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Greece
Skouries Project

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 Location:
4 km SE from Palaiochori, Greece

  Project Contacts:
23A Vasilissis Sofias Avenue
Athens
Greece
10674
Phone+30-214-687-0000
Fax+30-214-687-0095
WebsiteWeb
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  • Overview
  • Owners
  • Geology
  • Mining
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  • Reserves
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  • Fleet
  • Personnel
  • Filings & News

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Overview

StatusCare and Maintenance
Mine TypeOpen Pit & Underground
Commodities
  • Gold
  • Copper
Mining Method
  • Truck & Shovel / Loader
  • Sub-level open stoping (SLOS)
  • Paste backfill
Processing
  • Calcining
  • Dewatering
  • Filter press plant
  • Flotation
Mine Life20 years (as of Jan 1, 2022)
Construction of the Skouries Gold Project commenced in 2012 and was placed into care and maintenance in 2017. The restart of the project will be executed using a standard engineering, procurement, and construction management (EPCM) methodology. Target re-start of construction at Skouries in mid-2022.
Latest NewsEldorado Gold Files Technical Reports for Skouries and Lamaque     March 31, 2022


Owners

Source: p. 72
CompanyInterestOwnership
Aktor Enterprises Ltd. 5 % Indirect
Eldorado Gold Corp. 95 % Indirect
Hellas Gold is the 100% owner of the Skouries. Eldorado owns a 95% interest in Hellas Gold, with the remaining 5% held by Aktor Enterprises Ltd.

Deposit Type

  • Porphyry
  • Metamorphic hosted
  • Vein / narrow vein

Source: Source p.64-66

Summary:

The Skouries deposit is centred on a small (less than 200 m in diameter), pencil-porphyry stock that intruded schist and gneiss of the Vertiskos unit. The mineralized porphyry intrusion plunges steeply to the south-southwest and obliquely crosscuts the moderate to steeply north-east dipping limb of a district-scale F2 antiform. Mineralization has been tested to a depth of 920 m from surface as shown on Figure 7.3. Surface exposures and drill data indicate that the porphyry stock has a subtle north-east elongate geometry. The porphyry is characterized by at least four intrusive phases that are of probable quartz monzonite to syenite composition (Kroll et al. 2002; Frei, 1995) but contain an intense potassic alteration and related stockwork veining that overprints the original protolith. Potassic alteration and copper-gold mineralization also extend into the country rock; approximately two thirds of the Measured and Indicated Mineral Resources are hosted outside the porphyry with about a 50:50 split in gold-equivalent ounces. The potassic alteration is characterized by potassium feldspar overgrowths on plagioclase, secondary biotite replacement of igneous hornblende and biotite, and a fine-grained groundmass of K-feldspar-quartz with disseminated magnetite. Four main stages of veining are recognized:
• Early stage of intense quartz-magnetite stockwork (pre-ore stage).
• Quartz-magnetite veinlets with chalcopyrite ± bornite (initial ore stage).
• Quartz-biotite-chalcopyrite ± bornite-apatite-magnetite veinlets (main ore stage).
• Localized, late stage set of pyrite ± chalcopyrite-calcite-quartz veins (post-ore stage).

Skouries is typical of a gold-copper porphyry deposit. Mineralization occurs in stockwork veins, veinlets and disseminated styles typical of a porphyry, and has a subvertical, pipe-like shape. The multi-phase monzonite to syenite porphyries intruded into metamorphic basement rocks. Both igneous and metamorphic rocks contain high temperature potassic alteration (K-feldspar-biotite) and stockwork quartz-magnetite-chalcopyrite-bornite veins. The potassic zone in the surrounding country rock is surrounded by a high temperature inner propylitic alteration characterized by amphibole. The deposit, however, lacks extensive phyllic or argillic-advanced argillic zones typical of many porphyry systems. This may, in part, reflect a deeper level of erosion and the focused nature of the magmatic-hydrothermal system.


Mining Methods

  • Truck & Shovel / Loader
  • Sub-level open stoping (SLOS)
  • Paste backfill

Source: p.9-13

Summary:

The Skouries Project is designed as a two-phase mining operation. Phase 1 consists of a combined open pit and underground mine, operating over nine years. Phase 2 consists of mining from the underground mine only, for an additional 11 years. The total ore producing LOM is 20 years.

Phase 1 total mill feed rate is 8.0 Mtpa, consisting of a nominal 5.5 Mtpa from the open pit mine combined with 2.5 Mtpa from the underground mine. At the start of the mine life, during the initial two-year underground mine ramp-up period, the open pit feed rate is variable in order to maintain the 8.0 Mtpa mill feed. During Phase 1, 8.0 Mt of low-grade oxide ore is stockpiled to be rehandled for mill feed during Phase 2. Phase 1 is completed at the end of the open pit mine life in Year 9.

Phase 2 mine production, from Year 10 to the end of the LOM, is provided from the underground mine. Phase 2 mine development begins in Year 4 in order to allow a seamless ramp-up from the nominal Phase 1 production rate of 2.5 Mtpa. During the first four years of Phase 2, the mill feed
rate of 8.0 Mtpa is maintained by reclaiming oxide ore stockpiled during Phase 1, at a rate which balances the mill feed to 8.0 Mtpa through Year 13. From Year 15, Phase 2 mill feed is maintained at a nominal feed rate of 6.5 Mtpa, solely from underground mine production, which tails off in
Years 19 and 20.

Open pit mining will be by conventional truck-shovel operation, with an ore production rate of approximately 5.5 Mtpa, at a waste to ore stripping ratio of 1.03 The mining sequence will consist of drilling, blasting, loading, and hauling of ore and waste materials for processing and waste
disposal. Based on the modelled rock types, approximately 17% of the mined material is amenable to free digging; this material will not be blasted.

Drilling operations will be carried out continuously as part of the normal mining operation. Once full mine production is reached, drilling and blasting of approximately 1 Mt (dry) per month will be required to maintain production levels. Drilling and blasting activities will be carried out by Hellas Gold, with bulk explosives and associated blasting accessories being delivered to site as needed by an explosives contractor.

Waste material classified as red clay and overburden will not be drilled or blasted as it is considered free dig material. All other waste and ore material types (weak rock and hard rock) will be drilled and blasted.

The primary haul roads are designed at 25 m width, based on a 90 t haul truck. Other haul roads, to be used by contractor trucks, are designed for 55 t articulated haul truck with an overall roadway width of 15 m. Table 16.5 outlines the road widths for each truck class. Road grades are limited to 10% in-pit and ex-pit for the 90 t trucks and approximately 12.5% for the contractor trucks. Runaway lanes will be constructed as required for safe operations. The smaller 55 t haul truck has been selected for waste as the route which the waste needs to travel over to the various dump areas is winding along steep terrain.

The primary mining loading fleet will consist of a conventional 12 m3 diesel hydraulic excavator and two front-end loaders with 8.5 m3 and 12 m3 buckets.

Underground mining
The Skouries orebody that extends below the bottom of the open pit is amenable to a bulk underground mining method and has been evaluated under several different design approaches since the late 1990s, including block caving, SLC, and SLOS. SLOS has been confirmed as the most appropriate underground mining method for a number of reasons.

The underground portion of the Skouries Project will begin from the existing ramp from the surface to 385 masl. The ramp is currently developed to 35 m above the first production level, 350L. Mining will proceed to the 350L to establish major infrastructure and services. The 350L will serve as the mucking horizon for two test stopes, which are situated in the Crown Pillar and within the mining limits to enable a mineralized and accurate representation of the mining to be completed in Phase 1.

Underground mining will be by conventional underground mining techniques. The mining sequence will consist of drilling, blasting, loading, and hauling of ore and waste materials. During Phase 1, ore will be hauled to the surface crusher by truck. During Phase 2 ore will be hoisted to surface by a shaft. In Year 4, the shaft headframe construction will commence, and shaft excavation will begin in Year 6. Excavation of the shaft will continue through Year 8, with the entire materials handling system projected for completion six months prior to the beginning of Phase 2 in Year 10.

The design of the Skouries mine includes provision for remote mining technology (RMT), which has an impact on the cycle times of stopes and the productivity of equipment. This technology includes tele-remote operation of mechanized equipment by an operator located on surface or in a remote area of the underground mine.

The Phase 2 materials handling will involve shaft hoisting of ore to surface. There are no vertical production nor development ore or waste passes included in the mine design; all broken rock will be loaded using load haul dumps (LHDs) and transported via the ramps in haul trucks. Shaft hoisting is critical to enable a ramp-up to full Phase 2 production of 6.5 Mtpa from the Phase 1 production of 2.5 Mtpa. In order to hoist the material by shaft, underground crushing will be implemented. During Phase 2, all stope ore and some late development ore will be hoisted to surface via the shaft. Development waste will continue to be hauled to surface via the dual ramp system, but these quantities are expected to be minimal.


Crushing and Grinding
Flow Sheet: Source
Source: Source p.14, 174-176
Crusher / Mill TypeModelSizePowerQuantity
Gyratory crusher 1
Cone crusher 450 kW 2
SAG mill 9.75m x 4.57m 9.6 MW 1
Ball mill 7.01m x 9.75m 9.6 MW 1
Ball mill 4.6m x 7.0m 2.25 MW 1

Summary:

The ore is delivered by 90-t haul trucks from the open pit and 50-t haul trucks from underground to the primary crushing station dump pocket. The ore is then crushed by the gyratory primary crusher and the crushed ore is discharged via the primary crusher discharge feeder.

The transportation of the crushed ore from the primary crusher discharge to the covered, conical, crushed-ore stockpile is implemented using a belt conveyor system that is comprised of the primary crusher sacrificial conveyor and the primary crusher discharge conveyor. An over-belt magnet at the discharge of the sacrificial conveyor removes scrap metal before ore enters the ore stockpile.

An automatic dust suppression system will be installed at the crusher feeding point and at the crusher discharge feeder to prevent dust emission from the ore unloading and crushing operations.

The ore stockpile is covered and has a live storage capacity of 24,000 t, equivalent to one day of production. The stockpile area total storage capacity will be approximately 80,000 t, equivalent to slightly over three days of production.

The ore is extracted from the ore stockpile using three variable speed apron feeders, which are of 1,215 t/h total combined capacity and each one is driven by a 75 kilowatt (kW) motor. The feeders are located beneath the stockpile in a tunnel.

The feeders discharge onto a belt conveyor system, which is comprised of the ore reclaim sacrificial conveyor and the SAG mill feed conveyor, which reports to the SAG mill feed chute.

The primary grinding circuit is designed to reduce the feed ore with a particle size of 80% passing 150 mm to a product with a particle size of 80% passing 120 µm. The size reduction is achieved by a two-stage wet grinding circuit comprising a SAG mill driven by variable speed motors, a ball mill (with a fixed speed motor) and a pebble crushing circuit (SABC circuit).

The transfer size of the material between the SAG mill and the ball mill is in the range of 80% passing between 2.0 mm and 3.6 mm. The SAG mill has a diameter of 9.75 m and an effective grinding length of 4.57 m and is driven by two 4.8 MW motors with variable frequency drives (VFD) and including auxiliary lubrication circuits. The grinding media consists of 125 mm diameter balls made from high quality forged steel. The SAG mill liners are Cr-Mo alloy cast steel.

Two shorthead type cone crushers will be installed for the crushing of the oversize pebbles (+12 mm) produced by the SAG mill. Total crushing capacity is 254 t/h and each cone crusher will be driven by a 450 kW motor.

The primary ball mill has a diameter of 7.01 m and an effective grinding length 9.75 m and is driven by two 4.8 MW motors. The grinding media consists of 60 mm diameter balls made from high quality forged steel. The ball mill will be lined with rubber liners and lifters.

Both mills will be equipped with trunnion bearings and drive gear lubrication, drive protection and cooling systems. The SAG mill product flows to a vibrating screen with 12 mm openings. The oversize particles (> 12 mm) are transferred via the pebble conveyor No. 1 to the pebble crushers. The crushed product will be transferred back onto the SAG mill feed conveyor via the pebble conveyor No. 2.

The undersize particles (< 12 mm) flow to the concrete SAG and ball mill sump, where they are mixed with the ball mill product. In this sump, process water of controlled quantity is also added to control cyclone feed density and ball mill circulating load.

The slurry product of both mills is pumped to a 660 mm diameter hydrocyclone cluster. The hydrocyclone overflow slurry with solids content of, typically, 35% w/w and particle size of 80% passing 120 µm comprises the feed of the flotation circuit. The cyclone underflow slurry is directed to the ball mill feed chute. The grinding circuit operation is controlled by an automated control system to ensure that the product size for all types of ore is 80% passing 120 µm at the maximum daily ore feed of 24,000 t.

Concentrate regrinding is carried out by the regrind ball mill. The regrind ball mill has a diameter of 4.60 m and effective grinding length of 7.00 m. The mill is driven by a 2.25 MW motor and is equipped with lubrication, drive protection and cooling systems. The regrind mill has rubber lining and the regrinding media consists of forged steel balls of, typically, 25 mm diameter.


Processing

  • Calcining
  • Dewatering
  • Filter press plant
  • Flotation

Flow Sheet: Source
Source: Source

Summary:

For the first nine years of operation, the ore will be extracted from the open pit mine as well as from the underground mine for a total mill feed rate of 8.0 Mtpa. From the tenth year of operation until the depletion of Mineral Reserves, the plant will process ore extracted from the underground
mine at an average of around 6.5 Mtpa tailing off in Years 19 and 20. During years 10 to 14, previously stockpiled oxide ore will be re-handled to maintain mill feed at 8.0 Mtpa.

The plant will process the copper / gold ore at a projected LOM average head grade of 0.50% copper and 0.77 g/t gold. Anticipated LOM average payable recoveries are 87% for copper and 81% for gold. The mill will produce a flotation concentrate that contains an average of 26% copper and 27 g/t gold. Metallurgical tests have shown that the ore contains a small amount of palladium (Pd), which will be collected into the copper / gold concentrate during flotation.

The process plant design provides for a nominal 8.0 Mtpa of ore throughput. While gravity classification, secondary gravity classification and gold room circuits have been designed, installation has been deferred pending confirmation of the need for gravity concentration to meet designed overall gold recoveries.

The unit operations comprise of:
• Primary crushing and crushed ore stockpile.
• SABC grinding and pebble crushing.
• Flotation and regrinding.
• Flotation concentrate and tailings thickening.
• Flotation concentrate filtering, storage and loadout.
• Tailings filtration, conveying and paste fill production.
• Reagent preparation and services.

Flotation is carried out in six stages:
• Rougher.
• 1st cleaner.
• Cleaner scavenger.
• 2nd cleaner.
• 3rd cleaner.
• Additional cleaning, in order to produce a clean copper / gold concentrate while achieving
satisfactory recoveries.

Concentrate regrinding is carried out by the regrind ball mill.

The regrind ball mill operates in closed circuit with a cluster of 14 hydrocyclones (250 mm diameter), 10 duty and four on standby. The operation of the regrind circuit will be controlled by the central distributed control system (DCS) of the plant.

The regrinding circuit is fed with the concentrates of rougher and cleaner scavenger flotation as well as the regrind gravity concentration tailings and additional cleaner concentrate. These are directed to the hydrocyclone cluster. The regrind cyclone cluster overflow will flow to the 1st cleaning circuit. The regrind cyclone underflow feeds the regrind ball mill.

The final concentrate of the 3rd cleaning flotation stage is directed to a concentrate thickener of 12 m diameter. Flocculant solution is added to increase the solids sedimentation rate. The solids concentration in the thickener underflow is typically 60% w/w. The underflow is pumped to filter presses for filtration.

Recoveries & Grades:

CommodityParameterAvg. LOM
Gold Head Grade, g/t 0.77
Copper Recovery Rate, % 87
Copper Head Grade, % 0.5

Projected Production:

CommodityProductUnitsAvg. AnnualLOM
Gold Payable metal koz 1402,949
Gold Metal in concentrate koz 3,024
Copper Payable metal M lbs 1,411
Copper Metal in concentrate M lbs 1,467
Copper Concentrate kt 2,560
Gold Equivalent Payable metal koz 3126,569

Operational Metrics:

Metrics
Waste 59,224 kt *
Stripping / waste ratio 1.03 *
Ore tonnes mined, LOM 147,115 kt *
Tonnes milled, LOM 147,115 kt *
Annual milling capacity 8 Mt *
* According to 2022 study.

Reserves at September 30, 2021:
Mineral reserve cut-off grade are : $ 10.60/t NSR (open pit), $ 33.33/t NSR (underground).
Mineral resource cut-off grade are: 0.30 g/t Au Equivalent grade (open pit), 0.70 g/t Au Equivalent grade (underground) (=Au g/t + 1.25*Cu%);

CategoryTonnage CommodityGradeContained Metal
Proven 73,101 kt Gold 0.87 g/t 2,053 koz
Proven 73,101 kt Copper 0.52 % 381 kt
Probable 74,015 kt Gold 0.66 g/t 1,576 koz
Probable 74,015 kt Copper 0.48 % 359 kt
Proven & Probable 147,116 kt Gold 0.77 g/t 3,630 koz
Proven & Probable 147,116 kt Copper 0.5 % 740 kt
Measured 90,714 kt Gold 0.85 g/t 2,479 koz
Measured 90,714 kt Copper 0.51 % 466 kt
Indicated 149,260 kt Gold 0.53 g/t 2,551 koz
Indicated 149,260 kt Copper 0.44 % 652 kt
Measured & Indicated 239,974 kt Gold 0.65 g/t 5,030 koz
Measured & Indicated 239,974 kt Copper 0.47 % 1,118 kt
Inferred 67,657 kt Gold 0.37 g/t 814 koz
Inferred 67,657 kt Copper 0.4 % 267 kt

2022 Study Costs and Valuation Metrics :

MetricsUnitsLOM Total
Pre-Production capital costs $M USD 844.6
Expansion CapEx $M USD 171.9
Sustaining CapEx $M USD 846.6
Closure costs $M USD 26.6
Total CapEx $M USD 1,863
OP OpEx $M USD 244.8
UG OpEx $M USD 1,681
OP/UG OpEx $M USD 1,953
Processing OpEx $M USD 1,582
G&A costs $M USD 409.1
Total OpEx $M USD 3,944
Total Taxes $M USD 667,000
Royalty payments $M USD 193
Gross revenue (LOM) $M USD 9,853
Net revenue (LOM) $M USD 9,227
Net Income (LOM) $M USD 2,366
Pre-tax Cash Flow (LOM) $M USD 3,393
After-tax Cash Flow (LOM) $M USD 2,726
After-tax NPV @ 0% $M USD 2,726
After-tax NPV @ 5% $M USD 1,273
After-tax NPV @ 8% $M USD 788.5
After-tax IRR, % 19
After-tax payback period, years $M USD 3.7

Proposed Heavy Mobile Equipment as of January 22, 2022:
Source: Source p.168
HME TypeModelSizeQuantity
ANFO Loader Normet Charmec LC 605 2
Backhoe JCB 3X17 2
Cable bolter Sandvik DS421 2
Cable bolter Sandvik DS421 2
Dozer Caterpillar D8 3
Dozer Caterpillar 834K 1
Drill 2
Drill (long hole) Sandvik 5
Drill jumbo (two boom) Sandvik DD422i 5
Excavator 12 cu. m 1
Excavator Caterpillar 345 1
Grader Caterpillar 12M 1
Grader Caterpillar 16M 1
Loader 2
Loader (FEL) 8.5 cu. m 1
Loader (FEL) 12 cu. m 1
Load-Haul-Dump (LHD) Sandvik LH517 17 t 4
Load-Haul-Dump (LHD) Sandvik LH621 21 t 11
Personnel Carrier Normet LF100 &C122 Cassette 4
Raise boring rig Atlas Copco 34RH C QRS 2
Rock bolter Sandvik DS411 4
Scaler Normet Scamec 2000M 2
Trans Mixer Normet Ultimec LF700 3
Truck (fuel / lube) Normet Ultimec LF1000 2
Truck (haul) Volvo A45G 5
Truck (haul) Volvo FMX 520 10X4 12
Truck (haul) Volvo A60H 55 t 19
Truck (haul) Caterpillar 777 90 t 5
Truck (water) 30000 l 2
Truck (water) Nordberg 1352 2

Mine Management:

Job TitleNameProfileRef. Date
Consultant - Mining Mo Molavi LinkedIn Jan 22, 2022
Consultant - Recovery Methods Robert Chesher LinkedIn Jan 22, 2022
Engineering Manager Kostas Soultanis LinkedIn Apr 11, 2021

Staff:

EmployeesContractorsTotal WorkforceYear
30 58 88 2021
28 9 37 2020
29 5 34 2019
34 51 85 2018
45 406 451 2017
50 284 2016

Corporate Filings & Presentations:

DocumentYear
Corporate Presentation 2022
Technical Report 2022
Annual Information Form 2021
Management Discussion & Analysis 2021
Form 40-F 2019
Corporate Presentation 2018
Corporate Presentation 2018
Form 40-F 2018
Press Release 2018
Technical Report 2018
Form 40-F 2017
Corporate Presentation 2016
Form 40-F 2016
Other 2016
Technical Report 2011
Technical Report 2011

News:

NewsDate
Eldorado Gold Files Technical Reports for Skouries and Lamaque March 31, 2022
Eldorado Gold Announces Results of Skouries Project Feasibility Study; After-Tax NPV of US$1.3 Billion and IRR of 19% December 15, 2021
Eldorado Gold Receives Approval for Use of Dry Stack Tailings at Skouries April 29, 2021
Eldorado Gold Signs Amended Investment Agreement with the Hellenic Republic February 5, 2021
Eldorado Gold Places Skouries Project in Greece on Care and Maintenance November 9, 2017

Aerial view:

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