Metminco Ltd. has announced the results of further optimization work undertaken by independent consultants RungePincockMinarco (RPM) at Metminco’s 100%-owned Los Calatos copper-molybdenum project 80 km southeast of the city of Arequipa in southern Peru.

The new project model estimates average production of 100,100 mt/y of copper and 5,000 mt/y of molybdenum in concentrate over a 34-year mine life, representing 20% and 35% increases in copper and molybdenum production rates, respectively, when compared to the prior March 2013 scoping study. 

Total metric tons mined have increased by 24% to 811 million mt due to higher conversion ratios of the current mineral resource estimate. Further, due to an increase in open-pit mine life from 7 to 14 years, the planned, subsequent underground development and associated capital costs have been delayed until after the beginning of production from the open pit. This has contributed to a reduction in pre-production capital costs of 12%.

The optimized model calls for an open-pit mining rate of 75,000 mt/d. Open-pit tonnes treated would total 362 million mt grading 0.39% copper and 0.026% molybdenum at a strip ratio of 3.36:1 and a copper equivalent cut-off grade 0.15%. 

Open-pit mining would be followed by an underground block cave operation that would mine 449 million mt at grades of 0.56% copper and 0.035% molybdenum at a copper equivalent cut-off grade 0.35%. A sustained underground production rate of 70,000 mt/d can be achieved at an average drawpoint extraction rate of 120 mt/d. Detailed underground mine design and planning are required to ensure targeted production rates. Exploration drilling and geotechnical and hydrological work are required in support of the deepest mining level (Level 1300). 

Life-of-mine metal production is estimated at 3.4 million mt copper, 169,000 mt molybdenum, 547,000 oz gold, 18.4 million oz silver, and 405 mt rhenium. Cash operating costs are estimated at $1.06/lb of copper after by-product credits. Pre-production capital is estimated $1.32 billion.

A detailed metallurgical testwork program has been planned using nine geo-metallurgical samples that have been selected for the various ore types identified at Los Calatos. This program will include both grinding and flotation testwork and will confirm the relevant test metallurgical parameters for the pre-feasibility study. 

All of the proposed metallurgical tests will be carried out using sea water, as this will be the fluid medium of choice for the extraction process in the main commercial plant.