Resources and Reserves

Okvau Mineral Resource Estimate - April 2017

Okvau April 2017

Mineral Resource Estimate

 

Cut-off (Au g/t)

Indicated Resource

Inferred Resource

Total Resource

Tonnage (Mt)

Grade   (g/t Au)

Contained Au (Koz)

Tonnage (Mt)

Grade   (g/t Au)

Contained Au (Koz)

Tonnage (Mt)

Grade   (g/t Au)

Contained Au (Koz)

0.50

19.58

1.74

1,093

3.47

1.35

151

23.05

1.68

1,244

0.70

15.11

2.08

1,008

2.57

1.61

133

17.68

2.01

1,141

1.00

11.01

2.54

898

1.67

2.04

109

12.68

2.47

1,007

 

Ore Reserve Estimate - April 2017

 

Tonnes

Gold Grade

Contained Gold

Probable Ore Reserve

14.26Mt

1.98g/t Au

907koz

 

In relation to Mineral Resources and Ore Reserves, the Company confirms that all material assumptions and technical parameters that underpin the relevant market announcement continue to apply and have not materially changed.

For full details of Mineral Resource estimate and Ore Reserve estimate please refer to ASX announcement dated 1 May 2017.

 

Competent Persons Statements

The information in this report that relates to Exploration Results is based on information compiled by Mr Craig Johnson, who is an employee to the Company and who is a Member of The Australasian Institute of Geoscientists. Mr Craig Johnson has sufficient experience which is relevant to the style of mineralisation and type of deposits under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined in the 2012 Edition of the ‘Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves’. Mr Craig Johnson has reviewed the contents of this news release and consents to the inclusion in this announcement of all technical statements based on his information in the form and context in which it appears.

The information in this report that relates to the Mineral Resources for the Okvau Gold Deposit was prepared by EGRM Consulting Pty Ltd, Mr Brett Gossage, who is a consultant to the Company, who is a Member of the Australasian Institute of Mining & Metallurgy (AIG), and has sufficient experience relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person as defined by the 2012 edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". Mr Gossage has reviewed the contents of this news release and consents to the inclusion in this announcement of all technical statements based on his information in the form and context in which it appears.

Information in this announcement that relates to Ore Reserves for the Okvau Gold Deposit is based on, and fairly represents, information and supporting documentation prepared by Mr Glenn Williamson, an independent specialist mining consultant. Mr Williamson is a Fellow of the Australasian Institute of Mining & Metallurgy. Mr Williamson has sufficient experience which is relevant to the style of mineralisation and type of deposit under consideration and to the activity which he is undertaking to qualify as a Competent Person (or “CP”) as defined in the 2012 edition of the "Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves". Mr Williamson has reviewed the contents of this news release and consents to the inclusion in this announcement of all technical statements based on his information in the form and context in which it appears.

Mineral Resource Estimate

The Okvau Mineral Resource estimate used for the DFS (refer to ASX announcement dated 1 May 2017) was prepared by independent resource consultants EGRM Consulting Pty Ltd (Principal Geologist, Brett Gossage) of Perth, Australia in April 2017 and is reported in accordance with the guidelines defined in the 2012 Australasian Code for Reporting of Exploration Results, Mineral Resources and Ore Reserves (JORC Code, 2012 Edition). Mr Gossage is a geologist and resource estimation specialist with over 27 years of experience including substantial experience working on applicable deposit types. A site visit was completed by Mr Gossage in December 2016. A more detailed description of the methodology used to estimate the Mineral Resources is contained in Appendix One (refer to ASX announcement dated 1 May 2017). 

The Mineral Resource estimate for the Okvau Deposit, reported above selected cut-offs is summarised below.  A preferred lower cut-off grade 0.70g/t gold is selected to reflect the final economic cut-off determined based on the DFS parameters.

Okvau Mineral Resource Estimate - April 2017

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Okvau April 2017

Mineral Resource Estimate

 

Cut-off (Au g/t)

Indicated Resource

Inferred Resource

Total Resource

Tonnage (Mt)

Grade   (g/t Au)

Contained Au (Koz)

Tonnage (Mt)

Grade   (g/t Au)

Contained Au (Koz)

Tonnage (Mt)

Grade   (g/t Au)

Contained Au (Koz)

0.50

19.58

1.74

1,093

3.47

1.35

151

23.05

1.68

1,244

0.70

15.11

2.08

1,008

2.57

1.61

133

17.68

2.01

1,141

1.00

11.01

2.54

898

1.67

2.04

109

12.68

2.47

1,007

 

Drilling

The Okvau Deposit has been drill tested with a combination of Diamond (‘DD’) and Reverse Circulation (‘RC’) drilling. The figure below presents a drill hole plan with the gold mineralisation envelope.  The Okvau resource estimate covers approximately 500 metres of strike and 400 metres width of the mineralised vein system.

Okvau Drill Hole Plan (DD red and RC green) and Mineralisation Outline

The Okvau Mineral Resource estimate is based on a database of 217 drill holes, for a total of 42,257 metres. The database is comprised of 112 DD holes for 31,447 metres and 105 RC drill holes for 10,810 metres.  Drilling at Okvau is typically spaced at 25 metres by 25 metres centres in the top 100 metres of the deposit.  Below 100m vertical the drill spacing widens to 25 metres drill sections and 50 metres on or along section 

Sampling Techniques and Analysis Methods

DD core was sampled using half-core where the core is cut in half down the longitudinal axis and sample intervals were determined by the geologist based on lithological contacts, with 80% of the sample intervals being 1 metre in length and an additional 15% of the sample intervals being 2 metres in length. RC samples were split through either a two or three tier riffle splitter at the drill rig and sampled on 1 metre intervals.

Estimation Methodology

The lithological constraints and oxidation surfaces were generated by Emerald technical staff and were applied to the grade estimation.  The modelled lithology includes diorite and metasedimentary (hornfels) host rocks.  An oxidation surface representing the top of fresh rock was also modelled.

The grade estimate is based on a mineralisation constraint (estimation domain) generated with indicator kriging using drill holes coded with a mineralisation interpretation generated by Emerald technical staff.  The mineralisation interpretation was completed using a 0.5g/t gold lower cut-off grade and includes a maximum 5 metres of internal dilution plus 2 metres of external dilution, and was generated using the known geological controls on gold mineralisation. 

Okvau Deposit Oblique Section

The Mineral Resource gold estimate was determined using Multiple Indicator Kriging (‘MIK’) within the mineralisation zone constraints.  MIK is a non-linear or ‘recovered resource’ grade estimation method which estimates grades and tonnages for a targeted selective mining unit (‘SMU’) block size, inclusive of dilution and ore loss.  Secondary variables (sulphur, arsenic, bismuth, antimony, copper, and tellurium) have been estimated using Ordinary Kriging (OK).   

A ‘parent’ block size of 20 metres x 25 metres x 10 metres was used followed by a change of support estimate to a 5 metre x 5 metre x 5 metre SMU. The model was constrained by a topographic survey and the geological model.

The MIK estimate was generated using a multi-pass estimation approach, with the high confidence sample search parameters (estimation pass 1 with a sample search of 50 metres x 50 metres x 20 metres) expanded by 100% for each subsequent pass to estimate blocks not originally estimated in prior high confidence estimation passes.  The majority of categorised blocks were estimated searching to a maximum distance of 100 metres from data with the sample searches optimised based on geostatistical investigations and variography generated for both gold and indicator variables. 

The grade estimates are based on 2 metre down-the-hole composites of the RC and DD drilling.  High grade cuts were variously applied to the composite data to limit the influence of high grade outliers.  High grade cuts have been determined via outlier analysis studies with a high grade cut of 20g/t gold and 40g/t gold applied to the fresh hornfels and diorite domains respectively.  A 10 g/t gold high grade cut was applied to the oxide diorite domain composites and no high-grade cut applied to the hornfels oxide composites. To further limit extrapolation of high grade, additional high grade cuts of 6.98g/t gold and 8.88g/t gold were applied to the hornfels and diorite domains composites respectively for estimation passes 2 and 3. 

A bulk density data set of 9,371 determinations were collected throughout the deposit via the immersion method of core billets.  Based on the average bulk density grouped into fresh and oxidised samples and subdivided by lithology, bulk density was assigned to the block model for tonnage reporting.

Okvau Bulk Densities

Diorite Oxidised

Diorite Fresh

Hornfels Oxidised

Hornfels Fresh

Lithology

t/m3

Diorite Oxidised

2.82

Diorite Fresh

2.87

Hornfels Oxidised

2.76

Hornfels Fresh

2.78

 

Classification

The Okvau Deposit grade estimates have been classified in accordance with the guidelines set out in the JORC Code, 2012 Edition. The assessment of confidence levels of the key categorisation criteria, including the confidence of the resource development data, the geological interpretation, the drilling density and gold grade estimation is summarised in Appendix One.  The resource classification is based solely on the gold estimate.

In summary, high confidence estimates that are within approximately 30 metres of drilling or better were considered as Indicated Mineral Resources.  Inferred Mineral Resources were blocks that were not considered Indicated Resources but still within the interpreted mineralisation zone and within 75 metres of drilling (when estimated with pass 1 or 2) or within 40 metres of drilling for estimation pass 3.  A cross sectional interpretation was completed using criteria listed above and a wireframe solid produced to capture those blocks that could be considered as Indicated and Inferred Resources.

Mineral Resource Classification (Red is Indicated Resources and Green is Inferred Resources)

Mining and Ore Reserves

Mining Resources Pty Ltd completed all mining aspects of the DFS (refer to ASX announcement dated 1 May 2017) and compiled the Ore Reserve for the Project.

The Okvau Deposit will be mined via conventional open pit mining methods from a single pit which will be mined in stages to maintain a relatively constant mining rate whilst providing adequate ore for processing at consistent ore grades. Mining will be undertaken by drilling and blasting ore and waste with load and haul using mining contractors. The proposed core mining fleet is made up of 120 tonne class excavators and 91 tonne class mine haul trucks.

Pit Optimisation & Design

A number of Whittle optimisations were completed on the April 2017 Mineral Resource model and included all Resource categories including Inferred resources.  The results from the optimisations were considered in context of sensitivities, risks, contained ounces, mine life and total project size. The pit shell selected as a basis for the mine design was optimal in terms of maximisation of profitability based on the input parameters. It was chosen on the basis of stripping ratio, grade and contained gold and limitation of the operating cost risk in high strip ratio waste removal.

Selected Optimised Pit Shell

 

Selected Pit Shell

 

Mineralisation

14.49Mt

Grade

1.95g/t Au

Contained Gold

911koz

Waste

79.44Mt

Total Material

93.94Mt

Strip Ratio (t:t)

5.5:1

 

The final pit design was prepared to enable practical and efficient access to each bench and took into consideration the geotechnical design criteria. The final pit design has approximate dimensions of 650 metres by 600 metres to a maximum depth of 350 metres.

Comparison of Final Pit Design to Optimised Pit Shell

 

Selected Pit Shell

Final Mine Design

Difference

Mineralisation

14.49Mt

14.42Mt

-0.5%

Grade

1.95g/t Au

1.97g/t Au

+1.0%

Contained Gold

911koz

914koz

+0.3%

Waste

79.44Mt

82.31Mt

+3.6%

Total Material

93.94Mt

96.73Mt

+3.0%

Strip Ratio (t:t)

5.5:1

5.7:1

+4.1%

 

Inferred material accounted for only 7,000 ounces of gold or less than 1% of the total contained gold ounces and was excluded for the purposes of the DFS (refer to ASX announcement dated 1 May 2017).

 

The final pit design based on Probable Ore Reserves (Indicated Resources) only at a cut-off of 0.625g/t gold is shown below.

Final Pit Design Based on Indicated Mineral Resources at a Cut-Off of 0.625g/t Gold

 

Final Mine Design

(Indicated Resources Only)

Mineralisation

14.26Mt

Grade

1.98g/t Au

Contained Gold

907koz

Waste

82.47Mt

Total Material

96.73Mt

Strip Ratio (t:t)

5.8:1

Open Pit Design

Ore Reserve

The Ore Reserve for the Project has been completed in accordance with the JORC Code, 2012 Edition. The Ore Reserve is based on Indicated Mineral Resources and as such is stated as Probable Ore Reserves. A more detailed description is contained in Appendix One (refer to ASX announcement dated 1 May 2017).  

Ore Reserve Estimate

 

Tonnes

Gold Grade

Contained Gold

Probable Ore Reserve

14.26Mt

1.98g/t Au

907koz

The cut-off grade used in the estimation of the Ore Reserve is the non-mining, break-even gold grade taking into account modifying factors of mining recovery and dilution, metallurgical recovery, site operating costs, royalties and revenues. All these factors have been estimated to a DFS level. For reporting of Ore Reserves the calculated cut-off grade is 0.625g/t gold. The Ore Reserve estimate is reported within the open pit mine design prepared as part of the DFS (refer to ASX announcement dated 1 May 2017).