Ghana

Obuasi Mine

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Overview

Mine TypeUnderground
StatusActive
Commodities
  • Gold
Mining Method
  • Transverse open stoping
  • Longhole open stoping
  • Longitudinal retreat
Backfill type ... Lock
Production Start... Lock
Mine Life... Lock
SnapshotObuasi is an underground operation with the main accesses into the mine consisting of shafts and a single access decline. On receipt of the requisite approvals from the Government of Ghana, the Obuasi redevelopment project began in early 2019. Phases 1 and 2 of the redevelopment project have been completed, bringing capacity to 4,000tpd by mid-2022.

Phase 3 of the Obuasi redevelopment project, related primarily to capital expenditure to refurbish and return to service existing infrastructure around the KMS shaft, as well as to service the mine in deeper production areas, continued to progress. In 2023, the project achieved the following milestones: upgrading and licensing both the KMS Rock and Man Winders for operations; completing installation of two new shaft pipe columns increasing dewatering capacity by 200 litres per second; completing the KMS shaft down to 51-level; and completing mining of a new ore pass between the operational mine and 4,100 level rail.

Owners

SourceSource
CompanyInterestOwnership
AngloGold Ashanti plc. 100 % Indirect
AngloGold Ashanti (Ghana) Ltd. (operator) 100 % Direct
Obuasi gold mine is owned and operated by AngloGold Ashanti (Ghana) Limited (AAGL), a company registered in Ghana. AAGL through AngloGold Ashanti Holdings plc is wholly owned by AngloGold Ashanti plc.

Contractors

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Deposit type

  • Vein / narrow vein

Summary:

Geology
The mine is located within the Obuasi concession area in southwestern Ghana along the northeasterly striking Ashanti volcanic belt. The deposit is one of the most significant Proterozoic gold belts discovered to date. The Ashanti belt predominantly comprises sedimentary and mafic volcanic rocks, and is the most prominent of the five Birimian Supergroup gold belts found in Ghana.

Deposit type
The Birimian was deformed, metamorphosed, and intruded by syn- and post-tectonic granitoids during the Eburnean tectonothermal event around two billion years ago. Folding trends are dominantly north-northeast to northeast. Elongate syn-Birimian basins developed between the ridges of the Birimian system, and these were filled with the Tarkwaian molasse sediments made up primarily of conglomerates, quartzose and arkosic sandstones and minor shale units. Major faulting has taken place along the same trends. The Lower Birimian metasediments and metavolcanics are characterised and defined by argillaceous and fine to intermediate arenaceous rocks. These rocks are represented by phyllites, metasiltstones, metagreywackes, tuffaceous sediments, ash tuffs and hornstones in order of decreasing importance. Adjacent to the shear zones, these rocks are replaced by sericitic, chloritic and carbonaceous schists, which may be graphitic in places. Multiple lodes are a common feature. Mineralised shears are found in close proximity to the contact with harder metamorphosed and metasomatically altered intermediate to basic Upper Birimian volcanics. The competency contrast between the harder metavolcanic rocks to the east and the more argillaceous rock to the west is thought to have formed a plane of weakness. During crustal movement, this plane became a zone of shearing and thrusting coeval with the compressional phases.

Mineralisation style
Gold mineralisation is associated with shear zones and pervasive silica, carbonate and sulphide hydrothermal alteration which occur in tightly folded Lower Birimian schists, phyllites, meta- greywackes, and tuffs, along the eastern limb of the Kumasi anticlinorium. They are found near the contact with harder metamorphosed and metasomatically altered intermediate to basic upper Birimian volcanics. There are two broad styles of gold mineralisation including free milling quartz vein gold and sulphiderich, disseminated and refractory gold which form alteration haloes around the quartz vein lodes. Sulphide mineralisation is dominated by arsenopyrite and quartz mineralisation, which is associated with spatially variable, but exceptionally high-grade visible gold in quartz veins.

Mineralisation characteristics
Two main ore types are present, namely quartz vein and sulphide ore. The quartz vein type consists mainly of quartz with free gold in association with lesser amounts of various metal sulphides containing iron, zinc, lead and copper. This ore type is generally non-refractory. The sulphide ore type is characterised by the inclusion of gold in the crystal structure of arsenopyrite minerals. Higher gold grades tend to be associated with finer grained arsenopyrite crystals. The sulphide ore is generally refractory.

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

CommodityUnits2024202320222021202020162015
Gold koz  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe353
^ Guidance / Forecast.

Operational metrics

Metrics202320222021202020162015
Annual processing capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe2.4 Mt2.4 Mt
Tonnes processed  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe1 Mt
Ore tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe

Production Costs

CommodityUnits2023202220212020
Total cash costs Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
All-in sustaining costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
All-in costs Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
** Net of By-Product.

Financials

Units20232022202120202019
Sustaining costs M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Capital expenditures M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 246  
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Operating Income M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe
EBIT M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
EBITDA M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Book Value M USD  ....  Subscribe  ....  Subscribe

Heavy Mobile Equipment

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Personnel

Mine Management

Job TitleNameProfileRef. Date
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....................... Subscription required ....................... Subscription required Subscription required May 30, 2024
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EmployeesContractorsTotal WorkforceYear
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Aerial view:

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