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Guinea

Lefa Mine

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Overview

Mine TypeOpen Pit
StatusActive
Commodities
  • Gold
Mining Method
  • Truck & Shovel / Loader
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SnapshotLefa is one of the largest gold producer in the Guinea. The Lefa mine is a multi-deposit modern open pit operation which focuses on the development of two main open pits, Lero-Karta and Fayalala.

In 2023, Nordgold plans to commence an underground gold mine development at the Lefa mine. Lero-Karta will be the first underground gold mine in Guinea.

In light of the sanctions and ongoing regulatory actions, Nord Gold PLC's production numbers for the year 2022 are not available.

Owners

SourceSource
CompanyInterestOwnership
Government of Guinea 15 % Indirect
Nord Gold plc 85 % Indirect
Societe Miniere de Dinguiraye SA (operator) 100 % Direct
Lefa is owned by Société Minière de Dinguiraye S.A., in which Nordgold holds a controlling interest of 85% — with the remaining 15% held by the Guinean government.

Contractors

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Deposit type

  • Breccia pipe / Stockwork
  • Vein / narrow vein

Summary:

The Lefa gold mine lies within the Siguiri Basin, part of the Paleoproterozoic Birimian terrain of the West African Craton. Host lithologies are typically Paleoproterozoic (2.2-2.1 Ga) volcanosedimentary greenstone belts, metamorphosed to greenschist facies (or higher) and intruded by felsic plutons. Deformation is associated with a system of NE-SW trending crustal-scale ductile shear zones, related to the Eburnean orogeny, a protracted series of orogenic events spanning 2.2-2.0 Ga. These deformation zones are considered fundamental to the development of gold mineralisation.

Localised finely-laminated white and pale yellow limestones occur towards the north of the licence. Three post-Birimian sedimentary packages occur within the Lefa area, namely:
- Neoproterozoic fluvial and shallow marine sandstones;
- Eocene paleo-valley fill loosely consolidated sandstones; and
- post Post-Eocene transported colluvium.

Intrusive lithologies within the basin consist of basic to intermediate sheet intrusives and the Maléa intrusion. Two sets of dykes are identified, corresponding to a swarm which exhibits trends of circa 105-285° and 055-235°. In addition to the dykes, the basin is also intruded by numerous dolerite sills ranging from a few metres to tens of metres in thickness.

Mineralisation at Lefa is hosted within the “Lefa Corridor”, which lies within the Siguiri Basin. This is a zone which is some 10 km wide, underlain by an upper clay rich formation and a lower coarser arkosic layer, with gold occurrences more common in the latter. Apart from younger dolerites and sandstones, there is virtually no fresh outcrop. Often, the stratigraphy is affected by folding which is observed within the pits. Host lithologies for the mineralisation are typically a mixture of sandstones to finer grained mudstones and claystones. Bedding is moderately to steeply dipping and deformation is dominated by discrete faults. The entire stratigraphy has been intruded by massive dolerite dykes and sills, which typically form prominent hills and bluffs. These intrusions are typically thin (<1 m to >10 m) and tend to be fresh dolerites.

Mineralisation typically occurs in more permeable, altered, coarser grained sediments, within and adjacent to structures and fracture zones. Mineralisation is localised by a combination of lithological and structural controls, and as such, the dip and strike of mineralised zones, and to a lesser extent the style of mineralisation, varies considerably between individual deposits. Gold is often associated with stockwork and sheeted quartz-carbonate sulphide veining, stockworks of albite-carbonate-sulphide veinlets, or as sulphide rich haematitic breccias.

Pyrite is the dominant sulphide species. Gold is largely developed within fractures in pyrite grains, associated with quartz carbonate veining (± sulphides), and albite-carbonate-sulphide veinlets. The degree of sulphidation and silicification can vary. Traces of other sulphides, principally chalcopyrite, galena, pyrrhotite, arsenopyrite, bornite, tennantite, linneite and mackinauwite are present as vein, fracture fill and localised disseminations. Gold grains are rarely larger than 50 µm and is non-refractory. The typical alteration assemblage is albite, quartz, carbonate, pyrite, chlorite, and graphite. Albitisation is known to develop on the contact of faults in the coarser grained sediments but not in finer sediments, due to the reduced permeability.

Deformation and metamorphism appear to have been substantially more subdued within the Lefa Corridor when compared with other West African Birimian terrains. Within the Corridor, the basement stratigraphy is typically sub-horizontal, and fault offsets are rare. Primary mineral assemblages reflect low-grade regional metamorphism and are characterised by broad monoclinal folding.

Extensive weathering and lateritisation has occurred across the project area. Both transported and residual laterites, which can be up to 15 m thick can host gold mineralisation. The base of oxidation extends to over 100 m below surface and may be locally deeper in zones of fracturing and brecciation. The width and grade of primary mineralised zones appear to be little different from their equivalents within the saprolite profile.

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

CommodityUnits2021202020192018201720162015
Gold koz  ....  Subscribe  ....  Subscribe190188209195214
All production numbers are expressed as metal in doré.

Operational metrics

Metrics202020192018201720162015
Stripping / waste ratio  ....  Subscribe5.09 4.7 4.34 3.31 3.15
Ore tonnes mined  ....  Subscribe6,755 kt6.69 Mt6.46 Mt6,137 kt6,019 kt
Waste  ....  Subscribe34.4 Mt31,466 kt28,076 kt20,336 kt
Total tonnes mined  ....  Subscribe41.1 Mt38,155 kt34,539 kt26,473 kt
Tonnes processed  ....  Subscribe6.03 Mt6,181 kt6,911 kt6,599 kt6,558 kt

Production Costs

CommodityUnits2020201920182017
Total cash costs Gold USD  ....  Subscribe 944 / oz **   807 / oz **   713 / oz **  
All-in sustaining costs (AISC) Gold USD  ....  Subscribe 1,354 / oz **   1,205 / oz **   943 / oz **  
** Net of By-Product.

Operating Costs

Currency20202019201820172016
Processing costs ($/t milled) USD 11.3  12  11.7  9.53  9.25  

Financials

Units20212020201920182017
Capital expenditures M USD  ....  Subscribe  ....  Subscribe 89.9   74.6   47.9  
Sustaining costs M USD  ....  Subscribe 77.9   72.2   49.7  
Revenue M USD  ....  Subscribe  ....  Subscribe 263.5   239   263.5  
EBITDA M USD  ....  Subscribe  ....  Subscribe 84.3   87.4   114.5  
Operating Cash Flow M USD

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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