The Monte das Mesas concession for prospecting and research is located in the NW part of the Messejana fault. The favourable geostructural background of the occurrence of polymetallic massive sulphides, as well as the existence of geophysical anomalies detected during the various prospecting programmes, led to increased interest in this area, which is why it was decided to gain further knowledge of the area to the NNE of the Gavião concession and consequently find out whether there are mineral deposits that may be explored.

The prospecting and research agreement relating to the Alcácer area was signed by ESANMET, a company 100% owned by ESAN, on 23 November 2016, with the Portuguese State.

It has a surface area of 344.33 km² and is located in the municipalities of Alcácer do Sal and Grândola, in the district of Setúbal.

The surface geology that is observed in this area is dominated by the Tertiary sediments from the Sado Basin, which cover with variable thickness the Paleozoic rocks of the Iberian Pyrite Belt (FPI) and rocks of the Mértola formation of the Baixo Alentejo Flysch Group (BAFG). In this area some “windows” have been identified where Paleozoic rocks can be observed, particularly the windows of Valverde and Pedrogão, among others.

The prospecting and research agreement relating to the São Pedro das Cabeças area was signed by ESANMET, a company 100% owned by ESAN, on 23 November 2016, with the Portuguese State. It has a surface area of 133,175 km² and is located in the municipalities of Castro Verde, Ourique and Aljustrel, in the district of Beja.

The potential of this area lies in the fact that it is a parallel structure very close to the Neves Corvo-Rosário antiform where the Neves Corvo Mine, and several other historical holdings for copper and manganese, are located. The structure of Castro Verde is little known in depth, as only 7 mechanical probings have been carried out, and some geophysical anomalies that require further investigation have been identified.

Figure 1 – Location of the two main sectors (north and south) of the Lagoa Salgada polymetallic massive sulphide deposit on the left. Drill core samples illustrating the various types of mineralization present in the northern sector (Gos – Gossan; tMS – Transition Massive Sulphide; pMS – Primary Massive Sulphide; str- Stringer) and in the southern sector (A and B – Remobilized and fissural mineralization cutting late quartz veins; C – Remobilized and fissural mineralization cutting stratification with mineralization; D – Example of Semi Massive Sulphides).

The most recent Definitive Feasibility Study (2023) indicates total mineral resources of 27.56 million tons.

Table 1 – NI 43-101 Lagoa Salgada Mineral Resource Estimate (2023). Source: NI 43-101 Technical Report and DFS for the Lagoa Salgada Project (2023), Quadrante Engenharia

Mineral reserves, indicated in the same study, total 14.6 million tons, with 0.37% Cu and 1.84% Zn.

Table 2 – NI 43-101 Lagoa Salgada Mineral Reserve Estimate (2023). Source: NI 43-101 Technical Report and DFS for the Lagoa Salgada Project (2023), Quadrante Engenharia

This project is owned by the consortium EDM – Empresa de Desenvolvimento Mineiro & Redcorp, in which EDM has a 15% stake and Redcorp owns 85%. In turn, Redcorp is 80% owned by Ascendant Resources Inc. and 20% by the investment fund Mineral & Financial Investments Ltd. The consortium agreement between EDM and Redcorp was signed in September 2013. Ascendant Resources, based in Toronto (Canada), is focused on developing the Lagoa Salgada mining project, which aims to extract copper, lead, zinc, tin, gold and silver ores underground.

In 2022, this project was considered a PIN project (Project of National Interest), a status granted by the Portuguese Investment and Foreign Trade Agency (AICEP), making it the first mining project to gain this status in Portugal.

The discovery of the Gavião deposit in 1970 was a novelty in the Portuguese mining industry, and a precursor to the increased potential of the “Portuguese” pyrite belt that has been observed. It was a first sign of what is yet to develop in this metallogenic province, proven thereafter until the present situation.

This deposit was identified in the area of Aljustrel through 62 probings (a total of 19,555.34 metres drilled), by the then Sociedade Mineira de Santiago SMS, the predecessor of EDM.

Numerous mining exploration works were carried out in this area, in particular various geophysical survey campaigns (gravimetric, electromagnetic, magnetic and electric analysis), geochemical surveys and various drilling campaigns, most importantly those held in 2012 and 2013, together with Almina, which increased the degree of confidence with regard to the distribution of content and the extent of mineralization at depth.

So far a total of 101 drilling surveys have been carried out, with 37,764.29 metres drilled.

The exploration area is in the southwest sector of the Central Iberian Zone near the contact point with the Ossa Morena Zone and belongs to the Góis-Segura stannous-tungstiferous metallogenic belt. This strip has an area of approximately 8,000 km² and is known to possess large deposits which gave rise to the mines of Panasqueira (W-Sn-Cu), Argemela (Sn), Segura (W-Sn-Pb) and Góis (W-Sn).

The Góis region is located in the Serra da Lousã and is marked by steep reliefs, among which the Penedos de Góis are particularly notable. These reliefs consist of quartzite ridges dating back to the Ordovician period which belong to the Armorican Quartzite Formation, and reach an altitude of around 1,043 metres. The Penedos de Góis are hard land forms, rather elongated in a N30ºW direction. These reliefs are embedded in older schist and greywackes belonging to the Schist Greywacke complex of the Beiras Group, which dates back to the Neoproterozoic era, where the two previous lithologies predominate but conglomeratic levels also occur. The Schist Greywacke Complex is divided in this region into three formations, which bottom-up are: The Caneiro Formation, the Boque Serpins Formation and the Colmeal Formation.

To the northwest, the Schist Greywacke Complex is separated from sedimentary deposits of the Cretaceous to the Quaternary by the Góis fault. This fault, which runs in a NE-SW direction, is the main structure of the region and now has an inverse movement that causes the thrust of the older Schist Greywacke Complex over the more recent Meso-Cenozoic units.

The folding in the region is fairly well demonstrated across the whole area, anticlines and synclines being visible in a NW-SE direction corresponding to the 3rd stage of variscan deformation and associated cleavage. Several faults in dominant directions NNE-SSW, N-S and NE-SW occur in the area and may present locally significant fills of quartz.

Throughout the exploration area there are various known mineral deposits of Sn-W and Au-Ag(Sb), many of which are being mined on different scales.

The deposits and former Sn-W mines are located mainly in the NW sector of the exploration area and belonged to the Góis mining field. Mining in this metallogenic province reached its peak during World War II, the tungstiferous zone being the most productive area of Portugal at that time.

In 1957, the Góis Mining Field was founded with around seventeen concessions, including the Vale de Pião and Sandinha (Senhora da Guia Mine) concessions, which correspond to the most important tin and tungsten mines, respectively. The Senhora da Guia Mine operated between 1949 and 1972. During this period 8 levels of galleries were opened over a distance of 350 m and reaching a depth of 126 m. The operations focused on sub-vertical quartz veins with tungstiferous mineralization. The Vale Pião mine operated between 1946 and 1969 and mined sub-horizontal quartz veins, predominantly stanniferous mineralization. After the closure of the mine in the 1980s, the SFM carried out a prospecting campaign in which 25 surveys were conducted covering the area of the mining works and its surroundings, drilling a total of 3,200 metres.

The stannous-tungstiferous mineralizations mainly occur at the N-NW zone of the exploration area and are associated with non-outcrop granitic intrusions.

The mineralizations of Sn-W occur in two types of structures: veins and breccias/stockworks.

The vein structures, generally of a NW-SE direction, are characterized by quartzose filling with cassiterite, wolframite and, more rarely, scheelite. These may be sub-vertical and sub-horizontal, both lying in a general NW-SE direction. They have thicknesses not exceed 0.60 m and as well as the useful mineralization, they also contain sulphides (arsenopyrite, pyrite, sphalerite, pyrrhotite, chalcopyrite), mica, tourmaline and apatite. The Senhora da Guia Mine (W) essentially mined sub-vertical veins with wolframite. The Vale Pião Mine (Sn) mined sub-horizontal quartz veins, predominantly cassiterite and some wolframite.

The structures of the type breccia/stockwork are identified in two places: in the former Vale Pião Mine and the Vale Moreiro – Casal Loureiro sector. Installed in late Variscan to alpine shear zones (NNE-SSW), these structures have essentially tungstiferous, and to a lesser extent, stanniferous mineralization.

The auriferous mineralizations are associated with quartz vein structures and sulphides that occur in NW-SE shear zones.

At the Escádia Grande mine, auriferous mineralization occurs in vein structures of tabular and lenticular morphology in the general direction of N30º-55ºW, variable pitch of between 50º-60ºSW and thickness of between 0.50 to 0.70 m. The vein structures exhibit essentially quartzose filling with arsenopyrite strongly associated with the auriferous mineralization, but also other sulphides (galena, sphalerite, pyrite) and chlorite. This deposit is affected by faults in NNE-SSE and ENE-WSW directions, making significant tailings, in particular horizontal, which displace the mineralized structure.

The area of Vale Pião was also mined by the Romans for gold. In this sector, breccia were identified in a NNE-SSW direction with quartz and sulphides that may be the carrier structures of the auriferous mineralization.