REG - Great Southrn.Copper - Phase III Diamond Drilling Underway at Cerro Negro

Great Southern CopperAnnouncement

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RNS Number : 7559Y  Great Southern Copper PLC  10 September 2025

 

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.

 

 

10 September 2025

 

Great Southern Copper plc

("GSC" or the "Company")

 

Phase III Diamond Drilling Commences at Cerro Negro

 

Drilling planned to follow up on Phases I and II high-grade results and test
new targets

 

Great Southern Copper plc (LSE: GSCU), the company focused on
copper-gold-silver exploration in Chile, is pleased to announce that Phase III
diamond drilling has commenced at Cerro Negro, part of the Especularita
project.

 

Highlights:

·    Phase III diamond drilling commenced at Cerro Negro

·    Up to 2,000m drilling planned to test extensions to high-grade Cu-Ag
results in Phase I and II

·    First holes to target extensions to discovery hole DD007 which
intersected;

o  3.85m of 5.21% Cu and 318g/t Ag from 88m, and

o  5.00m of 5.59% Cu and 99.2g/t Ag from 115m, within a broader interval of

o  33.0m of 1.96% Cu and 60.6g/t Ag from 87m(1)

·   Drilling is also planned beneath shallow, leached intercepts at Lenses
3, 4 and 5, including a 22.5m leached intercept in hole DD012 which terminated
in;

o  3m @ 3.43% Cu and 164.7 g/t Ag from 24m(2)

·    Subsequent drillholes to target geochemical and geophysical targets
along trend to the south

·    The Company holds option to own 100% of the Cerro Negro prospect,
including the Mostaza mine

·    Prospect located at low elevation with excellent access to
infrastructure and mining services

 

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "We are
very excited to commence the full funded Phase III drilling at Cerro Negro,
which is the next step towards extending the deposit beyond the existing
Mostaza mine pit.

 

"Our knowledge of the deposit is significantly improved as a result of the
earlier drilling, particularly in regards to structure, geology and the
oxidation and leaching processes acting on the mineralisation near to surface.
Drilling beneath the oxidised 'leached' zone in the Lenses 2 to 5 area is a
priority for this programme and, if successful, will confirm the wider
potential of mineralisation in the area and will significantly expand the
priority areas for follow up drilling.

 

"We are also evaluating the addition of a second drilling rig, again subject
to rig availability, to ensure momentum is maintained and to accelerate
progress on the programme. We look forward to updating the market on Phase III
results as they become available."

Phase III Drilling:

 

Approximately 2,000m of diamond drilling is planned for the Phase III
programme which will focus on priority targets adjacent to and along strike
from the high-grade copper-silver mineralisation discovered at the Mostaza
Mine (Lens 2). In particular, drilling will initially focus on extending known
mineralisation beneath and along strike of earlier holes that appear to have
intersected shallow, leached portions of the lens rock which are depleted in
copper but elevated in silver suggesting that copper has been remobilised out
of the rock ("leached") during the near-surface oxidation process.

 

Later stages of Phase III drilling will target geochemical and geophysical
anomalies up to 1.5 km south along trend. This staged approach allows GSC to
build on the established high-grade system at Mostaza while systematically
testing the broader trend for additional Cu-Ag mineralised bodies.

 

Lens 2, DD007 results:

 

The mineralisation intercepted in hole CNG25-DD007, which returned 33m @ 1.96%
Cu and 60.6 g/t Ag from 87m, including the highest drill assays to date of
16.15% Cu and 646 g/t Ag(1), is interpreted to represent a possible extension
of the Lens 2 mineralisation identified in the Mostaza open pit. The
mineralised Lens comprises silica-altered breccia clasts within a
sulphide-rich matrix containing abundant chalcopyrite, bornite and pyrite. The
highest grades correlate with zones of semi-massive bornite-chalcopyrite
mineralisation. Phase III drilling will test the along-strike and down-dip
continuity of this lens, which remains open in all directions.

 

Lens 4:

 

Up to 400m south of Mostaza, mapping and drilling confirm a zone of
silicified, structurally controlled mineralisation with evidence of artisanal
workings. CNG25-DD012 intersected 22.5m of leached lens rock from surface,
transitioning sharply to sulphide mineralisation with 3m @ 3.43% Cu and 164.7
g/t Ag(2). Phase III drilling will test this sulphide mineralisation at depth
and along strike.

 

Lens 5:

 

Surface sampling at Lens 5 has returned assay grades up to 0.66% Cu and 86.3
g/t Ag from leached, oxidised outcrops of strongly silicified lens rock(3).
Geophysics highlights coincident chargeability and resistivity anomalies at
depth(4). Phase III drilling will provide the first drill test of this target.

 

Lens 2 - Mostaza mine (In-fill & Step-out):

 

In-fill drilling around the historical Mostaza open pit will refine the
geometry and grade continuity of the newly-discovered west-dipping high-grade
Cu-Ag deposit. Phase III step-out drilling will target extensions to the
mineralisation at depth and along strike.

 

Figure 1: Phase III drill plan, Cerro Negro prospect, Especularita Project,
Chile.

 

References:

1.    RNS  2553F (7 April 2025): Further "exceptional" assay results from
Mostaza

2.    RNS 5588M (12 June 2025): Cerro Negro Drilling Confirms Outstanding
Grades

3.    RNS 5192G (29 April 2025): Exploration results extends Cerro Negro

4.    RNS 9584U (12 August 2025): Geophysics Define New Cerro Negro Drill
Targets

 

 

 

 

 

Enquiries:

 

 Great Southern Copper plc             c/o BlytheRay
 Sam Garrett, Chief Executive Officer  +44 (0) 20 7138 3204

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

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

                                       GSC@blytheray.com

 

Notes for Editors:

 

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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