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Los Azules – Argentina (Exploration)

Los Azules is a 100% owned advanced-stage porphyry copper exploration project located in the Cordilleran region of San Juan Province, Argentina near the border with Chile. Los Azules is one of the world's largest undeveloped high-grade open pit copper projects, which contains significant growth potential.

Preliminary Economic Assessment for Los Azules

In November 2013 McEwen Mining filed an updated Preliminary Economic Assessment (PEA). The PEA included an updated resource estimate, which incorporated important additional mineralization identified through the 2012-2013 exploration drilling southwest of the main deposit. The resource contains 14.3 billion pounds of copper Inferred and 5.4 billion pounds of copper Indicated. Gold resources are 840,000 ounces Indicated and 2,580,000 ounces Inferred. Silver resources are 22.9 million ounces Indicated and 85.8 million ounces Inferred.

Exploration following the 2013 resource estimate represented the first time when a meaningful amount of deeper drilling has occurred at Los Azules, with holes exceeding 700 metres in depth. The deeper drilling has begun to identify a potential parallel trend, west of the original Los Azules orebody. Copper mineralization discovered within this trend occurs near surface and also at depth, down to 1,050 metres below surface. This is significant because it may indicate that the previous drilling, which was shallow and makes up the majority of the Los Azules resource, has not completely determined the potential of the deposit, which remains open at depth. As a result, many new exploration targets have emerged.

Mineral Resource Estimate Greater than 0.35%

Copper Grade
Contained Copper
(B lb)
Gold Grade
Contained Gold
(M oz)
Silver Grade
Contained Silver
(M oz)
Indicated 389 0.63 5.4 0.07 0.8 1.8   22.9
Inferred 1397 0.46 14.3 0.06  2.61.9 85.8 

Details on the parameters of the resource estimate are as follows:

  • The resource estimate is based on data from 185 drill holes comprising a total length of 59,518 metres of drilling completed to the end of March 2013. There were a total of 27,688 individual samples selected for analysis. The samples were collected and analyzed in accordance with industry standards. Splits from the drill core samples were submitted to either Alex Stewart in Mendoza or ALS Chemex or ACME in Santiago, Chile for fire assay and ICP analysis. Accuracy of results is tested through the systematic inclusion of standards, blanks and check assays.
  • The May 2013 mineral resource estimate for the Los Azules Copper Project was prepared under the direction of Robert Sim, P.Geo. of SIM Geological Inc. The mineral resource estimate uses drill hole sample assay results and the interpretation of a geologic model that relates to the spatial distribution of copper in the deposit. Interpolation characteristics were defined based on the geology, drill hole spacing and geostatistical analysis of the data. Block grade estimates were done using Ordinary Kriging with a nominal block size measuring 20 metres long, 20 metres wide and 15 metres high.
  • Resources are classified according to their proximity to sample data locations and are reported, as required under Canadian National Instrument 43-101 "Standards of Disclosure for Mineral Projects" ("NI 43-101"), according to the CIM Definition Standards for Mineral Resources and Mineral Reserves. Mineral resources which are not mineral reserves do not have demonstrated economic viability.
  • The quantity and grade of reported Inferred resources are uncertain in nature and there has been insufficient exploration to classify these Inferred resources as Indicated or Measured, and it is uncertain if further exploration will result in upgrading them to an Indicated or Measured category.
  • As required under NI 43-101, reasonable prospects for economic viability of the mineral resources has been exhibited by the application of a resource limiting pit shell built about copper grades in the model using a projected metal price of US$2.75 per lb Cu, mining costs of US$1.00 per tonne, milling and general and administrative costs of US$4.25 per tonne, 100% recoveries and an average pit slope of 34 degrees.

Los Azules Resource Map

The results of the PEA demonstrate that Los Azules has the potential to become one of the largest, lowest cost copper mines in the world. In addition, there remains excellent exploration potential to further expand the size of the existing mineral resource. Highlights from the PEA are shown below:

PEA Study Highlights*

(Base Case: $3.00/lb Copper and $1,300/oz Gold)

  • Pre-tax Net Present Value (“NPV”) of $3.0 billion (8% discount rate) and an Internal Rate of Return (“IRR”) of 17.6%.
  • After-tax NPV of $1.7 billion (8% discount rate) and an IRR of 14.3%.
  • Annual copper production during years 1 to 5 to average 255,000 tonnes (563 million lb), placing it in the top 3%¹ of copper mines in the world for the year 2012. Life of mine (“LoM”) annual copper production to average 171,000 tonnes (377 million lb) over 35 years.
  • Cash operating costs during years 1 to 5 to average $0.87/lb copper (net of gold by-product), placing it in the bottom 14%¹ in the world for the year 2012. Cash operating costs over entire mine life to average $1.08/lb copper (net of gold by-product).
  • Indicated resource of 5.4 billion pounds of copper and 0.8 million ounces of gold and Inferred resource of 14.3 billion pounds of copper and 2.6 million ounces of gold.
  • Initial capital costs to construct the mine and a 120,000 tonnes per day (“tpd”) process plant have been estimated at $3.9 billion.
  • Capital payback on a pre-tax basis has been estimated at 3.8 years.

¹ Based on internal market data.

The updated PEA contemplates the construction of a mine and process plant operating over a 35 year mine life at a throughput of 120,000 tpd. The mine would produce a copper cathode via a pressure oxidative leach process, in addition to heap leaching the lower grade mineralized material. Compared to the previous PEA released in December 2010, there have been two significant improvements to the project:

  1. Resource Size: Indicated and Inferred resources have increased by 184% and 55% respectively, which were slightly offset with decreases in respective grades of 14% and 12%. Overall, this has led to a 37% increase in mine life and 44% increase in total copper production.
  2. Process Methodology: The current PEA plans to produce copper cathode at site, whereas the 2010 PEA contemplated producing copper concentrate and transporting it via pipeline through Chile. The main advantages of producing copper cathode at site are that it eliminates this previously planned pipeline through Chile, which was a substantial risk for the project, as well as an overall increase in recovered metal, both copper and gold. An additional benefit is the removal of treatment and refining charges from the smelting process.

Pertinent Details of the PEA

Pre-tax NPV ($3.00/lb Cu, 8% discount rate) $3.02 billion
After-tax NPV $1.68 billion
Pre-tax IRR 17.6%
After-tax IRR 14.3%
Initial Capital Expenditure $3.92 billion
LoM Sustaining Capital $1.47 billion
LoM Average Operating Costs $8.65/t ore
First 5 Years Average C-1¹ Cash Costs (net of by-product credits) $0.87/lb Cu
LoM Average C-1 Cash Costs (net of by-product credits) $1.08/lb Cu
Nominal Mill Capacity 120,000 tpd
Average Tonnes of Mineralized Material Processed Annually – Mill 43 million tonnes
Average Tonnes of Mineralized Material Processed Annually - Heap Leach 6 million tonnes
Life of Mine 34.9 years
LoM Strip Ratio 0.76
LoM average annual copper production 171,000t or 377M lb
First 5 years average annual copper production 255,000t or 563M lb

¹ C-1 cash costs include at-mine cash operating costs, treatment and refining charges, mine reclamation and closure costs, and copper cathode and gold doré transportation and freight costs.

In comparing the economics of the 2013 PEA to the 2010 PEA, the pre-tax NPV discounted at 8% has increased from $2.8 billion to $3.0 billion and the IRR has decreased from 21.4% to 17.6%. In addition, the payback of pre-production capital has increased from 3.1 years to 3.8 years from the start of production. The previous PEA did not include economics that were calculated on an after-tax basis.

The Los Azules copper project is currently being advanced to a higher development level. The changes that have taken place in Argentina after 2015 motivated us to advance new studies, which will show improvements in capital and operating costs.

A new drilling program, designed on a combination of infill and exploration drilling, was initiated in 2016. The program continued throughout the first quarter of 2017, during which $6.3 million were spent. In addition, significant advances were made in determining the best logistics, power and infrastructure options and further economic and engineering modeling of the production. A new PEA and results from the drilling campaign are expected to be finalized during the second half of 2017.

Los Azules technical information and figure on this page were derived from

(1) the news release titled “McEwen Mining Announces Updated Preliminary Economic Assessment for the Los Azules Copper Project” released on September 23, 2013. To access the news release click here.  

(2) the news release titled “McEwen Mining Announces Q1 2017 Operating & Financial Results” released on May 4, 2017. To access the news release click here.  And

(3) the technical report titled “Canadian National Instrument 43-101 Technical Report, McEwen Mining Inc., Los Azules Porphyry Copper Project, San Juan Province, Argentina", with an effective date of August 1, 2013, prepared by Richard Kunter, FAusIMM, CP, QP, Robert Sim, PGeo, Bruce M. Davis, PhD, FAusIMM, James K. Duff, PGeo, William L. Rose, PE, Scott C. Elfen, PE, and Steven A. Pozder, PE, MBA, all of whom are qualified persons and all of whom but  James K. Duff  are considered independent of McEwen Mining, as defined by NI 43-101. To access the report click here.

Cautionary Notes

McEwen Mining reports its resource estimates in accordance with standards of the NI 43-101. These standards are different from the standards generally permitted in reports filed with the SEC. Under NI 43-101, McEwen Mining reports Measured, Indicated and Inferred resources, measurements which are generally not permitted in filings made with the SEC. According to Canadian NI 43-101 criteria, the estimation of measured resources and indicated resources involve greater uncertainty as to their economic feasibility than the estimation of proven and probable reserves. Under SEC Industry Guide 7 criteria, Measured, Indicated and Inferred resources are considered Mineralized Material. The SEC considers that in addition to greater uncertainty as to the economic feasibility of Mineralized Material compared to proven and probable reserves, there is also greater uncertainty as to the existence of Mineralized Material. U.S. investors are cautioned not to assume that Measured or Indicated resources will be converted into economically mineable reserves. The estimation of Inferred resources involves far greater uncertainty as to their existence and economic viability than the estimation of other categories of resources. 

Mineral resources which are not mineral reserves do not have demonstrated economic viability.

This website contains certain forward-looking statements and information and investors are encouraged to review our "Cautionary Note Regarding Forward Looking Statement". 


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