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
-
Complements and extends previous four phases of
metallurgical testing
- 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
- 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
- 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
- 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
-
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 |
HeadCharacterizationkg |
Sulfation Tests(5 kg
/dose)kg |
Minicolumns(h=30 cm,
Ø=6”)kg |
Columns(h=4 m,
Ø=4”)kg |
Reserve
Samplekg |
Totalkg |
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): https://www.globenewswire.com/NewsRoom/AttachmentNg/0e3441f0-c2e4-47e8-9535-932b8c25f6ae
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:
https://www.globenewswire.com/NewsRoom/AttachmentNg/0d62cbcc-876a-4c1f-adb3-6ecdd4f329ed
https://www.globenewswire.com/NewsRoom/AttachmentNg/f5ab004c-1958-4aa8-806d-a75e65650063
Figure 3. Fe head grade soluble and
insoluble
assays: https://www.globenewswire.com/NewsRoom/AttachmentNg/35cd5e27-77a2-4fdf-82a3-98a75cb20e46
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): https://www.globenewswire.com/NewsRoom/AttachmentNg/f2e203c5-5921-4d1a-b4ac-c9212d751601
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:
https://www.globenewswire.com/NewsRoom/AttachmentNg/e10b446f-6357-4a25-b949-446d7eaefae6
https://www.globenewswire.com/NewsRoom/AttachmentNg/4c3e8b1e-0316-4e28-98f6-60cb85e24826
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: https://www.globenewswire.com/NewsRoom/AttachmentNg/27d9c9c9-81a6-4a98-91f4-45c60a7d979b
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: https://www.globenewswire.com/NewsRoom/AttachmentNg/5fc5996f-80a1-4732-a4dc-d97cfde17e3a
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 |
Sample |
Granulometry |
Height(m) |
Diameter(in) |
Cured(days) |
DoseH2SO4(kg/t) |
DoseNaCl(kg/t) |
AgglomerationSolution |
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 |
Irrigation1(days) |
Irrigationrate
1(L/h-m2) |
IrrigationFrequency1(h/d) |
Irrigation Soln 1 |
Irrigation2(days) |
Irrigationrate
2(L/h-m2) |
IrrigationFrequency2(h/d) |
IrrigationSoln 2 |
TotalIrrigation(days) |
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: https://www.globenewswire.com/NewsRoom/AttachmentNg/716f05c4-c919-4349-bb08-d81220ae0d03
Figure 9. 4m column test results – acid
consumption, PEA and OPT
conditions: https://www.globenewswire.com/NewsRoom/AttachmentNg/0a1c0264-c639-4591-8d8b-b2c2bbe86065
The first key takeaway from the 4m column
testing program was the confirmation of a positive metallurgical
response for the PEA design conditions for CuT recovery and acid
consumption. The 2019 PEA metallurgical assumptions were generated
without having full-scale column test experimental results exactly
under the established conditions in the design criteria.
The results of the 4-meter columns demonstrate
that the OPT condition optimizes acid consumption maintaining or
improving copper recovery relative to PEA operating conditions.
For the oxidized samples, a reduction in acid
consumption of around 3-4 kg/t and an increase in recovery of
around 1% is observed. For the MIX and ENR samples, the saving in
acid consumption is greater at approximately 9 kg/t while
maintaining the PEA condition recovery. It should be noted that a
large driver of the difference between the savings of the oxidized
and sulfurized samples was because the dose of acid during
agglomeration was not increased in the optimized sulfide condition,
unlike the oxides where this reagent was increased from 20 to
25kg/t.
This result indicates that the OPT condition has
a net gain compared to the PEA conditions. Consistent with the
other leaching tests carried out, all the columns reached copper
recoveries that exceed the Solubility Ratio of the respective
composites. Additionally, all the oxide samples met or exceeded the
composite Leaching Potential, particularly the WAD composite which
recovered approximately 10 recovery points above the Leaching
Potential.
As seen on previous occasions, the MIX and ENR
samples reach an intermediate recovery value between the Acid
Solubility and the Leachable Potential.
Column Tests: ROM Leach
Container column leach
The container test was designed to individually
characterize the metallurgical response of coarse material in a
condition comparable to the first meter of a ROM operation. The
composite prepared was analyzed and a complete characterization
generated. 3 leaching tests were completed in ROM containers, 0.90
m 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. The
operating conditions for ROM containers are detailed below. The ROM
containers (BROC ROM, WAD ROM and CRIS ROM) consider 180 days of
irrigation with a sulfuric acid solution (10 g/L H2SO4).
N° |
Composite |
Granulometry |
Irrigation(days) |
Irrig
Rate(L/h-m2) |
Irrig Frequency(h/d) |
Irrig Soln(g/l) |
G-1 |
BROC ROM |
P100<8” |
180 |
6 |
24 |
RS-10 |
G-2 |
WAD ROM |
P100<8” |
180 |
6 |
24 |
RS-10 |
G-3 |
CRIS ROM |
P100<8” |
180 |
6 |
24 |
RS-10 |
Table 4. Container leach operating
conditions
Figure 10. Container column test results
– copper
recovery: https://www.globenewswire.com/NewsRoom/AttachmentNg/b2e96e1d-2ba5-449a-b500-1798f22e73ce
Recoveries in the ROM composites are lower than
Leaching Potential which is a result of the larger ROM particle
size. In the WAD sample, WAD-ROM (G-2), copper recovery is much
closer to the Leaching Potential relative to CRIS-ROM (G-1) and
BROC-ROM (G-3) samples. This is possibly an indication than the WAD
mineralization is more exposed after rock fracture, a
characteristic than will benefit its natural lower copper grade.
This may be an important upside lever for the ROM leach given the
significant portion its ore contribution while in operation will be
WAD ore. The PEA LOM ROM recovery assumption was 40%.
Figure 11. Container column test results
– acid
consumption: https://www.globenewswire.com/NewsRoom/AttachmentNg/d941b046-e0ca-4efa-9d55-d320a1b8a7c2
Net acid consumption is affected by the particle
size distribution of the samples. The higher the particle size the
lower the available surface for extraction reaction and gangues
neutralization which causes a reduction in acid consumption in the
range of 30% (G-1) and 50% (G-2, G-3) when compared to the AAC
assay. This is the same observation as the copper recovery results,
however with a positive impact.
The recovery in the containers is naturally less
than the recovery in the crushed ROM column tests given the
difference in particle size distribution and lack of curing. The
ROM extraction kinetics still maintain a positive slope at 180
days.
Sequential ROM column test
The sequential ROM column test was designed to
simulate the ROM design conditions of 10m ROM bench heights. For
the ROM G5 leaching (19.8% BROC ROM, 19.8% CRIS ROM and 60.4% WAD
ROM), 1 leaching test in 4 ROM columns in series was carried out,
each column 3m in height and 58cm in inside diameter. Each column
was loaded with approximately 1.45 tonnes of ROM G5 global
composite at ROM granulometry (100% under 8”) covering a total
height equivalent to 12m when considering the 4 ROM columns in
series together. Agglomeration or resting is not carried out, but
irrigation is carried out directly after loading. The operating
conditions for the ROM columns are detailed below.
N° |
Compose |
Granulometry |
Height(m) |
Inside Diameter(cm) |
Irrigation(days) |
Irrigation
Rate(L/h-m2) |
Frequency. Irrigation(h/d) |
Soln 12 days of Initial Irrig. |
Post Irrig. Soln |
R1A |
ROM G5 |
P100<8” |
3 |
58 |
180 |
6 |
24 |
RS-10 |
Refine SX |
R1B |
ROM G5 |
P100<8” |
3 |
58 |
180 |
6 |
24 |
Column Effluent R1A |
R1C |
ROM G5 |
P100<8” |
3 |
58 |
180 |
6 |
24 |
Column Effluent R1B |
R1D |
ROM G5 |
P100<8” |
3 |
58 |
180 |
6 |
24 |
Column Effluent R1C |
Table 5. Sequential ROM column operating
conditions
Figure 12. Sequential column total
copper
recovery: https://www.globenewswire.com/NewsRoom/AttachmentNg/9eedad6b-6f77-4399-a965-84902559730e
Figure 13. Recovery kinetics of
sequential ROM column
tests: https://www.globenewswire.com/NewsRoom/AttachmentNg/df063680-b5f7-47f8-b1ee-6ca6d1d6a3fc
The first 3-meter section (Column R1A)
demonstrates the highest recovery, with recovery decreasing towards
the lower sections (R1D lowes). The lower availability of acid in
the deeper levels partially affects the dissolution of copper.
Average overall recoveries are lower than the sample's Leaching
Potential given both the aforementioned effect of the acidity
profile and the effect of the larger particle size of a ROM sample
compared to the HL samples.
At the kinetic level, upper columns in the
sequence have higher available acid and hence a higher recovery
than the proceeding columns. It is also observed that at days
180-200 the slope of the recovery kinetics is still positive with
recovery yet to reach the asymptote. The convenience of extending
the cycle must be evaluated in terms of marginal recovery (kg Cu/kg
H+) relative to incremental acid consumed.
Figure 14. Sequential ROM column test
acid
consumption: https://www.globenewswire.com/NewsRoom/AttachmentNg/3a2fc362-6624-4753-9d26-7413d1ac7737
As with copper recovery, acid consumption
decreases towards the lower sections of the sequential column,
reaching a value very close to zero for Column R1D. This indicates
that the higher concentration of acid in solution in the upper
columns strongly affects consumption, and in greater proportion
than it affects the dissolution of copper, which opens
opportunities for the optimization of consumption without
materially impacting copper recovery. At the aggregate level for
the 12 meters, the ROM-G5 sample reached a consumption of 5.6 kg/t,
less than the 10 kg/t established in the PEA.
The results from the sequential ROM column tests
indicate the potential for a positive opportunity to improve
recoveries by extending the ROM leaching cycle and increasing acid
irrigation while maintaining manageable acid consumption
levels.
Next Steps
The main program for the Phase 5 metallurgical
program is now complete and limited additional work is expected to
be required during the DFS. The Company is currently completing
particle size distribution work to optimize final drill and blast
and crushing circuit designs for the updated heap leach design and
finalizing impurities balance analysis (under various operating
assumptions) of the PLS and raffinate circuit to inform the final
process design criteria for the DFS.
Overview of Leaching
Potential
The leaching potential of copper ores is defined
as acid soluble copper (CuS) plus cyanide soluble copper (CuCN)
divided by total copper (CuT). The acid 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 + CuCN)/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 copper
oxides, the metallurgical recovery has exceeded the leaching
potentials identified in sequential copper analysis.
Qualified Person
The Qualified Person for technical information
in this news release is Marcelo Jo, General Manager of Jo y Loyola
Process Consulting, a chemical engineer with more than 35 years of
experience and a Fellow of Chilean Mining Engineers Institute.
Metallurgical Qualified Person according the Chilean Mining
Committee for the purposes of NI 43-101.
The QP confirms they have visited the project
area, have reviewed relevant project information, is responsible
for the information contained in this news release, and consents to
its publication.
Contact InformationFor further
information please visit www.marimaca.com or contact:
Tavistock +44 (0) 207 920
3150Jos Simson/Oliver Lamb / Nick
Elwesmarimaca@tavistock.co.uk
Forward Looking Statements
This news release includes certain
“forward-looking statements” under applicable Canadian securities
legislation. There can be no assurance that such statements will
prove to be accurate, and actual results and future events could
differ materially from those anticipated in such statements.
Forward-looking statements reflect the beliefs, opinions and
projections on the date the statements are made and are based upon
a number of assumptions and estimates that, while considered
reasonable by Marimaca Copper, are inherently subject to
significant business, economic, competitive, political and social
uncertainties and contingencies. Many factors, both known and
unknown, could cause actual results, performance or achievements to
be materially different from the results, performance or
achievements that are or may be expressed or implied by such
forward-looking statements and the parties have made assumptions
and estimates based on or related to many of these factors. Such
factors include, without limitation: risks related to share price
and market conditions, the inherent risks involved in the mining,
exploration and development of mineral properties, the
uncertainties involved in interpreting drilling results and other
geological data, fluctuating metal prices, the possibility of
project delays or cost overruns or unanticipated excessive
operating costs and expenses, uncertainties related to the
necessity of financing, the availability of and costs of financing
needed in the future as well as those factors disclosed in the
annual information form of the Company dated March 25, 2022, the
final short form base prospectus and other filings made by the
Company with the Canadian securities regulatory authorities (which
may be viewed at www.sedar.com). Accordingly, readers should
not place undue reliance on forward-looking statements. Marimaca
Copper undertakes no obligation to update publicly or otherwise
revise any forward-looking statements contained herein whether as a
result of new information or future events or otherwise, except as
may be required by law.
Neither the Toronto Stock Exchange nor the
Investment Industry Regulatory Organization of Canada accepts
responsibility for the adequacy or accuracy of this
release.
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