REG - Great Southrn.Copper - Drilling Extends Mineralisation at Cerro Negro

Great Southern CopperAnnouncement

18/02/2026 07:15

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RNS Number : 4802T  Great Southern Copper PLC  18 February 2026

 

THIS ANNOUNCEMENT CONTAINS INSIDE INFORMATION AS STIPULATED UNDER THE UK
VERSION OF THE MARKET ABUSE REGULATION NO 596/2014 WHICH IS PART OF ENGLISH
LAW BY VIRTUE OF THE EUROPEAN (WITHDRAWAL) ACT 2018, AS AMENDED.  ON
PUBLICATION OF THIS ANNOUNCEMENT VIA A REGULATORY INFORMATION SERVICE, THIS
INFORMATION IS CONSIDERED TO BE IN THE PUBLIC DOMAIN.

 

 

18 February 2026

 

Great Southern Copper plc

("GSC" or the "Company")

 

Phase III Drilling Results Extends High-Grade Cu-Ag Mineralisation at Cerro
Negro

 

Mineralised system potentially broadening with depth and along trend
significantly extends the potential global mineral tenor of the Cu-Ag
discovery at Mostaza

 

Great Southern Copper plc (LSE: GSCU), the company focused on
copper-gold-silver exploration in Chile, is pleased to announce the latest
results from its Phase III drilling campaign at the Company's Cerro Negro
prospect, part of the Especularita project.

 

Highlights:

·      Assay results for holes DD033 and DD036 confirm potential for a
multiple lens system, with grades up to 3.29 % Cu and 186 g/t Ag, including
significant intervals;

 

o  DD036: 19.2m @ 1.02% Cu and 58.4 g/t Ag from 191m, including

§  3.0m @ 2.11% Cu and 119.9 g/t Ag from 199m, within a broader interval of

§ 39.6m @ 0.57% Cu and 34.7 g/t Ag from 170.6m

 

·      Results suggest significant potential for the mineralised system
to be broadening at depth with high-grade lenses occurring within a wider
lower-grade envelope of mineralisation

 

·      Anomalous Pb-Zn mineralisation including low-grade Cu-Ag suggests
potential for a zoned mineral system and could extend the potential deposit
width to over 80 metres thick.

 

·    Exploration drilling at Lens 5 (DD034) discovered sulphide Cu-Ag
mineralisation at depth beneath surface leached oxide mineralisation
consistent with both Lens 2 type high-grade Cu-Ag and mineralisation
identified in outcrop at Monolith 400m to the southeast, including

 

o  DD034: 5.0m @ 0.48% Cu and 45.22 g/t Ag from 62m

 

·    DD034 result significantly expands the copper endowment potential of
the Cu-Ag discovery within the near-Mostaza environment

 

·    Planning for Phase IV resource and exploration drilling is in
progress

 

·    GSC holds option to 100% of the Cerro Negro project including the
Mostaza mine

 

·    Project located at low elevation with excellent access to
mining-related infrastructure

 

 

 

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "The
confirmation of deeper high-grade mineralisation in DD033 and DD036, marks an
important step forward in our understanding of the Mostaza system where we are
now consistently intersecting multiple stacked high-grade copper-silver lenses
developed within a broader mineralised envelope.

 

"Importantly, the dacite-hosted crackle-vein mineralisation intersected at
depth in holes DD033 and DD036, and also now confirmed in hole DD034 at Lens
5, is consistent with the mineralisation mapped and sampled in outcrop at the
Monolith Zone some 400m to the southeast - indicating potential for a broader
bulk-tonnage copper-silver target that complements the expanding high-grade
lens-style mineralisation in Lens 2.

 

"Cerro Negro is increasingly demonstrating the characteristics of a scalable
copper-silver system with both discrete high-grade lenses within wider
lower-grade envelopes, and we continue to refine the geological model to guide
the next phase of drilling and prioritise high-impact targets along trend and
at depth.

 

"Further Phase III drill results are awaited, including reconnaissance scout
RC results, as well as results for metallurgical test work of the high-grade
copper-silver ore. Planning is now at an advanced stage for Phase IV drilling
at Cerro Negro which we hope will build on this momentum and further define
the broader-scale potential of the system."

 

Phase III Drilling:

 

Phase III drilling was completed in January 2026, comprising 17 diamond
drillholes for 2,923 metres and six RC holes for 1,032 metres(1). The Phase
III programme was designed to continue advancing the high-grade copper-silver
discovery at Mostaza by:

·    Infill and step-out drilling at the Mostaza deposit (Lens 2 and
adjacent lenses) to refine the geometry and continuity of the high-grade Cu-Ag
mineralisation.

·    Testing extensions of known mineralisation at nearby targets,
including Lenses 3, 4 and 5, where previous drilling intersected strongly
silicified but copper-leached lens rocks indicative of underlying sulphide
mineralisation.

·    First-pass scout RC drill testing of geochemical and geophysical
anomalies along the Mostaza Fault Zone to the south of the historic Mostaza
mine.

 

Figure 1: Cerro Negro Project. Plan view showing drillhole locations and
targets. Drillholes in this release are labelled.

 

 

Mostaza Lens 2 diamond drilling:

 

CNG25-DD033:  Drillhole DD033 (see Figure 1 and 3) was drilled as a step-out,
approximately 60m down-plunge from CNG25-DD019, which intersected 7.2m @ 1.47%
Cu and 122.3 g/t Ag from 99.9m(2).

The hole successfully extended the mineralised system to depth where it
intersected multiple "stacked" lenses, or zones, of higher-grade
mineralisation within broader envelopes of altered and mineralised material,
suggesting that the system may be thickening at depth.

 

In the hangingwall to the high-grade Cu-Ag mineralisation DD033 first
intersected a zone of sulphide-rich breccia (108-129.2 m) comprising intense
silicification with abundant pyrite-galena-sphalerite mineralisation. This
breccia is equivalent to that previously reported in DD031(3) and returned
anomalous Cu-Ag assay grades with highly anomalous Pb-Zn grades up to 0.87% Pb
and 1.09% Zn.

 

·    DD033:  21.2m @ 0.41% Zn, 0.16% Pb with 0.01% Cu, 3.5g/t Ag, from
108m, including

o  4m @ 0.77% Zn, 0.23 % Pb with 0.02 % Cu, 5.5 g/t Ag, from 117m

 

With increasing depth the hole then intersected a broad zone of
chalcocite-rich, clay-altered Cu-Ag mineralisation, comprising pervasive
crackle veinlet and disseminated chalcocite developed in a pervasively clay
altered dacite unit. Within this unit, two higher-grade zones are observed; an
upper zone developed near the hanging wall contact of the dacite, and a lower
zone occurring near the footwall contact.

 

·    Upper hangingwall zone:       8m @ 0.38% Cu and 28.6 g/t Ag
from 163m, and

 

·    Lower footwall zone:          2.9m @ 1.01% Cu and 79.7 g/t Ag
from 191m (hole ending in mineralisation)

 

Drillhole DD033 was terminated prematurely at 197.9m due to mechanical issues
while still within mineralised dacite. Therefore, a twin hole DD036, was
drilled a few metres away to test the full thickness and continuity of this
deeper mineralisation with the following results;

 

CNG25-DD036:  Drillhole DD036 was drilled as a twin to DD033 to confirm and
extend the mineralisation intersected at the bottom of hole DD033 (see Figure
1 and 3). DD036 intersected the same sequence, including the hangingwall
sulphide breccia zone with intense silicification and pyrite-galena-sphalerite
mineralisation between 100-131.15m (see Figure 2), with grades up to 0.24% Pb
and 0.93% Zn from 111.4m, as well as the deeper broad zone of dacite-hosted
chalcocite-rich mineralisation with grades up to 3.29% Cu and 186 g/t Ag (see
Figure 2) including;

 

·    Sulphide breccia zone:   19.75m @ 0.49% Zn, 0.12% Pb, 0.01% Cu,
2.8g/t Ag, from 111.4m

 

·    Upper hangingwall zone:   2.0m @ 0.55% Cu and 58.85 g/t Ag from
172m

 

·    Lower footwall zone:       19.2m @ 1.02% Cu and 58.4 g/t Ag from
191m, including

·        3.0m @ 2.11% Cu and 119.9 g/t Ag from 199m

 

The composite grade interval for the mineralised dacite (higher-grade
hangingwall, lower grade core, higher-grade footwall) in DD036 comprises;

 

 39.6m @ 0.57% Cu and 34.7 g/t Ag from 170.6m

 

 

Figure 2. Photos showing mineralisation styles in drillhole DD036. Left hand
photographs show the upper sulphide breccia Pb-Zn mineralisation zone, the
right-hand photographs show the deeper chalcocite-rich clay-altered dacite
breccia zone with quartz crackle-vein hosted and disseminated chalcocite.

 

These results for holes DD033 and 036 confirm the continuity and thickness of
the deeper Lens 2 mineralisation highlighting the development of multiple
high-grade Cu-Ag mineralised lenses, or zones, within a broader anomalous
Cu-Ag envelope which appears to be thickening with depth, although this may be
a structural or lithological effect.

 

To date evidence from core logging suggests that mineralisation styles within
the Mostaza deposit may vary according to host rock lithology. The dacite
(dyke?) lithology is now recognised as a favourable host where its brittle
character appears to have enhanced fracture permeability and mineralising
fluid flow along its contact margins.

 

Further drilling at depth and along strike is now required to better define
and understand both the nature and extent of the broadening scale of the Cu-Ag
mineralisation as well as the relationship of the Cu-Ag mineralisation to the
breccia-hosted Pb-Zn mineralisation. At present the Pb-Zn rich breccia is
interpreted as a later event to the Cu-Ag crackle-breccia mineralisation which
supports the concept of an evolving metal system at the upper levels of a
porphyry-high sulphidation epithermal system.

 

Figure 3. Interpreted geological cross section showing DD033 and DD036
results.

 

Cautionary Note: In Figure 3, the text box for Hole DD020 is incorrectly
labelled as DD019. The results for DD020 are as follows: 8.4m @ 1.49% Cu and
121.4 g/t Ag from 80.1m, including; 3.2m @ 2.63% Cu and 239.7 g/t Ag from
80.1m.

 

 

 

Lens 5 scout diamond drilling:

 

CNG25-DD034:  Drillhole DD034 represents the first exploration drill test of
Lens 5 (see Figure 1 and 5) where surface sampling previously returned assay
grades up to 0.66% Cu and 86.3 g/t Ag from oxidised and leached lens material.

 

The hole intersected a sequence of dacite units interbedded with volcanic
breccias and tuffs. From surface to approximately 60m depth, copper oxides are
hosted within quartz veinlets developed in dacite with the hole reporting a
broad zone of oxidised and leached Cu-Ag zone including;

 

·    58.1m @ 0.10% Cu and 7.14 g/t Ag from 0.9m

 

Below 60m depth, DD034 transitioned into sulphide chalcocite mineralisation
associated with quartz crackle veinlets and disseminations within dacite units
with assay results including;

 

·    5.0m @ 0.48% Cu and 45.22 g/t Ag from 62m

 

Mineralisation is highly anomalous in Cu-Ag-Sb and is consistent in style with
both the dacite-hosted crackle vein mineralisation observed in holes DD033 and
DD036 below the Mostaza mine 200m to the north, as well as the high-grade
Cu-Ag mineralisation observed in outcrop at the Monolith zone approx. 200m to
the southeast. Surface sampling at the Monolith target outlined a zone up to
50m wide returning up to 271 g/t Ag and 2.05% Cu, averaging 35.4 g/t Ag and
0.31% Cu across 48 samples, despite surface leaching(4).

 

This result has significant exploration implications where the mineralisation
style, characterised by brittle dacitic hosts, quartz crackle veining and
disseminated chalcocite, provides evidence of the potential for a broader
bulk-tonnage Cu-Ag target at Cerro Negro. This emerging target complements the
high-grade lens-style mineralisation delineated to date at Mostaza and
provides potential to significantly expand the overall scale and inventory of
the mineralised system at Cerro Negro.

 

CNG25-DD035: Drillhole DD035 was drilled as a step-out west of DD034 (see
Figure 1 and 5) and intersected dacite units like those in DD034 but without
significant quartz veining or associated mineralisation. The hole was lost at
53.4m due to technical problems. While no significant mineralisation was
intersected, the hole provides useful constraints on the geometry of Lens 5
and will inform ongoing structural reinterpretation and targeting for
follow-up drilling.

 

 

Figure 4. Photos showing mineralisation styles in drillhole DD034 (Lens 5).
The left photograph shows oxidized mineralisation with grades of 0.18% Cu due
to near-surface leaching. The right photograph shows texturally similar
unoxidized mineralisation (sulphide) with grades of 0.4% and 0.58% Cu. Note
how the Ag grades change less, due to Ag minerals being less affected by the
near-surface leaching.

 

Lens 2 extension:

 

CNG25-DD027:  Drillhole DD027 (see Figure 1 and 5) was drilled as a scissor
to DD007 and intersected a narrow interval of similar silica-altered
pyrite-chalcopyrite breccia returning 0.83m @ 2.54% Cu and 5.48 g/t Ag.

 

Although the mineralised interval in DD027 is significantly narrower than the
33 m @ 1.96% Cu and 60.6 g/t Ag intersected in DD007(5), the style of
alteration and sulphide assemblage confirms that drilling intersected the same
mineralised structural corridor.

 

The result is interpreted to reflect localised thinning or structural offset
of the mineralised lens, which is consistent with observations across the
Mostaza system where mineralisation occurs as discrete, variably developed
lenses that "pinch and swell" along the broader structurally controlled trend.

 

Lens 4:

 

CNG25-DD028:  Drillhole DD028, located approximately 400 metres south of the
Mostaza Mine in the Lens 4 area, was drilled beneath the mapped Lens 4
outcrop. The hole intersected a 7.2m wide zone of intensely silicified and
oxidised (leached) breccia from 34.15m, returning anomalous copper up to 0.12%
Cu and silver up to 6.11 g/t Ag.

 

The breccia contains boxwork textures after primary sulphides and abundant
iron oxides indicating intense near-surface leaching resulting in anomalous
but subdued grades, consistent with observations from adjacent drillholes in
the Lens 4 area. Deeper drilling will be required to intersect the sulphide
zone at Lens 4.

 

Figure 5. Plan map showing exploration drillhole locations and DD034 &
DD027 results

 

Next steps:

Drilling results are still pending for diamond and RC scout holes CNG25 037 -
046. Although final drill assay results are required to finalise plans for
Phase IV drilling at Cerro Negro, work has commenced in preparation for the
next phase of drilling. Geophysics surveys and drilling of the Monolith Cu-Ag
target are likely to be prioritised together with resource drilling of the
Mostaza deposit.

 

Results for metallurgical test work are also anticipated.

 

  References:

1.    RNS 4907O (13(th) Jan 2026): Phase III Drilling Completed at Cerro
Negro

2.    RNS 6908V (18(th) August 2025): Phase II Drilling Results Extends
Mostaza Deposit

3.    RNS 1749L (11(th) Dec 2025): Drilling extends mineralisation at Cerro
Negro

4.    RNS 1932D (14(th) October 2025): High Grade Ag-Cu Samples Expands
Monolith Target

5.    RNS 8896D (7(th) April 2025): Further "exceptional" assay results
from Mostaza

 

 

Enquiries:

 

 Great Southern Copper plc               https://gscplc.com/link/e9Q4Be (https://gscplc.com/link/e9Q4Be)
 Sam Garrett, Chief Executive Officer    +44 (0) 20 7138 3204

 SI Capital Limited
 Nick Emerson                            +44 (0) 1483 413500

 BlytheRay
 Tim Blythe / Megan Ray / Said Izagaren  +44 (0) 20 7138 3204

                                         GSC@blytheray.com

 

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About Great Southern Copper

 

Great Southern Copper PLC is a UK-listed mineral exploration company focused
on the discovery of copper-gold-silver deposits in Chile. The Company has the
option to acquire mining rights to 100% of Especularita project in the
under-explored coastal belt of Chile that is prospective for large scale
copper-gold-silver deposits. Chile is a globally significant mining
jurisdiction being the world's largest producer and exporter of copper.

 

The Especularita Project is located in the coastal metallogenic belt of Chile
which hosts significant copper mines and deposits, including Teck's Carmen de
Andacollo copper mine, and boasts excellent access to infrastructure such as
roads, power and ports. Significant historical small-scale and artisanal
workings for both copper and gold are readily evident in the exploration
project area. The coastal belt offers deposit type optionality for copper
including porphyry and IOCG style deposits as well as newly recognised
intrusive-related copper and gold deposits.

 

Great Southern Copper is strategically positioned to support the global market
for copper - a critical battery metal in the clean energy transition around
the world. The Company is actively engaged in exploration and evaluation work
programmes targeting both large tonnage, low to medium grade Cu-Au as well as
high-grade Cu-Ag-Au deposits.

 

Further information on the Company is available on the Company's website:
https://gscplc.com (https://gscplc.com)

 

Competent Person Statement

 

The information in this announcement that relates to exploration results is
based on and fairly represents information reviewed or compiled by Mr Sam
Garrett, a Competent Person who is a Member of the Australian Institute of
Geoscientists and a Fellow of the Society of Economic Geologists. Mr Garrett
is the CEO and a shareholder of Great Southern Copper PLC. Mr Garrett has
sufficient experience that is relevant to the styles of mineralisation and
types of deposit under consideration and to the activity being undertaken to
qualify as a Competent Person as defined in the 2012 Edition of the
"Australasian Code for Reporting of Exploration Results, Mineral Resources and
Ore Reserves". Mr Garrett has provided his prior written consent to the
inclusion in this announcement of the matters based on information in the form
and context in which it appears.

 

This announcement includes information that relates to Exploration Results
prepared and first disclosed under the JORC Code (2012) and extracted from the
Company's previous LSE announcements as noted, and the Company's Prospectus
dated 20 December 2021. Copies of these announcements are available from the
LSE Announcements page of the Company's website: www.gscplc.com
(http://www.gscplc.com) .

 

The Company confirms that it is not aware of any new information or data that
materially affects the information included within the Prospectus dated 20
December 2021.

 

Forward Looking and Cautionary Statements

Some statements in this announcement regarding estimates or future events are
forward-looking statements. They include indications of, and guidance on,
future earnings, cash flow, costs and financial performance. Forward-looking
statements include, but are not limited to, statements preceded by words such
as "planned", "expected", "projected", "estimated", "may", "scheduled",
"intends", "anticipates", "believes", "potential", "predict", "foresee",
"proposed", "aim", "target", "opportunity", "could", "nominal", "conceptual"
and similar expressions. Forward-looking statements, opinions and estimates
included in this report are based on assumptions and contingencies which are
subject to change without notice, as are statements about market and industry
trends, which are based on interpretations of current market conditions.
Forward-looking statements are provided as a general guide only and should not
be relied on as a guarantee of future performance. Forward-looking statements
may be affected by a range of variables that could cause actual results to
differ from estimated or anticipated results and may cause the Company's
actual performance and financial results in future periods to materially
differ from any projections of future performance or results expressed or
implied by such forward-looking statements. So, there can be no assurance that
actual outcomes will not materially differ from these forward-looking
statements.

 

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