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South Africa

Mponeng Mine

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Overview

Mine TypeUnderground
StatusActive
Commodities
  • Gold
Mining Method
  • Sequential grid mining
  • Breast stoping with strike pillars
Backfill type ... Lock
Production Start... Lock
Mine Life... Lock
SnapshotMponeng Mine is a deep-level gold mine and is the deepest mine in the world. The majority of production was always from Ventersdorp Contact Reef(VCR) with limited Carbon Leader Reef(CLR) mining commencing during 2020. Ore mined is processed at the Mponeng gold plant.

The CLR, historically mined at the adjacent Harmony wholly owned TauTona and Savuka Mines. In 2017, Savuka and Tau Tona mines commenced orderly closure. Harmony Gold has an opportunity to extend life-of-mine of Mponeng, known as the Mponeng deepening project:

- Savuka shaft pillar - The objective is to assess the feasibility of extracting both the VCR and CLR shaft pillars. The business case study is scheduled for completion in Q2 FY24.

- Tau Tona pillar - The objective is to extract the VCR and CLR shaft pillar. The feasibility study considering the extraction of the VCR shaft pillar is scheduled for completion in Q2 FY24. A feasibility study cof the CLR shaft pillar is scheduled for completion in Q3 FY24.

Owners

SourceSource
CompanyInterestOwnership
Harmony Gold Mining Company Ltd. (operator) 100 % Indirect
Mponeng is wholly-owned and operated by Harmony.

Contractors

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Deposit type

  • Conglomerate hosted

Summary:

Mponeng is situated on the northwestern margin of the Witwatersrand Basin of South Africa, one of the prominent gold provinces in the world. There are seven gold-bearing conglomerates within the lease area, of which only the Ventersdorp Contact Reef (VCR) and Carbon Leader Reef (CLR) are economically viable.

The Ventersdorp Contact Reef (VCR) is the main reef horizon mined at Mponeng Mine.

The VCR forms the base of the Ventersdorp Supergroup, which caps the Witwatersrand Supergroup through an angular unconformity. The overlying Ventersdorp Lavas halted the deposition of the VCR, preserving it in its current state. The Carbon Leader Reef (CLR), previously mined at Tau Tona and Savuka mines, is found within the Witwatersrand Supergroup. The CLR lies 900m beneath the VCR on Mponeng. The VCR is preserved across the Mponeng lease area and dips at approximately 22 degrees in a SSE direction.

The VCR was deposited on uneven footwall strata due to uplift and is now represented by a shallow angular unconformity. The footwall lithologies to the VCR therefore vary across Mponeng Mine as the unconformity cuts deeper in an easterly direction into older strata of the Witwatersrand Supergroup. Fluvial action during deposition of the VCR continually eroded and reworked the conglomerate, creating steep slopes and embayment’s between relatively undisturbed terraces.

The CLR conglomerate was deposited by several sedimentary cycles. Erosion and reworking of the conglomerate and quartzite sediments has resulted in the preservation of the CLR within the Central Rand Group of the Witwatersrand Supergroup.

Deposit type
The VCR consists of a quartz pebble conglomerate, which can be up to 3m thick in places. The footwall stratigraphy, following periods of uplift and erosion, controlled the development and preservation of the VCR, which is characterised by a series of channel terraces preserved at different relative elevations, and the highest gold values are preserved in these channel deposits.

The different channel terraces are divided by zones of thinner slope reef, which are of lower value and become more prevalent on the higher terraces and on the harder footwall units.

The relatively argillaceous protoquartzites of the Kimberley Formation in the central portion of Mponeng are covered by the best-preserved VCR conglomerates.

The Elsburg Formation in the west is relatively more durable while the eastern side of the mine is dominated by shales and siltstones of the Booysens formation.

VCR is poorly preserved on the Krugersdorp formation on the far eastern side of Mponeng.

The CLR is the other gold-bearing reef reported as part of the total Mineral Resource for Mponeng. The CLR is located near the base of the Johannesburg Subgroup, which forms part of the Central Rand Group of the Witwatersrand Supergroup of rocks.

The CLR has historically been mined extensively at Savuka and Tau Tona mines and the remaining portions thereof have now been transferred to Mponeng Mine. The CLR in the West Wits consists of, on average, a 20cm thick, tabular, auriferous quartz pebble conglomerate and three sedimentary facies. Economically, the most important facies is Unit 1, which overlies Unit 2. Unit 1 is a complex channel deposit that is only present along the eastern side of the West Wits lease area.

Unit 2 can be up to 2m thick. Unit 3 is exposed in the southern edges of the lease area and is the oldest of the conglomerates.

Mineralisation style
Gold mineralisation followed an episode of deep burial, fracturing and alteration. A variant of Archean gold-bearing hydrothermal fluid was introduced into the conglomerates and circulated throughout in hydrothermal cells. The fluids precipitated gold and other elements through reactions that took place at elevated temperatures along the reef horizon, which was the more favourable fluid conduit. In the case of the VCR, the resulting gold grades are mostly uniformly distributed throughout the reef package.

CLR mineralisation associated with the conglomerate occurs in the form of fine layers and stringers of pyrite rather than finely disseminated pyrite around the pebbles. Flyspeck carbon can be frequently found at the base of the conglomerate. The hydrocarbon precipitated also in thin, flat veins, usually at the base of the Carbon Leader conglomerate, and this is where the majority of the gold is concentrated.

The VCR displays strong alteration features, which can be explained by the hydrothermal fluids that infiltrated the reef and have overprinted on the original mineral assemblage. Portions of the reef contain authigenic sulphides such as pyrite, pyrrhotite, chalcopyrite, spahelerite and galena, incorporated in the conglomerate matrix. Gold associations with these mineral assemblages indicate a strong correlation of gold mobilisation and redistribution at the time of the hydrothermal fluid influx. There is also a strong association of gold with a chloritisation event focused along the reef horizon. The chlorite alteration gives a dark coloration to the reef. Gold was precipitated by cooling and reactions between the fluids and wallrock, in this case pyritic conglomerates. Gold mineralisation was enhanced in certain areas of high fluid throughput, which were often the sites of high carbon precipitation and early alteration in the case of the CLR.

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

Production in 2020 for the nine months to September 2020
CommodityUnits2024202320222021202020192018201720162015
Gold koz  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe243265224254219
All production numbers are expressed as metal in doré. ^ Guidance / Forecast.

Operational metrics

Metrics20232022202120192018201720162015
Hourly processing capacity  ....  Subscribe  ....  Subscribe
Tonnes processed  ....  Subscribe  ....  Subscribe  ....  Subscribe1.3 Mt1.2 Mt1 Mt1.1 Mt0.8 Mt

Production Costs

CommodityUnits2023202220212020201920182017
Cash costs Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe
Total cash costs Gold USD  ....  Subscribe 976 / oz   977 / oz   1,014 / oz  
All-in sustaining costs (sold) Gold USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 1,186 / oz   1,177 / oz   1,259 / oz  
All-in costs Gold USD  ....  Subscribe

Financials

Units20242023202220212020201920182017
Capital expenditures (planned) M USD  ....  Subscribe
Capital expenditures M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe 50   54   72  
Revenue M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe
Gross profit M USD  ....  Subscribe  ....  Subscribe  ....  Subscribe

Heavy Mobile Equipment

Fleet data has not been reported.

Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Nov 8, 2023
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....................... Subscription required ....................... Subscription required Subscription required Nov 8, 2023

EmployeesContractorsTotal WorkforceYear
...... Subscription required ...... Subscription required ...... Subscription required 2023
...... Subscription required ...... Subscription required ...... Subscription required 2022
...... Subscription required ...... Subscription required ...... Subscription required 2021
...... Subscription required 2020
...... Subscription required ...... Subscription required ...... Subscription required 2019
...... Subscription required ...... Subscription required ...... Subscription required 2018
...... Subscription required ...... Subscription required ...... Subscription required 2017
...... Subscription required ...... Subscription required ...... Subscription required 2016

Aerial view:

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