Australia region - Regional overview

Gold Fields' mining assets in the Australia region (GFA) include a 100% interest in the St Ives, Agnew and Granny Smith mines and a 50:50 interest in the Gruyere Joint Venture Project with Gold Road Resources located in the Yilgarn area of Western Australia.

Significant investment in ongoing brownfield (on-lease) exploration continued as an imperative given the orogenic style of mineralisation in the Yilgarn district (2017: A$98.6M; US$75.4M). Orogenic ore bodies, by their nature, generally support operations with relatively short LoM profiles at any point in time, three to five years of Proved and Probable Mineral Reserves is not unusual. Importantly, orogenic based assets tend to replenish Reserves through cyclical discovery and Resource to Reserve conversion. Our multi-year phased investment in exploration is aimed at realising each mine's geological endowment potential by locating and defining economic ore bodies that will support the next generation of mines. The GFA exploration strategy is supported by a dedicated team of geologists with broad expertise who work with the site teams to ensure an integrated approach to target generation, prospectivity mapping and exploration stage gating. Projects are frequently reviewed based on defined selection criteria and either terminated or aggressively advanced to drive project churn and maximise return on exploration expenditure.

Operational profiles   St Ives   Agnew   Granny Smith   Gruyere JV
Mining method   Open pit and
  Underground   Underground   Open pit

Infrastructure and mineral processing


Two open pits, two main underground mines and one gold processing plant with a capacity of 4.7Mtpa consisting of a single-stage SAG mill with a gravity circuit and five-stage carbon in pulp (CIP) circuit. Gold is recovered by electro winning.


Two underground complexes and one processing plant, with a capacity of 1.3Mtpa consisting of a three-stage crushing circuit, two-stage milling circuit, gravity circuit and CIP circuit.


One active underground mine. A processing plant with a capacity of 3.5Mtpa consisting of two crushing circuits, SAG and ball mills, leach and CIP circuits and a tailings retreatment circuit. However, it is mine constrained and currently operates at 1.5Mtpa on a campaign milling basis.


Construction is on budget and schedule for all required project infrastructure. Future processing plant with a capacity of 7.5Mtpa consisting of single stage crush, SABC circuit with pebble crushing circuit.

Main Gruyere open pit due to commence in H2 2018

Tailings storage facility (TSF)   Tailings stored in two paddock-type facilities and a new in-pit tailings storage facility at Leviathan, which will meet current LoM requirements.   TSF 4 established and commissioned in 2017 is projected to receive tails until 2025, thereafter stage 4 approvals can be established for a further seven years.   The TSF capacity is projected to last until 2021, with additional submissions completed for extensions to heights for two existing cells.   Construction of main TSF facility in progress. The TSF capacity is projected to last until 2030 for all main pit planned mining.
Mineralisation style  

Orogenic greenstone hosted (hydrothermal style).

Mineralisation typically structurally controlled and hosted by shear and fault zones and confined to well-defined prospective structural belts.

Mineralisation characteristics   Mineralisation zones discontinuous with short-range predictability.   Mineralisation zones with moderate to long-range geological continuity and shortrange grade continuity.
Exploration programmes required to drive discovery, define the mineralisation controls, establish
continuity and convert Mineral Resources to Mineral Reserves.

Regional geology

Three of the operations are located in the geological region known as the Norseman-Wiluna Archaean Greenstone Belt. This is part of the Yilgarn Craton, a 2.6 Giga annum (Ga) granite-greenstone terrain, which is well endowed with gold and nickel mineralisation.

Deposits are hosted within a diverse range of rocks, including basalts and dolerites, fine to coarse-grained sedimentary rocks, and felsic to intermediate intrusions. Host rocks are commonly metamorphosed to greenschist or lower amphibolite facies. Gold mineralisation is typically structurally controlled, occurring within a network of shear zones proximal to major regional faults. The most important gold mineralisation styles are shear hosted quartz-carbonate bearing breccia lodes and associated quartz vein arrays, together with finely disseminated gold associated with zones of strong hydrothermal alteration. Alteration comprises silica or albite-rich zones, associated with ankerite, sericite, biotite or amphibole, together with pyrite, pyrrhotite or arsenopyrite as sulphide bearing phases.

The recently acquired 50% interest in the Gruyere project and its exploration tenements encompass the Yamarna and Dorothy Hills Greenstone Belts, the eastern most known greenstone belts of the Archaean Yilgarn Craton. The greenstone belts of the Yilgarn Craton are the dominant host for gold mineralisation and mined production in Australia.

The Gruyere deposit is an Archaean orogenic gold deposit and is located on a flexure point of the regional-scale Dorothy Hills Shear Zone within the Dorothy Hills Greenstone Belt where the shear zone changes from a northerly direction to a north-north-westerly direction. Gold mineralisation is hosted within the steep easterly dipping Gruyere Porphyry, a medium grained quartz monzonite porphyry that has intruded the country rocks, elongated in the direction of the shear zone.

Exploration drilling and expenditure

On-lease exploration metres drilled and expenditure for the 12-month periods ended 31 December 2017 and 31 December 2016 are summarised below (exclusive of grade control drilling). The ongoing elevated levels of funding are significant in the context of the Western Australia (WA) gold mining industry and support the multi-year commitment to establishing a robust pipeline of projects that will deliver the next generation of mines.

The region maintains rigorous QA/QC protocols on all its exploration programmes. It draws on industry leading 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 2017        December 2016    
Exploration drilling  Metres 
Agnew  194,910  28.27  21.64        143,134  28.39  21.16    
Darlot  201  2.03  1.55        44,847  11.00  8.20    
Granny Smith  227,357  25.28  19.35        232,438  22.00  16.40    
St Ives  225,665  38.53  29.49        240,946  40.93  30.51    
Gruyere (100% of metres and 50% of costs) 32,699  4.45  3.41                   
Total  680,832  98.56  75.44        661,365  102.32  76.27    

Average 2017 exchange rate: US$=A$1.31
Drilling unit costs are affected by the length, type (diamond drill (DD), reverse circulation (RC), aircore or sonic), ground conditions, rig and site availability, as well as whether drilling is from surface or underground