technical report on the nechalacho deposit, thor lake project ...
technical report on the nechalacho deposit, thor lake project ...
technical report on the nechalacho deposit, thor lake project ...
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• The stope schedule was developed <strong>on</strong> <strong>the</strong> basis of mining <strong>the</strong> highest grade stopes first.<br />
Fur<strong>the</strong>r refinement of <strong>the</strong> stope schedule may lead to small increases in feed grades in<br />
<strong>the</strong> early years.<br />
• Mining of <strong>the</strong> sec<strong>on</strong>dary stopes is dependent up<strong>on</strong> <strong>the</strong> use of a suitable backfill,<br />
assumed to be paste fill with 4% cement added as a binder. Testwork to dem<strong>on</strong>strate<br />
that a suitable paste fill can be generated from <strong>the</strong> tailings has yet to be completed.<br />
Processing – C<strong>on</strong>centrator<br />
• Mineral processing testwork indicates that <strong>the</strong> TREO, ZrO 2 , Nb 2 O 5 and Ta 2 O 5 can be<br />
recovered in a flotati<strong>on</strong> circuit after crushing and grinding to 80% minus 38 µ with<br />
recoveries of 80% of <strong>the</strong> TREO, 90% of <strong>the</strong> zirc<strong>on</strong>ium oxide, 69% of <strong>the</strong> niobium oxide<br />
and 63% of <strong>the</strong> tantalum oxide to a flotati<strong>on</strong> c<strong>on</strong>centrate. The processing circuit also<br />
includes magnetic and gravity separati<strong>on</strong> stages. The design basis for <strong>the</strong> PFS was to<br />
take 18% of <strong>the</strong> feed to <strong>the</strong> c<strong>on</strong>centrate.<br />
• The c<strong>on</strong>centrate will be stored in covered c<strong>on</strong>tainers at Thor Lake and shipped to <strong>the</strong><br />
hydrometallurgical facility at Pine Point each summer using barges to cross Great Slave<br />
Lake.<br />
• Tailings from <strong>the</strong> flotati<strong>on</strong> plant will be stored in a Tailings Management Facility (TMF)<br />
located north-east of <strong>the</strong> mill site.<br />
Processing – Hydrometallurgical Plant<br />
• Metallurgical process testwork for <strong>the</strong> extracti<strong>on</strong> of <strong>the</strong> TREO, zirc<strong>on</strong>ium oxide, niobium<br />
oxide and tantalum oxide from <strong>the</strong> flotati<strong>on</strong> c<strong>on</strong>centrate was carried out and <strong>the</strong><br />
recoveries of 96% of <strong>the</strong> TREO, 93% of <strong>the</strong> zirc<strong>on</strong>ium oxide, 82% of <strong>the</strong> niobium oxide<br />
and 60% of <strong>the</strong> tantalum oxide were dem<strong>on</strong>strated in <strong>the</strong> laboratory.<br />
• The hydrometallurgical plant will c<strong>on</strong>sist of a c<strong>on</strong>centrate “cracking” process, using a<br />
combinati<strong>on</strong> of acid baking, caustic cracking, and leaching using sulphuric acid and<br />
sodium hydroxide as <strong>the</strong> primary reagents.<br />
• The hydrometallurgical process plant will c<strong>on</strong>sume a significant quantity of reagents,<br />
which are brought to site by rail to Hay River and <strong>the</strong>n by truck to <strong>the</strong> plant. A standal<strong>on</strong>e<br />
sulphuric acid plant is included to provide acid for <strong>the</strong> process.<br />
• The products from <strong>the</strong> hydrometallurgical plant will be a mixed rare earth oxides<br />
c<strong>on</strong>centrate, and separate zirc<strong>on</strong>ium oxide, niobium oxide and tantalum oxide<br />
c<strong>on</strong>centrates.<br />
Technical Report 43-101 – March 13, 2011 Page 1-5<br />
Prepared by Aval<strong>on</strong> Rare Metals Inc.