VANCOUVER – With 10 drill holes McEwen Mining has boosted the copper resource at its Los Azules project in Argentina by 20% compared to the last estimate just eight months ago, and the huge deposit remains open in every direction.
A new resource estimate reduced the deposit’s indicated count slightly compared to June estimate, leaving indicated resources at 310 million tonnes grading 0.65% Cu. Inferred resources, however, jumped 29% to reach 1.3 billion tonnes grading 0.49% Cu. Together the indicated and inferred resource tonnes contain 18.4 billion lb of copper.
Los Azules is a porphyry system in western San Juan province, which is home to a belt of porphyry copper deposits that straddle the Chilean-Argentinean border. Some of the copper deposits in this belt rank among the largest in the world, including Codelco’s El Teniente and Andina mines, Anglo American‘s Los Bronces mine, Antofagasta’s Los Pelambres mine, and Xstrata‘s El Pachon project.
Los Azules was already one of the world’s largest undeveloped open pit copper projects before the latest resource boost, but until last year, drills had not tested for mineralization below 650 metres depth. In 2012 McEwen changed that by drilling six deep holes.
The results suggest that there remains much mineralization yet to discover at the project. The deep drill holes started to identify a parallel trend to the west of the known Los Azules orebody, wherein mineralization occurs near surface and at depth. For example, hole 1291 intersected 160 metres of 0.61% Cu from 72 metres depth and then hit into 329 metres of 0.49% Cu from 562 metres down hole.
The depth part is interesting, as most of the 173 holes drilled at Los Azules to date have been shallow and therefore did not test the deposit’s deeper potential. The company will start to test that potential this year, with a 15,000-metre drill program underway. McEwen says the deep holes completed in 2012 illuminated “many new exploration targets.”
McEwen also plans to complete a new preliminary economic assessment (PEA), which is expected in the third quarter of the year. The new study will consider a larger operation than was modeled in the original PEA, incorporate the new resource tonnes, and assess the potential to process low grade material that was not considered in a heap leach scenario.
McEwen will also continue with metallurgical studies on producing a copper cathode at Los Azules instead of a concentrate. Cathode production offers two advantages: it eliminates the need for a concentrate pipeline through Chile and avoids Argentina’s concentrate export tax.
The company is now free to forge ahead apace at Los Azules, after settling a lingering lawsuit in November. The dispute dated back to 2009 and involved an option agreement between Xstrata and Minera Andes, the company that merged with U.S. Gold to form McEwen Mining in early 2012. By the time it reached court late last year Xstrata’s interest had also changed hands and the dispute was between McEwen and TNR Gold.
In the settlement McEwen gained clear title to the claim in question; the piece of land is not home to any known mineralization but would be needed if McEwen were to advance Los Azules to development. TNR retained its right to back-in for 25% ownership of certain claims in the northern half of the property, which are home to roughly 62% of the current Los Azules resource. TNR can exercise that right after McEwen delivers a positive feasibility study and to earn its stake the junior would have to pay two times the expenditures attributable to the back-in percentage, or 50% of the expenses on the claims to that point. TNR also received 1 million shares of McEwen.
McEwen’s share price was little changed on news of the expanded Los Azules resource estimate, gaining 2¢ to close at $3.08. The company has a 52-week share price range of $2.02 to $5.83 and has 213 million shares outstanding.
To read more Northern Miner articles, click here