This technical report provides an update on Aurizona processing operations, historical metallurgical testwork, and proposed plant modifications following suspension of mining activities.
Report context
The effective date of this report is March 27, 2015. The report presents an update on Aurizona mining operations, including updated Mineral Resources and withdrawal of all Mineral Reserves. Mining activities were suspended in February 2015, and the plant is processing a mineralized stockpile through approximately July 2015, after which the mine will be temporarily placed in care and maintenance pending additional exploration and a prefeasibility study incorporating a hardrock crush and grind circuit.
Processing route
Current plant configuration
The processing plant utilizes conventional processing technologies for the production of gold doré bars, which are shipped to offsite gold refineries. The processing plant is comprised of the following circuits for the processing of oxide ore: ore receiving; grinding; pre-leach thickener; carbon in leach gold recovery; gold elution; carbon acid washing; gold electro winning; induction fusion furnace; tailings thickening; and neutralization of the tailings pulp. Prior to the pre-leaching thickener, a portion of the coarser material gets classified by two Knelson concentrators for gravity gold recovery. The material is then smelted and shipped together with the rest of the product.
The current process plant has been operational since June 2010 with processing through the gravity concentration and CIL circuits. In 2012 process plant recovery enhancement initiatives were directed at improvements in CIL pulp carbon concentration, carbon inventory level and pre-leach circuit pulp feed density optimization.
Phase 1 expansion
A Phase 1 plant expansion focused on increasing the throughput of mineralized saprolite to a nominal rate of 10,000 tpd was undertaken in 2013 and 2014 and partially completed, including much of the procurement program. However, the previous geological model did not properly characterize the existence of a harder saprolite unit that could not be processed efficiently in the current processing plant. As a result, the nominal throughput production targets could not be met and rendered the existing plant as well as the Phase 1 expansion uneconomical to run. In retrospect, the installation of a more powerful crushing and grinding circuit rather than an expansion to the leaching and thickening would have been more appropriate given the upcoming hardrock phase of operations.
Historical metallurgical testwork
A series of historical metallurgical test programs were carried out on the saprolite, laterite and unweathered ("Fresh") mineralized material from Aurizona between 1994 and 2008. The results of these test programs were the basis for the feasibility study prepared for Aurizona's Piaba project. Additional metallurgical studies, including cyanidation testwork, comminution studies and solid/liquid separation studies have since been conducted and reported by Metcon Research.
Proposed hardrock circuit
The report recommends completing prefeasibility and/or feasibility studies for a crush and grind circuit so that hardrock can be processed and the resources and reserves updated to show the updated exploration program, as well as the upgraded process capacity. This will allow a mine plan to be developed based on a variety of blends consisting of both soft saprolite and hardrock.
Plant improvements
The Phase 1 expansion was partially completed along with a significant portion of the procurement process. Much equipment is on site awaiting installation. The report recommends completing the installation of the waste treatment plant, carbon kiln, pressure elution column and the high intensity leach circuit in order to improve processing capacity and efficiencies for the restart.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant throughput design (Phase 1 expansion) | 10,000 tpd | Proposed design for saprolite |
| 2014 total ore processed | 2,155,555 tonnes | Actual operating data |
| 2014 average process grade | 1.31 g/t Au | Actual operating data |
| 2014 average plant productivity | 281 t/hr | Actual operating data |
| 2014 average plant availability | 91% | Actual operating data |
| 2014 average metallurgical recovery | 88.1% | Actual operating data |
| 2014 gold production | 74,622 ounces | Actual operating data |
| Cumulative production through December 31, 2014 | 285,817 ounces | Actual operating data |
| Historical testwork period | 1994–2008 | Testwork on saprolite, laterite, fresh material |
| Additional metallurgical studies | Cyanidation, comminution, solid/liquid separation | Testwork by Metcon Research |
| Estimated tailings dam raise capacity | 2 additional years at current production | Proposed design |
Project website: https://en.cmoc.com/html/2025/News_1215/82.html
Technical qualifications
The report was prepared as a National Instrument NI 43-101 Technical Report. The qualified persons responsible for specific sections include Marc Leduc, P. Eng. (Sections 1, 7-12, 14-16, 20-28 and reviewer of all sections), Richard Pearce, P.E. (Sections 2–6, 18 and 19), and Deepak Malhotra, Ph.D. (Sections 13 and 17).
The report contains forward-looking information with respect to expected costs, capital expenditures, mine life, mineral resource estimates, expected grades, planned exploration activities, operating parameters, and plans to advance the project. Forward-looking statements are based on assumptions that may prove to be incorrect, and actual results may differ materially.
Mineral Resources are classified in accordance with the Canadian Institute of Mining, Metallurgy and Petroleum Standards on Mineral Resources and Reserves: Definitions and Guidelines. The report withdraws all Mineral Reserve estimates. An Inferred Mineral Resource has a great amount of uncertainty as to its existence and as to its economic and legal feasibility. It cannot be assumed that all or any part of an Inferred Mineral Resource will ever be upgraded to a higher category. Under Canadian rules, estimates of Inferred Mineral Resources may not form the basis of feasibility or pre-feasibility studies.
The report contains certain non-GAAP measures such as expected cash costs, which have non-standardized meaning under International Financial Reporting Standards and may not be comparable to similar measures used by other issuers.
Source: NI 43-101 Technical Report – Aurizona Mine Update, Brazil, March 27, 2015. Relevant sections include 1.11 Mineral Processing and Metallurgical Testing, 1.12 Process Plant, 1.14 Capital and Operating Cost Estimates, 1.15 Conclusions, and 1.16 Recommendations.
