Scout Drilling Commences at Artemisa North Target

Great Southern Copper PLC

13 May 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.

13 May 2026

Great Southern Copper plc

("GSC" or the "Company")

Scout RC Drilling Commences at Artemisa North Porphyry Copper Target

Piedras Blancas drilling confirms porphyry copper style alteration system

Great Southern Copper plc (LSE: GSCU), the company focused on copper-gold-silver exploration in Chile, is pleased to announce that scout RC drilling has commenced on the Artemisa North porphyry copper target at the Especularita Project, while drilling recently completed at the nearby Piedras Blancas target has confirmed evidence of a strong porphyry copper-style alteration system.

Highlights:

Artemisa North

·    Scout reverse circulation ("RC") drilling commences at Artemisa North porphyry copper prospect at the western margin of the La Colorada lithocap

·    Four holes planned to target interpreted phyllic alteration system plus test beneath historical copper workings

·    Rock chip geochemistry results from mine workings grade up to 1.21% Cu, 0.6g/t Au and 201ppm Mo

·    Large-footprint system open under shallow cover to the north and east

·    No previous drilling of the target

·    GSC holds rights to own 100% of the Artemisa North target

·    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.

Piedras Blancas

·    Scout RC drilling completed at Piedras Blancas prospect with four holes drilled for 574 metres ("m")

·    All holes successfully intersected strong porphyry type phyllic alteration with holes PBL26 RC001 and RC002 transitioning at depth to potassic alteration including 5-15% sulphide mineralisation

·    Style and intensity of alteration provides proof-of-concept confirmation of a porphyry copper type setting at Piedras Blancas intersected at shallower depths than expected and further increasing prospectivity of the broader La Colorada lithocap

·    Samples for all four holes at Piedras Blancas have been despatched to ALS Laboratories

·    GSC holds rights to own 100% of the Piedras Blancas target

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "Artemisa North is the second of four targets to be tested with scout RC drilling in the current porphyry exploration programme. This programme is focusing on targets on the western margin of the La Colorada lithocap that display geological, geochemical and spectral features that are characteristic of porphyry copper systems. In particular, we aim to confirm that large-footprint zones of leached and oxidised quartz-sericite-pyrite alteration mapped at surface may represent the "phyllic" alteration zone enveloping a copper-gold porphyry system. Our interpretation is that these prospects were once covered by the La Colorada lithocap, which has since been eroded, or partially eroded, exposing the "phyllic" alteration.

"Drilling is progressing well and, importantly, the alteration and mineralisation observed in the initial Piedras Blancas holes has provided encouraging support for our porphyry copper exploration model at La Colorada including recognition of both phyllic and potassic styles of alteration. We look forward to receiving and sharing the sample results of the drilling in due course.

"Meanwhile, exploration mapping and sampling activities are continuing at both the Cerro Negro and Viuda prospects as we prepare for the next phase of drilling across the Especularita Project."

Artemisa North Porphyry Target:

The Artemisa North prospect is located 1.5km south of the Piedras Blancas¹ prospect on the western margin of the extensive La Colorada lithocap that comprises the Company's principal porphyry copper target within its flagship Especularita project (Figure 1). The Especularita project is situated 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, 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 50km radius of over 50Mt of contained copper metal defined in mines and advanced projects.

Mapping and sampling at Artemisa North has defined a broad zone (>1 km²) of quartz-sericite-pyrite "phyllic" alteration and stockworking confirmed by ASD spectrography. The phyllic alteration zones upwards to quartz-alunite "advanced argillic" alteration on the surrounding hilltops that is interpreted to represent a distal remnant of the La Colorada lithocap alteration (Figure 2). Despite intense oxidation and leaching, rock chip and soil samples define local anomalies in Cu and Mo, and abundant green and black Cu-oxides are observed in historical artisanal mines exposed on the western and eastern margins of the phyllic zone.

The alteration zone remains open under shallow cover to the east towards the La Colorada lithocap, and to the north where it is interpreted to merge with the Piedras Blancas alteration zone.

Piedras Blancas Porphyry Target:

Drilling at the Piedras Blancas target has been completed with four scout RC holes drilled for a total of 574m. All holes intersected strong pervasive quartz-sericite-pyrite alteration providing proof-of-concept evidence for porphyry copper type phyllic alteration to depths of up to 120m from surface. The phyllic alteration comprises up to 5 - 10% disseminated and veinlet hosted pyrite mineralisation (Figure 3).

Holes RC001 and RC002 transitioned at depth into biotite-altered "potassic" alteration with 5 - 15% disseminated and veinlet hosted pyrite, traces of chalcopyrite and quartz veinlets.

The style and intensity of alteration and mineralisation identified in holes PBL26 RC001 and 002, in particular the potassic alteration, confirm that a porphyry copper type setting has been identified at Piedras Blancas at depths shallower than expected. These results further confirm and enhance the potential of the La Colorada lithocap to host one or more porphyry copper type systems at reasonable depths from surface. Further work will now focus on vectoring to the possible copper-rich core of the systems.

Scout RC Drill Programme and Sampling:

Scout reverse circulation (RC) drilling recently commenced at Artemisa North with a view to test the prospect for evidence of porphyry copper-gold mineralisation and to provide vectors towards targets beneath the undrilled Colorada lithocap. A preliminary test comprising up to 1000m of drilling in at least four scout RC holes is now underway to assess the alteration and mineralisation.

The RC drilling method employed at Especularita collects samples on two-metre intervals. Representative samples for each sample of the cuttings are collected in large, individually numbered plastic bags, which are then weighed and transferred to a riffle splitter where they are separated (or split), and homogenised, three times into two duplicate samples of approximately 5kg each. GSC personnel then ticket and label one of the ±5kg samples using preprinted ticket books.

Finally, standard reference materials (SRM's or Standards), blanks, and duplicate samples are inserted into the sample sequence for the purpose of quality assurance / quality control (QAQC). The second ±5kg sample is used for geological description and stored for reference. An additional reference selection of cuttings for each two-metre sample is also retained in labelled boxes as a record of the geology of the drill hole.

At the completion of each hole, the representative 5kg samples are transported as a batch from the field and delivered by Company employees to ALS Laboratories in Santago or La Serena where they are prepared for analysis (weighed, dried, crushed and pulverised). A subsequent 200g split of each sample pulp is then forwarded to the ALS geochemical laboratory in Lima, Peru, where samples are assayed for gold (30g fire assay with ICP-AES finish, ALS code AU-ICP21) and 48 major, base and trace elements by ICP-MS following a four-acid digest (ALS code ME-MS61).

RC drilling was selected for this initial proof-of-concept stage as it is faster and cheaper than diamond drilling and allows for the rapid testing of more targets for the same cost.

 

 

Figure 2: Geology map of the Piedras Blancas and Artemisa North prospects illustrating quartz-sericite-pyrite "phyllic" alteration zone and local artisanal mine locations where copper and gold were recovered from oxidised fracture stockwork zones.

 

 

Figure 3: Chip samples from Piedras Blancas drill holes RC001-004 demonstrating features of porphyry type alteration including; quart-sulphide veinlets overprinting quartz-sericite-pyrite (phyllic) altered rock (top left), coarse sulphide in quartz-sericite-chlorite-pyrite altered rock (top right), quartz veinlet hosting coarse pyrite+chalcopyrite (bottom left), disseminated chalcopyrite mineralisation in potassic altered rock (bottom right).

Next Steps at Especularita:

Following the completion of the Artemisa North scout RC drilling programme, the rig will proceed to the Artemisa South and Victoria prospects to complete similar drill tests targeting porphyry-related copper mineralisation.

Final results are awaited for Mostaza metallurgical test work conducted on Phase I and II high-grade core samples. Planning and permitting for Phase IV drilling at Mostaza are in progress.

Geophysics surveys are being planned for both the Cerro Negro prospect (extension of 2025 IP survey) and the La Colorada lithocap (AMT), anticipated to commence in May 2026.

Detailed prospect-scale mapping and sampling are continuing at the Viuda and Cerro Negro prospects. New results from this ongoing work, together with results of the planned geophysics surveys, will direct targeting for the next phase of drilling at both Cerro Negro and Viuda.

References:

1.    RNS 0948B (20 April 2026): Drilling commences on porphyry copper targets

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/

Enquiries:

Great Southern Copper plc	https://gscplc.com/link/rvnm2r
Sam Garrett, Chief Executive Officer	[phone]
SI Capital Limited
Nick Emerson	[phone]
BlytheRay
Tim Blythe / Megan Ray	[phone] [e-mail]

Subscribe to our news alert service: 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

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.

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.

 

END