Eritrea

Bisha Mine

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Overview

Mine TypeOpen Pit
Commodities
  • Copper
  • Zinc
  • Gold
  • Silver
Mining Method
  • Truck & Shovel / Loader
Production Start... Lock
Mine Life2028
ShapshotThe Bisha Copper-Zinc Mine is the key in production large-scale zinc mine in Eritrea.

Infrastructure construction for the Asheli Underground Mining Project is well underway.

Owners

SourceSource
CompanyInterestOwnership
Eritrean National Mining Corp. 45 % Indirect
Zijin Mining Group Co., Ltd 55 % Indirect
The Zijin Mining Group ultimately owns 55% equity interest in Bisha through Nevsun Eritrea, while Eritrean National Mining Corporation owns 45% equity interest in BMSC.

Deposit type

  • VMS

Summary:

The Bisha and Harena are large precious- and base metal-rich VMS deposits; Northwest, Hambok and Asheli are small to medium size VMS deposits.

The Property is underlain by Neoproterozoic upper green schist to lower amphibolite facies volcanics and sedimentary units of the Augaro Adobha Belt.

The Bisha Main deposit is a series of four massive sulphide lenses that occur over a 1.2 km north-south trending strike extent. The thickness of the lenses is variable up to 70 m. Mineralisation extends to a depth of 600 m below surface.

The massive sulphide bodies comprise a southern zone and a northern zone. The main part of the southern zone strikes approximately 345° and dips steeply to the west, with strike and dip lengths of some 600 m and 500 m respectively. The main part of the northern zone strikes approximately 0° and dips steeply to the west, with strike and dip lengths of some 500 m and 100 m respectively. The southern zone plunges 45° to the south. In the hanging walls of both the southern and northern zones, there are two smaller massive sulphide pods interpreted to be folded limbs of the two main zones.

The Gossan varies in composition from highly siliceous and ferruginous to massive goethite– hematite–jarosite. The Oxide Zone is up to 50 m deep and is composed of hematite, quartz and clays; in places, original rock textures are preserved. The Oxide zone is enriched in Au, Pb, Ba and Mo and depleted in Cu, Zn, Cd and Co.

The Soap Zone is a white, light yellow or light brown zone, and consists of clay, quartz, barite and possibly anglesite. The Acid Zone is dark grey, and consists of clay, quartz, galena and pyrite. Faint original textures of the protolith may be preserved in both. Both the Acid and the Soap are depleted in Cu, Zn, Cd, Co, Fe and Mn and strongly enriched in Au, Ag, Pb and Ba; they are poorly consolidated and drill recoveries in these zones are generally poor.

The Supergene Zone is up to 20 m thick, and has elevated Cu and Ba and depleted Zn, Cd and Mn. Sphalerite and chalcopyrite are replaced by chalcocite, covellite, digenite and native copper. The Pyrite Sand lies directly above the Supergene Zone and consists of unconsolidated recrystallised pyrite grains; Cu from this Zone has been remobilised and deposited in the Supergene Zone.

Some remobilisation of Cu and Ba from the Primary Zone upwards into the Supergene zone has occurred along steeply dipping basement structures.

The Primary Zone represents the original massive sulphide deposit. The mineralogy is comprised of pyrite and sphalerite, with minor chalcopyrite, covellite, pyrrhotite and galena.

The Harena massive sulphide mineralisation is a tabular body up to 60 m thick that strikes 040° true, dips approximately 60° to the northwest, and plunges shallowly to the southwest. It is defined by diamond and minor RC drilling along a strike length of approximately 900 m; the deposit is closed down dip but is open down-plunge to the southwest.

The primary massive sulphide units comprise mainly massive sulphide mineralisation with subordinate semi-massive sulphide and volcanic lithologies, and are predominantly made-up of fine to medium-grained subhedral to anhedral pyrite with interstitial and/or enriched layers of sphalerite and chalcopyrite and range from 0.4 m to 100 m thick, averaging 19.8 m. The massive sulphide units have a tabular to lensoidal shape, with the thicker parts of the mineralisation in elongated shallowly SW- plunging shoots. In each massive sulphide unit there is a typical volcanic hosted massive sulphide (VMS) zonation from a Cu-Au-Ag rich base to a Zn-Ba rich top. The associated stringer mineralisation below the massive sulphide occurs in about half the drillholes; where present it is up to 58 m thick and averages 6.6 m. The total mineralised package (massive sulphide plus stringer) averages 23 m thick.

The Northwest deposit comprises a series of poly- metallic massive sulphide lodes that have been defined over a strike length of 800 m, striking northeast, and dipping from 70° northwest to sub-vertical. The deposit is thickest at the centre, tapering to widths of less than 8 m at its strike limits. The central portion of the deposit is over 85 m wide. In cross-section, the deposit is a wedge that narrows down-dip. Resource drilling has effectively defined the deposit to a maximum of 250 m below surface. Exploration drilling indicates that a mineralised stringer vein system still exists at depths of 350 m below surface.

The Hambok deposit lies within the Western Nakfa terrane, and is part of a sequence of Late Proterozoic mafic to felsic volcanic rocks, and sedimentary rocks, including pelite, chert, and carbonate units. The deposit comprises a primary copper/zinc sulphide zone, representing the majority of the deposit, and a minor oxide gold component. The primary massive sulphide mineralisation is a single body, with a faulted displacement interpreted at depth in the northeast of the deposit. The massive sulphide zones strike at approximately 015°, dipping steeply to the east, with overall strike and dip lengths of some 975 m and 400 m, respectively. The thickness of the massive sulphide varies from about 5.0 m to 75 m.

The Asheli massive sulphide deposit is located within the felsic volcanic sequence. It is a tabular, steeply north-plunging body 400 m long by 100 m wide and up to 30 m thick composed of pyrite, sphalerite and chalcopyrite. The top of the deposit is 60 m below surface.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

CommodityUnits2023202220212020201920182017
Copper M lbs 00000000003718
Zinc M lbs 000000000000000276210
Silver koz 0000000000000000997
Gold oz 0000013,792
All production numbers are expressed as metal in concentrate. ^ Guidance / Forecast.

Operational metrics

Metrics202220212020201920182017
Annual ore mining capacity 00
Annual mining capacity 00000022 Mt
Annual processing capacity 000000002.4 Mt
Stripping / waste ratio 7.8
Ore tonnes mined 2,050,000 t
Waste 15,960,000 t
Tonnes processed 2,233,000 t

Production Costs

CommodityUnits2017
C1 cash costs Zinc USD 0.97 / lb  
C1 cash costs Copper USD 1.72 / lb  
C1 cash costs Zinc USD 0.88 / lb  
Net of By-Product.

Financials

Units202220212020201920182017
Sustaining costs M USD 26.1  
Capital expenditures M USD 37.4  
Operating Income M  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Gross profit M 12.6  USD
After-tax Income M  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Operating Cash Flow M  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe

Heavy Mobile Equipment

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Personnel

Mine Management

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EmployeesYear
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Aerial view:

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