technical report on the nechalacho deposit, thor lake project ...

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Based on the data, Melis Engineering designed a comminution circuit comprising crushing to - 15 mm followed by rod and ball milling to achieve the target grind of 80% passing 38 µm. The SAGDesign tests showed that the ore was amenable to semi-autogenous grinding (SAG) and this option may be examined again in future testwork and design studies. FLOTATION Numerous open circuit and locked cycle flotation tests have been done at SGS by Srdjan Bulatovic of SBM Mineral Processing and Engineering Services Ltd. Testwork is continuing but at the time of the pre-feasibility study, it had been established through work on numerous samples covering different ore grades and compositions that the flotation flowsheet should comprise grinding to 80% passing 38 µm, desliming at about 8 µm, the removal of magnetic materials followed by flotation. The flotation process detailed in the pre-feasibility study comprised a partial solution change, conditioning, rougher-scavenger flotation, four stages of counter-current cleaning, and a gravity upgrading step. At 18% mass pull to a final concentrate, the circuit described above was expected to yield 90% recovery of zirconium, 69% recovery of niobium, 63% recovery of tantalum, and 80% recovery of the rare earths and yttrium. Optimization of mass pull (affecting concentrate handling and hydrometallurgical operating and capital costs) vs. recovery (affecting revenue) for the concentrator, and the evaluation of the response of other ore samples will be carried out at the Feasibility stage. Testwork is continuing at SGS to evaluate other ore samples and to further increase the upgrading effect whilst holding, or improving, recovery levels through the rejection of biotite. When these tests are completed it is planned to operate a pilot plant comprising grinding, feed preparation, and flotation to both demonstrate the process and generate a bulk sample for ongoing hydrometallurgical work and, eventually, a hydrometallurgical pilot plant. HYDROMETALLURGY The minerals in the flotation concentrate are chemically refractory – especially zircon. Zircon is routinely decomposed (cracked) at several operations around the world using fused sodium hydroxide and this process has been extensively investigated by SGS Mineral Services on Thor Lake material. The tests have shown that caustic cracking will very effectively decompose not only the zircon but also all other value-bearing minerals. Technical Report 43-101 – March 13, 2011 Page 16-2 Prepared by Avalon Rare Metals Inc.
In a typical test, for example CCr-27, concentrate was treated with sodium hydroxide at 600°C for three hours, cooled, then water washed to remove excess sodium hydroxide and the phosphates and silicates formed in the cracking process. The solids were then leached with hydrochloric acid and yielded 96% zirconium extraction and more than 96% solubilization of the rare earths. Other approaches to the caustic cracking process have been investigated including cracking tests using sodium carbonate, cracking in an autoclave using strong caustic solution, cracking in the presence of reductants, and low temperature attrition milling with sodium hydroxide. Some of these tests provided encouraging results and further tests have been planned. Another approach to cracking refractory minerals is acid baking in which the feed material is mixed with concentrated sulphuric acid and held at a temperature of 200°C or more for a few hours. This method is widely used in China for decomposing the rare earth concentrates from Bayan Obo and elsewhere. SGS has investigated the use of acid baking for the Thor Lake concentrate and it has been seen to solubilize about 80% of the light rare earths and 50% of the heavy rare earths. Zircon extraction is minimal, less than 4%, even under extreme acid bake conditions clearly indicating the refractory nature of zircon. SGS Mineral Services has also investigated the use ammonium sulphate or ammonium chloride as acid baking reagents. Some elements were extracted but no further work is planned. A combination of acid baking and caustic cracking has also been investigated and shown to offer high recoveries and preferred reagent consumption levels and operating costs. As <strong>report</strong>ed in the previous Technical Report, extractions under favourable conditions are typified by the results of AB-19 in which overall zirconium recovery was 99%, overall light rare earth (lanthanum, cerium and neodymium) extraction was 98%, and extraction of the heavy rare earths and yttrium was 99%. Niobium extraction was 83% Although it is clear that a very effective process for solubilizing the valuable elements in the Thor Lake concentrate had been identified, testwork is continuing at SGS Mineral Services to further define the process parameters and optimize the flowsheet for the initial solubilization step. Extracting valuable elements from the refractory minerals of the concentrate is a key part of the hydrometallurgical process. Once the elements of interest are in solution, it is necessary to separately recover the zirconium, rare earths, yttrium, niobium and tantalum and this has been investigated in the laboratory. The flowsheet that was selected for the pre-feasibility study Technical Report 43-101 – March 13, 2011 Page 16-3 Prepared by Avalon Rare Metals Inc.
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TECHNICAL REPORT ON THE NECHALACHO
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TABLE OF CONTENTS 1. SUMMARY ......
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QUALITY ASSURANCE / QUALITY CONTROL
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Warehouse..........................
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LIST OF TABLES Table 1-1 Summary of
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Table 18-9 Mine Ventilation Quantit
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Table 18-54 Table 18-55 Pine Point
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LIST OF APPENDICES APPENDIX A Block
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Table 1-1 Summary of Mineral Resour
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Royalties. The net revenue generate
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• The products will be shipped in
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• Income taxes and NWT mining roy
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2. INTRODUCTION This report
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Figure 2-2 Project Sites, Thor Lake
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Table 2-1 Rare Earth Element Data A
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LIST OF ABBREVIATIONS Units of meas
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4. PROPERTY DESCRIPTION AND LOCATIO
Page 35 and 36: The mining leases have a 21-year li
Page 37 and 38: 5. ACCESSIBILITY, CLIMATE, LOCAL RE
Page 39 and 40: Fort Resolution is located on the s
Page 41 and 42: producing a tantalum concentrate, b
Page 43 and 44: Figure 7-2 Detailed Deposit Geology
Page 45 and 46: The nepheline-sodalite syenite host
Page 47 and 48: LATE TECTONIC FAULTS Faults are pre
Page 49 and 50: 8. DEPOSIT TYPES The mineral deposi
Page 51 and 52: The Ore (Nechalacho) Nepheline Soda
Page 53 and 54: from section to section - this may
Page 55 and 56: Table 9-1 Average Percent of Ore Mi
Page 57 and 58: The Nechalacho deposit alteration s
Page 59 and 60: 11. DRILLING Since 1977, diamond dr
Page 61 and 62: Foraco drill rig was added in Febru
Page 63 and 64: CORE LOGGING AND CORE RECOVERY The
Page 65 and 66: A high R 2 (and all regressions had
Page 67 and 68: 12. SAMPLING METHOD AND APPROACH A
Page 69 and 70: such as Illimausaq in Greenland, a
Page 71 and 72: 13. SAMPLE PREPARATION, ANALYSES AN
Page 73 and 74: limited set of elements; however, s
Page 75 and 76: CONCLUSIONS Avalon’s conclusions
Page 77 and 78: Tb and Dy) were routinely monitored
Page 79 and 80: As part of the QA/QC program, Avalo
Page 81 and 82: Table 14-4: Comparison of Niobium,
Page 83 and 84: shows more deviation, with ALS MS81
Page 85: 16. MINERAL PROCESSING AND METALLUR
Page 89 and 90: 17. MINERAL RESOURCE AND MINERAL RE
Page 91 and 92: 9. TREO equivalent is estimated by
Page 93 and 94: Table 17-4 Sample Information Avalo
Page 95 and 96: Figure 17-1 Distribution of REO Com
Page 97 and 98: Assay Statistics for Upper Zone* *
Page 99 and 100: CUT-OFF GRADE A previous public res
Page 101 and 102: underneath for SG measurement purpo
Page 103 and 104: Figure 17-4 Density Measurements AL
Page 105 and 106: was equal to 60 m by 60 m by 30 m a
Page 107 and 108: Table 17-12 Detailed Resource Break
Page 109 and 110: Table 17-13 Indicated Mineral Resou
Page 111 and 112: Figure 17-7 Outline of Area of Indi
Page 113 and 114: The recoveries estimated for the fl
Page 115 and 116: grades were based upon the grades w
Page 117 and 118: Figure 18-1 Thor Lake Site Layout T
Page 119 and 120: Scott Wilson RPA recommends the use
Page 121 and 122: During discussions with the mine de
Page 123 and 124: Figure 18-4 Mine Layout Some of the
Page 125 and 126: Figure 18-5 Mine Development Schema
Page 127 and 128: Table 18-2 Development Tonnage Brea
Page 129 and 130: Until the crusher is in place and t
Page 131 and 132: Lateral Development The access decl
Page 133 and 134: Equipment will be selected based up
Page 135 and 136: Table 18-6 Estimated Electrical Loa
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VENTILATION The mine ventilation is
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for closing unused areas and for ch
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Mine Fan Horse Power Using the same
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Paste Fill System A paste fill syst
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Communications Mine communications
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completion of the 30 m to 50 m long
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HEALTH AND SAFETY All crew will be
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The crushing plant is designed for
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Table 18-12 (Cont’d) Principal Pr
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Figure 18-9 Hydrometallurgical Plan
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The Pine Point hydrometallurgical f
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Decant pipeworks have been included
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• Development of pre-feasibility
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Design Basis The pre-feasibility le
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non-woven geotextile) to prevent da
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divert surface drainage away from r
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A high pressure (200 psi) compresse
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Fuel deliveries are assumed to be s
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Mill Supplies The key mill supplies
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Table 18-15 Surface Equipment Fleet
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Figure 18-10 Thor Lake Temporary Ba
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• Together with the unloading log
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it will be necessary to upgrade the
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Table 18-16 Hydrometallurgical Plan
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Table 18-17 Surface Mobile Equipmen
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Rare Earth FOB China* FOB China** P
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• loparite and eudialyte in alkal
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Table 18-18 Rare Earth supply - 200
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Table 18-20 Rare Earth Demand by Ap
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Table 18-22 Proposed New REO Projec
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in China. On this basis, Avalon is
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Determine Prices for Avalon’s Pro
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The balance of niobium supply is co
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epresenting about 18% of total zirc
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Table 18-25 Historic Chinese Export
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Figure 18-16 Tantalum Markets - 200
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the price for tantalum chemicals in
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Surface Hydrology The Thor Lake dra
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seven) have occurred more frequentl
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elative to uranium, the overall eff
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interviews conducted for the nearby
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Wildlife Early science-based wildli
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Other environmental permits/approva
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TAXES The NWT diesel tax has been i
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Table 18-31 Mine Capital Cost Estim
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Table 18-33 Surface Infrastructure
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Table 18-36 Indirect Cost Estimate
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Table 18-37 Contingency Allowance A
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Operating Cost Exclusions The opera
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Table 18-40 Underground Mine Cost S
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Table 18-41 Mine Cost Details Avalo
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Thor Lake Surface The Thor Lake sur
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Table 18-45 Sales and Marketing Cos
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Table 18-47 Rail Car Load Limits Av
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there will be no overhauls in the i
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Other supplies and freight will be
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Table 18-55 Hydrometallurgical Plan
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Table 18-56 Cash Flow Summary Techn
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The sensitivity of the base case 8%
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19. INTERPRETATION AND CONCLUSIONS
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• The Mineral Reserves, which hav
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20. RECOMMENDATIONS The authors of
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21. REFERENCES BCC Research (2009):
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MDN Inc (2010): News Release Melvil
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Wardrop Engineering Inc. (2009): Th
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23. CERTIFICATES OF QUALIFIED PERSO
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CERTIFICATE OF QUALIFIED PERSON I,
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CERTIFICATE OF QUALIFIED PERSON I,
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Section 416000 Section 416100 Secti
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Technical Report 43-101 - March 13,
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