Hydro geochemistry and balance between minerals and solutions in the mercurial zone of Azzaba, Northeast of Algeria

摘要

The mercury ore deposit of Azzaba is located on the northern flank of the Limestone Chain, south of Azzaba town, North East Algeria. Mercury among other metals is regarded as an environmental problem of this area, following its potential impact on the environment and also on the health of the people. The area of Azzaba is geologically characterized by the various mineral-bearing indices which level and which are classified in poly metal (Pb, Zn, Cu) and mercuro polymetallic (Hg, Pb, Zn, Cu). 15 groundwater samples were analyzed to understand the chemical composition by selected traces elements. The results showed that Hg, Pb and As was identified like contaminants in almost all the groundwater samples. The bicarbonated calcic facies is explained by the presence of cavernous limestone and the calcareous sandstone of the Paleocene Eocene. The chlorided sodic and sulphated calcic facies are found in sandy and clayey reservoirs of Oligocene. The mercury and lead norms are largely exceeded in groundwater the standards tolerated by WHO. Geochemical modeling carried out to study the possibility of metal precipitation and the formation of the secondary ores, shows a super saturation with regard to calcite, dolomite and aragonite and under saturation with respect to halite, the gypsum and anhydrite. The minerals of Hg, As, Pb are under saturated in groundwater of the region of study.