REG - Great Southrn.Copper - Mineralisation Extended at Monolith Target

Great Southern CopperAnnouncement

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RNS Number : 7344A  Great Southern Copper PLC  16 April 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.

 

 

16 April 2026

 

Great Southern Copper plc

("GSC" or the "Company")

 

Rock Chip and Channel Results Extend Cu-Ag Mineralisation at Monolith Target,
Cerro Negro

 

Mineralised system defined over a 700 metre by 400 metre area

 

Great Southern Copper plc (LSE: GSCU), the company focused on
copper-gold-silver exploration at its Especularita Project in Chile, is
pleased to report results from recent channel and rock chip sampling
programmes at the Monolith Target ("Monolith"), Cerro Negro Prospect.

 

Highlights:

·    All 15 exploration channel samples host Cu-Ag mineralisation

·    Channel sampling results include;

o  CH025: 6 m @ 0.29% Cu and 34.8 g/t Ag

o  CH030: 4m @ 0.53% Cu and 47.5 g/t Ag

o  CH033: 4m @ 0.38% Cu and 53.2 g/t Ag

·    Rock chip assay grades range up to 1.5% Cu and 95.8 g/t Ag

·    Copper and silver grades depleted due to surface weathering and
leaching

·    Vein, crackle-breccia and stockwork style Cu-Ag mineralisation very
similar to Mostaza

·    Mineralisation defined over a 700m by 400m area and open to the south
and west

·    GSC holds rights 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 and along trend of major copper deposits
including Los Pelambres, Altar and El Pachon.

 

 

Sam Garrett, Chief Executive Officer of Great Southern Copper, said:

 

"These exciting results from the Monolith target provide further compelling
evidence that the high-grade copper-silver mineralisation identified in
drilling at Mostaza now extends across a much broader system at Cerro Negro.

 

"The combination of strong channel sample grades, high-grade rock chips, and
widespread alteration demonstrates the scale potential of the system.
Importantly, the surface mineralisation is strongly weathered and leached,
reinforcing our belief that higher-grade sulphide mineralisation may be
preserved at depth.

 

"The copper-silver mineralised system identified at Monolith remains open to
the south and west, highlighting the significant growth potential of the
target. While work in these areas is continuing, we are now ready to commence
scout drilling at Monolith as part of the Phase IV drilling programme. This
work will be untaken alongside continued efforts to demonstrate the broader
district-scale potential at Cerro Negro."

 

 

Monolith Cu-Ag Target:

 

The Monolith high-grade Cu-Ag target is located. approximately 400m to the
southeast of the Mostaza mine at Cerro Negro, which itself comprises part of
GSC's Especularita project in northern Chile (Figure 1). The Especularita
project is located at low altitude within the Cretaceous-age coastal
metallogenic belt, within a northwest-southeast trending structural lineament
that links the project with notable large-scale porphyry Cu-Au mines, and
projects including Los Pelambres mine, Altar and El Pachon (Figure 1).

 

Figure 1: GSC's Especularita project is located at low altitude within the
coastal metallogenic belt of northern Chile, and within a 50km radius of over
50Mt of contained copper metal defined in mines and advanced projects.

 

Results of Surface Mapping and Sampling:

 

Geology mapping and channel sampling are being undertaken at the Monolith
target to follow up previously reported high-grade rock chip results, which
returned assay grades of up to 271 g/t Ag and 2.05% Cu¹.

 

Assay results for 13 rock chip grab samples range in grade up to 1.5% Cu and
95.8g/t Ag (Figure 2). The samples are notably also anomalous in
As-Ba-Sb-Mo-Pb-Zn, consistent with the high-level epithermal to intermediate
sulphidation environment interpreted for this type of mineralisation.

 

A total of 15 rock channel samples (comprising a total of 57 rock chip
samples) were collected across key structures and alteration zones, all of
which returned anomalous copper and silver values, confirming the continuity
of mineralisation across the target area. Significant results include (Figure
2):

 

·    CH025: 6m @ 0.29% Cu and 34.8 g/t Ag

·    CH030: 4m @ 0.53% Cu and 47.5 g/t Ag

·    CH033: 4m @ 0.38% Cu and 53.2 g/t Ag

·    CH032: 6m @ 26.5 g/t Ag

·    CH023: 6m @ 21.8 g/t Ag

 

These results demonstrate consistent Cu-Ag mineralisation over metre-scale
widths at surface. The predominance of oxide copper mineralisation and
elevated silver values is interpreted to reflect near-surface leaching,
suggesting potential for higher-grade sulphide mineralisation at depth,
analogous to the mineralisation intersected in drilling at Mostaza.

 

This work has significantly expanded the known extent of mineralisation,
defining a coherent alteration and mineralised footprint measuring
approximately 700m by 400m, in area and open to the south and west, where
further exploration work is continuing. Copper-silver mineralisation is hosted
in dacitic to rhyo-dacitic flow-banded lavas (interpreted as a resurgent dome
setting) and is characterised by copper oxide development associated with
crackle networks of quartz veinlets, as well as larger quartz-baryte veins and
breccia systems (Figure 4). Significantly, mineralisation observed at the
Monolith is consistent with the style of mineralisation associated with
similar dacitic rocks at Mostaza, located approximately 400m to the northwest.

 

The quartz veining is closely associated with pervasive silica-clay
alteration, forming a broad alteration envelope that hosts the mineralised
structures (Figure 3). These zones form an anastomosing network of veins,
breccias and stockworks, developed along the main ridge and extending down the
western flank of the hill. The geometry and distribution of these structures
indicate strong structural control, likely related to the broader Mostaza
Fault Zone.

 

 

Figure 2: Summary map of the Cerro Negro prospect with rock chip sample
locations (Ag g/t) (l) with alteration map of the Monolith target highlighting
significant channel rock chip results (r).

 

 

 

Figure 4: High-grade Cu-Ag mineralisation at the Monolith occurs in
silica-flooded breccia zones (upper left and lower left), shear-fault zones
with baryte veins (upper right) and crackle-vein breccia zones (lower right)
within silica-clay alteration haloes to the larger baryte-quartz-copper-silver
veins.

 

Next Steps:

 

Mapping and sampling continues to the south and west of the current work,
where the veins trend toward a significant zone of mapped breccia (Valle
Escondida Breccia), which is also yet to be sampled.

 

An extension to the earlier IP geophysics survey is being planned to cover the
Monolith zone, and planning and permitting are in progress to include scout RC
drilling within the Company's Phase IV drilling programme for Cerro Negro.

 

 

 

References:

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

 

 

 

Engage with the GSC management team directly by asking questions, watching
video summaries and seeing what other shareholders have to say. Navigate to
our Interactive Investor hub here: https://gscplc.com/ (https://gscplc.com/)

 

 

Enquiries:

 

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

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

 BlytheRay
 Megan Ray / James Mulligan            +44 (0) 20 7138 3204

                                       GSC@blytheray.com

 

Subscribe to our news alert service: https://gscplc.com/auth/signup
(https://gscplc.com/auth/signup)

 

 

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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