Eloro Resources Ltd. (TSX: ELO; OTCQX: ELRRF; FSE:
P2QM) (“Eloro”, or the “Company”) is pleased to provide an
update on its ongoing preliminary metallurgical testwork program
for the Iska Iska silver-tin polymetallic project (the “Project”)
in the Potosi Department, southern Bolivia. The ongoing work,
including flowsheet development testwork and mineralogical
characterization, is being carried out by Blue Coast Research Ltd.
(“Blue Coast” or “BCR”) based in Parksville, British Columbia, and
Mineral Concentration Laboratory of the National Faculty of
Engineering from the Technical University of Oruro (“UTO”),
Bolivia. The objective of the coordinated work programs is to
develop a geo-metallurgical understanding of the mineralized
domains and to obtain preliminary metallurgical recovery estimates
for the main valuable constituents of the mineralized material
currently identified at the Project.
Tom Larsen, CEO of Eloro, commented: “The Iska
Iska silver-tin polymetallic deposit is a remarkably extensive
system with multiple potential ore types which require more
metallurgical work than originally anticipated, especially for tin,
as outlined in this press release. The preliminary metallurgical
recovery estimates are a prerequisite for the release of the
Project’s maiden mineral resource (“MRE”). Consequently, the
release of the MRE has been delayed until this metallurgical work,
which is in progress, has been completed. All other work required
for the MRE has been largely completed by Micon International
Limited, including much of the reporting.”
Mr. Larsen continued, “I am very pleased to
announce the appointment of Mr. Mike Hallewell, B.Sc., F.I.M.M.M.,
F.S.A.I.M.M., F.M.E.S., C.Eng,, an internationally recognized
expert on tin metallurgy, as Senior Strategic Metallurgist for
Eloro. Going forward Mike will be working closely with our
metallurgical consultants to optimize our tin recovery and with our
geological team to define geo-metallurgical domains for mineral
resource definition and future potential production.”
Geometallurgical Domains Iska
Iska
The Iska Iska silver-tin polymetallic deposit
has many characteristics of the typical Bolivian tin deposits.
Extensive tin mineralization likely developed deep in the earth’s
crust with cassiterite forming at high temperatures from 350C to
500C. This major initial stage of magmatism drove the formation of
the major stratovolcano at Iska Iska some 18 to 15 million years
ago. Subsequently, when the magma chamber was depleted, the volcano
collapsed, forming a classic collapsed caldera. Resurgence of the
collapsed volcano included the intrusion of the Iska Iska porphyry,
followed by dacitic domes and brecciation such as the Santa Barbara
breccia pipe. These events were closely associated with widespread
porphyry-epithermal Ag-Zn-Pb mineralization, which partially
overprinted the pre-existing tin mineralization.
Figure 1 shows the distribution of Sn:Cu at Iska
Iska. The Sn:Cu ratio is an indicator of the presence of oxide tin
(cassiterite – shown in green, within the core) vs sulphide tin
(stannite – shown in red, making up the periphery). Tin is found
predominantly on the west side of the Santa Barbara deposit. Deep
drilling and magnetic modelling indicate that the tin porphyry is
present beneath the Iska Iska Porphyry. As previously reported, the
signature of the overall tin porphyry system based on magnetic data
likely extends for some 5 km by 3 km which includes the Casiterita
area to the southwest, which is currently being drill-tested (see
Eloro’s press release dated February 14, 2023). The longitudinal
section in Figure 1 covers a strike length of 2.5km.
Figure 1: Longitudinal Section Showing
Distribution of Sn/Cu ratio (Looking West-southwest). The core of
the Iska Iska deposit contains higher Sn and low Cu whereas the low
Sn/Cu ratio is predominantly at the top and on the margins of the
tin mineralization.
Metallurgical Testwork
The overall metallurgical testwork /
mineralogical characterization program has evolved into the
development of several potential flowsheets to best fit the
extensive mineralization identified within the Project area. The
main metallurgical studies in the ongoing development program
are:
1) Recovery of lead,
zinc and silver from polymetallic sulphide mineralization; and
2) Recovery of tin
from cassiterite-rich Iska-Iska mineralization and the adjoining
Casiterita property to the south-southwest of Iska Iska.
Future work will include recovery of gold and
copper, where they are found enriched within the system.
The geo-metallurgical program is being directed
by Mr. Mike Hallewell, C.Eng., a senior mineral processing
consultant based in Cornwall, England, who has extensive specialist
knowledge in the recovery of tin at mining operations and
exploration projects worldwide, and Richard Gowans, P.Eng.,
Principal Metallurgist for Micon International Limited, an
independent Qualified Person as defined under NI 43-101. The
mineralogical characterization testwork is being managed by Nichola
McKay P. Geo., MBA, an experienced Professional Geoscientist who
specializes in the development of geo-metallurgical programs.
Mineralogical and Geometallurgical
Characterization
Mineralogical testing of the Iska Iska resource
consists of three main campaigns:
1) On-site downhole
hyperspectral analysis with high resolution core imaging,
2) QemSCAN mapping of
polished thin sections selected from drill core across the resource
representing key lithologies and mineralization types, with
supporting X-ray diffraction and microprobe analysis, and
3) QemSCAN analysis
of ground metallurgical test feeds and selected test products.
A group of geometallurgical variability samples
are being tested using a standardized testing protocol that will
link metallurgical behaviour with mineralogy for samples from
different zones in the resource.
In parallel to the laboratory-based geomet work,
all QemSCAN data is being used as a training set for calibration /
correlation with the hyperspectral program, with the objective of
identifying key markers of tin mineral zonation that can be
populated through the resource.
Lead-Zinc-Silver Flotation
The initial metallurgical testwork, using
composite samples of sulphide mineralization from the Santa Barbara
polymetallic zone, comprised the development of a preliminary
flotation flowsheet to maximize lead, zinc and precious metals into
saleable concentrates. The results of this initial work were
presented in the Company’s press release dated June 13, 2022. These
preliminary results indicated good lead, zinc and silver recoveries
using conventional flotation technology.
The estimated recoveries based on preliminary
locked cycle flotation tests are 79.6% lead and 55.8% silver into a
lead concentrate, and 87.0% zinc and 32.0% silver into a zinc
concentrate (total silver recovery of 87.8%). These recoveries are
based on preliminary scoping level bench scale tests completed by
BCR in 2022 using two composite samples of polymetallic
mineralization. These tests were not optimized and improved
performance in terms of higher recoveries would be expected with
further mineralogical and metallurgical studies.
The next phase of Pb-Zn-Ag flowsheet development
testwork, following completion of the inaugural mineral resource
estimate, is to optimize the preliminary flowsheet, with integrated
mineralogy/metallurgy studies using a variety of samples
representing a range of lithologies and ore-types, and to undertake
silver deportment studies. The deportment and recovery of potential
by-products will also be investigated.
Tin Metallurgy
The recovery of cassiterite is usually conducted
using a mixture of gravity and tin flotation with removal of
sulphide minerals either prior to these processes and/or as part of
concentrate clean-up. Coarser cassiterite grain sizes tend to be
more amenable to gravity concentration, whereas finer cassiterite
particles are recovered by tin flotation down to ~6 microns, which
is normally discarded since it is too fine for current
beneficiation technologies. The different Iska Iska ore types are
currently being characterised to better understand the cassiterite
grain size and cassiterite associations with other minerals as a
function of ore type so as to better understand and estimate the
level of tin recovery in terms of geological space. Stannite is
present, but at this time will be assumed to deport as a tin loss
to sulphides.
Initial tin deportment studies undertaken on
various samples of mineralization obtained from the Project
exploitation drilling campaign have suggested the occurrence of
various forms of tin mineralization within the extensive
mineralized domains currently identified at the Project. The tin
mineralogy and physical competence is linked to geological
attributes. The styles of tin mineralization identified at the
Project can be characterized as follows:
Type A - High grade coarse-grained cassiterite
(tin oxide).This style of tin mineralization is the easiest to
process due to the coarser liberated tin mineralization that is
amenable to conventional mineral processing technologies, such as
gravity separation and flotation. This type of tin mineralization
is expected to predominate deeper in the deposit and also at
Casiterita where artisanal miners have previously produced high
grade (~50%) tin concentrates from cassiterite-quartz veins (see
Eloro’s press release November 22, 2022).
Type B – High/medium grade fine-grained
cassiterite. Tin-rich sulphide mineralization is typically found
below and west of the eastern Santa Barbara area Pb-Zn-Ag rich
polymetallic sulphide zones. This style of tin mineralization
requires fine to very fine grinding, sulphide removal via
flotation, tin flotation and fine particle gravity separation.
Type C – Medium grade fine-grained cassiterite
with significant wood tin (low temperature form of cassiterite).
Tin of this type occurs predominantly in areas with moderate to
strong oxidation which has leached sulphides and redeposited the
tin as wood tin. High grade Type A tin also may exist in this zone.
This form of tin has similar metallurgy to Type B, but good
recoveries can be obtained if Type A mineralization is present.
Type D - Medium grade stannite (copper-tin-iron
sulphide mineral). Stannite is not recoverable using conventional
tin mineral processing technology. Predominant stannite tin
mineralization tends to occur at the top and peripheral to the core
of the tin mineralization. Where stannite mineralization has been
oxidized and leached, the mineralization type becomes more Type B
or C depending on intensity of oxidation.
Tin metallurgical studies completed to date
include preliminary tests on two composite samples and the
development of a standard test protocol to assess the amenability
of tin mineralized samples to obtain a tin concentrate of
acceptable grade.
A high-grade tin composite made up of crushed
assay reject samples from exploration drilling was prepared and
used for preliminary metallurgical tests at UTO in Bolivia. The 67
kg composite sample, considered Type A tin (see description above),
comprised mineralized samples from drill holes DSB-32 (from 62.3 m
to 76.7 m) and DSB-33 (from 356.7 to 365.6 m). The sample was from
an oxidized zone and had an average tin grade of 1.68% Sn.
Scoping tests completed on this sample included
gravity separation tests using a shaking table and centrifugal
concentrator, and cassiterite flotation tests. Although not
optimized, the gravity only tests using both tables and centrifugal
concentrator resulted in a 39% tin grade concentrate with about 60%
recovery. Tests using a table only produced a concentrate
containing about 50% Sn although recovery was only around 30%.
Flotation tests at a non-optimum grind size resulted in about 50%
tin recovery into a 6% Sn concentrate. These preliminary test
results suggest a direct tin smelter feed concentrate can be
produced from this type of tin mineralization with about a 60%
recovery. The estimated tin recovery into a lower grade concentrate
suitable for feeding a tin-fuming process is about 75%.
Recent development tests by BCR using a
composite sample of crushed assay rejects from drill hole DSBU-03
containing 0.52% Sn, produced a tin-fuming feed concentrate with a
tin recovery of about 28%. Mineral characterization of this sample
via optical microscopy suggests that the tin mineralization
comprises mainly fine-grained cassiterite with minor fine wood tin
(Types B and C).
The preliminary flowsheet used by BCR comprised
sulphide flotation, which rejected approximately 92% of the
sulphide sulphur with less than 15% tin losses, gravity roughing
using a centrifugal concentrator and upgrading of sized rougher
product using a laboratory supper-panner, cassiterite flotation
with upgrading of sized re-ground flotation rougher product using a
laboratory supper-panner.
Following a detailed review of the test results
and testing procedure, a standard tin amenability test protocol has
been defined. This flowsheet will be used over the coming weeks by
BCR to test a variety of samples. Samples have been selected to
include a range of tin grades and types of tin mineralization.
Copper-Gold and Other Valuable
By-Products
Drilling has shown zones of mineralization with
gold grades above 1 g/t as well as zones with elevated levels of
copper. A metallurgical-mineralogical characterization program is
being planned to assess the potential for recovering these valuable
metals.
The future geo-metallurgical program also will
include studies to understand the deportment of other potential
metals such as bismuth and indium.
Qualified Person
Richard Gowans, P.Eng., Principal Metallurgist
for Micon International Limited, is an independent Qualified Person
as defined under NI 43-101. Mr. Gowans. Has reviewed and approved
the technical content of this news release.
Dr. Osvaldo Arce, P. Geo., General Manager of
Eloro’s Bolivian subsidiary, Minera Tupiza S.R.L., and a Qualified
Person in the context of NI 43-101, supervised all exploration work
at Iska Iska. Dr. Bill Pearson, P.Geo., Executive Vice President
Exploration Eloro, and who has more than 45 years of worldwide
mining exploration experience including extensive work in South
America, manages the overall technical program working closely with
Dr. Osvaldo Arce, P.Geo., Manager of Minera Tupiza. Dr. Quinton
Hennigh, P.Geo., Senior Technical Advisor to Eloro and Independent
Technical Advisor, Mr. Charley Murahwi P. Geo., FAusIMM of Micon
International Limited are regularly consulted on technical aspects
of the project.
Eloro is utilizing both ALS and AHK for drill
core analysis, both of whom are major international accredited
laboratories. Drill samples sent to ALS are prepared in both
ALS Bolivia Ltda’s preparation facility in Oruro, Bolivia and
the preparation facility operated by AHK in Tupiza with pulps sent
to the main ALS Global laboratory in Lima for analysis. More
recently Eloro has had ALS send pulps to their laboratory at Galway
in Ireland. Eloro employs an industry standard QA/QC program with
standards, blanks and duplicates inserted into each batch of
samples analyzed with selected check samples sent to a separate
accredited laboratory.
Drill core samples sent to AHK Laboratories are
prepared in a preparation facility installed and managed by AHK in
Tupiza with pulps sent to the AHK laboratory in Lima, Peru. Au and
Sn analysis on these samples is done by ALS Bolivia Ltda in Lima.
Check samples between ALS and AHK are regularly done as a QA/QC
check. AHK is following the same analytical protocols used as with
ALS and with the same QA/QC protocols. Turnaround time continues to
improve, as laboratories return to more normal staffing levels.
About Iska Iska
Iska Iska silver-tin polymetallic project is a
road accessible, royalty-free property, wholly controlled by the
Title Holder, Empresa Minera Villegas S.R.L. and is located 48 km
north of Tupiza city, in the Sud Chichas Province of the Department
of Potosi in southern Bolivia. Through its Bolivian subsidiary,
Eloro has an option to earn a 100% interest in Iska Iska.
Iska Iska is a major silver-tin polymetallic
porphyry-epithermal complex associated with a Miocene possibly
collapsed/resurgent caldera, emplaced on Ordovician age rocks with
major breccia pipes, dacitic domes and hydrothermal breccias. The
caldera is 1.6km by 1.8km in dimension with a vertical extent of at
least 1km. Mineralization age is similar to Cerro Rico de Potosí
and other major deposits such as San Vicente, Chorolque, Tasna and
Tatasi located in the same geological trend.
Eloro began underground diamond drilling from
the Huayra Kasa underground workings at Iska Iska on September 13,
2020. On November 18, 2020, Eloro announced the discovery of a
significant breccia pipe with extensive silver polymetallic
mineralization just east of the Huayra Kasa underground workings
and a high-grade gold-bismuth zone in the underground workings. On
November 24, 2020, Eloro announced the discovery of the SBBP
approximately 150m southwest of the Huayra Kasa underground
workings.
Subsequently, on January 26, 2021, Eloro
announced significant results from the first drilling at the SBBP
including the discovery hole DHK-15 which returned 129.60 g Ag eq/t
over 257.5m (29.53g Ag/t, 0.078g Au/t, 1.45%Zn, 0.59%Pb, 0.080%Cu,
0.056%Sn, 0.0022%In and 0.0064% Bi from 0.0m to 257.5m. Subsequent
drilling has confirmed significant values of Ag-Sn polymetallic
mineralization in the SBBP and the adjacent CBP. A substantive
mineralized envelope which is open along strike and down-dip
extends around both major breccia pipes. Continuous channel
sampling of the Santa Barbara Adit located to the east of SBBP
returned 442 g Ag eq/t (164.96 g Ag/t, 0.46%Sn, 3.46% Pb and 0.14%
Cu) over 166m including 1,092 g Ag eq/t (446 g Ag/t, 9.03% Pb and
1.16% Sn) over 56.19m. The west end of the adit intersects the end
of the SBBP.
Since the initial discovery hole, Eloro has
released a number of significant drill results in the SBBP and the
surrounding mineralized envelope which along with geophysical data
has defined an extensive target zone. In its September 20, 2022
press release, the Company reported that new downhole geophysical
data have significantly extended the strike length of the
high-grade zone at Santa Barbara a further 250m along strike to the
south-southeast from existing drilling. The 3D inverse magnetic
model which correlates very strongly with the conductive zone
suggested that the high-grade feeder zone may extend across the
entire caldera for as much as a further 1 km along strike for a
total potential strike length of at least 2 km. As reported, the
definition drill program was modified to sectionally drill this
potential extension to define a major open pittable deposit in the
valley of the caldera. As a result, the estimated completion date
for the maiden National Instrument 43-101 mineral resource was
pushed back to the end of Q1 2023.
The Company completed 84,495m in 122 drill holes
for the definition drill program in the Santa Barbara target area
as announced on November 27, 2022.
On November 22, 2022, Eloro announced the
acquisition of the Mina Casiterita and Mina Hoyada properties
covering 14.75 km2 southwest and west of Iska Iska. These
properties connect with the TUP-3 and TUP-6 claims previously
staked by Eloro. Eloro has also staked additional land in the area.
Following the acquisition, the total land package in the Iska Iska
area to be controlled by Eloro will total 1,935 quadrants covering
483.75 km2.
Artisanal mining in the 1960’s identified high
grade tin (Sn) veins on the Mina Casiterita property that are
hosted in an intrusive dacite. Production from 1962 to 1964 is
reported by the Departamento Nacional de Geología in Bolivia to be
69.85 tonnes grading 50.60% Sn.
Magnetic surveys recently completed by Eloro
have outlined an extensive, near surface, magnetic intrusive body
on the Mina Casiterita property immediately southwest of Iska Iska.
This intrusive hosts the previously mined high-grade tin veins and
is very likely the continuation of the porphyry tin intrusion
projected to be below the epithermal Ag-Sn-Zn-Pb mineralization at
Iska Iska.
The Porco adit from which previously reported
channel sampling returned 103m grading 521 g Ag eq/t (including g
117g Ag/t, 1.44 g Au/t, 0.54% Cu and 0.66% Sn) in altered basement
sediments, is located near the northeast part of the magnetic
anomaly, attesting to the potential strength and high-grade nature
of the mineralized system in the area.
Drilling is planned in the Porco area and on
Mina Casiterita commencing in February 2023 with geological
mapping, sampling and geophysical surveys now in progress on the
full land package across the Iska Iska region.
About Eloro Resources Ltd.
Eloro is an exploration and mine development
company with a portfolio of gold and base-metal properties in
Bolivia, Peru and Quebec. Through its Bolivian subsidiary, Eloro
has an option to acquire a 100% interest in the highly prospective
Iska Iska Property, which can be classified as a polymetallic
epithermal-porphyry complex, a significant mineral deposit type in
the Potosi Department, in southern Bolivia. A recent NI 43-101
Technical Report on Iska Iska, which was completed by Micon
International Limited, is available on Eloro’s website and under
its filings on SEDAR. Iska Iska is a road-accessible, royalty-free
property. Eloro also owns an 82% interest in the La Victoria
Gold/Silver Project, located in the North-Central Mineral Belt of
Peru some 50 km south of Barrick’s Lagunas Norte Gold Mine and Pan
American Silver’s La Arena Gold Mine.
For further information please contact
either Thomas G. Larsen, Chairman and CEO or Jorge Estepa,
Vice-President at (416) 868-9168.
Information in this news release may contain
forward-looking information. Statements containing forward looking
information express, as at the date of this news release, the
Company’s plans, estimates, forecasts, projections, expectations,
or beliefs as to future events or results and are believed to be
reasonable based on information currently available to the Company.
There can be no assurance that forward-looking statements will
prove to be accurate. Actual results and future events could differ
materially from those anticipated in such statements. Readers
should not place undue reliance on forward-looking information.
Neither the TSX nor its Regulation Services
Provider (as that term is defined in the policies of the TSX)
accepts responsibility for the adequacy or accuracy of this
release.
A photo accompanying this announcement is
available at
https://www.globenewswire.com/NewsRoom/AttachmentNg/b2e3ec73-2187-4597-a77e-c10d10570636
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