Integrated Annual Review 2012 Annual Financial Report 2012 Mineral Resources and Mineral Reserves Regional overview  

6.2.1 Near-mine exploration

A significant proportion of the recent increase in our international regions’ Mineral Resources and Mineral Reserves has been as a result of near-mine exploration.

Near-mine exploration forms the sustaining foundation of our overall growth strategy. As well as adding to our total Mineral Reserve base, near-mine exploration:

  • Extends the life of our existing mines and maintains or increases their option value
  • Ensures we can continue to leverage our existing infrastructure well into the future
  • Provides a robust platform for regional growth

During 2012, we completed 374,830 meters of near-mine drilling – compared to 345,625 meters in 2011. In 2013, we expect to carry out a lower level of activity, due to the reduction in our near-mine exploration budget. This is due to our immediate prioritisation of lower-risk, higher-return near mine growth projects to help support Group cash generation.

Open pit at Agnew, Australia
Open pit at Agnew, Australia

Australasia region

Mineral Resources and Mineral Reserves Overview 2012 - Australasia Region


During 2012, we continued to explore the Waroonga Main Lode – including the down-plunge of its three associated high-grade ore shoots to the north of the Kim Lode – using directional surface diamond drilling. The programme, which is focused on confirming the continuity and extent of the Fitzroy, Bengal and Hastings shoots, is known as the High Grade Shoots Project.

The project also further defined the apparent intersection with the Porphyry Link target zone between the Kim and Main Lodes – as well as the identification of extensions to the Porphyry Link target zone itself (which appears to coalesce with the main Kim shoot at depth).

Technical Short Form Report 2012 - Agnew

St Ives

The St Ives mine is a centre of excellence for near-mine exploration within Gold Fields, due to its sophisticated geology, range of underground and shallow deposits, and our long-term investment in its innovative near-mine exploration teams. In 2012, we carried out an extensive A$40 million (US$42 million) near-mine exploration programme at the mine. This was aimed at continuing to replace ore reserves as they get depleted.

As part of this programme, in the third quarter of 2012 we announced a new, high-grade shallow prospect at the Invincible ore deposit. Mineralisation was identified over a 1km strike and to a depth of 200 meters – and this was found to be open along the strike and at depth. Subsequent confirmation drilling resulted in the announcement of a maiden Mineral Resource estimate of 87,000 ounces, which brings the mine’s total Mineral Resource to 4.7 million ounces. This has had a significant impact on the mine’s overall Mineral Resources and will help underpin future production at the mine.

In addition, we carried out work to extend our Mineral Resources in the area between the Neptune and Revenge deposits – with positive results in the form of newly identified extensions, which added about 158,000 oz to the mine’s Mineral Resources. Likewise, high-grade mineralisation continued to be intersected on depth extensions of the Eastern Lodes at Cave Rocks.

On top of such efforts, we carried out significant early stage near-mine exploration to identify entirely new deposits (in addition to Invincible) – and to help underpin the mine’s mediumterm production pipeline. This included the identification of Target X in the Leviathan area.

Technical Short Form Report 2012 - St Ives

South America region

Mineral Resources and Mineral Reserves Overview 2012 - South America Region

Cerro Corona

In late 2012, we completed the first phase of a deep drilling programme under the Corona Deep Project, which has identified porphyry mineralisation at depths of 600 meters below the current pit design. This has potential similarities to a common form of gold-copper porphyry ‘pencil’ system that can extend to depths far greater than those currently identified at Cerro Corona. Although all six deep drill holes intersected porphyry-style copper-gold mineralisation below the current pit, assay results suggest a decreasing gold/copper ratio at depth.

We are carrying out a full evaluation of mining potential for the Corona Deep Project, which is due for completion in the first half of 2013. Depending on the results, this would potentially support plans for a first-pass deep drilling programme to support large-scale underground mining opportunities over the longer term.

Technical Short Form Report 2012 - Cerro Corona

Mills at Cerro Corona, Peru  
Mills at Cerro Corona, Peru  

West Africa region

Mineral Resources and Mineral Reserves Overview 2012 - West Africa Region


In late 2012, we completed a framework drilling programme on highly prospective targets linked to the Bonsa Hydrothermal Project. These were identified as part of a major, ongoing geological reinterpretation exercise. We are awaiting final assay results from the project. In addition, we focused on extending the previously lucrative Amoanda open pit to increase the mine’s Mineral Reserves and to support the Damang expansion. This included the testing of concepts to define the pit’s potential cut-back potential in the highly prospective mineralisation between Amoanda and Damang. Drilling results confirmed an extension to the north plunging Amoanda mineralisation.

Technical Short Form Report 2012 - Damang