Marimaca Announces Positive Final Results from the Phase 5 Metallurgical Program at the Marimaca Oxide Deposit
News Release
Marimaca Announces Positive Final Results from the Phase 5 Metallurgical Program at the Marimaca Oxide Deposit
Vancouver, British Columbia, June 15, 2022 – Marimaca Copper Corp. (“Marimaca Copper” or the “Company”) (TSX: MARI) is pleased to announce results of the Phase 5 Metallurgical testing program (the “Phase 5 Program” or the “Program”) for the Company’s flagship Marimaca Oxide Copper Project (“the MOD” or “the Project”), located in northern Chile. The Phase 5 Program represents the most comprehensive metallurgical study completed to date for the MOD and is the final phase expected prior to the planned commencement of the Definitive Feasibility Study.
The Phase 5 Program is an important de-risking event for Marimaca and confirms the results from the previous four phases of metallurgical testing, which indicate good leach kinetics and moderate acid consumption. Results from Phases 1-5 Metallurgy and the 2021 Variability Program (see announcement dated November 30, 2021) will form the basis for the updated process design criteria and metallurgical assumptions for the Definitive Feasibility Study.
Highlights
- Rigorous 5th phase metallurgical test-work program represents a milestone de-risking event for Marimaca, further
improving confidence in the expected metallurgical performance at the MOD
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Complements and extends previous four phases of metallurgical testing
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Program consisted of full-scale column testing, mini-column testing, container-leach testing, sulfation tests, acid sensitivity testing, Iso-pH testing, and head characterization for heap leach (“HL”) and run-of-mine (“ROM”) samples o
Robust sample set with several composites across all mineral subdomains through all phases of testing
- Confirms the understanding of the MOD’s metallurgical performance with results from Phase 5 consistent with Phases 1-
4 Metallurgy
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Results significantly improve the resolution of Marimaca’s geo-metallurgical dataset
- Confirms metallurgical performance in scaled-up, industrial height operating design conditions (4m columns)
- Provides further confidence in expected acid consumption with clear potential for optimizations to reduce acid
consumption demonstrated in both HL and ROM test results
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Testing also confirms very low levels of carbonates (<1%) and nitrates (<0.03%) in general within the MOD
- Results continue to demonstrate potential upside to recoveries when in industrial-scale operation o
Recoveries in the column and bottle roll tests generally exceeded the solubility ratio and leaching potential of the samples (see ‘Overview of Leaching Potential’), indicating a potentially larger proportion of total copper will be recovered in industrial-scale operations
- Completing final confirmatory work programs on particle size distribution and impurities balance to inform update process
design for the planned DFS
- Recovery and acid consumption models will be updated on the back of the 2022 geological and resource model update
planned for Q3, immediately following the completion of the 2022 infill drilling program
Hayden Locke, President and CEO of Marimaca Copper, commented:
“The Phase 5 Metallurgical Program completes the acquisition of an incredibly comprehensive metallurgical dataset for Marimaca. This is a critical de-risking milestone and we are very pleased with results.
“The results from Phase 5 further improve our confidence in the strong metallurgical performance at the MOD. In addition, several opportunities for optimizing acid consumption while maintaining or improving copper recoveries have been identified and will be integrated into our process design going forward.
“Similar to the trends identified in previous phases, copper recoveries continue to demonstrate upside beyond those projected by acid solubility and Leaching Potential given the longer leaching cycle of the black oxide component of copper oxide mineralization at Marimaca. This provides opportunities with respect to recoveries in industrial-scale operations beyond the positive results demonstrated in this phase of testing.
“Marimaca continues to distinguish itself as an exceptionally high-quality copper development project. This year’s infill and extensional drilling campaigns are progressing well, and we look forward to delivering our planned updated resource estimate in Q3.”
Program Overview
The Phase 5 Program was designed to confirm the PEA process design conditions and to evaluate potential optimization opportunities of both copper recovery and acid consumption identified during Phases 1 – 4 (see press release dated September 8, 2020). The results of the Phase 5 Program are positive, with optimization opportunities identified in most of the samples studied and tested.
Phase 5 was designed and executed under the supervision of Marcelo Jo of Jo & Loyola Process Consultants, who has 35 years’ experience in processing, and supported by Randolph E. Scheffel, a Consultant Metallurgical Engineer with over 45 years’ experience in copper processing.
Program Design – Heap Leach
- Sampling and sample preparation
- 5 composite samples collected representative of each mineral subzone: brochantite/atacamite (BROC), chrysocolla (CRIS), WAD, mixed (MIX), and enriched (ENR)
- Each composite was crushed in closed circuit to P90 at ½”. Crushing was monitored and simulated a PSD profile of a Metso-type industrial configuration. Care was taken not to over-grind the material to obtain the final product with a -100 # Tyler content of 10-12 %
- Sample allocation for each testing phase shown in Table 1
- Chemical Head Characterization & Mineralogical Analysis
- Characterization included sequential copper analysis, leaching potential, soluble impurities, analytic acid consumption, ICP, optical microscopy, QEMSCAN
- Iso-pH Bottle Roll Tests
- Conducted under constant pH and Cl conditions to examine the correlation to the analytical acid consumption (AAC) diagnostic testing method, improve the acid consumption modeling, and review copper recovery relative to leaching potential
- 3 Acid Level Sensitivity Bottle Roll Test
- Conducted to examine copper recovery and acid consumption sensitivity relative to acid concentration
- Sulfation Tests
- Conducted to determine the optimum agglomeration conditions for columns and minicolumns
- Minicolumn Tests
- Designed to characterize the crushed ore metallurgical behavior under irrigation at different acidity levels
- 32 leaching tests in mini-columns, 30 cm high, 6” in diameter and loaded with approximately 9 to 10 kg of sample each
- Column Tests
- Designed to confirm the viability of the PEA and optimized design conditions defined by the Phase 4 geometallurgy and METSIM dynamic simulation
- 10 leaching tests in columns, 4m high, 4” in diameter and loaded with approximately 52 to 60 kg of sample each
| Sample | Head Characterization kg | Sulfation Tests (5 kg /dose) kg | Minicolumns (h=30 cm, Ø=6”) kg | Columns (h=4 m, Ø=4”) kg | Reserve Sample kg | Total kg |
|---|---|---|---|---|---|---|
| BROC G5 | 12 | 15 (3 x 5 kg) | 120 (12 x 10 kg) | 120 (2 x 60 kg) | 365 | 632 |
| CRIS G5 | 12 | 15 (3 x 5 kg) | 120 (12 x 10 kg) | 120 (2 x 60 kg) | 365 | 632 |
| WAD G5 | 12 | 15 (3 x 5 kg) | 80 (8 x 10 kg) | 60 (1 x 60 kg) | 295 | 462 |
| MIX G5 | 12 | 15 (3 x 5 kg) | 80 (8 x 10 kg) | 60 (1 x 60 kg) | 210 | 377 |
| ENR G5 | 12 | 15 (3 x 5 kg) | 80 (8 x 10 kg) | 60 (1 x 60 kg) | 295 | 462 |
Table 1. Composite sample allocation across heap leach test program (G5 = Geometallurgy Phase 5)
Program Design – ROM leach
- Sampling and sample preparation
- Four composites were prepared: WAD-ROM, BROC-ROM and CRIS-ROM and a global composite ROM G5
- The global composite (ROM G5) was prepared representing utilizing the ore type distribution from the 2020 PEA mine plan for the ROM leach (60.4% WAD-ROM, 19.8% BROC-ROM and 19.8% CRIS-ROM)
- Chemical Head Characterization & Mineralogical Analysis
- Characterization included sequential copper analysis, leaching potential, soluble impurities, analytic acid consumption, ICP, optical microscopy, QEMSCAN
- Iso-pH Bottle Roll Tests
- Conducted under constant pH and Cl conditions to examine the correlation to the analytical acid consumption (AAC) diagnostic testing method, improve the acid consumption modeling, and review copper recovery relative to leaching potential
- 3 Acid Level Sensitivity Bottle Roll Test
- Conducted to examine copper recovery and acid consumption sensitivity relative to acid concentration
- Crushed Column Tests
- Conducted to define the maximum expected recoveries from the ROM composites and establish a comparative base with the crushed material
- 6 leaching tests in crushed columns, 1 m high, 6” in diameter and loaded with approximately 30 to 40 kg of composite per subzone (BROC ROM, WAD ROM and CRIS ROM) each crushed to P90 1/2”
- 1m3 Container test
- Conducted to individually characterize the metallurgical response of coarse material in a condition comparable to the first meter of a ROM operation
- 3 leaching tests were completed in ROM containers, 0.90m high, with a surface area of 1.06m2 (volumetric capacity of 0.96 m3) and loaded with approximately 1.8 tonnes of ROM composite per subzone (BROC ROM, WAD ROM and CRIS ROM) each, at ROM granulometry (100% under 8”)
- Agglomeration or curing is not carried out, but irrigation is carried out directly at any time, after loading
- Sequential ROM column
- Conducted to simulate the ROM design under PEA conditions using the ROM G5 global composite
- 1 leaching test in 4 ROM columns in series, each one 3m high, 0.58m in diameter and loaded with approximately 1.45 tonnes of ROM G5 global composite each at ROM granulometry (100% under 8”)
- Test covers a total height equivalent to 12m when considering the 4 columns in series
Results Discussion
Head Characterization – Copper Head Grade and Solubility Ratios
Figure 1. Copper Head Grade (CuT), with acid soluble (CuS) and sequential copper assays (CuCN)
As with the previous phases of test work, for the HL composites noted with ‘G5’ in Figure 1, samples were collected for each mineral subdomain at the MOD, meaning each zone is now covered by several samples. WAD mineralization (black oxides) at the MOD has a lower average CuT grade than green oxides (BROC and CRIS) which is in line with the composite sample head assays. Mixed and enriched mineralization at the MOD (MIX and ENR) generally has higher grades relative to green oxides, however with a lower proportion of acid soluble copper. This is also represented appropriately in the composites.
For the ROM composites, the material is coarser with grades similar to the HL samples for BROC and CRIS while for WAD, representative of the peripheral black oxide mineralization at the MOD, has significantly lower copper grades. The average grade of the global ROM G5 composite was 0.32% CuT.
BROC and CRIS composites present the highest sulfuric acid solubility (75-80%) and the lowest presence of secondary copper sulfide according to the cyanide soluble copper test results (<5%).
The WAD composites demonstrated a very marginal presence of secondary copper sulfide. Residual copper in both the HL and ROM composites was 50% or greater. Residual Copper typically reports as Chalcopyrite, however at the MOD, it also reports an important fraction of slow-dissolving black oxides which can have a significant recovery under industrial conditions due to the extended leaching time. The upside potential from the slow leaching black oxides is also present for the green oxide samples to a lesser extent, and partially in the MIX samples.
The MIX sample presents a high Leaching Potential (RS + RCN, 85%), however unlike the green oxides, >50% of the potentially leachable mineralization reports as secondary sulfide. The ENR sample’s Leaching Potential is further skewed towards secondary sulfides, with an oxide presence of ~12%.
All the HL (G5) composite samples report near 80% Leaching Potential other than the WAD composite.
Head Characterization – Other Elements
Each composite sample was also subjected to full ICP and head grade assays to evaluate the composition of each representative sample. Results again demonstrate the clean nature of Marimaca mineralization with very low levels of carbonate (<1%) and nitrates (<0.03%), which is an important characteristic for productive copper leaching in industrial scale operations.
Figure 2. Marimaca exhibits very low levels of carbonate and nitrates as demonstrated in the composite head analysis
Figure 3. Fe head grade soluble and insoluble assays
Iron has a large elemental presence at Marimaca given its nature as an IOCG deposit. Analytical FeT is close to 7-8% in all composites and forms an important component in the expected impurities balance for the deposit. This is marginally higher than average for porphyry copper operations in Chile, however, is typical for an IOCG deposit.
Analytical Acid Consumption
Analytical acid consumption results were in-line with those observed historically in Phases 1-4 metallurgical programs. Generally, the green oxides (BROC/CRIS) have a higher acid consumption relative to black oxides and secondary sulfides (WAD- MIX-ENR). ROM samples present a marginally higher AAC likely due to the weathering effect in the surface samples. Results are in line with the 40kg/t average LOM acid consumption assumption used in the PEA.
Figure 4. Analytical Acid Consumption across the HL and ROM composites (kg H2SO4/tonne)
Iso-pH Testing (bottle roll)
Iso-pH tests are conducted under constant pH and Cl conditions to examine the correlation to the analytical acid consumption (AAC) testing method, improve the acid consumption modeling, and review copper recovery relative to leaching potential.
Figure 5. Iso-pH test net acid consumption across HL and ROM composites
The 72-hour Iso-pH tests further show that recoveries in the HL oxide composites (BROC, CRIS, WAD) are generally higher than the Solubility Ratio and Leaching Potential. This can be explained by the presence of copper oxides with slow dissolution kinetics, not detected during soluble or sequential copper assays, but which can be recovered in tests of longer duration. MIX/ENR composite recoveries are generally greater than the solubility ratio but under the leaching potential. The oxidized component is recovered plus a fraction of secondary sulfides. Under industrial conditions, this recovery could be improved given the longer leaching time and conditions that favor oxidation given the higher availability of oxygen.
3 Acid Level Sensitivity Bottle Roll Test
The three-acid level sensitivity test was designed to evaluate the sensitivity of both copper recovery and acid consumption to variable concentration of acid – 2.5gpl, 5.0gpl and 10.0gpl H2SO4.
Figure 6. 3-acid level recovery
Like the results published in the 2021 Variability Program (see press release dated November 30, 2021), the 3-acid level sensitivity test demonstrated that total copper recovery is relatively insensitive to acid concentration, while the acid consumption shows a much steeper response and is notably higher when irrigated at 10gpl vs. 2.5gpl. This indicates that gangue species present are most sensitive to the acid content while copper species are not as affected by the different acidity levels. This is expected to allow further optimization of acid consumption for the deposit in industrial scale operations.
Heap Leach Sulfation Tests
Sulfation tests were carried out to confirm and optimize the agglomeration conditions for the column and mini-column tests. The tests are carried on 3 x 5kg samples from each composite, with three levels of acidity (20, 30 and 40 kg H2SO4 per tonne). Cu extraction, acid consumption and impurities dissolution were evaluated.
Figure 7. Total copper recovery per composite at various acid dosages in agglomeration phase
Copper extraction increased moderately with the acid dosage in the agglomeration phase. Close to the 50% of the Leaching Potential was recovered for the green oxide composites, while for the WAD composite ~40% is obtained. For mixed and enriched samples with the addition of salt Cu recovery reaches 20 to 30%. A key trade-off is copper recovery during curing vs. under heap leach irrigation while maintaining <40kg/t acid consumption. The strategy of using lower acid doses during curing (20-25 kg/t) is considered optimal.
Column Tests: Heap Leach
Each of the 5 heap leach composites was mechanically prepared at a granulometry of 90% passing ½” and leached in 4-meter columns to simulate the PEA dynamic heap leach height. Two conditions were tested – PEA assumptions (PEA), and an optimized condition (OPT) as defined by METSIM geo-metallurgical simulations based on results from Phases 1-4 metallurgy. Operating conditions are defined below.
The oxide columns (BROC G5, CRIS G5, WAD G5) underwent 52 (PEA) and 42 days (OPT) of irrigation with ILS solution (10 and 8 g/L H2SO4 for PEA and OPT conditions respectively), as well as 40 (PEA) and 50 days (OPT) of irrigation with raffinate solution (10 and 8 g/L H2SO4), respectively, to reach total irrigation time of 92 days. The sulfide columns (MIX G5, ENR G5) consider 55 and 42 days of irrigation with ILS solution (10 and 8 g/L H2SO4), as well as 55 and 68 days of irrigation with raffinate solution (10 and 8 g/L H2SO4) for PEA and OPT respectively, to reach a total irrigation of 110 days. The same raffinate solution is used for agglomeration as for the second irrigation cycle. The acid content in the raffinate solution is taken as additional and is not included in the agglomeration acid dose expressed in kg H2SO4/t which only represents the concentrated acid added.
| N° | Condition | Granulometry | Height (m) | Diameter (in) | Cured (days) | Dose | Dose | Agglomeration Solution | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sample | HSO 2 4 | NaCl | ||||||||||||
| (kg/t) | (kg/t) | |||||||||||||
| C1 | PEA | BROC G5 | P90<1/2" | 4 | 4 | 3 | 20 | 0 | RF-10 | |||||
| C3 | OPT | BROC G5 | P90<1/2" | 4 | 4 | 3 | 25 | 0 | RF-8 | |||||
| C7 | PEA | CRIS G5 | P90<1/2" | 4 | 4 | 3 | 20 | 0 | RF-10 | |||||
| C9 | OPT | CRIS G5 | P90<1/2" | 4 | 4 | 3 | 25 | 0 | RF-8 | |||||
| C13 | PEA | WAD G5 | P90<1/2" | 4 | 4 | 3 | 20 | 0 | RF-10 | |||||
| C14 | OPT | WAD G5 | P90<1/2" | 4 | 4 | 3 | 25 | 0 | RF-8 | |||||
| C17 | PEA | MIX G5 | P90<1/2" | 4 | 4 | 30 | 20 | 15 | RF-10 | |||||
| C18 | OPT | MIX G5 | P90<1/2" | 4 | 4 | 30 | 20 | 15 | RF-8 | |||||
| C21 | PEA | ENR G5 | P90<1/2" | 4 | 4 | 30 | 20 | 15 | RF-10 | |||||
| C22 | OPT | ENR G5 | P90<1/2" | 4 | 4 | 30 | 20 | 15 | RF-8 |
Table 2. Heap leach column testing agglomerating conditions
| c | Sample | Irrigation 1 (days) | Irrigation rate 1 (L/h-m2) | Irrigation | Irrigation Soln 1 | Irrigation 2 (days) | Irrigation rate 2 (L/h-m2) | Irrigation | Irrigation Soln 2 | Total Irrigation (days) | |||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frequency | Frequency | ||||||||||||
| 1 | 2 | ||||||||||||
| (h/d) | (h/d) | ||||||||||||
| C1 | BROC G5 | 52 | 12 | 24 | ILS-10 | 40 | 12 | 22 | RF-10 | 92 | |||
| C3 | BROC G5 | 42 | 15 | 24 | ILS-8 | 50 | 15 | 14 | RF-8 | 92 | |||
| C7 | CRIS G5 | 52 | 12 | 24 | ILS-10 | 40 | 12 | 22 | RF-10 | 92 | |||
| C9 | CRIS G5 | 42 | 15 | 24 | ILS-8 | 50 | 15 | 14 | RF-8 | 92 | |||
| C13 | WAD G5 | 52 | 12 | 24 | ILS-10 | 40 | 12 | 22 | RF-10 | 92 | |||
| C14 | WAD G5 | 42 | 15 | 24 | ILS-8 | 50 | 15 | 14 | RF-8 | 92 | |||
| C17 | MIX G5 | 55 | 12 | 24 | ILS-10 | 55 | 12 | 22 | RF-10 | 110 | |||
| C18 | MIX G5 | 42 | 15 | 24 | ILS-8 | 68 | 15 | 14 | RF-8 | 110 | |||
| C21 | ENR G5 | 55 | 12 | 24 | ILS-10 | 55 | 12 | 22 | RF-10 | 110 | |||
| C22 | ENR G5 | 42 | 15 | 24 | ILS-8 | 68 | 15 | 14 | RF-8 | 110 |
Table 3. Heap leach column testing irrigating conditions
Figure 8. 4m column test results – CuT recovery, PEA and OPT conditions
Figure 9. 4m column test results – acid consumption, PEA and OPT conditions