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Salares Norte, Chile

Salares Norte Project – 100% attributable to GFI

Strong enhancements to the resource model confidence will support completion of an interim phase feasibility study in Q1 2018, which will then be progressed toward full feasibility during 2018.

LOCATION

The Salares Norte Project is located in the Atacama region of Northern Chile. The nearest town is Diego de Almagro, about 190km by road to the west of the project. The project is centred on latitude of 26°0’42’ S and longitude of 68°53’35’ W, with elevations between 4,200m and 4,900m amsl.

Project history and ownership

Gold Fields discovered the mineralisation at Salares Norte in March 2011. To date, 511 holes totalling 142,496m have been drilled on the project (115 reverse circulation holes and 396 diamond drill holes).

The project is owned by Minera Gold Fields Salares Norte Ltda (MGFSNL), which holds 1,800ha of exploitation concessions (mining rights), with definitive title granted. MGFSNL also has an option to purchase agreement for an additional 1,200ha property attached to the project. Gold Fields Limited indirectly holds a 100% interest in MGFSNL. Access rights to the property have been granted by the government and applications for water rights have also been approved.

Geology and mineralisation

The Salares Norte Project is located in the northern part of the Maricunga Belt, an area with a predominance of Cenozoic volcanic rocks, comprising eroded strato-volcanos, volcanic domes and pyroclastic rocks. Mineralisation at Salares Norte is contained in a highsulphidation epithermal system, hosted mainly by a breccia complex along the contact of two volcanic domes of andesitic and dacitic composition. Mineral Resources have been delineated by drilling in two separate deposits, Brecha Principal and Agua Amarga, which are located about 500m apart. Most of the mineralisation known to date is oxidised. The sulphide mineralisation contains mainly pyrite. Preliminary metallurgical test results indicate gold extraction in the order of 92% using a conventional CIL process on samples of oxidised material.

Level of study, processing methodology, sustainability and permits

An interim scoping study was completed on the project in 2014, which showed positive results. The scoping study was updated in 2015 after additional drilling, metallurgical testing and cost analysis. The environmental impact declaration that was approved in January 2014 was amended in 2016 to permit continued exploration drilling.

A positive pre-feasibility study was completed for the Brecha Principal deposit in March 2017. Following additional drilling in 2017 mainly at Agua Amarga, Salares Norte reflects a significant improvement in Resource model resolution and confidence and is now at 95% indicated (SAMREC) for gold metal. An interim phase feasibility study for Brecha Principal and Agua Amarga using advanced mining study modifying factors will be completed in Q1 2018, to be followed by EIA submission. The project will advance toward an extended feasibility in 2018. The December 2017 Mineral Resource estimate for Salares Norte is supported by positive external audits from Santiago Gigola (geology consultant) and Optiro (resource estimation consultant).

As at all the Gold Fields operations and projects, a comprehensive sampling and assay QA/QC protocol is in place for Salares Norte using leading industry practice in data acquisition, reputable certified laboratories, and analytical controls.

Key development and material issues

  • Material improvements in Resource model resolution and confidence based on additional resource definition drilling
  • Year-on-year update shows -9% tonnes, +6% gold grade and -3% gold ounces with an increase in the Indicated Resource contribution from 52% to 95% for metal, reflecting overall robustness in the geology and resource modelling
  • The gold Mineral Resource decreased slightly from 3.8Moz to 3.7Moz and comprises 98% oxide material
  • The silver Mineral Resource increased from 43.8Moz to 49.5Moz due to additional drilling and enhanced silver grade domaining
  • All geological domains have been updated with improved geological definition and a better understanding of mineralisation controls. Sensitivity to domain boundary assumptions has decreased with the current average drill spacing approximating 22m for Indicated
  • Ongoing infill drilling at Agua Amarga directed to further derisk the deposit
  • A close spaced drilling campaign will be undertaken in 2018 H1, to confirm the short scale behaviour of geological boundaries and grade trends at Brecha Principal
  • Completed an airborne magnetic/radiometric survey over the district exploration areas and district mapping was continued to further define targets
  • Environmental baseline study completed in 2017. The EIA submission is planned for Q1, 2018
  • A Mineral Resource estimate update is scheduled for mid-2018 in conjunction with the feasibility study

The PFS for Brecha Principal and scoping study for Agua Amarga are scheduled for completion in 2017 and will benefit from the latest drill season campaign and updated resource and reserve modelling that is planned to support reporting a maiden Mineral Reserve for Brecha Principal in the latter half of 2017.

Mineral Resources

Salares Norte Classified Mineral Resource

Deposit Class Tonnes
(Mt)
Gold
(g/t)
Silver
(g/t)
Gold
(Moz)
Silver
(Moz)
 
Brecha Principal Indicated 15.610 5.18 83.06 2.601 41.683  
  Inferred 0.911 2.12 14.59 0.062 0.428  
  Sub-total 16.521 5.01 79.28 2.663 42.111  
Agua Amarga Indicated 5.345 5.18 40.09 0.890 6.890  
  Inferred 1.432 2.40 9.93 0.110 0.457  
  Sub-total 6.777 4.59 33.71 1.000 7.347  
  Total 23.298 4.89 66.03 3.663 49.458  
Total Mineral Resource Tonnes (Mt)     Grade Au and Ag = g/t     Content Au and Ag = Moz  
Classification Dec
2017
  Dec
2016
Dec
2015
    Dec
2017
  Dec
2016
Dec
2015
    Dec
2017
  Dec
2016
Dec
2015
 
Indicated - gold 21.0   12.1 6.8     5.2   5.1 4.5     3.491   1.963 0.977  
Inferred - gold 2.3   13.5 20.0     2.3   4.2 3.7     0.172   1.831 2.370  
Total - gold 23.3   25.6 26.8     4.9   4.6 3.9     3.663   3.794 3.347  
Indicated - silver 21.0   12.1 6.8     72.1   69.6 82.7     48.573   27.075 18.133  
Inferred - silver 2.3   13.5 20.0     11.7   38.4 37.4     0.885   16.670 24.001  
Total - silver 23.3   25.6 26.8     66.0   53.1 48.9     49.458   43.755 42.134  

Notes:

Mineral Resources are reported in accordance with SAMREC
Confidence classification assumes annual production-scale and open pit mining
These Mineral Resources are classified as Indicated and Inferred. The Competent Person has reasonable confidence in the Resources, but future drilling may materially change the Resource evaluation.
Attributable metal to Gold Fields is 100%
Commodity prices used in this study are US$1,400/oz gold and US$20/oz silver
Mineral Resources are constrained within a Whittle optimised pit shell taking into consideration mining, processing, administration costs, process recovery and sustaining capital
Mineral Resources are reported for material within a pit shell having positive value after process recoveries and costs for processing, refining, royalty and overhead have been applied. A variable cut-off is applied since the process costs and recoveries are dependent on the head grade. This resulted in an average economic cut-off of US$45.88/tonne - processed based on 1% royalty, average process recovery of 92% for gold 70% silver and refining costs of US$2.78/oz for gold and US$1.21/oz for silver
Mineral Resources are reported without mining dilution and ore loss. Mining dilution and loss were accounted for in-pit shell generation
Figures are rounded to reflect confidence. Some grades may not average exactly due to rounding. The Competent Person deems these small discrepancies to be immaterial

Factors affecting Mineral reconciliation year-on-year

Brecha Principal was stable year-on-year
Agua Amarga reported reduced tonnes due to revised pit slope angles and modelling changes informed by additional drilling, geological interpretation and resource model estimation
Significant improvement in Resource model confidence (SAMREC) from 52% Indicated to 95% Indicated on metal supported by an additional ~35km of drilling

Mineral Resource reconciliation (Gold – koz)

Drill holes completed to date showing collar and trace
Plan view, Salares Norte Project – Mineral Resource areas