Gold Fields

Mineral
Reserves

2018

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Mineral Resources and Mineral Reserves Supplement

Regional overview

Salient point

Mineral Resources

56.2Moz*

 
Mineral Resources

32.8Moz*

(-15% net of depletion)
 
(-12% net of depletion)

* 90.75% attributable to GFI

   

The new life-of-mine (LoM) plan addresses the previous disconnects between mine plan and execution and encompasses the revised strategy and new operating model. It remains anchored by the Rebase Plan design and fundamentals, with a specific renewed focus on improved operational efficiency and execution. The new plan sets out the foundation and installs the key enablers required to fully convert the mine to a fully mechanised bulk-efficient operation with an effective organisational culture supportive of mechanised operations.

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The key activities undertaken in 2018 to support implementation of the South Deep revised strategy are listed:

  • Fundamental restructuring initiated in Q3 2018, anchored by a new operating model centred on closing loss-making areas and consolidating mining activity to increase focus with a commensurate reduction in the workforce and size of the mobile equipment fleet
  • Progress was made on a number of technical and planning fronts:
    • Reduced the mining footprint in marginal areas by suspending Level 87 and largely limiting activity to sustaining services at South Shaft
    • Increased focus on fleet utilisation and reliability to improve overall performance
    • A reduction in capital associated with new mine development and non-critical path infrastructure
    • Significant advancement in the geotechnical programme enhancing ground support protocols and updated mine design and scheduling
    • Implementation of long-hole stoping rig improvements based on increased stope availability and enhanced stope turnaround times
  • Implementation of efficiency improvement programmes based on five Business Improvement (BI) initiatives and supporting enabling projects:
    • Enabling visible felt leadership
    • Reinvigorating the leadership system
    • Improving and enhancing the effectiveness of mining face time
    • Facilitating and sustaining key enabling logistics
    • Implementation of Horizon 1 I&T systems

Going forward, emphasis is placed on South Deep showing substantive progress and traction on the mine’s core strategic project themes, key performance indicators and enablers in the short to medium term. This is important in establishing the operation’s capacity to achieve profitability and deliver the LoM plan steady-state volumes.

Operation

South Deep
Asset fundamentals
General location  

South Deep gold mine is situated in the magisterial districts of Westonaria and Vanderbijlpark (Gauteng province), some 45km SW of Johannesburg at latitude 26º 25’S and longitude 27º 40’E. It is accessed via the N12 provincial road between Johannesburg and Potchefstroom.

Climate  

The regional climate is classified as Cwb (warm temperature, winter dry, warm summer) under the Köppen-Geiger climate classification.

Licence status and
holdings
 

South Deep converted its mining right (old order) to new order mining rights in July 2010, as required by the Mineral and Petroleum Resources Development Act 28 of 2002 (as amended). The new order mining rights have been granted in respect of the mining area totalling 4,268ha – including the area known as Uncle Harry’s.

Operational
infrastructure and
mineral processing
 

The workings are accessed from the surface through two shaft systems, the Twin Shaft Complex (main and ventilation shafts), of which the main shaft comprises a single-drop to 110A level, a depth of 2,998m, the vent shaft to 110 level (2,947m) and the South Shaft Complex, which is a sub vertical system (three operating shafts) to 95 level at a depth of 2,786m.

The mine is divided into three main areas:

  1. Current Mine (CM), characterised by selective mining methods scattered over a large area originally exploited by means of conventional tabular mining. CM is accessed from four active levels (90, 93 and 95) from both the South Shaft and Twin Shaft complexes
  2. The North of Wrench (NoW) area, directly south of CM, comprises six mining corridors separated by regional pillars that extend southwards to the Wrench fault. A bulk non-selective mining method is applied here resulting in a higher Resource to Reserve conversion ratio
  3. South of Wrench (SoW) East and West, situated south of NoW, which will be mined in the same manner as NoW

South Deep gold mine operates one on-property gold plant. The comminution circuit comprises two stage milling with a free gold recovery circuit and gold recovery is carried out using a conventional leach / Carbon in Pulp (CIP) circuit. Final product from both the free gold and CIP circuits is smelted into bullion.

Tailings storage facility  

South Deep utilises one TSF known as the Doornpoort TSF. The TSF footprint is designed to accommodate the LoM tonnage after backfill. The first phase of the dam was completed in 2011 and the top of the starter wall has been reached with the first wall raise completed in January 2018. Based on the current LoM plan, the Phase 2 TSF infrastructure expansion will be required in 2020.

Mineralisation
characteristics
 

  1. Mineralisation hosted by conglomerates (reefs)
  2. Laterally continuous with long-range predictability
  3. Clear patterns of predictable mineralisation governed by sedimentary characteristics
  4. Ore body definition and resource modelling programmes are ongoing
Local geology and
deposit type
 

The reef horizons exploited in the South Deep LoM include the Ventersdorp Contact Reef (VCR) and the Upper Elsburg formation conglomerates. In the western half of the mining lease area, the VCR occurs as a single reef horizon that overlies footwall lithologies of the Turffontein Subgroup. The Upper Elsburg reefs, sub cropping below the VCR in a NNE trend, comprise multiple stacked reef horizons forming an easterly-divergent clastic wedge as illustrated in the schematic section below.

This wedge attains a thickness of approximately 120m to 130m in the vicinity of the eastern boundary of the mining right area. The Upper Elsburg Reefs constitute 100% of the South Deep Mineral Reserve ounces, VCR has been excluded from Reserves and contributes only to Mineral Resources in the 2018 reporting.

LoM   It is estimated that the current Mineral Reserves will be depleted in 2093 (75 years).
Sustainable
development
 

South Deep reports its level of compliance in respect of its Social and Labour Plan and Mining Charter commitments, on an annual basis. Furthermore, during Q4 2018, a compliance inspection was conducted by the Department of Mineral Resources (DMR) on the title conditions contained in South Deep’s new order mining right.

The Department of Water Affairs and Sanitation approved the integrated water use licence lodged in May 2015. South Deep is currently reviewing its water management plan to align with the new licence.

A consolidated Environmental Management Plan (EMP), current EMPs were approved in 2010 and 2012, was submitted for approval during Q4 2016, and is still under review by the DMR. During Q1 2018, the mine conducted an external compliance audit of the EMP and improved its score from 96% of 2016 to 98% in 2018. The mine’s Safety and Environmental Management Systems are OHSAS18001 and ISO14001: 2015 certified. The mine is certified in compliance with the ICMC.

 

SCHEMATIC WEST/EAST SECTION THROUGH THE SOUTH DEEP ORE BODY
map
WEST WITS LINE
map

Regional geology

South Deep is located in the West Rand Goldfield on the NW rim of the Witwatersrand Basin. This basin comprises a 6,000m-thick sequence of predominantly clastic sedimentary rocks, the upper part of which, the Central Rand Group, is characterised by the occurrence of auriferous and uraniferous quartz-pebble conglomerates (reefs) that are sporadically interspersed between finer grained quartzitic units. All major reef units are developed above unconformity surfaces. The angle of unconformity is typically greatest near the basin margin and decreases toward more distal areas. The most fundamental control to the gold distribution remains the association with quartz-pebble conglomerates on intra-basinal unconformities.

The Witwatersrand Basin reefs are considered to represent extensive fluvial deposits into a yoked basin, some 350km long in an ENE direction, and 200km wide in a NNW direction. The reefs are continuous as a consequence of the regional nature of the erosional surfaces. Preferential reef development within channel systems and sedimentary features such as facies variations and channel frequency assist in mapping out local gold distributions. Refer to the asset fundamentals table above for information on local geology and mineralisation style.

Resource definition/mine definition drilling and expenditure

The Mineral Resource base is predominantly classified as Measured and Indicated, with only 6% assigned to the Inferred category. Accordingly, with the surface exploration programme completed by Gold Fields in 2013 and subsequently incorporated with the results of the 3D vibroseis seismic survey undertaken earlier, drilling is now focused on resource and mine definition as opposed to exploration, which is effectively limited to the long-inclined borehole (LIB) drilling. The current drilling strategy and standard operating procedure aims at profiling the necessary resource confidence level to support and derisk the short, medium and long-term mine design and schedule. To this end, two distinct drilling programmes are employed:

  1. Resource definition drilling: provides Mineral Resource information for the medium-term excavation design. This drilling is conducted from footwall infrastructure and is executed in two phases ahead of the advancing destress cut echelon. The first phase is on a 60m to 120m grid, up to 300m ahead of the face. The second phase uses LIBs, attaining a 300m grid, up to 1,000m ahead of the destress echelon. Resource definition drilling provides additional data for structural definition, stratigraphic modelling, facies determination and assaying for grade estimation
  2. Mine definition drilling: effectively infill grade control drilling, is the final stage of drilling and data acquisition prior to stoping and provides high-resolution Mineral Resource information for the short-term excavation design. Underground channel sampling is not utilised because of safety, access, logistical constraints and spatial control due to the massive nature of the ore body. The drilling programme is customised to meet the specific needs of the operation and occurs within the destress cuts and provides the infill drilling to the existing Resource definition drilling to achieve an approximate 30m x 30m grid to support long-hole stoping. The data generated is used for local scale facies determination, structural definition, stratigraphic modelling and assaying for resource estimation. Cover drilling is conducted simultaneously and is a series of low inclined cover holes (-30°) from within the destress cut to enhance detail on geological structure. Up to four holes are drilled per corridor up to a depth of 100m ahead of the advancing cut, and will facilitate a series of geophysical surveys for increased geological confidence and for geotechnical modelling and domaining purposes

On-lease metres drilled and expenditure for the 12-month period ended 31 December 2018 are summarised below.

In accordance with the SAMREC Code, South Deep maintains rigorous quality assurance and quality control (QA/QC) protocols on all its resource definition programmes. It draws on industryleading practice for data acquisition and utilises accredited laboratories which are regularly reviewed both internally and externally. Analytical QA/QC is maintained and monitored through the submission of blanks, certified reference material and duplicates, plus umpire laboratory checks.

  December 2018     December 2017
  Metres         Metres      
Operation drilled ZARM US$M     drilled ZARM US$M  
Grade control drilling 8,871 19.97 1.51     6,724 20.93 1.69  
LIB drilling 1,775 4.44 0.34     2,248 4.46 0.36  
Only LIB drilling is classed as exploration drilling