REG - Great Southrn.Copper - Third Drill Rig Mobilising to Cerro Negro

Great Southern CopperAnnouncement

Tue 07:20

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RNS Number : 0337H  Great Southern Copper PLC  11 November 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.

 

 

11 November 2025

 

Great Southern Copper plc

("GSC" or the "Company")

 

Third Drill Rig Mobilising to Cerro Negro to Commence Scout RC Drilling

 

Drilling to test Mostaza Fault Zone and hanging wall mineralisation where new
rock chip samples grade up to 2.56 % Cu and 293 g/t Ag

 

Great Southern Copper plc (LSE: GSCU), the company focused on
copper-gold-silver exploration in Chile, is pleased to announce that a third
drill rig is being mobilised to its Cerro Negro prospect, part of the
Company's Especularita Project in Chile, and will commence scout reverse
circulation ("RC") drilling of targets along the Mostaza Fault Zone ("MFZ") as
well as newly identified outcropping mineralisation in the hanging wall
volcanics, where recent mapping has identified oxide copper mineralisation.

 

Highlights:

·      Phase III drilling at Cerro Negro has expanded with the
mobilisation of a third drill rig to site

·     Scout RC drilling to commence initial testing of the MFZ, 1.5
kilometres ("km") south of the Mostaza mine

·      Drilling to also test newly identified oxide copper
mineralisation in the hanging wall of the MFZ

·      Results for 22 outcrop samples collected in the hanging wall
volcanics return grades up to 2.56% Cu and 293 g/t Ag

·    Programme comprises up to 2,000 metres ("m") of RC drilling, which is
designed to accelerate testing of multiple high-priority prospects and expand
the scale of the Cerro Negro mineralised system

·    Two diamond drill rigs are currently in operation, testing extensions
to GSC's high-grade Cu-Ag discovery at Mostaza mine

·    GSC 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:
"Exploration at Cerro Negro has taken its next exciting step-up with the
addition of a third drill rig, joining the two diamond drill rigs currently in
operation on site. This expanded drilling capacity will enable us to rapidly
test the multiple high-priority exploration targets that we have identified
along the Mostaza trend through mapping, geophysics and geochemistry
programmes.

 

"The new rig will commence scout RC drilling of the Mostaza Fault Zone, south
of the Company's Mostaza mine. It will also test recently identified zones of
oxide copper located in the hanging wall volcanics to the fault, which have
not previously been drill-tested and have the potential to significantly
extend the scale of near-surface copper mineralisation in the Cerro Negro
system.

 

"With copper and silver prices continuing to push historical highs, this new
development will significantly accelerate our ability to evaluate the
broader-scale potential of the system and continue building on the excellent
results achieved to date."

 

 

Scout RC Drilling:

 

The initial scout RC drillholes, up to a total of 1,000m, will test a series
of outcropping lenses located along the southern extension of the Mostaza
Fault trend, 1-1.5km south of the historic Mostaza Mine. These lenses show
strong silica alteration with crackle breccia and boxwork textures
characteristic of surface-leached mineralised lenses elsewhere at Cerro Negro.

 

Surface sampling of the leached silicification has returned assays of up to
86.4 g/t Ag(2), with anomalous molybdenum (Mo), copper (Cu), arsenic (As) and
antimony (Sb) - a geochemical signature consistent with the high-grade
mineralisation at the Mostaza Mine. Due to intense surface leaching, copper
grades are subdued in outcrop but are interpreted to represent the uppermost,
weathered portions of mineralised lenses (Figure 1a).

 

The targets coincide with gradient array IP chargeability and conductivity
anomalies extending along the trend(3).

 

Rock Chip Sampling Results:

 

Scout RC drilling will also test newly identified oxide copper mineralisation
outcropping in the hanging wall (west-side) of the MFZ  with a minimum 1,000m
of additional RC drilling. Although outcrop in this area is predominantly
obscured by gravel and talus deposits draining from the dacite dome to the
east, windows of outcropping brecciated andesitic volcanic rock with oxide
copper mineralisation are mapped and sampled along a 1.5km trend south of the
mine which is open to the south along the fault trend (Figure 1b).

 

Assay results for 22 samples collected over a 1.5km trend in the west hanging
wall area (Figure 2) yield grades up to 2.56% Cu and 293 g/t Ag, with 10
samples (45%) being anomalous in copper (>0.1% Cu) and 15 samples (68%)
being anomalous in silver (>5 g/t Ag). These results also point to
potential leaching of copper in the oxide, near-surface environment.

 

 

Figure 1: Oxidised silicified lens rock within the Mostaza Fault Zone (MFZ)
south of the Mostaza pit (l); oxide copper in fractured and brecciated
volcanics within the MFZ hanging wall (r).

 

 

Figure 2: Map of Ag-Cu-Mo-Sb rock chip geochemistry for the Cerro Negro
Prospect, Especularita. The Mostaza Fault Zone (MFZ) is well defined by
anomalous Mo geochemistry. To the west, the hanging wall oxide copper zone is
a new target for near-surface oxide copper deposits to be tested with RC
drilling.

 

Phase III Diamond Drilling:

 

The Phase III diamond drilling programme is on-going with two drill rigs
targeting the Mostaza high-grade Cu-Ag mineralisation below the existing open
pit as well as testing extensions to the mineralisation in the Lens 3-5
area(4). As at the end of October 2025, 1,340m of drilling has been completed
in 10 drill holes and 572 samples have been delivered to ALS Laboratories in
Santiago for geochemical analysis. Assay results are pending. Logging,
processing and sampling of core is on-going in conjunction with geological
interpretation and modelling of the Mostaza Cu-Ag deposit.

 

Drill hole CNG25-DD036 is currently in progress in the north end of the
Mostaza pit as a re-drill (twin-hole) to CNG25-DD033 which intersected two
mineralised lenses before being prematurely terminated (due to rig
malfunction) at 197.9m. The breakdown occurred whilst the hole was in
chalcocite-mineralised lens rock 1  (#_ftn1) (Figure 3) that appears to
represent a third, newly discovered lens. Re-drill hole DD036 will aim to test
the full width of this deeper mineralised lens.

 

To the south, CNG25-DD035 is drilling beneath Lens 5 which hosts oxide copper
in outcropping silicified dacite overprinted by quartz crackle-breccia.

 

Figure 3: Newly identified mineralised lens rock in HQ core samples from hole
CNG25-DD033. Examples of coarse black disseminated and crackle-hosted
chalcocite(?) occurs in silicified dacitic breccia at 192.8m (l) and 193.1m
(r). The hole terminated prematurely in this mineralised lens rock at 197.9m.
These samples have not been assayed and are for reference only, and no
guidance for copper grade is provided. Refer to Cautionary Note below.

 

 

 

 

 

Cautionary Note:

Photographs of un-assayed drill core used in this RNS are for reference
purposes only to describe the style of mineralisation encountered in the drill
hole and do not provide information as to the metal grade of the rock where
that rock has not yet been sampled and assayed. Readers are cautioned not to
interpret metal grades or mineralisation widths from photographs of core or
visual descriptions where no corresponding assays are reported or yet
available.

 

  References:

1.    Cautionary Note

2.    RNS 5192G (29 April 2025): Exploration Results Extend Cerro Negro

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

4.    RNS 7559 (10 September 2025): Phase III diamond drilling underway at
Cerro Negro

 

 

 

 

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.

 

 1  (#_ftnref1) See Cautionary Note

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