VANCOUVER, BC, June 28,
2023 /CNW/ - MANTARO PRECIOUS METALS
CORP. (TSXV: MNTR) (OTCQB: MSLVF) (FSE: 9TZ) (the
"Company" or "Mantaro") is pleased to report results from a
petrographic study on drill core from the Company's maiden drill
program at the Gold Hill gold deposit in Bolivia. This report represents a final stage
of verification prior to release of a maiden mineral resource
estimate.
Highlights:
- Gold deposition at La Escarcha, including gold grades
intercepted in the maiden drill program, is primary and not related
to supergene effects. This has positive implications for gold
grades at depth.
- Gold occurs as free-milling native gold present primarily at
quarts-carbonate crystal boundaries and along fractures within
quartz and pyrite.
- Gold grain size and shape, and likelihood that a significant
percentage of native gold will liberate freely
during comminution, is consistent with the results of
bench-scale metallurgical tests which reported excellent gold
recovery by gravity and cyanidation.
- Sulphide content is generally low, which in conjunction with
abundant acid-neutralizing carbonate gangue minerals, have positive
implications for tailings
Dr Chris Wilson, FAusIMM (CP),
FSEG, FGS, principal consultant to Mantaro comments, "The
findings of the petrological study and bench-scale metallurgical
testing by SGS, have further de-risked the project. Given that
Golden Hill is a permitted mining concession, the petrographic data
will assist in review of near-term mining scenarios, and design of
a high reward Phase 2 drill program to target along strike and
deeper extensions of La Escarcha mineralized system."
A petrographic study was conducted on 32 drill core samples from
the Company's maiden drill program at La Escarcha and Gabby.
Samples were collected at vertical depths of 20 to 120 meters below
surface and are representative of the style and grade of
mineralization intercepted.
The primary objective of the petrographic study was to: (1)
better understand the mineralogical signature of the auriferous
quartz-carbonate shear zones, (2) quantify gold grain size,
distribution and morphology, (3) characterize gold-gangue (waste)
mineral relationships for input into metallurgical studies, and (4)
provide input for future exploration targeting. A combination of
thin section, polished block microscopy and scanning electron
microscope ("SEM") backscattered electron mapping was used.
Petrographic work was complemented by extensive core-logging,
thereby, placing the study's findings into the broader 3D framework
of the deposit and the structural and hydrothermal evolution of the
mineralized system. The work was completed by Specialist
Exploration Services LLC and overseen by Dr Chris Wilson, principal geological consultant to
the Company, who has over 35 years of petrographic and analytical
experience of mineral deposits and associated hydrothermal
systems.
Gold Grades at La Escarcha are
Primary and Not Supergene Enriched
Supergene (or surface weathering) processes are characterized by
the breakdown of primary sulphide minerals through contact with
acidic rain and near-surface groundwater. Chemical reactions
liberate gold from sulphides as they are converted to iron oxides
such as limonite, hematite and goethite. Supergene process may
result in an enriched near-surface zone with elevated gold grades.
Understanding if supergene enrichment has affected near-surface
gold grades is critical to drill targeting the deeper potential of
the mineralized system.
Petrographic examination of drill core from La Escarcha
confirmed the presence of free gold with pyrite and arsenopyrite.
Mineralization is of primary (or hypogene) character and there is
no evidence of oxidation or supergene processes. This is highly
significant as it indicates that gold grades reported from the
Company's near-surface maiden drill program are not enhanced by
surficial processes, but are primary hypogene grades formed during
deposition of gold and sulphides from mineralizing fluids.
It is worth noting that primary sulphide mineralization in
orogenic or greenstone-hosted gold systems worldwide extends over
vertical intervals of greater than 1 km — as evidenced by drilling
and/or mining of many peer group deposits. Drilling by the Company
at La Escarcha has focused on a "small panel" of generally less
than 90 vertical meters over a limited strike length of only
400 m. The absence of supergene
enrichment confirms the depth potential of the system and has
allowed the Company to confidently plan further high-reward
step-back and step-holes at La Escarcha.
Dr Chris Wilson further comments,
"enrichment of near-surface gold grades through supergene
process is a potential concern when using near surface drill
results to target deeper extensions of the mineralized system. The
absence of supergene process in near-surface drill core intercepts
at Golden Hill indicates that assay results reflect primary or
hypogene grades — confirming the robust depth potential of the
system. As a fully permitted mining concession, Mantaro is able to
re-commence drilling at any time, without the need for further
permits."
Gold is Free Milling and Not
Refractory
Bench-scale metallurgical testing on an underground bulk sample
conducted by SGS and previously reported by Mantaro demonstrated
excellent recovery of gold by gravity (74%) and cyanide (94%).
Metallurgy was conducted on a 170 kg sub-sample of a 10 tonne
underground sample with head grade of 5.53 g/t Au, which is
consistent with grades noted in the maiden drill program.
Petrographic study confirms that gold presents as flecks and
grains of generally between 25 to 100 microns diameter with coarse
outliers of up to 2 mm diameter. Gold occurs at
quartz-carbonate-feldspar crystal boundaries and along fractures in
quartz and sulphides (mainly pyrite). As such, gold should freely
liberate during commination by simple crushing and milling. This is
consistent with (1) the metallurgical recoveries reported by SGS,
and (2) historical mine production records which demonstrated
robust gravity recovery.
Dominant gangue (or waste) minerals include
quartz-carbonate-feldspar-mica and between 2 to 12% sulphides —
comprising primarily pyrite and arsenopyrite, lesser pyrrhotite and
traces of chalcopyrite. Total sulphide content is typical of
hypogene mineralization in greenstone-hosted orogenic gold deposits
worldwide. Sulphide content is variable with pyrite and
arsenopyrite predominantly forming in more micaceous fabrics — this
should not impact the liberation of gold during milling.
Gold Grain Size, Morphology and
Gravity Recovery
Gold grain size and morphology, and the extent to which gold
liberates freely from gangue minerals, are fundamental parameters
affecting gold recovery by gravity. Specifically:
- Grain Size: Gold grain size exerts a fundamental control
on the efficiency of gravity recovery. Gold particles greater than
20 to 30 microns diameter are generally well recovered by
gravity.
- Grain Morphology: Equant gold grains are more amenable
to gravity recovery than flakey and foil shaped gold grains.
- Liberation: Native gold can be recovered using gravity
techniques given it has an SG of 19.3 as compared to gangue (waste)
minerals which generally have an SG of 2.5 to 4.0. For this reason,
it is important that gold grains liberate freely from the waste
minerals. Gold grains which remain encapsulated within, or attached
to gangue minerals, form composite particles with an average
specific gravity significantly less than that of pure gold. Such
composite particles may not present to gravity recovery.
Petrographic examination has demonstrated that most gold
particles within maiden intercepts at Golden Hill are coarser than
30 microns, are generally equant to oval in shape, and the dominant
position on crystal boundaries and fractures suggest robust and
complete liberation. A number of very fine gold grains are noted
within pyrite and arsenopyrite, but collectively this component is
a minor fraction of the total gold endowment.
Tailings Mineralogy
Petrographic study, in conjunction with detailed core logging,
confirms that gold mineralization at Golden Hill is hosted in
quartz-carbonate shear zones with generally low to locally moderate
sulphide component. The dominant sulphides are pyrite and
arsenopyrite — both preferentially developed in metasediment wall
rocks.
Major gangue minerals consist of quartz-carbonate-feldspar and
micaceous metasediments. Carbonate minerals are acid neutralizing —
which in conjunction with the generally low sulphide content —
suggests that tailings will not generate significant acid. This is
consistent with observations of the historical tailings.
Mantaro continues petrographic study for input into further
bench-scale metallurgical tests designed to improve and optimize
first-pass tests which reported 74% gravity gold recovery.
Specifically, further petrology and bench-scale metallurgical
testing will focus on fine-tuning the comminution and gravity flow
path to ensure that smaller gold particles (<20 microns) which
are encapsulated within pyrite are freely liberated. Whilst this
fine gold component represents a relatively small percentage of the
total gold endowment, Mantaro is confident that gravity recovery
can be further optimized.
Dr Chris Wilson, further
comments, "in addition to establishing that gold grade
intercepts from the maiden drill program are primary or hypogene in
nature and not associated with supergene enrichment, petrology has
also confirmed that native gold is free-milling and not refractory.
Gold grain size and morphology, and common occurrence of native
gold at crystal boundaries and along fractures in gangue minerals,
is consistent with recovery of gold via gravity and/or cyanidation
flow-paths. Low to locally moderate sulphide content, and abundance
of acid neutralizing carbonate minerals, is a significant positive
with respect to tailings characteristics."
Qualified Person
Dr. Christopher Wilson, Ph. D.,
FAusIMM (CP), FSEG, a Qualified Person under National Instrument
43-101, has reviewed and approved the technical information
contained in this news release.
About Mantaro Precious Metals
Corp.
Mantaro Precious Metals Corp. is a British Columbia company that holds a
diversified portfolio of gold and silver focused mineral properties
in Bolivia and Peru. The Company holds an option to acquire
up to an 80% interest in the advanced Golden Hill orogenic gold
property ("Golden Hill"), located in the underexplored Precambrian
Shield, Bolivia.
In Peru, the Company has a 100%
interest in the high-grade Santas Gloria silver property as well as
a 100% interest in each of the La Purisima, Cerro Luque and Huaranay properties.
Forward-Looking
Statements
Information set forth in this news release contains
forward-looking statements that are based on assumptions as of the
date of this news release. These statements reflect management's
current estimates, beliefs, intentions and expectations. They are
not guarantees of future performance. The Company cautions that all
forward looking statements are inherently uncertain and that actual
performance may be affected by a number of material factors, many
of which are beyond the Company's control. Such factors include,
among other things: risks and uncertainties relating to Company's
limited operating history, ability to obtain sufficient financing
to carry out its exploration programs and the need to comply with
environmental and governmental regulations. Accordingly, actual and
future events, conditions and results may differ materially from
the estimates, beliefs, intentions and expectations expressed or
implied in the forward-looking information. Except as required
under applicable securities legislation, the Company undertakes no
obligation to publicly update or revise forward-looking
information.
The forward-looking statements contained in this news release
are made as of the date of this news release. Except as required by
law, the Company disclaims any intention and assumes no obligation
to update or revise any forward-looking statements, whether as a
result of new information, future events or otherwise.
Neither the TSX Venture Exchange nor its Regulation Service
Provider (as that term is defined in the policies of the TSX
Venture Exchange) accepts responsibility for the adequacy or
accuracy of this release.
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SOURCE Mantaro Precious Metals Corp.