(MENAFN- ProactiveInvestors)Copper North (CVE:COL) continues to restructure its finances and optimize its flagship Carmacks copper gold and silver project. The Company plans to revise enhance a preliminary economic assessment (PEA) from July 2014 with the new leach plan which will have a positive impact on project economics. According to the July PEA the project is expected to produce some 30 million pounds of LME Grade A copper cathode per year as well as 17300 ounces of gold and 165000 ounces of silver. In a statement the company said that the project economics based on the July 2014 PEA 'are now quite out of date and do not properly represent the leach plan and associated project economics'. Indeed Copper North has reduced capex focusing on a metallurgical test work program that began last September demonstrating that the oxide resource at Carmacks had favourable leach dynamics. In January the company noted that the optimal leaching process for the recovery of copper gold and silver is an agitated leach tank as it does away with the $50 million double liner heap leach pad. "The metallurgical test results have been very instructive; a finer crush on leach materials coupled with increased temperatures in the leach circuit results in much improved leach kinetics. Leach times are very fast. The test work has yielded much improved leach efficiency and reduction of operational and environmental risks" said Copper North's president and CEO Dr. Harlan Meade. Copper North's new processing plan consists of crushing to minus 19mm followed by rod mill grinding to minus 1mm then acid leaching copper in an agitated leach tank followed by gold and silver leaching in similar tanks and cyanide destruction for final waste materials. Cathode copper sheets will be produced by processing the copper leachate in a standard solvent extraction electro-winning (SXEW) plant while gold and silver will be recovered using Merrill Crowe to produce doré bars. The tests have shown that a hotter acid leach – achieved efficiently by transferring waste heat from the manufacturing of sulphuric acid to the leach tanks - for copper improves the overall recovery and significantly shortens the leach time. With a grind size of minus 1mm and a leach temperature of 40 degrees Celsius recoveries of 88% were achieved within 4 to 6 hours less than half the time for a coarser grind of 2mm at ambient temperature. Acid is removed from the residue in the copper circuit while the slurry is pumped into the gold-silver agitated leach tank for cyanidation which after an optimal period of about 12 hours allows for recoveries of approximately 80% gold and 62% for silver. The leachate from the cyanide tanks is sent to a Merrill Crowe circuit to recover gold and silver as a doré bar for refining. A SART circuit is used to remove copper cyanates producing a small amount of copper-rich sulphide that will add to the total copper recovery. Batch test work including locked cycle tests have so far confirmed the promising leach dynamics while defining recoveries reagent consumption and optimal equipment requirements. The final steps in the test work are to determine the procedure to filtrate the waste materials in preparation for waste disposal utilizing the "dry-stacked tailings" method. By resorting to an agitated tank leach Copper North avoids the expensive large lined leach pads that formed the basis of the October 2012 Feasibility Study and the July 2014 Preliminary Economic Assessment. Having completed the agitated tank leach facility metallurgical test work the company can now proceed with the engineering design and cost estimation of the processing facility. The improvements based on the new metallurgical test results should lead to a reduction of equipment size in the leach circuit as compared to the previous studies. Along with the savings achieved by switching to the agitated tank leach Copper North will cut costs further by sourcing engineering and equipment procurement in China. The Beijing General Research Institute of Mining and Metallurgy (BGRIMM) will perform detailed design and costing of the leach tank circuits acid plant SXEW and Merrill Crowe facilities using the recent data as part of the new PEA. In a statement Copper North said it now expects initial capital costs of US$150M for the project which is about 30% less than the July 2014 PEA. The Carmacks project is located in the Yukon and mineral resources contained in the proposed mining area are 11.98 million tonnes of measured and indicated resources grading 1.07% copper 0.456 grams per tonne (g/t) gold and 4.58 g/t silver. In 2015 the company has launched a drilling program to expand the mineral resources in pursuit of extending the potential mine life. Demand for copper which is used as a conductor of heat and electricity as well as a building material and as a constituent of various metal alloys remains strong.
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