Marimaca Copper Corp. (“Marimaca Copper” or the “Company”) (TSX:
MARI) is pleased to announce results of the variability test work
metallurgical program (the “Variability Program” or the “Program”)
for the Company’s flagship Marimaca Copper Project (“Marimaca” or
“the Project”), located in northern Chile. The variability test
work was completed as a component of the Company’s ongoing Phase 5
Metallurgical program and additional associated studies, which are
expected to be completed in early Q1 2022. The ongoing 2021
metallurgical campaign is focused on finalizing the metallurgical
characterization of the Project to a bankable level and builds on
the results from the Phase 4 Metallurgical program
(see
September 9 2020 announcement).
The Variability Program was designed to
investigate the variability of the Marimaca ore body by assessing
copper recovery, acid consumption and impurity dissolution
characteristics within each mineralogical domain (ore type). This
Program represents an important de-risking milestone for Marimaca
by increasing certainty and predictability of the metallurgical
response for each ore type and spatially across the deposit, and to
refine process design criteria prior to the Feasibility Study
targeted for 2022.
Highlights
- Results from the
Variability Program demonstrate uniform metallurgical behaviour
within each mineral zone when considering acid consumption and
copper recoveries
- A total of 412
composites across each of the 5 mineral zones within the Marimaca
Mineral Resource (Brochantite, Chrysocolla, WAD, Mixed and
Enriched) were analyzed
- Results
significantly improve the resolution of the Marimaca
geo-metallurgical model and will allow for rigorous modeling of
recovery and acid consumption across mine blocks ahead of the
planned 2022 Feasibility Study
- The Program is a
core component of the Company’s Phase 5 metallurgical testing
program, the second program undertaken since the 2020 Preliminary
Economic Assessment (“PEA”) (refer to announcement on 4
August 2020), which projected average life of mine
metallurgical recoveries in the heap leach of approximately
76%
- For the oxide
mineral zones (BROC, CRIS, WAD), recoveries generally exceeded the
solubility ratio and leaching potential of the samples (see
Leaching Potential Overview), indicating a potentially larger
proportion of the copper is acid soluble and will be recovered in
commercial-scale heap leaching
- The Variability
Program represents a significant de-risking milestone and will form
the basis for defining recovery and processing assumptions for
Feasibility Study and eventual operational mine plans
- MOD infill
drilling is underway, and MOD Depth Extension (MAMIX) infill
drilling is currently being planned
Hayden Locke, President and CEO of
Marimaca Copper, commented:
“One of the key risks of any project is
variability in the metallurgical performance of a deposit when
moving laterally or vertically. We have completed an incredibly
rigorous programme encompassing over 400 hundred samples spread
evenly across the deposit in both vertical and horizontal
directions. This provides us with a significant amount of data to
underpin our assumptions with respect to both the expected copper
recoveries and acid consumption of each mining block.
“Importantly, the programme continues to give us
a high degree of confidence that the assumptions used in our 2020
PEA, with respect to copper recoveries and acid consumptions, are
valid. In fact, we have identified several areas for optimization
and may see some improvement relative to the PEA assumptions.
“We have commenced the infill drilling campaign
for the MOD and are currently planning for infill drilling the
recently discovered deeper extensions of the MOD (MAMIX). The
objective is to bring additional copper tonnes into an eventual
updated Mineral Resource Estimate in the first half of 2022, which
we will use as the basis for our Feasibility Study.”
Program Overview
A total of 412 variability composite samples
were selected and analyzed for the Program. Samples were selected
using spatial criteria across the PEA open-pit mineable resource
area, subdivided into macroblocks of 75m x 75m x 25m (Figure 1). A
total of 4,491 RC samples were processed through rigorous
variability criteria screening and formed the basis for the 412
composites.
The program design consisted of three
components:
- Chemical Head
Characterization.
- Characterization
included sequential copper analysis, leaching potential, soluble
impurities, analytic acid consumption, and others
- 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
Figure 1. Composite Sample Mineral Subzones
https://www.globenewswire.com/NewsRoom/AttachmentNg/2006a981-cf48-48b0-87ec-a4a14aab6efe
Results Discussion
Analytical Acid Consumption
(AAC)
The average total AAC of the sample population
was 40.79 kg/t with <10% of the samples returning an AAC of
>60 kg/t. Green oxides tend to have a higher acid consumption
than the balance of the mineral subzones (45-50 kg/t relative 30-40
kg/t). This difference is explained by marginal incremental
carbonate content relative to WAD, MIX and ENR. All mineral
subzones present low AAC variability and the same consistency was
observed across the additional soluble impurities tested as part of
the Analytical Acid Consumption assay (Fe, Al, Mg, Mn). In general,
uniform behavior is observed within the mineral subzones.
Figure 2. Analytical Acid Consumption
Test
https://www.globenewswire.com/NewsRoom/AttachmentNg/f875c978-4e30-46c4-9c98-c79459e0a0b0
Iso-pH tests
Similar to results observed in the Phase 4
metallurgical program, the majority of the composite samples
returned recoveries that exceeded the solubility ratio, indicating
that all of the acid soluble copper was recovered as well as
additional copper not reported in the soluble copper assays.
Additionally, the BROC, CRIS and WAD samples generally returned
recoveries that exceeded the leaching potential, while the MIX and
ENR samples reached recoveries between the solubility ratio and the
leaching potential. WAD demonstrates the greatest recovery margin
above the leaching potential. Currently this is interpreted as the
presence of black oxides that are not detected in the head
characterization tests but it can be recovered in longer tests
given their slower leach kinetics. This can also be observed in the
BROC and CRIS subzones, but to a lesser extent. Results observed
for the MIX and ENR samples are as expected for the test
conditions, as, to achieve higher recoveries of secondary sulfides,
longer leach time or additional agglomeration and curing stages are
required to increase recoveries.
Figure 3. Copper recovery vs. leaching
potential
https://www.globenewswire.com/NewsRoom/AttachmentNg/202f9a48-0866-45b3-9020-4ce797517bbd
The iso-pH acid consumption test also demonstrated a strong
correlation between when compared with the AAC test which provides
strong validation for the results.
Figure 4. Acid consumption – AAC method vs.
Iso-pH results
https://www.globenewswire.com/NewsRoom/AttachmentNg/aba392a8-f601-4709-a250-1e73fce77fdb
3 Acid Level Sensitivity
Test
Copper recoveries did not demonstrate
significant sensitivity to acid level test between 2.5 gpl, 5 gpt
and 10 gpl. A slightly higher copper recovery is observed with
higher acidity, but the effect is very limited. The sensitivity of
acid consumption to acid level was higher than the copper recovery
sensitivity. Acid consumption decreases materially at lower
acidity. This is a known characteristic of the Marimaca ore and
will play an important role in the processing plant operating
condition design. Follow up tests are currently being designed to
investigate further.
Figure 5. Acid level
sensitivities
https://www.globenewswire.com/NewsRoom/AttachmentNg/f6e418eb-383c-4824-848f-e82a9c009a3b
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 29, 2021, 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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