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Marimaca Copper Corp
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Close 2021-10-13 C$ 4.34
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Marimaca Copper drills 488 m of 0.48% CuT at Marimaca

2021-10-13 09:22 ET - News Release

Mr. Hayden Locke reports


Marimaca Copper Corp. has released results from the extensional drilling campaign at the Marimaca oxide deposit (MOD) and initial drilling results from the Roble target, located less than three kilometres northeast of the MOD.

The reverse circulation (RC) drilling campaign below the MOD open-pit limits has intersected significant zones of mixed, enriched and some primary sulphide mineralization, indicating the potential for the expansion of the MOD's future leachable mineral resource estimate (MRE) and complementing the previous drilling, which also encountered significant extensions of mineralization at depth (refer to news release of May 5, 2021). A total of 3,120 metres in 12 re-entry holes were drilled as extensions from the bottom of historic MOD drill holes and tested the continuation of mineralization below the existing resource pit shell. Preliminary results suggest the potential to add high-grade resources to the MOD MRE.

At the Roble target, a discovery campaign of 2,570 m over 12 shallow RC holes was completed with broad zones of oxide mineralization encountered from surface, providing additional potential to grow the company's oxide resource base.


  • Significant extensions at depth of known copper mineralization at the MOD, complementing previously reported deeper drilling, have potentially positive implications for future scale and mine life of the operation;
  • MAR-17 extended: 488 m at 0.48 per cent total copper (CuT) from four m, including:
    • New intersection of 284 m at 0.63 per cent CuT from 208 m, including 126 m at 1.13 per cent CuT;
  • MAR-70 extended: 416 m at 0.56 per cent CuT from 14 m, including:
    • New intersection of 206 m at 0.73 per cent CuT from 224 m;
  • LAR-06 extended: 332 m at 0.66 per cent CuT from 48 m, including:
    • New intersection of 52 m at 0.78 per cent CuT from 328 m;
  • MAR-82 extended: 306 m at 0.56 per cent CuT from four m, including:
    • New intersection of 106 m at 0.76 per cent CuT from 204 m;
  • MAR-06 extended: 274 m at 0.51 per cent CuT from 14 m, including:
    • New intersection of 80 m at 0.78 per cent CuT from 208 m;
  • MAR-55 extended: 252 m at 0.40 per cent CuT from 114 m, including:
    • New intersection of 64 m at 0.59 per cent CuT from 302 m;
  • MAR-78 extended: 234 m at 1.15 per cent CuT from 108 m, including:
    • New intersection of 90 m at 0.31 per cent CuT from 252 m;
  • MAR-44 extended: 268 m at 0.66 per cent CuT from 68 m, including:
    • New intersection of 96 m at 0.84 per cent CuT from 200 m;
  • MAR-80 extended: 228 m at 0.69 per cent CuT from 100 m, including:
    • New intersection of 60 m at 1.07 per cent CuT from 268 m;
  • Average leaching potentials for all new intersections range from 90.8 per cent to 27.2 per cent with an average of 58.7 per cent;
  • The company has identified several alternatives to optimize recoveries for materials with lower leaching potentials and will examine these in more detail in the coming months;
  • Full details of extensional holes and leaching potentials in an attached table;
  • At Roble, discovery drilling intersected shallow oxide mineralization extending 600 m along and 400 m across strike:
    • ROR-03 intersected 62 m of 0.34 per cent CuT from six m, including 48 m at 0.41 per cent CuT;
    • ROR-01 intersected 10 m at 0.58 per cent CuT from 36 m within a broader intersection of 138 m at 0.12 per cent CuT;
    • ROR-04 intersected 44 m at 0.27 per cent CuT from 10 m, including 18 m at 0.41 per cent CuT from 10 m.
  • Weak or thinner mineralization was intersected at Roble in ROR-02, as well as at the Nepal and Pele targets, located immediately south of Roble.

Sergio Rivera, vice-president, exploration, of Marimaca Copper, commented: "The depth extensions below the MOD continue to highlight the mineralizing system is potentially significantly larger than currently defined and we remain excited about the grades and widths of mineralization over an area extending approximately 400 m by 350 m with extensions up to nearly 300 m downhole.

"Robles also provides another target for follow-up work, complementing the recent discoveries at Cindy and Mercedes, where we continue to target delineating shallow oxide resources to form part of the future mine plans in the MOD development. Two thousand twenty-one has been an exceptional year on the exploration front, with all three conceptual exploration targets drilled yielding shallow oxide materials as well as a significant, higher-grade extension at depth below the MOD."

Hayden Locke, president and chief executive officer of Marimaca Copper, commented: "These drill intersections, when combined with the historical intersections, give a true sense of the potential scale of Marimaca. Given the very strong grades in many extensional intersections and their average leaching potentials, we believe this material could form part of an expanded leachable resource for the MOD. There are several processing combinations to recover the non-leachable portions of this material, and we will examine the technical and economic viability of each to decide the optimum path to copper recovery.

"We have also had exploration success in our surrounding package, with the first three satellite targets -- Cindy, Mercedes and Robles -- tested and all showing promise for additional, near-surface, leachable resources.

"We believe the depth extensions at the MOD and the success at our satellite targets have the potential to add material additional tonnes to the mine life at Marimaca. We are currently reviewing the results with our metallurgical team before planning further drilling campaigns in addition to the infill drilling to move the inferred resources to higher-confidence categories."

Overview of drilling campaign objectives and results -- MOD depth extension program

The company completed a 12-hole re-entry program of historic drill holes in the southern portion of the MOD. The depth extension holes were drilled as continuations of historic drill holes at the MOD and were designed to test the continuation of mineralization at depth as follow-up to results from the initial five-hole extension drilling campaign completed in April, 2021 (refer to announcement on May 5, 2021), including 106 metres at 0.39 per cent CuT from 500 m in MAR-127 Ext and 78 m at 0.50 per cent CuT from 310 m in MAR-35 Ext. Holes MAR-17 Ext, MAR-06 Ext, MAR-82 Ext, MAR-55 Ext, MAR-81 Ext, MAR-70 Ext, MAR-44 Ext, MAR-80 Ext, MAR-78 Ext and LAR-06 Ext intersected continuous zones of mixed, enriched and some primary sulphide copper mineralization below the base of the MOD. Sequential copper analysis of all samples is complete, with leaching potentials mainly exceeding 50 per cent (refer to an attached table for further information).

The MOD depth extension drill holes were re-entries of historical holes and commenced at depths ranging from 200 m to 300 m downhole to new final depths of 450 m to 500 m. Drilling intersected the downdip extension of known mineralization into new zones of mixed, enriched and sulphide mineralization. Controlling structures intersected across the northeast- and northwest-orientated drill holes were generally consistent with the known structural controls at the MOD.

The majority of these mineralized zones were not captured in the historical MRE (refer to news release on Dec. 2, 2019) used to develop the mine plan for the preliminary economic assessment, which was released in June, 2020. MAR-17 Ext, MAR-82 Ext and MAR-06 Ext were drilled in a northwest orientation while MAR-81 Ext, MAR-55 Ext, MAR-44 Ext, MAR-80 Ext, MAR-78 Ext, LAR-06 Ext and MAR-70 Ext were drilled in a northeast orientation.

Overview of drilling campaign objectives and results -- Roble program

Roble is located less than three kilometres to the northeast of the MOD, within the northeast-trending Roble fault system. This is a splay off the regional-scale Naguayan fault system, which is an important control for mineralization at the MOD. Previous geophysical, geochemical and reconnaissance work successfully identified and delineated three discrete areas of consistently subcropping copper mineralization, each extending over approximately 600 metres by 400 metres, separated by gravel and sand cover -- Roble, Nepal and Pele (refer to June 29, 2021, news release).

The 12-hole discovery RC drill program tested initial targets identified in the 2020 and 2021 generative exploration campaign. Results have demonstrated clear potential for the delineation of additional near-surface oxide resources, with shallow, low-grade to moderate-grade mineralization intercepted at the Roble and Nepal targets. The 12 holes were drilled predominantly in a northwest orientation with intercepted mineralization largely controlled by the northeast-trending Roble fault and associated splays.

Overview of leaching potential

The leaching potential of copper ores is defined as acid-soluble copper (CuS) plus cyanurable copper (CuCN) divided by total copper (CuT). The solubility ratio (CuS/CuT) for copper oxides such as atacamite, brochantite and chrysocolla, which dissolve quickly when exposed to acid, is a good predictor of leachability. However, where the mineralization has several copper-bearing minerals with different dissolution characteristics under these leaching conditions, the copper acid solubility ratio may materially underestimate the acid leaching potential for heap leach operations, especially where some copper sulphides such as chalcocite, covellite and bornite are present, as these sulphides can be partially dissolved under oxidation conditions. For this reason, it is common to assay for cyanide-soluble copper when assaying leachable copper mineralization. This gives an indication of the total leaching potential ((CuS plus CuCN) divided by CuT) because cyanide dissolves some of the copper sulphides that may be present in the sample and assumes that, during the leaching operation, some oxidation reactions, such as ferric leaching and/or cupric chloride leaching, occur. Due to these reactions during sulphide leaching, it can be inferred that copper dissolution in a leaching operation may materially exceed the copper acid solubility ratio identified.

Marimaca has conducted five phases of metallurgical testing and has noted that, in several mineral subzones, especially those with higher proportions of black oxides, the metallurgical recovery has exceeded the leaching potentials identified in sequential copper analysis.

Sampling and assay protocol

True widths cannot be determined with the information available at this time. RC holes were sampled on a two-metre continuous basis, with dry samples riffle split on site and one-quarter sent to the Andes Analytical Assay preparation laboratory in Calama and the pulps then sent to the same company's laboratory in Santiago for assaying. A second quarter was stored on site for reference. Samples were prepared using the following standard protocol: drying; crushing to better than 85 per cent passing minus-10 mesh; homogenizing; splitting; pulverizing a 500-gram to 700-gram subsample to 95 per cent passing minus-150 mesh; and a 125-gram split of this sent for assaying. All samples were assayed for per cent CuT (total copper) and per cent CuS (acid-soluble copper) by AAS. A full quality assurance/quality control program, involving insertion of appropriate blanks, standards and duplicates was employed with acceptable results. Pulps and sample rejects are stored by Marimaca Copper for future reference.

Qualified person

The technical information in this news release, including the information that relates to geology, drilling and mineralization, was prepared under the supervision of or has been reviewed by Sergio Rivera, vice-president of exploration, Marimaca Copper, a geologist with more than 36 years of experience and a member of the Colegio de Geologos de Chile and of the Institute of Mining Engineers of Chile, and who is the qualified person for the purposes of National Instrument 43-101 responsible for the design and execution of the drilling program.

The qualified person confirms he has visited the project area, has reviewed relevant project information, is responsible for the information contained in this news release and consents to its publication.

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