the Cardiac Creek deposit. The panel of Gunsteel Formation shale is currently interpreted to represent the limb of a steeply inclined overturned syncline and the steeply dipping western limb of a large anticline that straddles Silver Creek. The Gunsteel Formation shales are underlain by the dolomitic to weakly calcareous siltstones of the Silurian Siltstone of the Road River Group. This siltstone straddles Silver Creek and represents the core of a large anticline that is central to the property. Along the eastern flanks of the antiform the Silurian Siltstone is immediately overlain by medium grey fossiliferous limestone of the Kwadacha Reef. The limestone is characterized by abundant crinoids, brachiopods, corals and other fossils (MacIntyre, 2008) and typically outcrops along the eastern banks of Silver Creek.

Erosion of the limestone by the local streams and creeks feeding into Silver Creek from the east has produced steep cliffs and gorges with waterfalls. Locally, immediately overlying the limestone is a thin lens of chert pebble conglomerate containing millimetre- to centimetre-sized grains hosted in a silty shale matrix (Baxter, 1996c). The rocks of the Gunsteel Formation are recognized above this conglomerate unit and are exposed across much of the eastern half of the property and have been folded into a number of minor synforms and antiforms. Mappable units within the Gunsteel Formation include the “Pinstripe shale” and chert pebble conglomerate. The pinstripe shale is exposed along ridge tops in the central area of the property and is characterized by black silty shale interbedded with thinly bedded, light creamy-grey siltstone (Baxter, 1996c). The eastern edge of the property is bounded by a steep east-dipping thrust fault depositing Road River Group limestone on top of the Earn Group stratigraphy (MacIntyre, 2005).

In general, the geology of the Akie property has been described as a large anticlinorium bound by outwardly dipping thrust faults (MacIntyre, 1998). Minor thrusting and faulting is observed across the property, each producing an unknown degree of displacement. Drilling on the Akie property has focused on the rocks of the Gunsteel Formation rather than those of the Akie, Warneford and Paul River Formations, the Silurian Siltstone and other rocks of the Road River Group.

The Cardiac Creek deposit is hosted by the siliceous, carbonaceous black shale of the Gunsteel Formation. The deposit is situated towards the base of the Gunsteel Formation near the Gunsteel Formation shale / Road River Group contact and separated by a thin sliver of debris flows and silty to turbiditic shale associated with the Paul River Formation. The deposit is interpreted to be a SEDEX-type lead-zinc-silver body of mineralization. The mineralization is represented by a “sheet-like” tabular body of interbedded sulphides and shale trending northwest-southeast, striking at 130°, dipping at 70° southwest, and ranging in thickness from 5 m to 50 m. The mineralized horizon can be traced over 7 km from the Bear Valley Creek southeast to the Akie River. The known and potentially economic portion of the deposit has an approximate strike length of 1,500 m with a dip extent of at least 850 m. The sulphide mineralogy of the deposit is relatively simple, dominated by pyrite, sphalerite, and galena with barite (sulphate). Internal company petrological reports have identified a rare occurrence of Stannite (Sn oxide) (Lehne, 1995); however, no systematic petrological study of the mineralogy has taken place. Analytical data collected from drill hole sampling indicate that the Cardiac Creek deposit is enriched in the following suite of elements: Pb, Zn, Ag, Ba, Fe, Cd, Sn, Tl, Hg, S, Pd, In, and Ga.

Mining Methods

• Longhole stoping

Summary:

Mining of the Akie deposit will be conducted using bulk underground mining methods. The mine will be accessed using a primary decline ramp which will connect Portal One at 1055 mASL to the 920 level and serve as both as the primary production haulage route as well as a fresh air source. Additionally, a second portal will be constructed up-slope at the 1220 level to serve as the primary fresh air intake and to provide secondary egress. Levels will be located throughout the mine at 20 m vertical increments from (580 to 1320 levels), which will be connected by a primary spiral ramp, sized at 5.5 mW x 6 mH and located in the footwall of the deposit.

The primary stoping method for the Akie deposit will be longitudinal long-hole with paste backfill replacement in the mined-out voids. Thinner portions of the orebody will be mined using longitudinal longhole methods but employ permanent pillars to avoid the requirement for cemented self-standing backfill.

The mined rock will be extracted from the mine at a rate of approximately 4,000 t/d which will be crushed and fed to a Dense Media Separator (DMS) prior to grinding and flotation. Approximately 25% of mine yield will be floated in the DMS plant, resulting in a milling rate of 3,000 t/d.

Underground haul trucks will take the broken rock to surface and dump it on the portal pad. The mineralized material will then be loaded into surface trucks and transported to the mill, a distance of approximately 2.6 km. A production pass chute will be located on the 920 level for truck loading. All mine tonnes above the 920 level will be fed to chutes on each level that connect to this production pass. Mine tonnes below the 920 level will be loaded directly into trucks for haulage out of the mine.

Once a mining panel has been exhausted, the space will be backfilled using either cemented paste or conventional cemented rock fill (CRF). Stopes less than 10.0 m wide, and all stopes not requiring self-supported fill walls will be filled with loose rock fill. Paste backfill will utilize 73% of the process tailings over the life of mine.

Additionally, 100% of the potentially acid generating (PAG) rock generated from development activities will be used as CRF or loose rock fill underground. Non-potentially acid generating (NPAG) rock will be stored on surface and where possible, used in the construction of site infrastructure. DMS reject (the float rock) will also be stored on surface.

Stope sills will be driven at 5.0 mW x 5.0 mH at 20 m vertical increments. Stopes will in general be a maximum of 20 m along strike, making a typical maximum exposed hanging wall and footwall of 20 mL x 25 mH. Where the orebody is greater than 16 m in width, two parallel sill drives will be used to ensure adequate drill coverage and to provide multiple extraction points for mucking.

Production drilling will be done using 64 mm downholes for most of the stopes, using drop raises, slots, and drill rings for extraction.

In situations where the final uppermost stopes of the panel form a crown pillar beneath backfill, stopes will be extracted using uphole drilling and inverse raises.

After a stope has been extracted, it will be filled with self-standing paste or CRF backfill, allowing the mining of the next, adjacent stope.

Nominally, panels will be comprised of 30 individual stopes; six stopes along strike by five stopes high. Thus, the typical panel will have a length of 120 m along the strike and a height of 105 m, spanning five mining levels.

Comminution

Crushers and Mills

Summary:

The process plant will include:
- Three stages of crushing;
- Two stages of ball mill grinding in reverse closed-circuit with cyclones;

Material from the underground mine will feed a crushing plant that consists of three stages of crushing. The plant will process 222 t/h of material, operate 18 h/d and produce a final product P80 of 8.8 mm.

Primary Crushing
Material will be stockpiled near the jaw crusher or direct dumped through an 800 mm static grizzly into a dump pocket. Stockpiled ROM material will be re-handled by a front-end loader and fed into the crusher. The material will discharge through the static grizzly into a 40 t live feed hopper. Oversize material from the static grizzly will be removed for later size reduction using a rock breaker.

A vibrating grizzly feeder will draw material from the feed hopper at a rate of 222 t/h. The vibrating grizzly oversized material will feed directly into a 762 mm x 1,067 mm (30” x 42”) jaw crusher with an installed power of 110 kW. The undersized -75 mm material will bypass the crusher and feed directly onto the screen feed conveyor. The primary crushing stage will produce a product P80 of approximately 100 mm at a crusher closed side setting (CSS) of 89 mm.

The screen feed conveyor will collect crushed product from all three stages of crushing and feed a 2,438 mm x 6,096 mm (8’ x 20’) double-deck vibrating screen. The top deck will have an aperture size of 35 mm, and the +35 mm material will be conveyed to the secondary crusher. The bottom deck will have an aperture size of 12 mm, and the -35 mm, +12 mm material will be conveyed to the tertiary crusher. The -12 mm final product, at an estimated P80 of 8.8 mm, will discharge onto the Stockpile Feed Conveyor and be transferred to the Crushed Material Stockpile.

Secondary Crushing
Material from the secondary crusher feed conveyor will discharge into a cone crusher with an installed power of 132 kW. The secondary crusher will reduce the material to a nominal product P80 of approximately 25 mm using a CSS of 25.4 mm. Crushed product will be transferred to the screen feed conveyor and be circulated back to the double-deck screen.

Tertiary Crushing
Material from the Tertiary Crusher Feed Conveyor will discharge into a cone crusher with an installed power of 160 kW. The tertiary crusher will reduce the material to a nominal product P80 of 12 mm with a CSS of 12.7 mm. Crushed product will be transferred to the Screen Feed Conveyor and be circulated back to the double-deck screen.

Crushed Material Stockpile
The double-deck screen undersize, with a final P80 product size of 8.8 mm, will be conveyed to the Crushed Material Stockpile. The stockpile will provide 4,000 t, or twenty-four hours, of live storage capacity. Two belt feeders, located in a corrugated tunnel under the stockpile, will be installed with variable frequency drives (VFD) to control the reclaim rate feeding the DMS circuit. Each belt feeder will be capable of providing the total throughput of 181 t/h.

Grinding
The grinding circuit will consist of a primary ball mill followed by a secondary ball mill. The primary ball mill will operate in open circuit, while the secondary ball mill will operate in reverse closed circuit with a cluster of hydro-cyclones. The grinding circuit will be able to process a nominal throughput of 136 t/h (fresh feed) and produce a final product P80 of 56 µm.

Sinks and fines from the DMS circuit will feed a 4.3 m diameter x 7.3 m long overflow ball mill via the ball mill feed conveyor. The mill will be installed with a 2,238 kW induction motor. A belt-scale on the feed conveyor will monitor feed rate. Water will be added to the ball mill to maintain the slurry charge in the mill at a constant density of 70%. Slurry will overflow from the ball mill onto a trommel screen attached to the discharge end of the mill. The trommel screen oversize will discharge into a trash bin for removal from the system.

Product from the primary ball mill, at an approximate T80 transfer size of 250 µm, will flow into the cyclone feed pump box and combine with the secondary ball mill discharge before being pumped up to a cluster of ten (eight operating / two standby) 375 mm hydro-cyclones for size classification. The coarse underflow will flow by gravity to the secondary ball mill for additional grinding, while the fine overflow, at a final product P80 of 56 µm, will report to the Pb conditioning tank. The hydro-cyclones have been designed for a 300% circulating load.

Cyclone underflow will feed a 4.3 m diameter x 7.3 m long overflow ball mill with an installed power of 2,238 kW. Ground slurry will overflow from the ball mill onto a trommel screen attached to the discharge end of the mill. The trommel screen oversize will discharge into a trash bin for removal from the system, while the undersize will flow into the cyclone feed pump box.

Both ball mills are the same size to allow for common spares.

Processing

• Flotation
• Dense media separation
• Dewatering
• Filter press

Summary:

The ZincX’s Akie Project focuses on developing the Cardiac Creek Pb/Zn/Ag deposit. The recent metallurgical test program completed at Base Metallurgical Labs in Kamloops, BC (BL0148) has demonstrated that standard Pb and Zn sequential flotation, with pre-concentration using dense media separation (DMS), can yield an overall Pb recovery of 46.2%, at a concentrate grade of 45.1% Pb, and a Zn recovery of 88.9%, at a concentrate grade of 52.4% Zn (BL0148-LCT21). Results from this test program were used to develop the corresponding process design criteria, mechanical equipment list, flowsheets and operating costs.

The process plant will include:
- Three stages of crushing;
- Dense media separation;
- Two stages of ball mill grinding in reverse closed-circuit with cyclones;
- Sequential Pb and Zn flotation circuits, each incorporating three cleaning stages;
- Concentrate dewatering circuits using thickeners and pressure filters;
- Concentrate storage and load-out facilities; and - Dewatering, filtering and storage of dry stack tailings.

The crushing plant will have a throughput of 4,000 t/d with average life of mine (LOM) head grades of 1.48% Pb, 13 g/t Ag and 7.63% Zn. The circuit will operate at an availability of 75%, resulting in an hourly throughput of 222 t/h. The DMS, milling and flotation circuits will operate 24 h/d, 365 d/a with an estimated availability of 92%. DMS pre-concentration will reject 25% of the plant feed as waste; the milling, flotation, and dewatering circuits are designed for a throughput of 3,000 t/d.

The three-stage crushing circuit will reduce the material to a product size of 80% passing (P80) 8.8 mm. The DMS circuit will then reject 25% of the feed material while maintaining metal recoveries of 96.3% Pb and 98.5% Zn. The subsequent two stage grinding circuit will target a P80 grind size of 56 µm, before Pb and Zn are recovered into concentrates using sequential flotation. Zn rougher and Zn 1st cleaner tailings, designated as final tailings, will be thickened and pressure filtered to a moisture content of 15% and transferred to a dry stack tailings facility.

The recovery method will consist of the following unit operations:

- Primary Crushing – A vibrating grizzly feeder and jaw crusher in open circuit, producing a final product P80 of 100 mm;

- Secondary / Tertiary Crushing – Two stages of cone crushing in closed circuit with a double deck vibrating screen, producing a final product P80 of 8.8 mm;

- Crushed Material Stockpile and Reclaim – A 24 h live capacity stockpile (4,000 t) with two reclaim belt feeders feeding the DMS circuit;

- Dense Media Separation – Dense media cyclones with a cut SG of 2.80 to pre-concentrate sulphide minerals and reject waste material;

- Primary Grinding – A ball mill in open circuit, producing a T80 transfer size of approximately 250 µm;

- Secondary Grinding – A ball mill in reverse closed circuit with a cluster of hydro-cyclones, producing a final product P80 of 56 µm;

- Pb Flotation – Rougher and cleaner flotation to produce a saleable Pb concentrate;

- Pb Rougher Concentrate Regrind – A stirred regrind mill in open circuit, reducing Pb rougher concentrate to a P80 of 10 µm;

- Pb Concentrate Dewatering – A 4 m diameter high- rate thickener to achieve an underflow solids density of 55%, and a pressure filter to reduce the concentrate to a final moisture content of 8%;

- Zn Flotation – Rougher and cleaner flotation to produce a saleable Zn concentrate;

- Zn Rougher Concentrate Regrind – A stirred regrind mill in open circuit, reducing Zn rougher concentrate to a P80 of 15 µm;

- Zn Concentrate Dewatering – A 12 m diameter high-rate thickener to achieve an underflow solids density of 55%, and a pressure filter to reduce the concentrate to a final moisture content of 8%; and

- Final Tailings Dewatering – A filter plant to reduce final tailings to a moisture content of 15% for dry stacking.

Water Supply

Summary:

The following water types will be used in the process plant:

Process Water – Overflow water from the Pb and Zn concentrate thickeners will be used as process water. This water will be used predominantly in the grinding circuit to dilute slurry to the required densities.

Fresh Water – Fresh water for the process plant will be pumped from a fresh water supply, such as the local water course or an impoundment which may potentially be located adjacent to the process plant. Fresh water will be used as reagent make-up water, gland water and process make-up water. The estimated fresh water consumption in the process plant will be 17 m3 /h, and approximately 117 m3/h for potable water.

Reclaim Water – Water reclaimed from the tailings filter plant will be used as process water in the grinding and flotation circuits. Based on the water balance and a dry stack moisture content of 85%, 322 m3/h of water will be reclaimed from the tailings filter plant.

Production

Operational metrics

Personnel

Job Title	Name	Profile	Ref. Date
VP Exploration	Ken MacDonald		Dec 30, 2023