Source:
p. 31
Skeena acquired 100% ownership of Eskay Creek in October 2020.
Summary:
The Eskay Creek deposit is known as an outstanding example of a high-grade, precious metal rich epithermal volcanogenic massive sulphide (VMS) deposit that formed in a shallow submarine setting. The deposit has features and characteristics typical of a classic VMS deposit: it formed on the seafloor in an active volcanic environment with a rhyolite footwall and basalt hanging wall, having chlorite-sericite alteration in the footwall and sulphide formation within a mudstone unit at the seafloor interface. What differentiates the Eskay Creek deposit from other VMS deposits are the high concentrations of gold and silver, and an associated suite of antimony, mercury, and arsenic. These mineralization features, along with the high incidence of clastic sulphides and sulphosalts, are more typical of an epithermal environment with low formation temperatures.
Several distinct styles of stratiform and discordant mineralization are present at the Eskay Creek Project, defined over an area approximately 1,400 m long and up to 500 m wide (The main body of mineralization, the 21B Zone, is a stratiform tabular body of gold-silver-rich mineralization roughly 900 m long, 60 to 200 m wide, and locally exceeding 20 m thick. Individual clastic sulphide beds range from 1-100 cm thick and become progressively thinner up sequence). Ore is composed of beds of clastic sulphides and sulphosalts containing variable amounts of barite, rhyolite, and mudstone clasts. Imbricated, laminated mudstone rip-up clasts were observed locally at the base of the clastic sulphide-sulphosalt beds, indicating turbiditic emplacement of some beds. In the thickest part of the orebody, pebble and cobble-sized clasts occur in a northward trending channel overlying the Eskay Rhyolite. The beds grade laterally over short distances into thinner, finer-grained, clastic beds and laminations.
Gold and silver occur as electrum and amalgam while silver mainly occurs within sulphosalts. Precious metal grades generally decrease proportionally with decrease in total sulphides and sulphosalts. Clastic sulphoside beds contain fragments of coarse-grained sphalerite, tetrahedrite, lead-sulphosalts with lesser freibergeite, galena, pyrite, electrum, amalgam, and minor arsenopyrite. Stibnite occurs locally in late veins, as a replacement of clastic sulphides, and appears to be confined to the central, thickest part of the deposit., suggesting a locus for late hydrothermal activity. Cinnabar is rare and is found associated with the most abundant accumulations of stibnite. Barite occurs as isolated clasts, in the matrix of bedded sulphides and sulphosalts, and also as rare clastic or massive accumulations of limited extent. Barite is more common towards the north end of the deposit.
Early exploration efforts focused on discordant-style, precious metal mineralization hosted in sulphide veins within the rhyolite, felsic intrusions, and the footwall volcanic units. Following recognition of more significant stratiform mineralization, exploration expanded further to the north, defining the 21 Zone deposits. Distinct zones were defined by variations in location, mineralogy, texture, and precious metal grades (Edmunds et al, 1994).
Stratiform style mineralization is hosted in black carbonaceous mudstone and sericitic tuffaceous mudstone of the Contact Mudstone located between the Rhyolite and the Hanging Wall Andesite. The stratiform-hosted zones include the 21B Zone, the NEX Zone, the 21A Zone (characterized by arsenic-antimony-mercury sulphides), the barite-rich 21C Mudstone Zone, and the 21Be Zone. Stratigraphically above the 21B Zone and usually above the first basaltic sill, the mudstones also host a localized body of base metal-rich, relatively precious metals-poor, massive sulphides referred to as the Hanging Wall or HW Zone.
Summary:
The Project is located predominantly to the south of Tom Mackay Creek with a small portion extending to the north. Infrastructure will be located on the south side of Tom Mackay Creek, with the pit extending to the north beyond Tom Mackay Creek. Underground mining has previously been conducted in the northern portion of the Project at depth. The potential for underground development beneath the open pit was examined in preliminary evaluations during the 2021 PFS but was not included as part of the PFS. There is still potential for the inclusion of underground mining in future mining studies.
Each pit phase was designed to accommodate the proposed mining fleet. Mining will occur on 8 m benches with catch benches spaced either 8 or 16 m vertically depending on lithology type. The haul roads will be 30.2 m in width with a road grade of 10%.
The mine schedule plans to deliver 26.4 Mt of mill feed grading 3.37 g/t Au and 94.4 g/t Ag over a mine life of 10 years. Waste tonnage totalling 212 Mt will be placed into either non-acid generating (NAG) or potentially acid-generating (PAG) waste destinations. The overall strip ratio is estimated at 8.0:1. The mine schedule assumed a maximum of 2.9 Mt/a of feed will be sent to the process facility using a suitable ramp-up in year 1. A maximum descent rate of eight benches per year per phase was applied.
The proposed mine life includes 30 months of pre-stripping and 10 years of mining. Mill feed will be stockpiled during the pre-production years, with three grade stockpiles envisaged. A technical sample will be mined in Year -3 so that process performance of the mill can be evaluated on a bulk sample.
The mine equipment fleet is anticipated to be leased to lower capital requirements. Pre-production mining will be completed with 11.5 m3 loaders and 91 t rigid body trucks. This smaller fleet is better suited to the lower production tonnage requirements and narrower working conditions. With full production starting in Year 1, the primary loading units will be 22 m3 hydraulic shovels. Additional loading will be completed by a 23 m3 loader. The smaller loaders will shift to working at the primary crusher and site maintenance roles (snow removal, etc.). It is expected that one of the 11.5 m3 loaders will be at the primary crusher full time. The main production haulage trucks will be conventional 144 t rigid body trucks from Year 1 onwards. The support equipment fleet will be responsible for the usual road, pit, and waste rock storage facility (WRSF) maintenance requirements, but due to the climate conditions expected, will have a larger role in snow removal and water management.
Grade control will be completed with a separate fleet of RC drill rigs, with a 10 m x 5 m pattern in ore and 20 m x 10 m pattern in waste. Blasthole sampling will also be part of the initial grade control program to determine the best sampling method for operations.
There will be three WRSFs that will store the NAG waste. The largest will be located to the immediate west of the north and south pits, and two smaller WRSFs will be constructed to the west and northeast of the North pit respectively. A portion of the NAG waste will also be disposed of in the North pit as backfill. The WRSF design used a swell factor of 1.30. For the WDW facility, the lift height will be 20 m. Assuming a 37° face slope, the overall slope will be 26.5° with 13.6 m berm widths. A 37° face slope was also used for the in-pit backfill WRSFs. PAG waste will be sent to the TMSF to be submersed below water.
Pit designs were developed for the north and south pit areas. The north pit will consist of five main phases, while the south pit will only contain a single small phase. The pit optimization shells used to determine the ultimate pits were also used to outline areas of higher value for targeted early mining and phase development.
Equipment sizing for ramps and working benches is based on the use of 144 t rigid-frame haul trucks. The operating width used for the truck is 6.9 m. This means that single lane access is 23.3 m (twice the operating width plus berm and ditch) and double lane widths are 30.2 m (three times the operating width plus berm and ditch). Ramp gradients are 10% in the pit and WRSF for uphill gradients. Working benches were designed for 35–40 m minimum mining width on pushbacks. As the haul road grades exceed 5%, runaway lanes or retardation barriers will need to be incorporated into final execution designs as the project progresses to more detailed stages.
Flow Sheet:
Crusher / Mill Type | Model | Size | Power | Quantity |
Jaw crusher
|
.......................
|
|
|
1
|
Cone crusher
|
.......................
|
|
|
1
|
SAG mill
|
|
7.3m x 4.3m
|
3.8 MW
|
1
|
Ball mill
|
|
|
3.1 MW
|
1
|
Ball mill
|
|
5.5m x 9.0m
|
4.9 MW
|
1
|
Regrind
|
|
|
3 MW
|
1
|
Regrind
|
|
|
1.6 MW
|
1
|
Summary:
The crushing facility will be a single-stage crushing circuit that will process the run-of-mine (ROM) ore at a nominal processing rate of 473 t/h in Year 1 to Year 4 and 440 t/h from Year 5 onwards. The crushing facility will operate at 70% availability. The major equipment and facilities at the ROM receiving and crushing areas will include:
• Stationary ROM bin grizzly;
• ROM surge bin;
• Vibrating grizzly feeder;
• Primary jaw crusher;
• Coarse ore stockpile; and
• Stockpile reclaim apron feeders.
The ROM ore will be trucked from the open pit and dumped directly into the ROM surge bin or stockpiled on the ROM storage pad, which can be reclaimed by a front-end loader (FEL) for continuous feed. The ROM ore from the ROM bin will be withdrawn by the vibrating grizzly feeder where the coarse oversize will report directly into a single jaw crusher. The feed material will be crushed and will discharge from the crusher onto the primary crusher discharge conveyor delivering feed material to the coarse ore stockpile. The significant route length (725 m with 150 m lift) from the primary crusher to the coarse ore stockpile will require an overland conveyor.
The coarse ore stockpile feed overland conveyor will be fitted with a weightometer to monitor crushing plant throughput and assist with operational and metallurgical accounting. The coarse ore reporting to the coarse ore stockpile feed overland conveyor will be transferred to the coarse ore stockpile area. The coarse ore stockpile will provide 8 hours of live capacity.
Coarse ore from the stockpile will be reclaimed by two apron feeders at a combined nominal rate of 310 t/h discharging ore to the SAG mill feed conveyor to be fed into the SAG mill. The SAG mill feed conveyor will be equipped with a weightometer to provide data for feed-rate control to the grinding circuit.
Grinding and Classification
The primary grinding circuit for Year 1 to Year 4 will consist of only a SAG mill and ball mill in a closed circuit with classifying cyclones. A pebble crusher will be installed at the end of Year 4 and will start operating in Year 5. The primary grinding circuit for Year 5 onwards will consist of a SAG mill, pebble crusher and ball mill in a closed circuit with classifying cyclones.
The proposed ball mill circulating load is a nominal 250% of new feed.
The primary grinding circuit is designed for a product size 80% passing size (P80) of 100 µm. The SAG mill will be driven by a single 3.8 MW wound rotor drive motor (WRIM) with a liquid resistance starter (LRS) and slip energy recovery (SER) unit to allow for variable speed operation. The single pinion ball mill will be driven by a single 4.9 MW fixed speed WRIM with an LRS.
As required, steel balls will be added into the SAG mill and ball mill using a ball bucket and kibble system to maintain grinding efficiency.
Process water will be added with the coarse ore to the SAG mill to achieve a slurry density of approximately 70% solids (by weight). The SAG mill discharge will pass through a trommel screen. During Year 1 to Year 4, screen oversize will be returned to the SAG mill feed conveyor. Once the pebble crusher is installed and operated from Year 5 onwards, the trommel screen oversize will be transferred to the pebble crusher via a pebble crusher feed conveyor and the crusher product returned to the SAG mill feed conveyor. Undersize from the trommel screen will discharge directly into the cyclone feed pump box, where it will be diluted with process water and pumped to the cyclone distribution manifold via a cyclone feed pump. Cyclones will classify the feed slurry to achieve overflow stream of 30% solids (by weight) comprising product sized particles, whilst the cyclone underflow fraction of 72% solids (by weight) will report to the ball mill.
Cyclone underflow will be ground in the ball mill. Ball mill discharge will flow through the ball mill discharge trommel screen and remove any trash or broken mill balls, which will then be discharged to a concrete ball mill scats bunker. Trommel screen undersize will discharge into the cyclone feed pump box and combined with SAG mill trommel undersize.
The cyclone overflow will report to a trash screen via gravity, which will remove trash to a trash bin. Trash screen undersize will then flow by gravity to the rougher flotation circuit.
Maintenance activities in the grinding and classification area will be serviced by the mill area crane, which will be used for ball mill charging duties and maintenance activities. Spillages in the grinding and classification area will be pumped by the mill area sump pump into the cyclone feed pump box.
Processing
- Filter press plant
- Dewatering
- Flotation
Flow Sheet:
Summary:
The plant will process material at a nominal rate of 2.9 Mt/y for Years 1 to 4 and 2.7 Mt/y for the remaining years with an average head grade of 3.2 g/t Au and 94 g/t Ag. The plant is designed to operate two shifts per day, 365 d/y with an overall plant availability of 92%. The process plant feed will be supplied from the Eskay Creek open pit mine and the process plant will produce gold concentrate to be sold to refineries.
The processing plant will consist of the following:
• Single stage crushing circuit (jaw), fed from the open pit mine;
• Coarse ore stockpile with reclaim system, fed from an overland conveyor;
• Primary grinding including a SAG mill, pebble crusher (installed at Year 4), and ball mill in closed circuit with hydrocyclones;
• Rougher flotation with conventional concentrate regrind and two stages of cleaning;
• Slimes classification via two stages of hydrocycloning, fed from the rougher flotation tails;
• Secondary grinding an ........

Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Gold
|
Recovery Rate, %
| 84.2 |
Gold
|
Head Grade, g/t
| 3.4 |
Gold
|
Concentrate Grade, g/t
| 46 |
Silver
|
Recovery Rate, %
| 87.3 |
Silver
|
Head Grade, g/t
| 94.4 |
Silver
|
Concentrate Grade, g/t
| 1,375 |
Reserves at April 7, 2021:
Open Pit Constrained Mineral Resource Statement Reported at 0.7g/t AuEQ Cut-Off Grade by Domain.
Underground Mineral Resource Statement Reported at a 2.4 g/t AuEQ Cut-Off Grade for Long-Hole Mining and 2.8 g/t AuEQ Cut-Off Grade for Drift and Fill Mining.
Category | OreType | Tonnage | Commodity | Grade | Contained Metal |
Proven
|
In-Situ (OP)
|
13.5 Mt
|
Gold
|
4.25 g/t
|
1.85 M oz
|
Proven
|
In-Situ (OP)
|
13.5 Mt
|
Silver
|
124 g/t
|
53.7 M oz
|
Proven
|
In-Situ (OP)
|
13.5 Mt
|
Gold Equivalent
|
5.81 g/t
|
2.53 M oz
|
Probable
|
In-Situ (OP)
|
12.9 Mt
|
Gold
|
2.46 g/t
|
1.02 M oz
|
Probable
|
In-Situ (OP)
|
12.9 Mt
|
Silver
|
64 g/t
|
26.5 M oz
|
Probable
|
In-Situ (OP)
|
12.9 Mt
|
Gold Equivalent
|
3.26 g/t
|
1.35 M oz
|
Proven & Probable
|
In-Situ (OP)
|
26.4 Mt
|
Gold
|
3.37 g/t
|
2.87 M oz
|
Proven & Probable
|
In-Situ (OP)
|
26.4 Mt
|
Silver
|
94 g/t
|
80.2 M oz
|
Proven & Probable
|
In-Situ (OP)
|
26.4 Mt
|
Gold Equivalent
|
4.57 g/t
|
3.88 M oz
|
Measured
|
In-Situ (OP)
|
17,312 kt
|
Gold
|
4.2 g/t
|
2,322 koz
|
Measured
|
In-Situ (UG)
|
345 kt
|
Gold
|
5.2 g/t
|
58 koz
|
Measured
|
In-Situ (OP)
|
17,312 kt
|
Silver
|
118 g/t
|
65,908 koz
|
Measured
|
In-Situ (UG)
|
345 kt
|
Silver
|
67.3 g/t
|
747 koz
|
Measured
|
In-Situ (OP)
|
17,312 kt
|
Gold Equivalent
|
5.8 g/t
|
3,213 koz
|
Measured
|
In-Situ (UG)
|
345 kt
|
Gold Equivalent
|
6.1 g/t
|
68 koz
|
Indicated
|
In-Situ (OP)
|
20,342 kt
|
Gold
|
2.2 g/t
|
1,439 koz
|
Indicated
|
In-Situ (UG)
|
506 kt
|
Gold
|
4.9 g/t
|
79 koz
|
Indicated
|
In-Situ (OP)
|
20,342 kt
|
Silver
|
52.5 g/t
|
34,362 koz
|
Indicated
|
In-Situ (UG)
|
506 kt
|
Silver
|
35.8 g/t
|
583 koz
|
Indicated
|
In-Situ (OP)
|
20,342 kt
|
Gold Equivalent
|
2.9 g/t
|
1,903 koz
|
Indicated
|
In-Situ (UG)
|
506 kt
|
Gold Equivalent
|
5.3 g/t
|
87 koz
|
Measured & Indicated
|
In-Situ (OP)
|
37,654 kt
|
Gold
|
3.1 g/t
|
3,761 koz
|
Measured & Indicated
|
In-Situ (UG)
|
851 kt
|
Gold
|
5 g/t
|
137 koz
|
Measured & Indicated
|
In-Situ (OP)
|
37,654 kt
|
Silver
|
82.8 g/t
|
100,270 koz
|
Measured & Indicated
|
In-Situ (UG)
|
851 kt
|
Silver
|
48.6 g/t
|
1,330 koz
|
Measured & Indicated
|
In-Situ (OP)
|
37,654 kt
|
Gold Equivalent
|
4.2 g/t
|
5,116 koz
|
Measured & Indicated
|
In-Situ (UG)
|
851 kt
|
Gold Equivalent
|
5.7 g/t
|
155 koz
|
Inferred
|
In-Situ (OP)
|
5,239 kt
|
Gold
|
1 g/t
|
174 koz
|
Inferred
|
In-Situ (UG)
|
429 kt
|
Gold
|
4.1 g/t
|
57 koz
|
Inferred
|
In-Situ (OP)
|
5,239 kt
|
Silver
|
25 g/t
|
4,203 koz
|
Inferred
|
In-Situ (UG)
|
429 kt
|
Silver
|
57 g/t
|
787 koz
|
Inferred
|
In-Situ (OP)
|
5,239 kt
|
Gold Equivalent
|
1.4 g/t
|
231 koz
|
Inferred
|
In-Situ (UG)
|
429 kt
|
Gold Equivalent
|
4.9 g/t
|
67 koz
|
Corporate Filings & Presentations:
Document | Year |
Corporate Presentation
|
2022
|
...................................
|
2021
|
...................................
|
2019
|
- Subscription is required.
News:
News | Date |
Skeena Resources Ltd.: Groundbreaking Agreement Between Province and Tahltan Central Government Provides Further Certainty for Eskay Creek
|
June 6, 2022
|
Skeena Announces 21A West Zone Expansion Discovery at Eskay Creek Including 8.95 g/t AuEq over 34.00 metres
|
March 9, 2022
|
Skeena Announces Expansion of New 23 Zone at Eskay Creek: 2.00 g/t AuEq over 40.50 metres
|
January 26, 2022
|
Skeena Announces Discovery of New 23 Zone at Eskay Creek: 2.33 g/t AuEq over 59.91 metres and 1.08 g/t AuEq over 90.00 metres
|
January 19, 2022
|
Skeena Discovers Additional High Grade Mineralization at Eskay Creek Albino Waste Facility Including 10.13 g/t AuEq over 16.77 metres
|
December 8, 2021
|
Skeena Files Prefeasibility Study Technical Report for Eskay Creek
|
September 1, 2021
|
Skeena Completes PFS for Eskay Creek: After-Tax NPV(5%) of C$1.4B, 56% IRR and 1.4 Year Payback
|
July 22, 2021
|
Skeena Discovers Additional High Grade Mineralization in Former Eskay Creek Waste Facility Including 13.09 g/t AuEq over 13.68 metres
|
May 31, 2021
|
Skeena Discovers High Grade Mineralization in Former Eskay Creek Waste Facility Including 6.89 g/t AuEq over 22.80 metres
|
May 25, 2021
|
Skeena Announces Filing of Eskay Creek Technical Report
|
May 21, 2021
|
Skeena Intersects 4.94 g/t AuEq over 8.20 metres at Eskay Creek in New Mineralized Corridor
|
May 4, 2021
|
Skeena Announces 5.3 Moz at 4.3 g/t AuEq Measured and Indicated Resources at Eskay Creek
|
April 7, 2021
|
Skeena Intersects 12.51 g/t AuEq over 19.15 metres in 21C Zone Infill Drilling at Eskay Creek
|
March 2, 2021
|
Skeena Discovers New In-Pit Mineralization at Eskay Creek Including 4.80 g/t AuEq over 30.50 metres
|
February 17, 2021
|
Skeena Intersects 13.86 g/t AuEq over 25.27 metres in Hanging Wall Zone at Eskay Creek
|
February 10, 2021
|
Skeena Intersects Thick 58.50 metre Interval Grading 4.06 g/t AuEq within 21C Zone Development Buffer at Eskay Creek
|
February 3, 2021
|
Skeena Intersects Thick Intercepts Grading 5.67 g/t AuEq over 71.85 m and 9.15 g/t AuEq over 25.50 m within 21C Zone Development Buffer at Eskay Creek
|
January 28, 2021
|
Skeena Intersects Thick Intercept Grading 9.12 g/t AuEq over 49.60 metres within the 21C Zone Development Buffer at Eskay Creek
|
January 19, 2021
|
Skeena Adds Near Surface Mineralization in 22 Zone with 6.00 g/t AuEq over 26.28 metres
|
January 6, 2021
|
Skeena Drills Thick Intersection of 3.80 g/t AuEq over 42.80 metres in 22 Zone Infill Drilling at Eskay Creek
|
December 8, 2020
|
Skeena Intersects 36.75 g/t AuEq over 18.32 metres in 21A Zone Infill Drilling at Eskay Creek
|
November 24, 2020
|
Skeena Intersects 5.29 g/t AuEq Over 56.34 Metres in 22 Zone Infill Drilling at Eskay Creek
|
November 19, 2020
|
Skeena Intersects 4.48 g/t AuEq over 28.50 metres at Eskay Creek
|
October 27, 2020
|
Skeena Intersects 7.83 g/t AuEq over 42.59 m in 21C Zone Infill Drilling at Eskay Creek
|
October 20, 2020
|
Mexus Heap Leach Pad Work Continues; Two Gold Recovery Systems To Be Operational by Year End
|
October 19, 2020
|
Skeena Intersects 7.01 g/t AuEq over 20.00 metres in 21C Zone Infill Drilling at Eskay Creek
|
October 14, 2020
|
Skeena Closes Transaction to Acquire 100% of Eskay Creek
|
October 5, 2020
|
Skeena Discovers Mineralization at Eskay Deeps
|
September 15, 2020
|
Skeena Intersects 11.03 g/t AuEq over 39.66 metres in 21A Zone Infill Drilling at Eskay Creek
|
September 9, 2020
|
Skeena Intersects 25.03 g/t AuEq over 35.42 metres in 21A Zone at Eskay Creek New Discovery of Deep Mineralization in Lower Mudstones
|
August 25, 2020
|
Barrick Signs Definitive Agreement on Eskay Creek
|
August 4, 2020
|
Skeena to Acquire 100% of Eskay Creek
|
July 6, 2020
|
Skeena Intersects 33.82 g/t AuEq Over 22.50 Metres at Eskay Creek
|
May 5, 2020
|
Skeena Intersects 4.11 g/t AuEq over 22.08 metres at Eskay Creek
|
April 23, 2020
|
Skeena Intersects 22.59 g/t AuEq Over 14.33 Metres at Eskay Creek
|
February 26, 2020
|
Skeena Intersects 14.82 g/t AuEq Over 31.30 Metres at Eskay Creek
|
February 11, 2020
|
Skeena Intersects 14.73 g/t AuEq over 36.85 m at Eskay Creek
|
January 14, 2020
|
Skeena Files PEA Technical Report for Eskay Creek
|
December 20, 2019
|
Skeena Intersects 19.73 g/t AuEq over 17.00 m in HW Zone at Eskay Creek
|
November 21, 2019
|
Skeena Delivers Robust Project Economics for Eskay Creek: After-Tax NPV5% of C$638M, 51% IRR and 1.2 Year Payback
|
November 7, 2019
|
Skeena Intersects 314.07 g/t AuEq Over 2.21 m in Lower Mudstone at Eskay Creek
|
October 22, 2019
|
Skeena Intersects 10.56 g/t AuEq Over 27.50 m at Eskay Creek
|
September 25, 2019
|
Skeena Intersects 18.13 g/t AuEq over 22.65 metres in New High-Grade Vent at Eskay Creek
|
September 9, 2019
|
Skeena Initiates Metallurgical Optimizations and Preliminary Economic Assessment for Eskay Creek
|
March 26, 2019
|
Skeena Announces Upgraded Pit Constrained Resource Estimate for Eskay Creek
|
February 28, 2019
|
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