New Cu-Au Exploration Target Identified at Viuda

Great Southern Copper plc (LSE: GSCU), the company focused on copper-gold-lithium exploration in Chile, is pleased to announce that results from exploration mapping and sampling at its Viuda prospect confirm the potential for a new untested porphyry Cu-Au system.

Highlights:

• High-grade copper-gold-silver mineralisation associated with stockwork and vein breccia
• Rock chip samples from artisanal workings range up to 3.5% Cu, 13.85g/t Au and 56.6g/t Ag
• 10 samples (18%) return assay grades >1.0% Cu
• Mapping demonstrates typical large-scale porphyry copper-type geology and alteration,
• Scale of system similar to known porphyry Cu-Au deposits, such as Bajo de Alumbrera
• No evidence of historical exploration drilling
• Excellent prospect access with potential to fast-track drill testing,
• Coastal metallogenic belt location with excellent access to infrastructure

Viuda prospect:

The Viuda prospect was acquired by the Company earlier this year1,2 as part of the Artemisa Option Agreement which now forms the broader Especularita Project located in the coastal metallogenic belt of Chile.

The prospect comprises 16km2 of concessions centred upon a prominent hill of resistive siliceous rock surrounded by a large bowl-shaped depression, or "bajo", of clay-altered granodiorite - a geological setting typical of many porphyry copper and copper-gold systems. (Figure 1). Recent exploration work by GSC includes prospect-scale mapping and sampling with 55 rock chip grab samples collected and assayed.

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "The discovery of additional porphyry style Cu-Au-Ag alteration and mineralisation at Viuda is very exciting and further emphasises the potential of the Especularita Project to host multiple porphyry copper centres.

"While we prepare for drilling at Mostaza, it is encouraging to know that our targeted exploration programme is resulting in more grass-roots prospects being elevated to drill-ready status, thus providing the Company with an enviable pipeline of drill-target opportunities."

Viuda prospect geology and mineralisation:

The Viuda prospect is dominated by a prominent ridge of leached, silica altered (advanced argillic) dacitic volcanics, or dacite dome rocks which occupies the central core of the alteration system (Figure 2).

The central siliceous alteration is surrounded by a 2km-wide zone of silica-sericite-clay altered granodiorite with overprinting quartz-pyrite stockwork vein mineralisation of varying intensity (phyllic alteration). The phyllic altered granodiorite forms a characteristic depression, or bowl-like morphology, recognised by its characteristic yellowish colour anomaly against the darker more resistive andesitic volcanic rocks into which the granodiorite intruded (Figure 3). Although oxidised and leached, the weathered, phyllic-altered rocks typically host low-grade copper-gold (>0.1% Cu) with higher grade mineralisation occurring in late structurally-controlled vein-breccias and stockworks where assay grades range up to 3.5% Cu, 13.8g/t Au and 56.6g/t Ag.

The size, intensity and distribution of the alteration zones, together with widespread evidence of disseminated and veinlet sulphides and highly anomalous Cu, Au and Mo in rock-chip samples, indicates that the Viuda prospect represents the upper parts of a partially exposed and leached porphyry Cu-Au system with good potential for downward zonation into underlying secondary and primary copper-gold mineralisation in the core of the deposit.

The surface geology, scale and setting of Viuda is analogous to known porphyry copper deposits such as Bajo de Alumbrera in Argentina (605Mt @ 0.54% Cu, 0.64g/t Au3).

Rock chip sampling and results:

All rock chip samples collected are located using hand-held GPS units (WGS84 zone 19S datum, UTM coordinate system) and allocated a unique sample number using a ticket-book system.

Assay results for the 55 rock and float grab samples collected in this programme range up to 3.5% Cu, 13.85g/t Au and 56.6g/t Ag. Significantly, 34 samples (62%) returned anomalous copper grades of >0.1% Cu with 10 samples (18%) assaying over 1.0% Cu. In addition to Cu-Au-Ag, the samples were also variably anomalous in Ba, Mo, Sb, Sr, Zn which is consistent with the interpreted upper levels of the porphyry-epithermal system.

Next steps:

Results to date indicate potential for porphyry style Cu-Au mineralisation at Viuda. A programme of further detailed mapping and sampling will commence with the aim to elevate the prospect to drill-ready status. Subject to the results of the detailed work, drill targeting may be enhanced by ground magnetics and IP geophysical surveys.

Figure 1: Location of Viuda porphyry Cu-Au prospect, Especularita Project, Chile. The centre of the prospect is recognised as a prominent hill of silicified dacite surrounded by phyllic-altered granodiorite.

Figure 2: Central Viuda prospect surrounded by artisanal copper-gold workings. Note sealed access road. Advanced argillic altered dacite (Upper right) forms central core to the alteration system, surrounded by qtz-py crackle-veined sericite-clay-silica altered granodiorite (Lower right).

Figure 3: Same-scale view of geological setting of Viuda exhibiting characteristic zoned alteration patterns defined by a broad yellow leached phyllic zone (bottom) compared with the Bajo de Alumbrera deposit in Argentina (top). The deposit contains historical and actual reserves of 605 Mt of ore, with an average grade of 0.54 percent Cu and 0.64 g/t Au3.

References:

• RNS 0741E (22 Feb 2024); GSC expands Especularita project with two agreements.
• RNS 1134S (12 Jun 2024); GSC signs purchase option agreement for Artemisa.
• J., 2003: Geology of the Bajo La Alumbrera Porphyry Copper-Gold Deposit, Argentina, in Economic Geology, Vol 98, pp. 1535-1574

Forward Looking and Cautionary Statements