REG - Great Southrn.Copper - Phase II Drilling Results Extends Mostaza Deposit

Great Southern CopperAnnouncement

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RNS Number : 6908V  Great Southern Copper PLC  18 August 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.

 

 

18 August 2025

 

Great Southern Copper plc

("GSC" or the "Company")

 

Final Phase II Drilling Results Extends High-grade Mostaza Cu-Ag Deposit

 

New Mineralised Zone Identified at Lens 1

 

Great Southern Copper plc (LSE: GSCU), the company focused on
copper-gold-silver exploration in Chile, is pleased to announce final drilling
results from the Phase II programme at Cerro Negro including first drill
results from Lens 1, located approximately 150 metres ("m") north of Lens 2 at
Mostaza.

 

Highlights:

·    Final Phase II drill assay results confirm continuity of high-grade
Cu-Ag mineralisation at Mostaza with significant intervals including;

o  CNG25 DD019: 7.2m @ 1.47% Cu and 122.3 g/t Ag from 99.9m, including;

·    1.4m @ 3.75% Cu and 319.1 g/t Ag from 103.5m

o  CNG25 DD020: 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

·    First confirmed mineralised intercepts from Lens 1, 150m north of
Lens 2 at Mostaza include;

o  CNG25 DD025: 3.0m @ 0.91% Cu and 61.7 g/t Ag from 28m including;

·    1m @ 1.38% Cu and 88.6 g/t Ag from 29m

·    25 holes completed in Phases I and II with all holes intersecting the
target mineralisation zone

·    7 holes demonstrate evidence of "leached" copper from the silicified
lenses

·    Metallurgical and structural studies in progress

·    Phase III drilling planned to commence in late August, subject to rig
availability, targeting Lenses 3 - 5 and extensions of Lens 2

·    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: "These
high-grade copper-silver results continue to build our understanding of the
geometry and continuity of the mineralisation at Mostaza. Although holes DD021
to DD023 did not encounter high-grade mineralisation, they provide valuable
geological information, helping to refine our model.

 

"We are also excited to report the first mineralised intercept from Lens 1 in
DD025 - our first ever drill intersection into Lens 1, which provides
encouragement for follow-up drilling. These results represent an important
step in our broader campaign to define a potentially significant cluster of
mineralised lenses at Cerro Negro.

 

"Drill planning is well advanced for our Phase III programme, which we hope to
commence in late August, subject to drill rig availability. This is an
exciting time for GSC as we begin the next step to attempt to explore the
growth potential of this high-grade asset."

Phase II Drilling:

 

Drillholes CNG25 DD019-020 and 022-025 were designed to further test the
continuity of high-grade copper-silver mineralisation within the Lens 2
deposit and to provide a first-pass assessment of Lens 1, located approx.150m
north of the Mostaza pit (Figure 1). All results have now been received for
the Phase II drilling programme.

 

Figure 1: Cerro Negro Project. Plan view showing the open pit and extensions
of mineralisation at depth and along trend to the north and south. Drillholes
in this release are labelled.

 

Mostaza Lens 2 (DD019-20 & 022-023):

 

Drillholes CNG25 DD019 and DD020 were drilled as 80m and 40m down-dip
step-outs from CNG25 DD004 (Figure 1) and were designed to test the hypothesis
that the Mostaza mineralisation is truncated by a fault at shallow levels on
the northern side of the pit but remains continuous at depth.

 

Both holes intersected strongly altered and silicified "lens" rock hosting
disseminated and crackle-hosted sulphide mineralisation dominated by
chalcocite and lesser bornite, returning significant intervals of;

 

o  DD019:  7.2m @ 1.47% Cu and 122.3 g/t Ag from 99.9m, including

§ 1.4m @ 3.75% Cu and 319.1 g/t Ag from 103.5m

o  DD020:  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

 

These results provide strong evidence for the down-dip continuity of the
deposit, which remains open at depth (Figure 2a). Table 1 provides a summary
of significant intercepts for all holes drilled to date.

 

Drillhole CNG25 DD022 was drilled as a 40m step out along strike to the
north-west of DD020. It intersected multiple zones of altered "proto-lens"
with anomalous Cu-Ag but no high-grade intercepts.

 

Drillhole CNG25 DD023 was drilled as an exploratory hole testing the southern
extension of the deposit. The hole intersected a broad zone of "lens" rock
which displays evidence of leaching consistent with its low Cu-Ag grade. This
may be a result of post-mineral fault displacement which is also evident.
Structural studies of the core are in progress to evaluate the potential
effects of fault and dyke displacement of the mineralisation.

 

Ongoing interpretation of the drill core suggests that the mineralisation
forms as a tabular, northwest-dipping deposit (Figure 2a-d), distinct from and
with higher Cu-Ag grades than the historically mined steeply dipping lens
structures evidenced in the pit wall and tested by historical drilling.
Integration of recent and historical drill data, surface geological mapping,
and geophysical surveys (IP and AMT) has significantly improved the
understanding of the deposit's architecture.

 

This evolving geological model is guiding drill planning and target generation
for the next phase of exploration at both Mostaza and along trend.

 

Lens 1 (DD024-025):

 

Holes CNG25 DD024 and DD025 represent the company's first drill tests beneath
the interpreted Lens 1, approximately 150m north of the Mostaza open pit
(Figure 1).

 

DD025 returned a shallow intercept of 3.0m @ 0.91% Cu and 61.7 g/t Ag from
28m, including 1.0m @ 1.38% Cu and 88.6 g/t Ag from 29m. This marks the first
confirmed mineralisation beneath Lens 1 and provides encouragement for
follow-up drilling (Figure 2b).

 

DD024 intersected anomalous Cu and Ag up to 0.23% Cu and 10.0 g/t Ag within
structurally controlled silicified breccias similar to those seen at Mostaza,
suggesting favourable host rocks are present.

 

Next steps:

 

Detailed logging of the core, including structural and petrographic studies,
is in progress to better define the deposit model and assist with targeting of
Phase III exploration drilling. Samples from mineralised intercepts in the
Phase II programme have also been included within the preliminary
metallurgical study which is ongoing.

 

In addition, the discovery of multiple zones of less altered and mineralised
lenses in the hanging-wall of the deposit is highly encouraging and these will
be investigated for their potential to zone into high-grade lenses at depth
and as such potentially develop a "stacked lens" type system.

 

The success of the 2D pole-dipole IP and resistivity modelling at identifying
the high-grade mineralisation plus dykes and fault structures suggests that a
follow-up programme of in-fill survey IP lines may be considered.

 

Planning of Phase III drilling is well advanced and anticipated to commence in
late August, subject to rig availability. Drilling will target extensions to
the high-grade Lens 2 mineralisation, specifically in the Lenses 3, 4, and 5
areas, where previous holes were drilled too shallowly and intersected
oxidised and copper-leached lenses.

 

 

 

 

Figure 2: Preliminary drill-section interpretations for the Mostaza deposit,
Cerro Negro. Mineralisation intervals are reported as down-hole widths.

 

 

 Hole_ID            From    (m)     To         (m)          Interval (m)        Cu         (%)          Ag        (g/t)

 CNG25 DD001        27              47                      20                  3.31                    269.9
              incl  31              38                      7                   5.72                    489.6
              incl  35              38                      3                   6.62                    562.7

 CNG25 DD002        38.9            43.1                    4.2                 1.73                    126.5

 CNG25 DD003        36.6            55.2                    18.6                1.85                    146.6
              incl  39              52                      13                  2.48                    198.1
              incl  48              51                      3                   3.31                    254.7
              incl  50              51                      1                   4.64                    406

 CNG25 DD004        Leached lens rock

 CNG25 DD005        35              56                      21                  2.9                     246.7
              incl  37              52                      15                  3.79                    328.4
              incl  40              52                      12                  4.24                    369.5
              incl  45              52                      7                   5.08                    449.6
              incl  45              47                      2                   6.05                    547.5

 CNG25 DD006        132.54          132.91                  0.46                0.08                    24.9

 CNG25 DD007        87              120                     33                  1.96                    60.6
              incl  88              91.85                   3.85                5.21                    318
              and   115             120                     5                   5.59                    99.2
              incl  116.4           118.9                   2.5                 9.67                    175.4

 CNG25 DD008        0               31                      31                                          7.1
              incl  0               1.2                     1.2                 0.512                   31.3
              and   8               22                      14                                          9.6

 CNG25 DD009        Oxide zone - leached lens rock

 CNG25 DD010        6               25                      19                                          30.52
              incl  10.2            19                      8.8                                         58.02
              and   18              23                      5                   0.31                    23.7

 CNG25 DD011        Oxide zone - leached lens rock

 CNG25 DD012        7               24                      17                                          8.7
              incl  16              24                      8                                           13.1
                    24              27                      3                   3.43                    164.7

 CNG25 DD13         26.1            40                      13.9                1.74                    153.4
              incl  26.1            34                      7.9                 2.35                    227.6
              incl  29              32                      3                   3.54                    405.3

 CNG25 DD014        Oxide zone - infill sampling results pending

 CNG25 DD015        30.2            31.7                    1.5                 0.39                    19.94
                    41.15           51.05                   9.9                 5.47                    442.5
              incl  43              49                      6                   6.61                    542.4
              and   44              46                      2                   8.18                    669

 CNG25 DD016        85.8            87                      1.2                 1.21                    76.3
                    89              96.5                    7.5                 4.48                    342.6
              incl  89.8            96.5                    6.7                 4.96                    381.2
              and   96              96.5                    0.5                 10.4                    503

 CNG25 DD017        71              84.1                    13.1                1.18                    48.7
              incl  76              84.1                    8.1                 1.76                    68.1
              and   76              80                      4                   2.61                    97.6

 CNG25 DD018        82              84                      2                   0.48                    33.9
                    118.3           122.5                   4.2                 0.68                    58.8
              incl  118.9           122.5                   3.6                 0.75                    65.4
                    128.7           136.1                   7.4                 0.66                    63
              incl  129.7           135.5                   5.8                 0.81                    78.1
              and   133             134.9                   1.9                 1.12                    108.4

 CNG25 DD019        99.9            107.1                   7.2                 1.47                    122.3
              incl  103.5           104.9                   1.4                 3.75                    319.1

 CNG25 DD020        80.1            88.5                    8.4                 1.49                    121.4
              incl  80.1            83.3                    3.2                 2.63                    239.7

 CNG25 DD021        1               2.2                     1.2                 0.5                     27.3
                    93.3            94                      0.7                 0.34                    17.8
                    99.9            101.65                  1.75                0.59                    28.5
              incl  99.9            101                     1.1                 0.84                    41.4
                    103.85          105.18                  1.33                0.21                    8.5

 CNG25 DD022        84.0            84.7                    0.7                 0.15                    2.6
                    99.1            100.0                   0.9                 0.13                    5.4

 CNG25 DD023        Leached lens 2 rock

 CNG25 DD024        28.0            29.0                    1.0                 0.14                    5.7
                    32.0            33.0                    1.0                 0.23                    10.0

 CNG25 DD025        28.0            31.0                    3.0                 0.91                    61.7
              incl  29.0            30.0                    1.0                 1.38                    88.6

Table 1: Summary of significant drill intercepts for Phase I and II drill
programmes, Mostaza mine, Cerro Negro Project. Mineralised interval meterage
is reported as down-hole widths.

 

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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