White Dam Gold Project Dump Leach

Transcription

1 ALTA 2015 White Dam Gold Project Dump Leach A division of Midas Engineering Group Mineral Engineering Technical Services PO Box 5778 St Georges Tce WA 6831 P: (+61 8) F: (+61 8) ABN W: E: info@metsengineering.com > M i n e r a l P r o c e s s i n g > E n g i n e e r i n g D e s i g n > T r a i n i n g > S p e c i a l i s t S e r v i c e s

2 DISCLAIMER With respect to all the information contained herein, neither Mineral Engineering Technical Services, nor any officer, servant, employee, agent or consultant thereof make any representations or give any warranties, expressed or implied, as to the accuracy, reliability or completeness of the information contained herein, including but not limited to opinions, information or advice which may be provided to users of the document. No responsibility is accepted to users of this document for any consequence of relying on the contents hereof. COPYRIGHT Passing of this document to a third party, duplication or re-use of this document, in whole or part, electronically or otherwise, is not permitted without the expressed written consent of Mineral Engineering Technical Services. ACKNOWLEDGEMENTS This document is a dynamic record of the knowledge and experience of personnel at Mineral Engineering Technical Services. As such it has been built upon over the years and is a collaborative effort by all those involved. We are thankful for the material supplied by and referenced from various equipment manufacturers, vendors, industry research and project partners.

3 Key Attributes Pragmatic, efficient, complete engineering through quality, personalised & exceptional service delivery Working globally since 1988 Dynamic and innovative niche consultancy Dedicated team providing customised service Specialist in mineral processing & engineering projects Unique solution finder

4 Introduction Small low grade resource in South Australia Dump leach considered high risk Cyanide soluble copper present Limited testwork and large diameter columns Development Risk management Actual performance Conclusions

5 Local Terrain

6 Project Location Located 80 km west of Broken Hill in South Australia g/t Au JV Polymetals & Exco Resources Small low grade short life project Dump leach rarely undertaken in Australia

7 Porous Wetting Sandstone, gneiss, amphibolites, pegmatite, schist & albite Ore porous when placed in water Ore amenable to dump leaching Sample representivity based on diamond drill core representing geology and grade Surface costeans used for testing Ore contains gold, silver, low levels of copper and zinc

8 Core samples

9 Advantages Heap or dump leaching is favourable for the following reasons: Low capital expenditure and operating costs (relatively when compared to milling options) Rather quick installation to set up operations it is advantageous for smaller companies to set up Simple process with low levels of training required for routine operations No tailings dam hence lower capital costs and less exposure to environmental risks

10 Disadvantages However, there are some disadvantages that should be mentioned including: Reduced metal recovery compared to milling Less certainty- high failure rate Cash flow delays at start up High inventory of valuable metals Leach kinetics slow to change and difficult to analyse potential problems that can develop High risk especially for low grade ores with little margin for error Management is critical

11 Orebody

12 Resource Drilling-Block Model

13 Gold ore Resources Model Resource Category Tonnes Grade Mt g/t Au Indicated Inferred obm_v2ok_005.bmf Total Indicated Inferred obm_v2ok_005r.bmf Total

14 Gold Price What gold price to use? Should gold be sold forward?

15 Staged Open Pit Mine Plan

16 Mining Schedule

17 Metallurgical Objectives Process selection- (dump vs heap leaching) Permeability, slumping, ponding Crush size sensitivity Leach kinetics Reagent consumption Sampling variability Heap and pond design, irrigation & pumping Economic project

18 Metallurgical testwork Gold not spotty 1.65 g/t Au gave 80.3% recovery using 0.7 kg/t cyanide and 0.36 kg/t lime Bottle rolls Percolation tests Slumping Crush size sensitivity Large column testwork Assay by size of the residue indicated similar leaching through all the size fractions Variability samples

19 Large Column Tests

20 Master Composite

21 Risk Analysis Geological Not fully understanding the mineralogy and lithology of the ore body. Sampling Poor representivity of the various ore types and accounting for variability within the deposit. Metallurgical Pre start-up. The amenability of the deposit to crush size sensitivity, acid consumption, leach kinetics, percolation rates, scale formation and copper recovery. Post start-up. Poor accounting procedures. Cannot measure performance. Process Design Under sizing the crushing plant, ponds, pipes, not agglomerating, reticulation system, geotechnical issues. Flowsheets should be simple and not sensitive to capital costs. Management Lack of experience, no planning, no scheduling, cutting costs, failure to sample, assay and monitor, fly in fly out issues, bad contracts, lack of foresight, poor grade control. Operational Poor training, supervision and methods, Stacking methods, Cost Structure Changes in metal prices, reagent costs, power costs, consumable costs. More serious in overseas countries. Environmental Managing the water balance, failure of heaps, leaks of liners, government intervention, and closure costs. Financial Insufficient funds for drilling, metallurgical testing, feasibility studies, slow cash flow- slow leach cycle time.

22 Site Plan Layout & Design

23 Dump Leach Flowsheet ORE FEED ILS STAGE PLS STAGE LIXIVIANT WATER MAKE- UP PRODUCT RECOVERY ILS POND PLS POND BARREN SOLUTION POND

24 Operational Strategy Jaw crushing only Pad construction- clay and 1 mm HDPE. 20 mm sand on top followed by 300 mm aggregate Lime addition-milk of lime added to trucks Stacking-16m by 40m cells. Truck dumping and ripping Pipes & irrigation-wobblers to reduce evaporation, lined ponds Leach kinetics- test samples in laboratory Adsorption Desorption plant-carbon contactors, AARL stripping Water supply- nearby bore field kl/day Power supply- portable diesel generators Camp- 20 man camp

25 Cyanide Soluble Copper ph-potential Diagram for the copper-cyanide-water system Low levels of copper 2.0 Difficulty determining free cyanide 1.0 Cu 2+ CuO CuO 2 2- Preg robbing Cu 2 O Cu(CN) 3 2- Carbon fouling E h 0.0 Cu(CN) 2 - Oxygen demand -1.0 Cu Cu 2 O Blending & management [Cu] = 10-4 M [CN] = 10-3 M ph

26 Cyanide Soluble copper

27 Percolation No agglomeration No cement addition Limit height Monitor Not an issue

28 Project Schedule

29 Water Balance-Summer & Winter

30 Predicted Recovery Critical issue for funding Economics very sensitive to recovery

31 CAPEX

32 OPEX Units Oxide Fresh Gold Price A$/oz Royalty % Price Realised A$/oz Price Realised A$/g Administration Costs $/t ore Processing Costs $/t ore Rehabilitation $/bcm ore Grade Control $/t ore Mining Supervision $/t Metallurgical Recovery % Cut-off Grade g/t Au Major processing cost is cyanide and lime

33 Free Cash flow

34 Metallurgical Accounting Starter cells Procedures and sampling before operations Laboratory column tests Solution volume measurement Assays of solutions

35 Gold Production

36 Conclusions The actual recovery was better than expected Costs were lower than predicted Additional ore was discovered and mined The risks were managed- copper was not an issue Dump leaching was appropriate for this ore body Project performed better than expected Small gold projects can be profitable

37 Acknowledgement Thanks to companies for permission to publish Thanks also to all colleagues, laboratory staff and other consultants for their help and contribution. Thanks to vendors for the photos

38 THANK YOU