Adventus and Salazar Provide Positive Update of Metallurgical Results for El Domo Deposit, Curipamba Project

NOTE – THIS RELEASE REPLACES A PREVIOUSLY FILED VERSION WHICH INCORRECTLY ORDERED GEOMETALLURGICAL ZONE PERCENTAGES IN THE FIRST PARAGRAPH. THE CORRECTED RELEASE IS AS FOLLOWS.   

TORONTO, Feb. 20, 2020 /PRNewswire/ - Adventus Mining Corporation ("Adventus") (TSX-V: ADZN; OTCQX: ADVZF) and Salazar Resources Limited ("Salazar") (TSX-V: SRL) (collectively the "Partners") are pleased to provide a positive update of metallurgical results from a test work program for the Curipamba project that has been ongoing since the completion of the Preliminary Economic Assessment ("PEA") in the second quarter of 2019.  The test work program has achieved material improvements over the PEA results using the same three composites collected and produced from the mixed, zinc, and copper geometallurgical zones that respectively comprise of 58.7%, 28.6%, and 12.7% of the diluted Mineral Resource in the PEA open pit mine plan. Composite materials were taken from the 2018 infill drilling program at the El Domo volcanogenic massive sulphide ("VMS") deposit, which is located within the approximately 21,500-hectare Curipamba project located in central Ecuador. The published NI 43-101 Technical Report summarizing the results of the PEA is available on SEDAR with an effective date of June 14, 2019.

Highlights

• Improved quality and marketability of copper concentrates – all three composite samples show improved copper concentrate quality and marketability from the base case Locked Cycle Tests ("LCT") presented in the PEA using cyanide as a reagent.
  • Mixed Composite LCT results:
    • In the copper concentrate, a copper grade of 26.7% was achieved at 81% recovery
    • Lead and zinc content of the copper concentrate was reduced to 0.7% and 6.8% respectively – a great improvement from the PEA results
    • In the zinc concentrate, a zinc grade of 55.9% was achieved at 81.3% recovery
  • Copper Composite LCT results:
    • In the copper concentrate, a copper grade of 28.7% was achieved at 80% recovery
    • Lead and zinc contents in the copper concentrate were reduced to 0.3% and 2.3% respectively from the PEA results
  • Zinc Composite LCT results:
    • In the copper concentrate, a copper grade of 23% was achieved at 74% recovery
    • Lead and zinc contents in the copper concentrate were significantly improved and reduced to 1.4% and 12.7% respectively from the PEA results
    • In the zinc concentrate, a zinc grade of 56.6% was achieved at 81.5% recovery
• Potential to significantly increase precious metal recovery – leach test work of the cleaner tailings streams of all three composites using cyanide indicates that gold and silver recovery could be significantly increased and may be a candidate for the sulphidization-acidification-recycling-thickening ("SART") process that would also recover additional copper while significantly reducing reagent consumption.
• Reduction in acid-generating waste – geochemical characterization studies on potential waste rock from the open pit has identified that three key strata in the hanging wall rocks are non-acid generating which could have positive implications for waste management. All waste rock was previously assumed to be acid generating in the PEA.
• Lead concentrate is possible – production of a lead concentrate from both the mixed and zinc composites was shown to be possible, which could improve the quality of the copper and zinc concentrates, reduce waste, and potentially offer a saleable lead concentrate by-product.

Metallurgical Test Work
The metallurgical test work completed since the PEA was designed to improve the overall quality of the concentrates by reducing metal cross contamination. This included the removal assessment for lead into a separate concentrate while defining a process solution for the zinc geometallurgical zone. In addition, the test work focused on resolving gold mineralogy to characterize losses to the process tailings and to investigate solutions for their recovery to increase precious metal content in the concentrate material. The test work was led by and conducted at Base Metallurgical Laboratories Ltd. ("BML") in Kamloops, British Columbia, Canada. 

Optimization test work was completed on the same three composites defined in the PEA, the mixed, zinc, and copper geometallurgical zones. For the mixed and zinc composites, the PEA results showed that copper concentrates contained high levels of zinc and lead when using a traditional zinc sulphate and cyanide depression scheme. The recent test work investigated a sulphur dioxide-based depression scheme using sulphurous acid (H₂SO₃) or sodium metabisulphide (SMBS), as a potential solution to diminish cross contamination. Both the mixed and zinc composites demonstrated better zinc rejection under the sulphur dioxide-based reagent schemes, notably in the copper concentrate at similar copper recovery. The improved rejection of zinc from the copper concentrate, using SMBS, was noted for the mixed composite and resulted in significantly improved zinc circuit performance as well.  

The test work also demonstrated that a lead concentrate could be removed from the copper concentrate using a cyanide reverse circuit. The lead concentrates were relatively low grade, approximately 37 to 39% lead, but its recovery from the feed to the concentrate was 55% for the mixed composite and 67% for the zinc composite. The LCT results are shown in Table 1.

For the Partners, improving precious metal recovery, notably gold, was a key objective of the recent test work.  A detailed gold deportment study was conducted on cleaner tailings streams for all three composites in order to identify the mineralogical forms of gold loss. Six streams underwent deportment studies as there are two tailings streams from each composite – a bulk rougher tailings stream that is high volume and low grade, and a cleaner tailings stream. The cleaner tailings streams represented most of the gold losses in the process.

For the mixed and zinc composite cleaner tailings streams, about two-thirds of the gold occurred as visible metal alloys. The remaining third of the gold was in solid solution, principally with pyrite. In the copper composite cleaner tailings stream, this was reversed with about one-third of the gold being visible as a metal alloy and the remaining two-thirds occurring in a solid solution with pyrite. Not all the visible gold occurred as free grains, with much of the gold interlocked with other sulphides. 

Table 1: Locked Cycle Test Results for Zinc, Mixed and Copper Composites

Based on the abundance and form of gold in the cleaner tailings streams, cyanide leaching tests were performed to determine gold extraction rates. The best extraction rates were achieved by fine regrinding (9 µm K₈₀) and high cyanide concentrations (5,000 ppm). At these conditions about half of the gold in the tailings streams was extracted. This represents an increase in gold recovery from the feed of about 15%, 11%, and 39%, silver recovery from the feed of about 12%, 8% and 29% and copper recovery from the feed of about 6%, 6% and 10% for mixed, zinc and copper composites, respectively. Leach results are shown in Table 2.  

Table 2: Leach Test Results on Cleaner Tails for Zinc, Mixed and Copper Composites

As a result of the high levels of soluble copper in the cleaner tailings streams, cyanide consumptions were very high, but copper was notably extracted to the leach liquor. This extraction result suggests that the SART process could be a good candidate for optimization, which can recover copper as a precipitate and regenerate cyanide for recycling. Additional leach work is being planned for 2020 in order to investigate the viability of the SART process for the project.

The positive results from the recent metallurgical test work are a significant advancement for the future engineering development of the El Domo deposit within the Curipamba project, including direction for additional metallurgical test work in 2020. The current LCT and leach test results require further optimization in order to more fully evaluate and quantify the opportunity value of SART process implementation on the project. A follow-on work program is now being designed at BML that will be incorporated into future process designs and engineering studies that will cumulate in a Feasibility study that is anticipated to commence in the second half of 2020.

Geochemical Characterization of Potential Waste Rock
The Partners engaged pHase Geochemistry Inc. ("pHase") to conduct geochemical characterization of the rock units that comprise the host strata for El Domo. This work program has been running in parallel with the metallurgical program at BML. Work has focused on the potential waste materials from the open pit and underground mining environments and the level of acid rock drainage ("ARD") and metal leaching potential as a key consideration in future engineering studies and waste management plans.

To date 170 samples that are both spatially and volumetrically representative of the rock units hosting El Domo have undergone analytical geochemistry, including acid-base accounting, whole rock, and trace element analysis. Analytical work is being done with Bureau Veritas Laboratories in Burnaby, British Columbia, Canada.

Neutralization potential of the host strata was shown to be low in most rock units; however, one of the most important analytical results from this geochemical characterization study are that three rock units are anticipated to be non-acid generating. The identification of non-acid generating strata could have a materially positive effect on waste management planning, materials handling during all phases of the project lifespan, and with further study, could have a positive impact on direct operating capital, capital expenditures, and sustaining capital over life of mine. Two rock units tested in this phase of work are anticipated to be potentially acid generating, whereas the remaining seven are expected to be a mix between non and potentially acid generating.

A subset of the above samples was submitted for mineralogical review by QEMSCAN, metal leach extraction testing, and humidity cell testing. The humidity cell testing is ongoing and should be completed later in 2020.   Additional ARD work is planned for the first half of 2020 on metallurgical products such as samples from each of the geometallurgical zones.

Qualified Persons
Tom Shouldice, P.Eng., President and Principal Metallurgist for Base Metallurgical Laboratories Ltd. is the Independent Qualified Person for the metallurgical information contained in this news release. Mr. Shouldice, P.Eng., has been directly involved in the planning, implementation, laboratory work, and reporting of all results. 

Shannon Shaw, P.Geo., President and Principal Geochemist for pHase Geochemistry Inc. is the Independent Qualified Person for the geochemical characterization and acid-rock drainage information contained in this news release. Ms. Shaw, P.Geo., has been directly involved in the planning, implementation, interpretation of laboratory work, and reporting of all results.

The technical and scientific information of this news release has been reviewed and approved as accurate by Mr. Jason Dunning, M.Sc., P.Geo., Vice President Exploration for Adventus, a non-Independent Qualified Person, as defined by NI 43-101.

About Adventus
Adventus Mining Corporation (ADZN.V) (ADVZF.OTCQX) is a well-financed exploration and project development company, focused in Ecuador. Its strategic shareholders include Altius Minerals Corporation, Greenstone Resources LP, Resource Capital Funds, Wheaton Precious Metals Corp., and the Nobis Group of Ecuador. Adventus is leading the exploration and engineering advancement of the Curipamba copper-gold project in Ecuador as part of an earn-in agreement to obtain a 75% ownership interest. In addition, Adventus is engaged in a country-wide exploration alliance with its partners in Ecuador, which has incorporated the Pijili and Santiago projects to date. Adventus also has an investment portfolio of equities in several junior exploration companies as well as exploration projects in Ireland with South32 as funding partner. Adventus is based in Toronto, Canada, and is listed on the TSX-V under the symbol ADZN and trades on the OTCQX under the symbol ADVZF.

About Salazar
Salazar Resources (SRL.V) (CCG.F) is a mineral resource company engaged in the exploration and development of mineral deposits in Ecuador and Colombia. The company has a proven Ecuadorian discovery team led by ex-head of Newmont Ecuador, Fredy Salazar; a team of 40 people including fifteen geologists; three drill rigs and an unrivalled Ecuadorian 'grass roots' network. The Salazar team has been involved with many discoveries in Ecuador, including Curipamba (Adventus Mining and Salazar Resources), Fruta Del Norte (Lundin Gold), the Mozo deposit, Cangrejos (Lumina Gold) Rio Blanco (Junefield Mineral Resources and Hunnan Gold), and Gaby (ENAMI).

Salazar Resources aspires to be Ecuador's leading project generator with the right partners at the right time making the company self-funding. Salazar Resources has an agreement with Adventus on the Curipamba VMS discovery, whereby Adventus can earn 75% of the project by funding exploration and development expenditures of US$25 million before October 2022. A feasibility study is expected to be completed during 2021, after which Adventus is required to fund 100% of the development and construction expenditures to commercial production. In addition, Salazar Resources has a funded exploration alliance with Adventus on two other projects, Pijili and Santiago, within a defined Area of Interest. Salazar Resources is advancing its 100% owned Rumiñahui, Macara, and Los Osos projects with the aim of making Ecuador's next significant copper-gold discovery.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release.

This press release contains "forward -looking information" within the meaning of applicable Canadian securities laws. Any statements that express or involve discussions with respect to predictions, expectations, beliefs, plans, projections, objectives, assumptions or future events or performance (often, but not always, identified by words or phrases such as "believes", "anticipates", "expects", "is expected", "scheduled", "estimates", "pending", "intends", "plans", "forecasts", "targets", or "hopes", or variations of such words and phrases or statements that certain actions, events or results "may", "could", "would", "will", "should" "might", "will be taken", or "occur" and similar expressions) are not statements of historical fact and may be forward-looking statements.

Forward-looking information herein includes, but is not limited to, statements that address activities, events or developments that Adventus and Salazar expect or anticipate will or may occur in the future. Although Adventus and Salazar have attempted to identify important factors that could cause actual actions, events or results to differ materially from those described in forward-looking information, there may be other factors that cause actions, events or results not to be as anticipated, estimated or intended. There can be no assurance that such information will prove to be accurate, and actual results and future events could differ materially from those anticipated in such information. Accordingly, readers should not place undue reliance on forward-looking information. Adventus and Salazar undertake to update any forward-looking information except in accordance with applicable securities laws.

SOURCE Adventus Mining Corporation