McEwen Copper: Los Azules Progress Report #4

Long intercepts with good grades

222.0 m of 0.95% Cu including 44.0 m of 1.38% Cu (AZ22158)
238.0 m of 0.58% Cu including 10.0 m of 1.10% Cu (AZ22161)
194.0 m of 0.56% Cu including 8.0 m of 1.04% Cu (AZ22163)

TORONTO, Aug. 04, 2022 (GLOBE NEWSWIRE) -- McEwen Copper Inc., a subsidiary of McEwen Mining Inc. (NYSE: MUX) (TSX: MUX), is pleased to report the latest assay results from its Los Azules project, which continues to deliver long intercepts of good grades.

The drill program underway has three important objectives:

• Improve confidence in the resource by converting Inferred mineral resources to the Indicated category;
• Accelerate project advancement with metallurgical, hydrological and geotechnical drilling and
• Test the limits of the depth extension of the higher-grade mineralization.
  

Results from this drilling program will be used to update the 2017 Los Azules PEA (Preliminary Economic Assessment). The updated version will be released in Q1, 2023.

The 2017 PEA was calculated using prices of $3/lb copper, $1,300/oz gold and $17/oz silver price. It projected robust economics, driven by large operating margins, large annual production, a short payback period and long mine life (link to the report: http://www.mcewenmining.com/files/technical_reports/los_azules/LosAzulesPEA_Rev0_20171016.pdf). Drilling has halted for the winter and will resume in October when spring arrives in Argentina.

Earlier this year, Mining Intelligence ranked Los Azules as one of the world’s top five largest undeveloped porphyry copper deposits that is not already owned by a major mining company.

The opportunity to expand the deposit at depth remains open for further testing. While the median depth of drill holes within the Los Azules resource database is 175 meters (m), it is not uncommon for porphyry copper mineralization to extend well beyond a kilometer or more of depth. Numerous drill holes have encountered strong copper grades below the 2017 PEA pit bottom. Only three holes have been drilled to a depth of a kilometer and all encountered mineralization.

The highest-grade mineral domains at Los Azules are clearly the hydrothermal and magmatic breccias and late-stage quartz veins which can extend kilometres to depth. There are numerous examples of such deposits in Argentina and Chile. The most recent is Filo Mining’s spectacular assay results of earlier this year. The Filo deposit is 300 kilometres north of Los Azules, also in the San Juan province, Argentina.

The deepest occurrence of a breccia at Los Azules is at a hole depth of some 810 m in drill hole AZ1299 and deepest occurrence of late-stage quartz veins is found at 990 m down the same hole.

A dedicated exploration program associated with higher grade domains at Los Azules has not yet been conducted. Most holes drilled to date are vertical and intersect the breccias at very low angles. Improving our understanding of the nature and distribution of the highest-grade mineral zones at Los Azules is a priority for the upcoming drilling seasons.

The most recent drill results are presented below in the cross-section Figures 1 to 4. These display the current inclined and historic vertical holes, with histograms of total copper content along their length, overlayed on a simplified interpretation of overburden, leached, enriched and primary mineral zones, and the 30-year pit shell (shown by green line), as defined by the 2017 PEA.

Section 30-30', shown in Figure 1, includes hole AZ22158, with an attractive intercept of 222.0 m grading 0.95% Cu, and including an interval of 44.0 m grading 1.38% Cu. Partial results were reported in the Los Azules Progress Report #3 published on June 23, 2022. Hole AZ22166 was stopped at the arrival of winter and will be completed in spring.

Figure 1 – Cross-section 30-30’

A photo accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/9d669f48-1246-4926-81e9-f52b8c14ba75

Section 36-36’, shown in Figure 2, received eight new drill holes during the recent campaign. The final intercept reported was hole AZ22162, which targeted the gap between hole AZ22138 (522.1 m grading 0.42% Cu) and AZ22139.

Hole AZ22162 returned 348.0 m grading 0.28% Cu, while also ending in enriched mineralization. It appears to correlate well with historic hole AZ0838 (188.3 m grading 0.27% Cu).

Figure 2 – Cross-section 36-36’

A photo accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/959dc2c8-4d5c-4a71-9f81-229dab4c8e82

Cross Section 44-44' shown in Figure 3 presents hole AZ22163 (194.0 m grading 0.56% Cu). AZ22163 includes 8.0 m of high-grade 1.04% Cu and supports 146.0 m of high-grade 1.10% Cu reported in historic hole AZ0620. Hole AZ22167 (80.4 m grading 0.21% Cu) results are as expected and similar to the historic hole LA0402.

Figure 3 - Cross-section 44-44’

A photo accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/cf4ca450-eab9-43fa-ba4a-2f010c0c31cd

Cross-section 48-48'shown inFigure 4, profiles three new holes. Hole AZ22149 (296.4 m grading 0.55% Cu including 54 m of 1.38% Cu), drilled just west of the center of the section, was released in our June 23 exploration update. Hole AZ22161, drilled east of the center of the section, with 238.0 m grading 0.58% Cu and including 10 m of 1.10% Cu, supports historic intercepts in adjacent holes AZ1060A (221.0 m grading 0.53% Cu) and AZ18136 (194.0 m grading 0.43%Cu), all below the 30-year pit shell, indicating significant potential for mineralization at depth.

Holes AZ22147 and AZ22165 were drilled off the west and east flanks to delimit margins of the deposit and did not encounter significant mineralization.

Figure 4 - Cross-section 48-48’

A photo accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/8d64800f-fa2f-479b-9f4d-93e6763b3281

Figure 5 - Locations of the cross-sections on the plan of the deposit

A photo accompanying this announcement is available at https://www.globenewswire.com/NewsRoom/AttachmentNg/9848f4e5-c2ee-4ac1-85f9-ba7e786577e3

The Los Azules deposit is sequentially sub-divided into 50 m cross sections beginning at the southeast end of the deposit and progressing to the northwest. Section 36-36’ is approximately the mid-section of the deposit. As a matter of cross-referencing results presented in the Los Azules Progress Report #3 published on June 23, 2022, note that Section 36-36’ was previously identified as Section A-A’ and Section 48-48’ as Section C-C’. Section 40-40’ identifies with Section B-B’ and was not included in this release as no new results have been added there.

Drilling resumes in October, and the plan is to complete 45,500 m.

Link to Drilling Results and Hole Collar Locations and Lengths for January to May 2022 at Los Azules: https://www.mcewenmining.com/files/doc_news/archive/2022/202208_LosAzules/2022_08_Los_Azules_Update_4.xlsx (alternatively see Tables 1 and 2 at the end of this press release).

Technical Information

The technical content of this news release has been reviewed and approved by Stephen McGibbon, P.Geo, SVP Exploration of McEwen Mining and a Qualified Person as defined by NI 43-101.

All samples were collected in accordance with generally accepted industry standards. Drill core samples usually taken at 2 m intervals are split and submitted to Alex Stewart International laboratory in Mendoza, Argentina for the following assays: gold determination using fire assay fusion and an atomic absorption spectroscopy finish (Au4-30); a 39 multi-element suite using ICP-OES analysis (ICP-AR 39); copper content determination using a sequential copper analysis (Cu-Sequential). An additional 19-element analysis (ICP-ORE) was performed for samples with high sulfide content.

The Company carries out a Quality Assurance / Quality Control program consistent with NI 43-101 and industry best practices utilising a combination of standards and blanks approximately one in every 25 samples. Results are monitored as the final certificates are received and any re-assay requests are sent back immediately. Pulp and prep duplicate sample analyses are also taken as part of the QAQC process. Approximately 5% of sample pulps are sent to a secondary laboratory for check assays. In addition, the assay lab performs its own internal QAQC checks with results available in the certificates for review by the Company.

Table 1 – Drill Results January-May 2022 at Los Azules

Table 2 - Hole Collar Locations and Lengths for January-May 2022 Drill Results at Los Azules