Great Southern Copper plc (LON: GSCU) Ground Magnetics Survey Commences at Viuda

Ground Magnetics Survey Commences at Viuda Gold Prospect

Targeting Maricunga-style porphyry Au-Cu deposits

Great Southern Copper plc (LON: GSCU), the company focused on copper-gold-silver exploration in Chile, is pleased to announce that it has commenced a ground magnetic survey at its Viuda porphyry Au-Cu prospect (“Viuda”) at the Company’s Especularita project.

Highlights:

·      Ground magnetics commences with a 250 line-kilometre survey at Viuda

·      Exploration targeting large-scale Maricunga porphyry Au-Cu type deposits

·      Previous scout drilling intersected broad zones of gold mineralisation, including¹;

o  DD004: 6.7m @ 0.39 g/t Au & 0.12% Cu from 43.1m, within broader interval of:

§ 121.5m @ 0.11 g/t Au & 0.05% Cu from 6.5m, and

o  DD002: 14.2m @ 0.21 g/t Au & 0.11% Cu from 11m, within broader interval of:

§ 73m @ 0.14 g/t Au & 0.1% Cu from 11m

·      High gold grades hosted in stockwork veining within magnetic porphyry intrusive

·      Phase II drilling at Viuda is anticipated in early 2026

·      GSC has option to earn 100% of the Viuda prospect

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

Porphyry Au deposits in Chile:

Scout drilling by GSC at Viuda earlier this year confirmed that gold and copper mineralisation is associated with stockwork and sheeted dark-banded and A-type quartz veinlets within widespread intermediate-argillic and magnetite-albite-chlorite altered diorite porphyry intrusives. The mineralisation and alteration are typical of Maricunga-style gold porphyry systems, such as Kinross Gold’s Lobo-Marte deposit (6.7Moz Au at 1.3 g/t²), Maricunga (4.3 Moz at 0.7 g/t³) and Rio2’s Fenix deposit (1.77 Moz Au at 0.48 g/t Au⁴).

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: “Previous work by the company, including drilling, has established mineralisation and alteration at Viuda that are consistent with a Maricunga-style porphyry gold system, a style which has not previously been reported within the coastal metallogenic belt of Chile. In particular, scout drilling has demonstrated that higher grades of gold are associated with a magnetic porphyry intrusive.

“This ground magnetics survey is planned to identify potential magnetic intrusives that will assist the company in vectoring its next phase of drilling at Viuda, which is anticipated to commence within the first quarter of 2026. I look forward to keeping shareholders and the wider market informed as exploration at Viuda progresses and as results from the ground magnetic survey are received and interpreted.”

Viuda Prospect:

The Viuda and Viuda Negra prospects, located approximately 15km to the southwest of the Company’s Cerro Negro, comprises 18km² of concessions centred upon a prominent hill of resistive silicified rock (Chingay Hill) and surrounded by a 2km wide bowl-shaped depression (“bajo”) of dominantly albite-pyrite-clay altered volcanics and intrusive rocks – a geological setting typical of many porphyry deposits, formed by supergene weathering and oxidation.

Viuda Negra is located approximately 1km to the east of Chingay Hill, and recent scout drilling intersected broad intervals of anomalous gold including¹;

·    DD004: 6.7m @ 0.39 g/t Au & 0.12% Cu from 43.1m, within broader interval of:

o  121.5m @ 0.11 g/t Au & 0.05% Cu from 6.5m

The discrete higher-grade interval in DD004 is associated with a porphyritic microdiorite intrusive phase which is over-printed by abundant banded and A-type quartz veinlets and intense, magnetite-rich potassic alteration. This is interpreted as an early-mineral porphyry phase and suggests that higher-grade centres may be present elsewhere within the system.

Ground magnetics survey:

The Viuda ground magnetics survey comprises a 250 line-kilometre survey with east-west orientated grid-lines and a line spacing of 50m (Figure 1). The survey is being completed by Santiago-based Southern Geophysics and covers the full extent of the clay-altered “bajo” which defines the prospect.

The survey is designed to identify potassic-altered magnetic intrusive bodies that are potentially indicative of porphyry Au-Cu mineralisation as identified in hole DD004 of the scout drilling programme.

Figure 1: Oblique Google image of the Viuda and Viuda Negra prospect illustrating grid lines of the ground magnetics survey.

  References:

1.    RNS 4145X (01 September 2025): Results of scout drilling at Viuda Negra

2.    Kinross Gold 2024 Annual Mineral Resource and Resource Statement

3.    Kinross Gold 2015 Annual Mineral Resource and Resource Statement

4.    NI 43-101 Technical Report on the Feasibility Study for the Fenix Gold Project

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