GSC Expands Target at Mostaza Mine, Cerro Negro

Great Southern Copper plc (LSE: GSCU), the company focused on copper-gold and lithium exploration in Chile, is pleased to announce that the scale of the target for the Company's maiden drilling programme at the Mostaza mine has increased due to the recognition of significant zones of additional Cu-Ag mineralisation in historical drill-hole assays and surface rock chip samples. Preparations for the start of drilling continue with archaeological and environmental surveys now completed, and the selection of the drilling company via tender.

Highlights:

• Historical drilling at the Mostaza mine included 25 diamond holes for a total of 1,024m. Drilling targeted high-grade lenses of Cu-Ag mineralisation with intercepts above 1% Cu summarised on historical plans and sections. Intercepts below this grade were not shown.
• 16 of the 25 historical holes were finished in anomalous copper mineralisation (>0.1% Cu) and 4 of the holes failed to reach the high grade target.
• Ongoing compilation of the historical data, together with re-interpretation and 3D modelling of assays and geology has identified a significant halo of additional copper mineralisation located either side of the high-grade lenses. These haloes represent an important expansion of the mineralised potential as shown by the following examples calculated using a cut-off of 0.1% Cu:

§ VDH4: 17m @ 0.62% Cu and 45.06ppm Ag from 18m, expanded to

• 40m @ 0.4% Cu and 23.08ppm Ag from 0m.

§ VDH9: 18m @ 0.72% Cu and 31.7ppm Ag from 18m, expanded to

• 40m @ 0.44% Cu and 16.55ppm Ag from 0m.

§ EDH15: 14m @ 1.92% Cu and 118ppm Ag from 36m

• Incl 8m @ 2.63% Cu and 153ppm Ag from 37m, expanded to
• 54m @ 0.62% Cu from 10m (Ag assays not continuous).

§ EDH24: 8m @ 0.88% Cu and 69.0ppm Ag from 57m, expanded to

28m @ 0.38% Cu from 44m (Ag assays not continuous), and

§ EDH25: 6m @ 1.05% Cu and 81.0ppm Ag from 49m, now expanded to

• 33m @ 0.53% Cu from 46m (Ag assays not continuous).
• In addition, the inclusion of this additional mineralisation allows for inclusion of drill hole intercepts not considered in the original high-grade resource calculation, such as:
• VDH1: 31m @ 0.48% Cu and 18.04ppm Ag from 0m.
• The Cu-Ag halo mineralisation has the potential to significantly increase the size of the Mostaza deposit.
• Preparation for the start of drilling at Mostaza is underway with archaeological and environmental surveys completed and a drill contractor selected via bidding process.
• On-going exploration at Cerro Negro identifies additional copper mineralisation hosted in multiple structures parallel to the Mostaza trend further expanding global copper potential.

Cerro Negro is situated within the Company's Especularita project ideally located close to national infrastructure including main highways, powerlines, and towns. The project is located 170km from the port city of Coquimbo, and 130km from Antofagasta Minerals' copper concentrate port at Los Villos. The area lies at an elevation between 800 and 1200m and is accessible year-round for all exploration and mining activity (Figure 1).

Sam Garrett, Chief Executive Officer of Great Southern Copper, said: "Exploration at Cerro Negro is rapidly advancing with three key objectives - drill beneath the historic Mostaza open pit to develop a high-grade copper-silver-gold resource, expand the Mostaza deposit along strike targeting extensions to the mineralised structures, and explore at depth targeting large-scale porphyry copper type deposits.

"It is very encouraging to identify this additional potential before any metres have even been drilled at Mostaza. This newly recognised mineralisation has the potential to significantly increase the size of the Mostaza deposit and provides additional optionality for potential future mining operations.

"The discovery of additional copper-mineralised structures hosted in the advanced argillic lithocap above the Mostaza mine is also very significant in terms of our porphyry copper exploration at Cerro Negro. The potential of these anastomosing mineralised structures to grade downward into porphyry type mineralisation is a genuine target vector.

"The copper bank at Cerro Negro is building and we eagerly await the start of drilling. Drill sites have been selected and reviewed by the drilling contractor and permitting for the drilling programme is progressing with archaeological and environmental surveys already completed."

Mostaza Cu-Ag-Au Mine:

The Mostaza Cu-Ag-Au gold mine at Cerro Negro was previously owned and mined by Antofagasta Minerals with mixed oxide and sulphide ores processed at their nearby Parral flotation plant1 also located within GSC's group of concessions.

High-grade Cu-Ag-Au mineralisation at Mostaza is hosted in a north-south trending shear zone which is intruded by felsic dykes and breccias which have been overprinted by intense advanced argillic to phyllic alteration. Copper mineralisation is dominated by hypogene stromeyerite (copper-silver) and chalcocite, covellite, digenite, bornite, plus lesser chalcopyrite and pyrite1 as disseminations and in quartz veinlets, crackle networks and breccias

The high-grade mineralisation forms steeply-dipping tabular bodies, or lenses, which appear to "pinch and swell" along the shear zones, however, this interpretation may be a result of low drill density. Five lenses have been identified within the Mostaza "Near-Mine" area with historical mining activity at Lenses 1 and 2.

Historical exploration is limited to the near-mine area with 25 diamond holes completed for a total of 1,024m (Figure 1). Significant intercepts for the drilling are summarised in Table 1 below. Only 14 of the 25 holes are believed to have reached target depth with the deepest hole drilling to only 92m. In 1981 these results, together with rock channel sampling of mine workings, were used to calculate an internal non-JORC mineral resource estimate for Lens 1 and 2 reported at 190,600t of measured & indicated sulphide with grades of 1.2% Cu, 80 g/t Ag, and 0.45 g/t Au, plus an additional 63,000t of inferred sulphide resource at depth1 (The 1981 Historical Mineral Resource Estimate - HMRE)2.

The drilling clearly demonstrated that the high-grade Cu-Ag mineralisation is open both at depth and along strike, however, no further drilling or exploration activity has since been conducted at Mostaza.

3D Modelling of the Mostaza Cu-Ag Deposit:

Investigation of the historical drill data and 3D modelling of the deposit by GSC has subsequently revealed that the high-grade, structurally controlled mineralisation at Mostaza is enveloped by a broad halo of lower-grade copper mineralisation (>0.1% Cu).

Significantly, 16 of the 25 historical drill holes were terminated in anomalous copper mineralisation of >0.1% Cu plus 4 of the holes reportedly failed to reach target depths. Significant intervals (>0.1% Cu) are reported in Table 1. Consequently, to date, the extent of the mineralisation at Mostaza is only limited by the depth of drill holes.

3D modelling of the deposit is in progress to map the high-grade mineralisation and controlling structures, plus assisting with drill targeting (Figure 2). In addition, calculation of the 0.3% Cu cut-off shell clearly demonstrates the increased size of the deposit (Figure 3).

Table 1: Significant intercepts for historical resource and exploration drill holes at Mostaza mine, Cerro Negro. New intervals calculated using a 0.1% Cu cut-off are indicated in italics.

Figure 1: Map of the Mostaza Mine area adapted from the 1981 Historical Mineral Resource Estimate, showing historical drill holes and geological cross-sections on the pre-mining topography. To date mining activity has only centred on Lenses 1 and 2, with minimal exploration and drilling outside of the mine area.

Figure 2: Oblique view of the Mostaza trend looking to the SE showing Lens 2 (red and yellow) and the surface expression of the other lenses and alteration zones along trend to the south.

Figure 3: Oblique section view of the Mostaza open pit looking to the NNE showing high-grade Cu-Ag-Au mineralisation (>1.0% Cu) in Lens 2 (red) with newly recognised halo mineralisation >0.3% Cu (orange). Historical drill holes traces are shown in blue.

Forward Looking and Cautionary Statements