HISTORICAL ASPECTS

São Domingos is a mining centre with known activity since pre-roman and roman times, with extraction of gold, silver and copper. A British company exploited the area from 1858 to 1966, who built a typical mining village with autonomy.

The large area covered by the mine is the result of extraction of more than 25 millions tons of ore (copper concentrate production) from which 9.9 millions tons of cupriferous pyrite were processed as an elementary source of sulphur. The ore was transported through a 15km railway, built to this end, to Pomarão harbour, on Guadiana River, where it was then connected with the Mediterranean Sea.

Nowadays there is a general urbanisation plan for the recovery of the village and also the modernisation of Pomarão harbour for recreation. The area will be converted into a mining museum attraction.

CHARACTERISTICS

The climate is mediterranean with atlantic and/or continental influences, characterised by long dry summers and short winters. The air daily medium temperature is 16-17.5ºC, varying between 5°C to 40°C during the year.

The population density is low and main activity was dedicated to mining of sulphide deposits.

Most of the area is covered by thin soils, and natural rock outcrops are abundant.

São Domingos belongs to the Iberyan Pyrite Belt, with the outcropping area sequences formed by a unique vertical mass of cupriferous pyrite associated to zinc and lead sulphide. At surface level, due to weathering processes, a reddish-brown gossan cap, resulting on anomalous concentrations of limonite and hematite bodies, represents the top of the massif ore.

The area of study, including the open pit, village and Pomarão harbour, is 60km².

ENVIRONMENTAL PROBLEMS

The landscape has a high degradation level with approximately 750 000 tons of waste mining material. The enormous pit, left by extraction works, 122m deep, is filled with acid waters (pH=1,7). The mining effluent during productive phase has been estimated on 2hm³/year, leading to critical environment situation. The acid drainage from the reservoir contaminates soils and groundwater along several km, affecting values of pH and fluid conductivity on a dam nearby.