The Role of Gypsum Karst in Contaminant Transportation from Agh Darreh Tailing Dam in Iran

Agh Darreh tailing dam located in 23 km north of Takab, west Azarbayjan province is used for disposal of mine tailings. The tailing dam and its reservoir were constructed on gypsiferous marlstones. This is emphasis on geotechnical and environmental importance of the site. Although construction of dams on gypsum rocks were not yet prohibited, but the dissolution of gypsum in contact with water is always impendent, vulnerable and warning. Gypsiferous member of Qom formation with conduit karst characteristics outcrops in some parts of reservoir and foundation of tailing dam. The role of gypsiferous member of Qom formation on cyanide transport from tailing dam is identified using the environmental monitoring data, hydro geological and hydro geochemical measurements and geophysical investigations. The study area is tectonically active. Karst springs and conduits have aligned along the structural fractures in Qom formation. The conduits have a controlling role on groundwater flow direction. Evolution of this conduits under dam foundation provide a hydraulic connection between southwest area of tailing dam reservoir and its downward that leads to contamination of karst springs in downward of the dam.