First Drillhole at Cerro Negro

Great Southern Copper plc (LSE: GSCU), the company focused on copper-gold-lithium exploration in Chile, is pleased to provide an update on its Phase 1 drilling programme at the Cerro Negro project in northern Chile, where diamond drilling at the historical Mostaza mine commenced on 5 January 20251.

Highlights:

• First diamond drillhole, CNG25 DD001, has been completed for 103.5m depth, as part of the initial drill plan at Mostaza for up to 5 to 10 diamond drillholes for up to 500-1,000m
• CNG25 DD001 intersected 20 metres* of intensely altered and mineralised rock between 27m and 47m depth, confirming Cu-Ag mineralisation continuity below the historical open pit
• CNG25 DD001 targeted the path of historical drillhole EDH-25, which recorded 25.33m of 0.53% Cu, including 6m of 1.05% Cu and 81g/t Ag, and 9m of 0.92% Cu and 73g/t Ag1
• The mineralised intercepts for CNG25 DD001 closely correlate with EDH-25, confirming the lens occurs as a west-dipping tabular body that is open and untested at depth
• All CNG25 DD001 samples have been dispatched for assaying
• Second drillhole, CNG25 DD002, has been completed for 61.60m and intersected the same alternation zone and mineralisation target as drillhole CNG25 DD001. The core is being processed and evaluated for sampling
• The third drillhole, CNG25 DD003, is now underway

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "We are pleased to complete our first diamond drillholes at the Mostaza mine as part of our initial plan of 5 to 10 diamond drillholes totalling 500 to 1,000 meters. The drillhole reached a depth of 103.5 meters and intersected 20 meters of intensely altered and mineralised rock between 27 and 47 meters depth. The intersection aligns closely with historical drilling, indicating a west-dipping tabular body that remains open and untested at depth.

"Our drilling programme at the Mostaza mine is progressing well with the second hole now complete and the third underway. We look forward to providing further updates as we continue to build our understanding of this promising target."

Diamond drill campaign at Cerro Negro

The first hole, CNG25 DD001, was drilled to 103.5m depth and intersected 20 metres* of intensely altered and mineralised rock between 27m and 47m depth down-the-hole confirming both the continuity and thickness of Cu-Ag mineralisation below the historical open pit.

Mineralisation is of high-sulphidation epithermal style and occurs as abundant veinlets, crackle networks and disseminations of hypogene chalcocite and bornite with trace pyrite and chalcopyrite, associated with quartz-baryte gangue and quartz-alunite-dickite/pyrophyllite alteration that overprints earlier pervasive illite alteration (see Figure 1). This is the same style of mineralisation as seen in the bottom of the open-pit and historical stockpiles where exploration rock sampling by GSC geologists returned up to 4.64% Cu and 177ppm Ag2.

The mineralisation and its associated alteration occur in a structurally controlled "lens" or "lode" of inter-mineral polymictic rock-flour matrix breccia, bounded on both sides by metric andesitic dykes with intensely clay-altered and faulted contacts.

CNG25 DD001 was designed to drill across the path of historical drillhole EDH-25 that reported 25.33m of 0.53% Cu, including 6m of 1.05% Cu and 81g/t Ag, and 9m of 0.92% Cu and 73g/t Ag1. The contacts of the mineralised intercepts from EDH-25 show a very close correlation with the contacts reported here for CNG25 DD001 (see Figures 2 & 3), confirming the lens is a west-dipping tabular body that remains untested at depth (historical drill core and geological descriptions are not available).

Figure 1. Cerro Negro Project, Mostaza Mine: Photographs of drill core from CNG25 DD001 Left: Crackle and veinlet hosted chalcocite-bornite (black mineral) cutting illite and locally quartz-alunite-dickite/pyrophyllite altered polymictic breccia (30.4m depth). Right: 5cm thick vein of steely-black chalcocite mineralisation (33.2m depth).

Figure 2. Cerro Negro Project, Mostaza Mine: Long section of Lens 2 showing the location of where phase 1 drillholes are projected to intersect the mineralised lens. Completed holes are shown in green and current drilling in yellow. Historical resource blocks, underground mine workings, and drillhole assay results are shown for reference. Hole CNG25-DD001 is located approximately on local grid section S+00 (see Figure 3). (GSCU has not been able to independently verify the historical channel sample or drillhole assay results).

Figure 3. Cerro Negro Project, Mostaza Mine: Geological cross section S+00 (local mine grid) showing the location of drillhole CNG25 DD001and a preliminary geological interpretation. Note the extrapolations from diamond hole DD001 to the historical drillholes EDH25, EDH 23 and EDH15 are based on assay results only because historical drill core and logs are unavailable.

The wall rocks on either side of the lens are dominated by red polymictic rock-flour matrix breccias with textural characteristics suggestive of a phreatic or phreatomagmatic origin, including fluidisation and injection textures, lack of sorting, and possible juvenile fragments, with the pronounced red colour due to hematite alteration probably caused by the oxidising gasses that formed the breccia. On the west side the red polymictic breccia is in faulted contact with regionally extensive black monomictic volcanic breccias. To the east the red breccia remains open and may form part of a large dome-diatreme complex typical of the upper parts of porphyry-epithermal systems.

Drilling at Cerro Negro continues with drillhole CNG25 DD002 recently completed at 61.60m. CNG25 DD002 intersected the same alternation zone and mineralisation target as drillhole CNG25 DD001. The core is being processed and evaluated for sampling. The third drillhole, CNG25 DD003, is now underway. The Company looks forward to providing further updates as results arise.

*Apparent thickness: There is not sufficient geological information currently to calculate true thickness.

References:

• RNS 3120K (31 October 2024): Cerro Negro Results Up To 4.64% Cu and 177ppm Ag
• RNS 2189S (06 January 2025): Diamond drilling commences at Cerro Negro

*Apparent thickness: There is not sufficient geological information currently to calculate true thickness.

Forward Looking and Cautionary Statements