Pilot 3 : São Domingos - Portugal

Pilot Case Study - São Domingos, Portugal

São Domingos Mine (Iberian Pyrite Belt) – Portugal



The Iberian Pyrite Belt (IPB) extends from southern Portuguese Alentejo province along Spanish Andalucía close to Seville. It constitutes one of the most important metallogenic provinces for Volcanogenic Massive Sulphide deposits worldwide, including worldclass deposits as well as medium size deposits like the S. Domingos Mine. An irregular tract of superficial iron-staining and gossan extends southeast from the orebody, partly lying along the slopes of a shallow to moderately incised valley. This drains southeast wards from a point about 500m away from the mine. The volcanic rock sequence in the mine is not well exposed and the structure is tectonically complex. The upper volcanic levels are covered by a thick turbiditic sequence (Flysch Group) and the allochthonous Phylite Quartzite (PQ) group caps the volcanic pile. The outcropping area was formed by a unique vertical mass of cupriferous pyrite associated with zinc and lead sulphides, elongated in an E-W direction. This orebody was exploited to a depth of 120m below the topographic surface as an open pit mine and from this depth down to 420m. Mining accesses consisted of wells and galleries. S. Domingos Mine has a long-time span history of mining exploitation. The first products were extracted by incineration processes, separated and the richest nodules were submitted to a fusion process. The leaching of the poor products was carried out in cementation tanks but this process was abandoned in 1868 due to technical difficulties and high costs. When copper prices dropped, the material was leached in a raw state making the recovery more efficient. The ore treatment methodology followed by the mine management, with implications in the present day dumps, were as follows: 

1) separation of 2% cut off Cuinto four piles, fine and poor material;
2) crushing of the richest and coarse grained material into pieces of more or less 5 cm;
3) accumulation of Cu<2% in piles with interior channels made of gravel material for easy circulation of the air, sandstone chimneys to control the temperature of this exothermic process;
4) the leaching of the piles with water controlling the temperature to avoid spontaneous combustion of the mined material and excessive formation of sulphuric acid that could make a poor cement and raise the iron consumption (Gaspar, 1998).

The ore was exported for sulphuric acid production; the leaching products had 14% of Cu and were lidded to the tanks to decant particles and sent to cementation tanks. The iron used in the process was about 20 000t a year. From the 4 Mt of copper mineralization extracted from 1870 until 1887, 334 575 t were transported to the treatment facilities in Achada do Gamo and 378 320 t of washed product and 85 046t of copper concentrate were exported. A railway was built in 1858, linking S. Domingos Mine to the Pomarão Harbour, in the Guadiana River, from where the ore was transported to the Atlantic Ocean. In Swansea, UK, part of the material was treated for copper and part was to obtain gold and silver (Gaspar, 1998). Waste mining material such as slags, heap dumps and tailings, either concentrated or dispersed in the area, are still enriched in hazardous elements such as Zn, Pb, Sb, Cu, As, Hg and Cd. These waste materials leached by rainwater and stream waters can have highly acid generating potential, due to sulphide oxidation and Fehydrolisis, which increases dissolution and mobility of elements. They constitute hot spots for waters, soils and plants contamination.
Present day mine dumps cover large areas and were mapped accordingly to tailings composition.


  • High-resolution geochemical mapping of mining wastes for recovery of critical raw materials. Use of remote sensors (drones) to calculate volumes/ tonnage and validate the geochemical data obtained. Chemical extraction tests of wastes materials. At least 10 bioleaching tests in lab-scale for the recovery of strategic metals and securing of tailings in columns and shake flasks.

Services to be Validated

  • Develop innovative technologies for extraction of raw materials in the European Union
  • Increase the domestic EU sourcing of raw materials
  • Improve responsible supply of raw materials to Europe in line with the EU principles for sustainable raw materials
  • Application of advanced prospecting technologies and active-passive sensors and their possible hybridization to optimize the recovery and possible use of materials located in waste streams from mining scenarios and whose use has not been feasible with the usual recovery techniques
  • Application of advanced data acquisition and processing technologies to waste and mining and industrial products stockpiles in order to know their structure, not only in terms of type of material but also their composition and even their size and shape

Partner Roles

  • LNEG – Facilities Owner
  • ACCELI – UAV Technology Provider
  • USAL – electromagnetic survey system and analytics technology provider
  • UNP – miniaturised X-ray fluorescence system and analytics technology provider
  • TUC/TUBAF – bioextraction technologies provider
  • MUON – stockpiles assessment technology provider

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EN V Funded by the EU POS

This project has received funding from the European Union’s Horizon Europe Research and Innovation Programme under Grant Agreement no. 101138432

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