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Ghana
Bogoso / Prestea Mine

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 Location:
6 km SW from Bogoso, Ghana

  Address:
P. O. Box 11
Bogoso
Ghana
Phone  ...  Subscription required
Fax233-03120-20295
WebsiteWeb
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  • Overview
  • Owners
  • Geology
  • Mining
  • Processing
  • Production
  • Reserves
  • Costs & Financials
  • Fleet
  • Personnel
  • Filings & News

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Overview

StageProduction
Mine TypeUnderground
Commodities
  • Gold
Mining Method
  • Cut & Fill
  • Alimak
  • Shrinkage stoping
Processing
  • Gravity separation
  • Agitated tank (VAT) leaching
  • Concentrate leach
  • Carbon in leach (CIL)
  • Elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)
Mine Life5 years (as of Jan 1, 2018)
The Bogoso-Prestea operations are located in south-western Ghana, approximately 40km from the Wassa gold mine. Recently, production was delivered from the Bogoso-Prestea open pits and the Prestea underground gold mine. In the second half of 2018, Prestea became an underground-focused operation and the open pit operations ceased production. The Bogoso refractory open pit operation was closed in 2015.
Latest NewsGolden Star Completes Sale of the Bogoso-Prestea Gold Mine to Future Global Resources     October 1, 2020


Owners

Source:
CompanyInterestOwnership
Government of Ghana 10 % Indirect
Future Global Resources Ltd. 90 % Indirect
Golden Star Bogoso/Prestea Ltd. 100 % Direct
Golden Star (Bogoso Prestea) Limited (GSBPL) is 90% owned by Golden Star Resources (GSR) and 10% by the Ghanaian government.

Oct. 1, 2020 /CNW/ - Golden Star Resources Ltd. (NYSE American: GSS) (TSX: GSC) GSE: GSR) ("Golden Star" or the "Company") is pleased to announce that it has completed the sale of its 90% interest in the Bogoso-Prestea Gold Mine ("Bogoso-Prestea") in Ghana to Future Global Resources Limited ("FGR").

Deposit Type

  • Vein / narrow vein


Summary:

The Prestea-Bogoso mineralization occurs at the southern end of the Ashanti Greenstone Belt, where 11 gold deposits, mined or under exploration, are localized principally along three steep to subvertical major crustal structures. Rock assemblages from the southern area of the Ashanti Belt were formed during a period spanning from 2,080 to 2,240 million years (Ma) with the Sefwi Group being the oldest rock package and the Tarkwa sediments being the youngest. The Ashanti Belt is host to numerous gold occurrences, which are believed to be related to various stages of the Eoeburnean and Eburnean deformational events.

The geology of the Prestea mine site is divided into four main litho-structural assemblages, which are fault bounded and steeply dipping to the west. This suggests that the contacts are structurally controlled and that the litho structural assemblages are unconformable. These packages are, from the eastern footwall to the western hanging wall, the Tarkwaian litho structural assemblage, the tectonic breccia assemblage, the graphitic Birimian sedimentary assemblage, and the undeformed Birimian sedimentary assemblage.

At Prestea, the principal structure is the mineralized quartz vein, known as the Main Reef, which is relatively continuous and has been modelled and mined over a strike length of some 6 km and to a depth of approximately 1,450 m below surface (35 Level [L]). The subordinate West Reef and East Reef, in the immediate hanging wall and footwall, respectively, of the former structure, are discontinuous. West Reef occurs some 200 m into the hanging wall of the Main Reef structure and, at present, is known to occur over a strike length of 800 m and has currently been defined by underground drilling between 550 to 1,150 m below topography as far as the 30 L.


Mining Methods

  • Cut & Fill
  • Alimak
  • Shrinkage stoping


Summary:

The planned mining method is mechanized shrinkage mining. This method uses mechanical raise climber technology (Alimak) together with longholes drilled from the raise climber. The method is an advance in terms of safety and productivity from conventional hand-held shrinkage mining. Safety is greatly enhanced both in raise development and stoping operations by having miners protected from rockfalls and removed from working on the broken muck pile. The productivity (per miner) is enhanced by introducing short longholes for stope production.

A typical cycle for Alimak stoping is:

- Raise development in the centre of a stoping block;
- Raise hangingwall rock support;
- Drilling of longhole blast rings;
- Relocation of the raise climber infrastructure to the top of the stoping block, blasting of longhole rings and swell mucking; then,
- Final draw-down mucking and possible waste backfilling.

Small diesel and electric 2 m3 LHD’s will be used for rock haulage from the base of the stoping panel. Mine development will be by hand held drills with LHD mucking. Tramming of ore and waste along the two main levels (17 and 24) will be via an upgraded rail haulage system to Central Shaft.

The rib pillars between stopes are planned to be 3 m wide along the strike of the orebody. Stopes will be 20 m wide separated by these pillars. The pillars will run the entire length of each of the Alimak stopes and are not planned to be recovered.

Mine Ventilation Service’s (MVS) engineers completed a detailed ventilation system design for the mechanized shrinkage mining. The emphasis of the study was to determine ventilation infrastructure and fan duties required for the West Reef development, using phased ventilation modeling.

In areas where diesel equipment is used a factor of 0.08 m3 /s per kW of motor power is used. This is not only for dilution of diesel particulate matter but also for dilution of heat and dust.

The Prestea Underground (PUG) workings extend over a distance of 6 km along strike and down to a maximum depth of about 1,450 m below surface. The two primary shafts of the Prestea mine are the Central and Bondaye shafts.

The Central shaft is the primary access to the underground mining levels and it extends to a depth of 1,238 m below surface to 30 Level (L). Numerous levels were developed off the shaft to provide access to the Main Reef stoping areas. Traditional narrow vein mining methods were employed, primarily shrinkage stoping and captive cut and fill. Run of mine (RoM) material and waste were trammed to the Central shaft to loading pockets located below 20 L, 25 L, and 30 L, which served to load the RoM into skips for conveyance to the surface bins. The total capacity of the system at its peak may have been around 1,300 to 1,600 t/day.

The Bondaye shaft extends to a depth of 1,103 m, but unlike the Central shaft there is no dedicated rock handling system at Bondaye, and cars were loaded into the cages and raised to surface.

In addition to the Central and Bondaye shafts, there are several internal shafts. The No. 4 and No. 6 shafts are located to the south of the Central shaft. No. 4 shaft extends from 23 L to 35 L and was used as the primary access to 35 L, the lowest developed level in the mine. No. 6 shaft extends from 24 L to 31 L.


Crushing and Grinding


Processing

  • Gravity separation
  • Agitated tank (VAT) leaching
  • Concentrate leach
  • Carbon in leach (CIL)
  • Elution
  • Solvent Extraction & Electrowinning
  • Cyanide (reagent)

Flow Sheet: Subscription required

Summary:

Ore from the PUG West Reef is trucked to GSR’s Bogoso operation, a distance of approximately 15 km, where the ore will be processed through the existing process facility producing 2,480 kg/a or 80,000 oz/a of gold at an overall recovery of 94%.

The processing facility at Bogoso consists two plants to separately process refractory and nonrefractory (oxide) ores. As the PUG ore is non- refractory ore it will be processed through a modified Oxide circuit that utilizes conventional CIL for gold recovery. The circuit includes the following unit processes:

- Run-of-mine (RoM) receiving
- Crushing
- Milling and classification circuit (cyclones)
- Gravity concentration
- Thickening
- Feed storage tanks
- Carbon-in-leach (CIL) circuit
- Upgrade / refurbishment of high intensity cyanide leach reactor (Acacia)
- Gold room and recovery
- A new CIL tailings disposal line
- Services (compressed air, instrument air, oxygen, g ........

Recoveries & Grades:

CommodityParameter20192018201720162015
Gold Recovery Rate, %  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required
Gold Head Grade, g/t 1.561.22.852.211.32
Subscription required - Subscription is required.

Production:

CommodityUnits20192018201720162015
Gold oz  ......  Subscription required  ......  Subscription required130,33189,673114,150
All production numbers are expressed as metal in doré.
Subscription required - Subscription is required.

Operational Metrics:

Metrics20192018201720162015
Ore tonnes mined  ......  Subscription required  ......  Subscription required  ......  Subscription required1,499,656 t1,710,916 t
Waste  ......  Subscription required  ......  Subscription required  ......  Subscription required4,039,768 t3,603,153 t
Tonnes processed  ......  Subscription required  ......  Subscription required  ......  Subscription required
Subscription required - Subscription is required.

Reserves at December 31, 2019:

CategoryTonnage CommodityGradeContained Metal
Proven & Probable 856 kt Gold 11 g/t 302 koz
Measured & Indicated 24,942 kt Gold 3.27 g/t 2,624 koz
Inferred 2,348 kt Gold 6.93 g/t 523 koz

Commodity Production Costs:

CommodityUnits20192018201720162015
Cash costs Gold USD  ......  Subscription required  ......  Subscription required 632 / oz 800 / oz 1,108 / oz
Subscription required - Subscription is required.

Financials:

Units20192018201720162015
Capital expenditures M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 23.1  
Revenue M USD  ......  Subscription required  ......  Subscription required  ......  Subscription required  ......  Subscription required 132  
Subscription required - Subscription is required


Proposed Heavy Mobile Equipment as of December 31, 2017:
HME TypeModelSizeQuantity
Alimak climber 5
....................... Subscription required ....................... Subscription required 1
....................... Subscription required ....................... Subscription required 3
....................... Subscription required ....................... Subscription required 3
Subscription required - Subscription is required.

Mine Management:

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Oct 1, 2020
....................... Subscription required ....................... Subscription required Subscription required Oct 1, 2020
Subscription required - Subscription is required.


Corporate Filings & Presentations:

DocumentYear
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2019
................................... Subscription required 2018
................................... Subscription required 2018
Technical Report 2017
Press Release 2016
Feasibility Study Report 2015
Technical Report 2013
Subscription required - Subscription is required.

News:

NewsDate
Golden Star Completes Sale of the Bogoso-Prestea Gold Mine to Future Global Resources October 1, 2020
Golden Star Announces a Binding Agreement for the Sale of the Bogoso-Prestea Gold Mine for a Purchase Price of up to $95 million July 27, 2020
Golden Star Reports Initial High Grade Extension Drilling Results from Prestea Underground Gold Mine and Project Update June 3, 2019
Golden Star Resources Achieves Commercial Production at Prestea Underground Gold Mine February 1, 2018
Golden Star Resources Reports Two Fatalities at Prestea Underground Gold Mine January 2, 2018

Aerial view:

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