Mineral formation in an acid pit lake from a high-sulfidation ore deposit: Kirki, NE Greece

Abstract

Open pit mining of base-metals from the high-sulfidation epithermal type deposit of Kirki (Thrace, NE Greece) resulted in the formation of an acid pit lake by infilling of the open cast by rain and draining waters after mine closure. The high toxic metals content of the ore, the limited buffering capacity of host rocks and the direct exposure of the ore zone to weathering result in an intense release of metals into the pit lake. The acidic and oxidative pit lake waters show high concentrations of trace metals. A mineral precipitate, covering the floor of the pit lake, comprises secondary anglesite, several species of the jarosite-group, rozenite, melanterite, wroewolfeite, gypsum, bukovskyite, beaverite, scorodite and minor goethite. The mineral precipitate presents a significant heavy metal content indicating effective removal of metals from the acid waters. Compared to other pit lakes in high-sulfidation type deposits it has a higher metal load, consistent with the mineralogy and grade of ore in pit walls.