Drilling Results at Teresita & Abundante Prospects

Results confirm Intrusive-related and breccia-hosted mineralisation systems with all drill holes intersecting anomalous gold and copper mineralisation

Great Southern Copper plc (LSE: GSCU), the company focused on copper-gold-lithium exploration in Chile, is pleased to announce that final results have been received and assessed for its scout RC drilling programmes at the Abundante and Teresita prospects.

Highlights:

• All assay results received for 1018m reconnaissance drilling comprising 15 scout RC holes completed across two prospect areas at GSC's Especularita prospect
• All scout RC holes intersected anomalous gold and copper mineralisation
• Results strongly support and validate the IRGS target model at Teresita and provide significant impetus for follow-up exploration
• Significant intercepts (including previously reported results)1 include;

§ ESP23RC002: 17m at 0.52% Cu from 24m

Incl, 4m of 0.97% Cu from 30m

§ ESP23RC004: 21m at 0.31% Cu from 19m

Incl, 1m of 1.83% Cu from 38m

§ ESP23RC010: 20m at 0.57g/t Au, 5.48g/t Ag and 0.43% Cu from 35m

• Incl, 3m at 1.1 g/t Au, 8.71g/t Ag and 0.79% Cu from 39m and,
• And 3m at 1.65g/t Au, 9.03g/t Ag and 0.69% Cu from 48m

§ ESP23RC015: 6m at 0.48% Cu from 7m, and

• Incl, 1m at 2.12% Cu from 10m
• Coincident anomalous As-Bi-Co-Sb-Te provides important pathfinder geochemistry for follow-up exploration at Teresita and further supports the IRGS model

Next Steps:

Assay results from scout RC drilling have confirmed the IRGS model type for mineralisation at Teresita where high-grade gold and copper is hosted in quartz-sulphide veins that are over-printed near surface by late-stage carbonate veining. Individual veins within the broader Teresita system "pinch and swell". However, quartz-sulphide veins may become more coherent with depth below the surface carbonate alteration. Gold and copper grades vary throughout the system. Evidence of high-grade cores to the veins with broader lower-grade haloes is encouraging. Anomalous Ag-As-Bi-Sb-Co-Te pathfinder geochemistry is significant from an exploration perspective.

Follow-up exploration at Teresita will focus on delineating the vein targets in more detail for Phase 2 prospect-scale drilling programmes. This work may include detailed grid-based soil geochemistry across the whole system and geophysics (magnetics, IP, EM).

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "The mineralised vein system at Teresita is very large - comprising multiple veins over 5km in cumulative strike length - and these exciting early reconnaissance drill results give us strong impetus to aggressively advance our exploration of this system.

"The results strongly support our interpretation that the quartz-sulphide-carbonate vein system at our Victoria prospect also represents another IRGS target, adding a second exciting large-scale project to our portfolio. Additionally, the potential to discover additional systems in the district is also significant as our regional exploration programmes continue.

"With the Victoria and Aurelia copper-gold prospects also advancing toward drill-ready status, our drilling pipeline is looking very strong. Due diligence work at our newly acquired Cerro Negro and Artemisa prospects is in progress and will likely add new high-priority drill targets to the pipeline, all of which gives the Board and our stakeholders a lot to look forward to."

Drilling programme and sampling:

GSC has recently completed two scout RC drilling programmes at the Teresita and Abundante prospects comprising a total of 15 drill holes for 1,018 metres (Figure 1). Assay results for holes ESP23RC001 to ESP23RC010 where reported previously1 and final assay results have now been received for holes ESP23RC011 to ESP23RC015. The programmes targeted surface mapping and rock chip geochemistry results and were designed to confirm the interpreted IRGS and breccia styles of mineralisation. Collar details for the drill holes are summarised in Table 1 below.

The RC drilling method employed at Especularita generates between 35 - 40kg of rock cuttings, or "chips", per metre. Representative samples for each metre 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 metre 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 were 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).

Table 1: Drill collar details for Teresita-Abundante scout drilling programmes, Especularita project.

Teresita drilling:

At Teresita 534m of drilling was completed in nine RC scout drill holes (ESP23RC007 to ESP23RC015) to test for Au-Cu mineralisation in quartz-carbonate vein-breccias. The Teresita quartz-carbonate vein swarm has a cumulative strike length over 5km and rock chip samples returned grades up to 13.7g/t Au2 and 7.22% Cu3.

Reconnaissance scout holes were drilled to test the continuity, thickness, and grade of quartz-carbonate vein-breccias below the surface outcrops, where they vary from less than a metre to several metres in width and from barren to mineralised. Holes ESP23RC007, RC008 and RC013 tested the Central Vein, hole RC009 the Grossa Vein, hole RC010 the Gato Negro vein, hole RC014 the Pampa Vein, and finally, holes RC011, RC012 and RC015 tested the Michaela veins (Figure 1). All holes intersected the mineralised veins at depth with anomalous Au (>0.1g/t Au) and Cu (>0.1% Cu) grades reported in assay results for all holes (Table 2).

Holes RC007, RC008 and RC013 targeting the Central Vein intersected an anastomosing sheeted quartz vein zone with sporadic, weakly anomalous Au and Cu, separate to a barren carbonate-only zone. Hole RC009 at Grossa cut a weakly anomalous quartz-carbonate vein and a deeper barren granular quartz zone.

At Gato Negro, hole ESP23RC010 cut well mineralised chalcopyrite-pyrite-quartz-carbonate vein-breccia between 35-55m down-hole (Figure 2). Significant gold, silver, and copper intervals reported previously1 include;

• 20m with 0.57 ppm Au, 5.48 ppm Ag, 0.43% Cu from 35m, including:

o 7m with 0.68 ppm Au, 4.33 ppm Ag, 0.42% Cu from 35m including

§ 3m with 1.1 ppm Au, 8.71 ppm Ag, 0.79% Cu from 39m including

1m with 2.03 ppm Au, 15.65 ppm Ag, 1.31% Cu from 40m, and

o 9m with 0.73 ppm Au, 8.06 ppm Ag, 0.59% Cu from 46m, including

§ 3m with 1.65 ppm Au, 9.03 ppm Ag, 0.69% Cu from 48m.

Holes targeting the Michaela veins all intersected narrow quartz-sulphide veins near surface with hole ESP23RC015 intersecting high-grade copper mineralisation including (Figure 3);

1m of 2.12% Cu and 0.083g/t Au from 10m

Figure 1: Collar location map for scout RC drillholes at Teresita and Abundante with rock chip gold assays, Especularita.

Figure 2: Examples of cross-sections for scout RC holes (l) ESP23RC010 targeting Gato Negro vein, and (r) ESP23RC015 targeting the Micaela vein, Teresita prospect, Especularita.

Table 2: Anomalous intersections for Teresita-Abundante scout RC drilling programme. Note: down-hole intercept lengths do not necessarily represent true-widths.

References:

• RNS 6635G (13 March 2024): 10-15m wide vein intersected at Teresita.
• RNS 5675F (11 July 2023): High grade Cu-Au in rock chip samples from Teresita.
• RNS 2146H (22 Nov 2022): Early exploration at Especularita identifies multiple copper targets and completion of drilling at San Lorenzo.

Forward Looking and Cautionary Statements